HBASE-17732 Coprocessor Design Improvements

------------------------------------------------------
TL;DR
------------------------------------------------------
We are moving from Inheritence
- Observer *is* Coprocessor
- FooService *is* CoprocessorService
To Composition
- Coprocessor *has* Observer
- Coprocessor *has* Service

------------------------------------------------------
Design Changes
------------------------------------------------------
- Adds four new interfaces - MasterCoprocessor, RegionCoprocessor, RegionServierCoprocessor,
  WALCoprocessor
- These new *Coprocessor interfaces have a get*Observer() function for each observer type
  supported by them.
- Added Coprocessor#getService() to base interface. All extending *Coprocessor interfaces will
  get it from the base interface.
- Added BulkLoadObserver hooks to RegionCoprocessorHost instad of SecureBulkLoadManager doing its
  own trickery.
- CoprocessorHost#find*() fuctions: Too many testing hooks digging into CP internals.
  Deleted if can, else marked @VisibleForTesting.

------------------------------------------------------
Backward Compatibility
------------------------------------------------------
- Old coprocessors implementing *Observer won't get loaded (no backward compatibility guarantees).
- Third party coprocessors only implementing Coprocessor will not get loaded (just like Observers).
- Old coprocessors implementing CoprocessorService (for master/region host)
  /SingletonCoprocessorService (for RegionServer host) will continue to work with 2.0.
- Added test to ensure backward compatibility of CoprocessorService/SingletonCoprocessorService
- Note that if a coprocessor implements both observer and service in same class, its service
  component will continue to work but it's observer component won't work.

------------------------------------------------------
Notes
------------------------------------------------------
Did a side-by-side comparison of CPs in master and after patch. These coprocessors which were just
CoprocessorService earlier, needed a home in some coprocessor in new design. For most it was clear
since they were using a particular type of environment. Some were tricky.

- JMXListener - MasterCoprocessor and RSCoprocessor (because jmx listener makes sense for
  processes?)
- RSGroupAdminEndpoint --> MasterCP
- VisibilityController -> MasterCP and RegionCP

These were converted to RegionCoprocessor because they were using RegionCoprocessorEnvironment
which can only come from a RegionCPHost.
- AggregateImplementation
- BaseRowProcessorEndpoint
- BulkDeleteEndpoint
- Export
- RefreshHFilesEndpoint
- RowCountEndpoint
- MultiRowMutationEndpoint
- SecureBulkLoadEndpoint
- TokenProvider

Change-Id: I813145f2bc11815f52ac703563b879962c249764

hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/BackupObserver.java

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.backup;
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -34,6 +35,7 @@ import org.apache.hadoop.hbase.client.Connection;
 import org.apache.hadoop.hbase.client.ConnectionFactory;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.util.Pair;
@@ -43,8 +45,14 @@ import org.apache.yetus.audience.InterfaceAudience;
  * An Observer to facilitate backup operations
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
-public class BackupObserver implements RegionObserver {
+public class BackupObserver implements RegionCoprocessor, RegionObserver {
   private static final Log LOG = LogFactory.getLog(BackupObserver.class);
+
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public boolean postBulkLoadHFile(ObserverContext<RegionCoprocessorEnvironment> ctx,
     List<Pair<byte[], String>> stagingFamilyPaths, Map<byte[], List<Path>> finalPaths,

hbase-backup/src/test/java/org/apache/hadoop/hbase/backup/TestBackupDeleteWithFailures.java

@@ -24,6 +24,7 @@ import static org.junit.Assert.assertTrue;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -37,6 +38,7 @@ import org.apache.hadoop.hbase.client.Connection;
 import org.apache.hadoop.hbase.client.SnapshotDescription;
 import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -67,9 +69,7 @@ public class TestBackupDeleteWithFailures extends TestBackupBase{
     POST_DELETE_SNAPSHOT_FAILURE
   }
 
-  public static class MasterSnapshotObserver implements MasterObserver {
-
-
+  public static class MasterSnapshotObserver implements MasterCoprocessor, MasterObserver {
     List<Failure> failures = new ArrayList<Failure>();
 
     public void setFailures(Failure ... f) {
@@ -79,6 +79,11 @@ public class TestBackupDeleteWithFailures extends TestBackupBase{
       }
     }
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preSnapshot(final ObserverContext<MasterCoprocessorEnvironment> ctx,
         final SnapshotDescription snapshot, final TableDescriptor hTableDescriptor)
@@ -121,8 +126,8 @@ public class TestBackupDeleteWithFailures extends TestBackupBase{
 
 
   private MasterSnapshotObserver getMasterSnapshotObserver() {
-    return (MasterSnapshotObserver)TEST_UTIL.getHBaseCluster().getMaster()
-      .getMasterCoprocessorHost().findCoprocessor(MasterSnapshotObserver.class.getName());
+    return TEST_UTIL.getHBaseCluster().getMaster().getMasterCoprocessorHost()
+        .findCoprocessor(MasterSnapshotObserver.class);
   }
 
   @Test

hbase-client/src/main/java/org/apache/hadoop/hbase/Coprocessor.java

@@ -20,7 +20,9 @@
 package org.apache.hadoop.hbase;
 
 import java.io.IOException;
+import java.util.Optional;
 
+import com.google.protobuf.Service;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.yetus.audience.InterfaceStability;
 
@@ -53,9 +55,22 @@ public interface Coprocessor {
     STOPPED
   }
 
-  // Interface
+  /**
+   * Called by the {@link CoprocessorEnvironment} during it's own startup to initialize the
+   * coprocessor.
+   */
   default void start(CoprocessorEnvironment env) throws IOException {}
 
+  /**
+   * Called by the {@link CoprocessorEnvironment} during it's own shutdown to stop the
+   * coprocessor.
+   */
   default void stop(CoprocessorEnvironment env) throws IOException {}
 
+  /**
+   * Coprocessor endpoints providing protobuf services should implement this interface.
+   */
+  default Optional<Service> getService() {
+    return Optional.empty();
+  }
 }

hbase-client/src/main/java/org/apache/hadoop/hbase/CoprocessorEnvironment.java

@@ -30,7 +30,7 @@ import org.apache.hadoop.hbase.client.Table;
  * Coprocessor environment state.
  */
 @InterfaceAudience.Private
-public interface CoprocessorEnvironment {
+public interface CoprocessorEnvironment<C extends Coprocessor> {
 
   /** @return the Coprocessor interface version */
   int getVersion();
@@ -39,7 +39,7 @@ public interface CoprocessorEnvironment {
   String getHBaseVersion();
 
   /** @return the loaded coprocessor instance */
-  Coprocessor getInstance();
+  C getInstance();
 
   /** @return the priority assigned to the loaded coprocessor */
   int getPriority();
@@ -67,4 +67,13 @@ public interface CoprocessorEnvironment {
    * @return the classloader for the loaded coprocessor instance
    */
   ClassLoader getClassLoader();
+
+  /**
+   * After a coprocessor has been loaded in an encapsulation of an environment, CoprocessorHost
+   * calls this function to initialize the environment.
+   */
+  void startup() throws IOException;
+
+  /** Clean up the environment. Called by CoprocessorHost when it itself is shutting down. */
+  void shutdown();
 }

hbase-client/src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java

@@ -681,8 +681,7 @@ public class HTableDescriptor implements TableDescriptor, Comparable<HTableDescr
 
   /**
    * Add a table coprocessor to this table. The coprocessor
-   * type must be org.apache.hadoop.hbase.coprocessor.RegionObserver
-   * or Endpoint.
+   * type must be org.apache.hadoop.hbase.coprocessor.RegionCoprocessor.
    * It won't check if the class can be loaded or not.
    * Whether a coprocessor is loadable or not will be determined when
    * a region is opened.
@@ -696,8 +695,7 @@ public class HTableDescriptor implements TableDescriptor, Comparable<HTableDescr
 
   /**
    * Add a table coprocessor to this table. The coprocessor
-   * type must be org.apache.hadoop.hbase.coprocessor.RegionObserver
-   * or Endpoint.
+   * type must be org.apache.hadoop.hbase.coprocessor.RegionCoprocessor.
    * It won't check if the class can be loaded or not.
    * Whether a coprocessor is loadable or not will be determined when
    * a region is opened.
@@ -717,8 +715,7 @@ public class HTableDescriptor implements TableDescriptor, Comparable<HTableDescr
 
   /**
    * Add a table coprocessor to this table. The coprocessor
-   * type must be org.apache.hadoop.hbase.coprocessor.RegionObserver
-   * or Endpoint.
+   * type must be org.apache.hadoop.hbase.coprocessor.RegionCoprocessor.
    * It won't check if the class can be loaded or not.
    * Whether a coprocessor is loadable or not will be determined when
    * a region is opened.

hbase-endpoint/src/main/java/org/apache/hadoop/hbase/coprocessor/AggregateImplementation.java

@@ -31,11 +31,11 @@ import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.NavigableSet;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.Cell;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.hadoop.hbase.client.Scan;
@@ -60,8 +60,8 @@ import org.apache.hadoop.hbase.regionserver.InternalScanner;
  * @param R PB message that is used to transport Promoted (<S>) instance
  */
 @InterfaceAudience.Private
-public class AggregateImplementation<T, S, P extends Message, Q extends Message, R extends Message> 
-extends AggregateService implements CoprocessorService, Coprocessor {
+public class AggregateImplementation<T, S, P extends Message, Q extends Message, R extends Message>
+extends AggregateService implements RegionCoprocessor {
   protected static final Log log = LogFactory.getLog(AggregateImplementation.class);
   private RegionCoprocessorEnvironment env;
 
@@ -156,7 +156,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
         results.clear();
       } while (hasMoreRows);
       if (min != null) {
-        response = AggregateResponse.newBuilder().addFirstPart( 
+        response = AggregateResponse.newBuilder().addFirstPart(
           ci.getProtoForCellType(min).toByteString()).build();
       }
     } catch (IOException e) {
@@ -211,7 +211,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
         results.clear();
       } while (hasMoreRows);
       if (sumVal != null) {
-        response = AggregateResponse.newBuilder().addFirstPart( 
+        response = AggregateResponse.newBuilder().addFirstPart(
           ci.getProtoForPromotedType(sumVal).toByteString()).build();
       }
     } catch (IOException e) {
@@ -262,7 +262,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
       } while (hasMoreRows);
       ByteBuffer bb = ByteBuffer.allocate(8).putLong(counter);
       bb.rewind();
-      response = AggregateResponse.newBuilder().addFirstPart( 
+      response = AggregateResponse.newBuilder().addFirstPart(
           ByteString.copyFrom(bb)).build();
     } catch (IOException e) {
       CoprocessorRpcUtils.setControllerException(controller, e);
@@ -310,7 +310,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
       }
       List<Cell> results = new ArrayList<>();
       boolean hasMoreRows = false;
-    
+
       do {
         results.clear();
         hasMoreRows = scanner.next(results);
@@ -371,7 +371,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
       List<Cell> results = new ArrayList<>();
 
       boolean hasMoreRows = false;
-    
+
       do {
         tempVal = null;
         hasMoreRows = scanner.next(results);
@@ -413,7 +413,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
    * It is computed for the combination of column
    * family and column qualifier(s) in the given row range as defined in the
    * Scan object. In its current implementation, it takes one column family and
-   * two column qualifiers. The first qualifier is for values column and 
+   * two column qualifiers. The first qualifier is for values column and
    * the second qualifier (optional) is for weight column.
    */
   @Override
@@ -437,7 +437,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
       List<Cell> results = new ArrayList<>();
 
       boolean hasMoreRows = false;
-    
+
       do {
         tempVal = null;
         tempWeight = null;
@@ -461,7 +461,7 @@ extends AggregateService implements CoprocessorService, Coprocessor {
       ByteString first_sumWeights = ci.getProtoForPromotedType(s).toByteString();
       AggregateResponse.Builder pair = AggregateResponse.newBuilder();
       pair.addFirstPart(first_sumVal);
-      pair.addFirstPart(first_sumWeights); 
+      pair.addFirstPart(first_sumWeights);
       response = pair.build();
     } catch (IOException e) {
       CoprocessorRpcUtils.setControllerException(controller, e);
@@ -500,8 +500,8 @@ extends AggregateService implements CoprocessorService, Coprocessor {
   }
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   /**
@@ -527,5 +527,5 @@ extends AggregateService implements CoprocessorService, Coprocessor {
   public void stop(CoprocessorEnvironment env) throws IOException {
     // nothing to do
   }
-  
+
 }

hbase-endpoint/src/main/java/org/apache/hadoop/hbase/coprocessor/Export.java

@@ -28,6 +28,7 @@ import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.TreeMap;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -35,7 +36,6 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.Cell;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseConfiguration;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
@@ -87,8 +87,7 @@ import org.apache.hadoop.util.ReflectionUtils;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public class Export extends ExportProtos.ExportService
-        implements Coprocessor, CoprocessorService {
+public class Export extends ExportProtos.ExportService implements RegionCoprocessor {
 
   private static final Log LOG = LogFactory.getLog(Export.class);
   private static final Class<? extends CompressionCodec> DEFAULT_CODEC = DefaultCodec.class;
@@ -312,8 +311,8 @@ public class Export extends ExportProtos.ExportService
   }
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-endpoint/src/main/java/org/apache/hadoop/hbase/security/access/SecureBulkLoadEndpoint.java

@@ -21,14 +21,13 @@ package org.apache.hadoop.hbase.security.access;
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.fs.Path;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
@@ -48,6 +47,7 @@ import org.apache.hadoop.hbase.regionserver.SecureBulkLoadManager;
 import com.google.protobuf.RpcCallback;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
+import org.apache.yetus.audience.InterfaceAudience;
 
 /**
  * Coprocessor service for bulk loads in secure mode.
@@ -55,8 +55,7 @@ import com.google.protobuf.Service;
  */
 @InterfaceAudience.Private
 @Deprecated
-public class SecureBulkLoadEndpoint extends SecureBulkLoadService
-    implements CoprocessorService, Coprocessor {
+public class SecureBulkLoadEndpoint extends SecureBulkLoadService implements RegionCoprocessor {
 
   public static final long VERSION = 0L;
 
@@ -176,7 +175,7 @@ public class SecureBulkLoadEndpoint extends SecureBulkLoadService
   }
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 }

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/ColumnAggregationEndpoint.java

@@ -21,12 +21,12 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.ColumnAggregationProtos.ColumnAggregationService;
@@ -45,13 +45,13 @@ import com.google.protobuf.Service;
  * The aggregation implementation at a region.
  */
 public class ColumnAggregationEndpoint extends ColumnAggregationService
-implements Coprocessor, CoprocessorService {
+implements RegionCoprocessor {
   private static final Log LOG = LogFactory.getLog(ColumnAggregationEndpoint.class);
   private RegionCoprocessorEnvironment env = null;
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/ColumnAggregationEndpointNullResponse.java

@@ -20,12 +20,12 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.client.Scan;
@@ -47,14 +47,12 @@ import com.google.protobuf.Service;
  * response values.
  */
 public class ColumnAggregationEndpointNullResponse
-    extends
-    ColumnAggregationServiceNullResponse
-implements Coprocessor, CoprocessorService  {
+    extends ColumnAggregationServiceNullResponse implements RegionCoprocessor {
   private static final Log LOG = LogFactory.getLog(ColumnAggregationEndpointNullResponse.class);
   private RegionCoprocessorEnvironment env = null;
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/ColumnAggregationEndpointWithErrors.java

@@ -20,12 +20,12 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.DoNotRetryIOException;
 import org.apache.hadoop.hbase.HConstants;
@@ -48,14 +48,14 @@ import com.google.protobuf.Service;
  * coprocessor endpoints throwing exceptions.
  */
 public class ColumnAggregationEndpointWithErrors
-    extends
-    ColumnAggregationWithErrorsProtos.ColumnAggregationServiceWithErrors
-implements Coprocessor, CoprocessorService  {
+    extends ColumnAggregationWithErrorsProtos.ColumnAggregationServiceWithErrors
+    implements RegionCoprocessor {
   private static final Log LOG = LogFactory.getLog(ColumnAggregationEndpointWithErrors.class);
   private RegionCoprocessorEnvironment env = null;
+
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override
@@ -73,7 +73,7 @@ implements Coprocessor, CoprocessorService  {
   }
 
   @Override
-  public void sum(RpcController controller, ColumnAggregationWithErrorsSumRequest request, 
+  public void sum(RpcController controller, ColumnAggregationWithErrorsSumRequest request,
       RpcCallback<ColumnAggregationWithErrorsSumResponse> done) {
     // aggregate at each region
     Scan scan = new Scan();

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/ProtobufCoprocessorService.java

@@ -21,7 +21,6 @@ package org.apache.hadoop.hbase.coprocessor;
 import com.google.protobuf.RpcCallback;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.ipc.RpcServer;
@@ -34,6 +33,7 @@ import org.apache.hadoop.hbase.ipc.protobuf.generated.TestRpcServiceProtos;
 import org.apache.hadoop.hbase.util.Threads;
 
 import java.io.IOException;
+import java.util.Optional;
 
 /**
  * Test implementation of a coprocessor endpoint exposing the
@@ -41,13 +41,12 @@ import java.io.IOException;
  * only.
  */
 public class ProtobufCoprocessorService extends TestRpcServiceProtos.TestProtobufRpcProto
-    implements CoprocessorService, Coprocessor {
-  public ProtobufCoprocessorService() {
-  }
+    implements MasterCoprocessor, RegionCoprocessor {
+  public ProtobufCoprocessorService() {}
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestAsyncCoprocessorEndpoint.java

@@ -23,28 +23,21 @@ import static org.junit.Assert.fail;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.util.Optional;
 
-import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.ServerName;
 import org.apache.hadoop.hbase.client.ConnectionFactory;
 import org.apache.hadoop.hbase.client.RetriesExhaustedException;
-import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.client.TestAsyncAdminBase;
-import org.apache.hadoop.hbase.coprocessor.TestRegionServerCoprocessorEndpoint.DummyRegionServerEndpoint;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.DummyRegionServerEndpointProtos;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.DummyRegionServerEndpointProtos.DummyRequest;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.DummyRegionServerEndpointProtos.DummyResponse;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.DummyRegionServerEndpointProtos.DummyService;
-import org.apache.hadoop.hbase.ipc.CoprocessorRpcChannel;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
-import org.apache.hadoop.hbase.ipc.RemoteWithExtrasException;
-import org.apache.hadoop.hbase.ipc.ServerRpcController;
 import org.apache.hadoop.hbase.ipc.protobuf.generated.TestProtos;
 import org.apache.hadoop.hbase.ipc.protobuf.generated.TestRpcServiceProtos;
-import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
 import org.apache.hadoop.hbase.testclassification.MediumTests;
 import org.junit.BeforeClass;
@@ -56,7 +49,6 @@ import org.junit.runners.Parameterized;
 import com.google.protobuf.RpcCallback;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
-import com.google.protobuf.ServiceException;
 
 @RunWith(Parameterized.class)
 @Category({ ClientTests.class, MediumTests.class })
@@ -133,14 +125,14 @@ public class TestAsyncCoprocessorEndpoint extends TestAsyncAdminBase {
     }
   }
 
-  static class DummyRegionServerEndpoint extends DummyService implements Coprocessor, SingletonCoprocessorService {
+  public static class DummyRegionServerEndpoint extends DummyService
+      implements RegionServerCoprocessor {
 
-    public DummyRegionServerEndpoint() {
-    }
+    public DummyRegionServerEndpoint() {}
 
     @Override
-    public Service getService() {
-      return this;
+    public Optional<Service> getService() {
+      return Optional.of(this);
     }
 
     @Override

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestClassLoading.java

@@ -54,7 +54,12 @@ public class TestClassLoading {
   private static final Log LOG = LogFactory.getLog(TestClassLoading.class);
   private final static HBaseTestingUtility TEST_UTIL = new HBaseTestingUtility();
 
-  public static class TestMasterCoprocessor implements MasterObserver {}
+  public static class TestMasterCoprocessor implements MasterCoprocessor, MasterObserver {
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+  }
 
   private static MiniDFSCluster cluster;
 
@@ -69,7 +74,7 @@ public class TestClassLoading {
   private static Class<?> regionCoprocessor1 = ColumnAggregationEndpoint.class;
   // TOOD: Fix the import of this handler.  It is coming in from a package that is far away.
   private static Class<?> regionCoprocessor2 = TestServerCustomProtocol.PingHandler.class;
-  private static Class<?> regionServerCoprocessor = SampleRegionWALObserver.class;
+  private static Class<?> regionServerCoprocessor = SampleRegionWALCoprocessor.class;
   private static Class<?> masterCoprocessor = TestMasterCoprocessor.class;
 
   private static final String[] regionServerSystemCoprocessors =
@@ -110,8 +115,9 @@ public class TestClassLoading {
   }
 
   static File buildCoprocessorJar(String className) throws Exception {
-    String code = "import org.apache.hadoop.hbase.coprocessor.*;" +
-      "public class " + className + " implements RegionObserver {}";
+    String code =
+        "import org.apache.hadoop.hbase.coprocessor.*;" +
+            "public class " + className + " implements RegionCoprocessor {}";
     return ClassLoaderTestHelper.buildJar(
       TEST_UTIL.getDataTestDir().toString(), className, code);
   }
@@ -539,19 +545,6 @@ public class TestClassLoading {
     assertEquals(loadedMasterCoprocessorsVerify, loadedMasterCoprocessors);
   }
 
-  @Test
-  public void testFindCoprocessors() {
-    // HBASE 12277: 
-    CoprocessorHost masterCpHost =
-                             TEST_UTIL.getHBaseCluster().getMaster().getMasterCoprocessorHost();
-
-    List<MasterObserver> masterObservers = masterCpHost.findCoprocessors(MasterObserver.class);
-
-    assertTrue(masterObservers != null && masterObservers.size() > 0);
-    assertEquals(masterCoprocessor.getSimpleName(),
-                 masterObservers.get(0).getClass().getSimpleName());
-  }
-
   private void waitForTable(TableName name) throws InterruptedException, IOException {
     // First wait until all regions are online
     TEST_UTIL.waitTableEnabled(name);

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorServiceBackwardCompatibility.java

@@ -0,0 +1,116 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import com.google.protobuf.RpcCallback;
+import com.google.protobuf.RpcController;
+import com.google.protobuf.Service;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.coprocessor.protobuf.generated.DummyRegionServerEndpointProtos.*;
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests to ensure that 2.0 is backward compatible in loading CoprocessorService.
+ */
+@Category({SmallTests.class})
+public class TestCoprocessorServiceBackwardCompatibility {
+  private static HBaseTestingUtility TEST_UTIL = null;
+  private static Configuration CONF = null;
+
+  public static class DummyCoprocessorService extends DummyService
+      implements CoprocessorService, SingletonCoprocessorService {
+    static int numCalls = 0;
+
+    @Override
+    public Service getService() {
+      return this;
+    }
+
+    @Override
+    public void dummyCall(RpcController controller, DummyRequest request,
+        RpcCallback<DummyResponse> callback) {
+      callback.run(DummyResponse.newBuilder().setValue("").build());
+      numCalls++;
+    }
+
+    @Override
+    public void dummyThrow(RpcController controller, DummyRequest request,
+        RpcCallback<DummyResponse> callback) {
+    }
+  }
+
+  @BeforeClass
+  public static void setupBeforeClass() throws Exception {
+    TEST_UTIL = new HBaseTestingUtility();
+    CONF = TEST_UTIL.getConfiguration();
+    DummyCoprocessorService.numCalls = 0;
+  }
+
+  @AfterClass
+  public static void tearDownAfterClass() throws Exception {
+    TEST_UTIL.shutdownMiniCluster();
+  }
+
+  @Test
+  public void testCoprocessorServiceLoadedByMaster() throws Exception {
+    CONF.setStrings(CoprocessorHost.MASTER_COPROCESSOR_CONF_KEY,
+        DummyCoprocessorService.class.getName());
+    TEST_UTIL.startMiniCluster();
+
+    TEST_UTIL.getAdmin().coprocessorService().callBlockingMethod(
+            DummyCoprocessorService.getDescriptor().findMethodByName("dummyCall"), null,
+        DummyRequest.getDefaultInstance(), DummyResponse.getDefaultInstance());
+
+    assertEquals(1, DummyCoprocessorService.numCalls);
+  }
+
+  @Test
+  public void testCoprocessorServiceLoadedByRegionServer() throws Exception {
+    CONF.setStrings(CoprocessorHost.REGIONSERVER_COPROCESSOR_CONF_KEY,
+        DummyCoprocessorService.class.getName());
+    TEST_UTIL.startMiniCluster();
+    TEST_UTIL.getAdmin().coprocessorService(
+        TEST_UTIL.getHBaseCluster().getRegionServer(0).getServerName()).callBlockingMethod(
+            DummyCoprocessorService.getDescriptor().findMethodByName("dummyCall"), null,
+        DummyRequest.getDefaultInstance(), DummyResponse.getDefaultInstance());
+    assertEquals(1, DummyCoprocessorService.numCalls);
+  }
+
+  @Test
+  public void testCoprocessorServiceLoadedByRegion() throws Throwable {
+    CONF.setStrings(CoprocessorHost.REGION_COPROCESSOR_CONF_KEY,
+        DummyCoprocessorService.class.getName());
+    TEST_UTIL.startMiniCluster();
+    TEST_UTIL.getConnection().getTable(TableName.valueOf("hbase:meta")).batchCoprocessorService(
+            DummyCoprocessorService.getDescriptor().findMethodByName("dummyCall"),
+        DummyRequest.getDefaultInstance(), Bytes.toBytes(""), Bytes.toBytes(""),
+        DummyResponse.getDefaultInstance());
+    assertEquals(1, DummyCoprocessorService.numCalls);
+  }
+}

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRegionServerCoprocessorEndpoint.java

@@ -22,9 +22,9 @@ import static org.junit.Assert.assertTrue;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.ServerName;
@@ -102,21 +102,12 @@ public class TestRegionServerCoprocessorEndpoint {
         ((RemoteWithExtrasException) controller.getFailedOn().getCause()).getClassName().trim());
   }
 
-  static class DummyRegionServerEndpoint extends DummyService implements Coprocessor, SingletonCoprocessorService {
+  public static class DummyRegionServerEndpoint extends DummyService
+      implements RegionServerCoprocessor {
 
     @Override
-    public Service getService() {
-      return this;
-    }
-
-    @Override
-    public void start(CoprocessorEnvironment env) throws IOException {
-      // TODO Auto-generated method stub
-    }
-
-    @Override
-    public void stop(CoprocessorEnvironment env) throws IOException {
-      // TODO Auto-generated method stub
+    public Optional<Service> getService() {
+      return Optional.of(this);
     }
 
     @Override

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRowProcessorEndpoint.java

@@ -310,7 +310,7 @@ public class TestRowProcessorEndpoint {
    * So they can be loaded with the endpoint on the coprocessor.
    */
   public static class RowProcessorEndpoint<S extends Message,T extends Message>
-  extends BaseRowProcessorEndpoint<S,T> implements CoprocessorService {
+  extends BaseRowProcessorEndpoint<S,T> {
     public static class IncrementCounterProcessor extends
         BaseRowProcessor<IncrementCounterProcessorTestProtos.IncCounterProcessorRequest,
         IncrementCounterProcessorTestProtos.IncCounterProcessorResponse> {
@@ -417,7 +417,7 @@ public class TestRowProcessorEndpoint {
 
       @Override
       public FriendsOfFriendsProcessorResponse getResult() {
-        FriendsOfFriendsProcessorResponse.Builder builder = 
+        FriendsOfFriendsProcessorResponse.Builder builder =
             FriendsOfFriendsProcessorResponse.newBuilder();
         builder.addAllResult(result);
         return builder.build();
@@ -469,7 +469,7 @@ public class TestRowProcessorEndpoint {
       }
 
       @Override
-      public void initialize(FriendsOfFriendsProcessorRequest request) 
+      public void initialize(FriendsOfFriendsProcessorRequest request)
           throws IOException {
         this.person = request.getPerson().toByteArray();
         this.row = request.getRow().toByteArray();
@@ -546,7 +546,7 @@ public class TestRowProcessorEndpoint {
             // Delete from the current row and add to the other row
             Delete d = new Delete(rows[i]);
             KeyValue kvDelete =
-                new KeyValue(rows[i], CellUtil.cloneFamily(kv), CellUtil.cloneQualifier(kv), 
+                new KeyValue(rows[i], CellUtil.cloneFamily(kv), CellUtil.cloneQualifier(kv),
                     kv.getTimestamp(), KeyValue.Type.Delete);
             d.add(kvDelete);
             Put p = new Put(rows[1 - i]);

hbase-endpoint/src/test/java/org/apache/hadoop/hbase/regionserver/TestServerCustomProtocol.java

@@ -24,10 +24,10 @@ import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HRegionLocation;
@@ -38,7 +38,7 @@ import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.client.coprocessor.Batch;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.PingProtos;
 import org.apache.hadoop.hbase.coprocessor.protobuf.generated.PingProtos.CountRequest;
@@ -75,8 +75,7 @@ public class TestServerCustomProtocol {
   static final String HELLO = "Hello, ";
 
   /* Test protocol implementation */
-  public static class PingHandler extends PingProtos.PingService
-  implements Coprocessor, CoprocessorService {
+  public static class PingHandler extends PingProtos.PingService implements RegionCoprocessor {
     private int counter = 0;
 
     @Override
@@ -125,8 +124,8 @@ public class TestServerCustomProtocol {
     }
 
     @Override
-    public Service getService() {
-      return this;
+    public Optional<Service> getService() {
+      return Optional.of(this);
     }
   }
 
@@ -320,7 +319,7 @@ public class TestServerCustomProtocol {
       // rows from 1 region
       assertEquals(1, results.size());
       verifyRegionResults(locator, results, ROW_A);
-  
+
       final String name = "NAME";
       results = hello(table, name, null, ROW_A);
       // Should have gotten results for 1 of the three regions only since we specified
@@ -343,12 +342,12 @@ public class TestServerCustomProtocol {
       // test,,1355943549657.c65d4822d8bdecc033a96451f3a0f55d.
       // test,bbb,1355943549661.110393b070dd1ed93441e0bc9b3ffb7e.
       // test,ccc,1355943549665.c3d6d125141359cbbd2a43eaff3cdf74.
-  
+
       Map<byte [], String> results = ping(table, null, ROW_A);
       // Should contain first region only.
       assertEquals(1, results.size());
       verifyRegionResults(locator, results, ROW_A);
-  
+
       // Test start row + empty end
       results = ping(table, ROW_BC, null);
       assertEquals(2, results.size());
@@ -358,7 +357,7 @@ public class TestServerCustomProtocol {
         results.get(loc.getRegionInfo().getRegionName()));
       verifyRegionResults(locator, results, ROW_B);
       verifyRegionResults(locator, results, ROW_C);
-  
+
       // test empty start + end
       results = ping(table, null, ROW_BC);
       // should contain the first 2 regions
@@ -368,7 +367,7 @@ public class TestServerCustomProtocol {
       loc = locator.getRegionLocation(ROW_C, true);
       assertNull("Should be missing region for row ccc (past stop row)",
           results.get(loc.getRegionInfo().getRegionName()));
-  
+
       // test explicit start + end
       results = ping(table, ROW_AB, ROW_BC);
       // should contain first 2 regions
@@ -378,7 +377,7 @@ public class TestServerCustomProtocol {
       loc = locator.getRegionLocation(ROW_C, true);
       assertNull("Should be missing region for row ccc (past stop row)",
           results.get(loc.getRegionInfo().getRegionName()));
-  
+
       // test single region
       results = ping(table, ROW_B, ROW_BC);
       // should only contain region bbb

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/BulkDeleteEndpoint.java

@@ -21,6 +21,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeSet;
 
@@ -28,7 +29,6 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HConstants.OperationStatusCode;
@@ -36,7 +36,7 @@ import org.apache.hadoop.hbase.client.Delete;
 import org.apache.hadoop.hbase.client.Mutation;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.example.generated.BulkDeleteProtos.BulkDeleteRequest;
 import org.apache.hadoop.hbase.coprocessor.example.generated.BulkDeleteProtos.BulkDeleteRequest.DeleteType;
@@ -57,7 +57,7 @@ import com.google.protobuf.Service;
 
 /**
  * Defines a protocol to delete data in bulk based on a scan. The scan can be range scan or with
- * conditions(filters) etc.This can be used to delete rows, column family(s), column qualifier(s) 
+ * conditions(filters) etc.This can be used to delete rows, column family(s), column qualifier(s)
  * or version(s) of columns.When delete type is FAMILY or COLUMN, which all family(s) or column(s)
  * getting deleted will be determined by the Scan. Scan need to select all the families/qualifiers
  * which need to be deleted.When delete type is VERSION, Which column(s) and version(s) to be
@@ -65,16 +65,16 @@ import com.google.protobuf.Service;
  * which needs to be deleted.When a timestamp is passed only one version at that timestamp will be
  * deleted(even if Scan fetches many versions). When timestamp passed as null, all the versions
  * which the Scan selects will get deleted.
- * 
+ *
  * <br> Example: <pre><code>
  * Scan scan = new Scan();
  * // set scan properties(rowkey range, filters, timerange etc).
  * HTable ht = ...;
  * long noOfDeletedRows = 0L;
- * Batch.Call&lt;BulkDeleteService, BulkDeleteResponse&gt; callable = 
+ * Batch.Call&lt;BulkDeleteService, BulkDeleteResponse&gt; callable =
  *     new Batch.Call&lt;BulkDeleteService, BulkDeleteResponse&gt;() {
  *   ServerRpcController controller = new ServerRpcController();
- *   BlockingRpcCallback&lt;BulkDeleteResponse&gt; rpcCallback = 
+ *   BlockingRpcCallback&lt;BulkDeleteResponse&gt; rpcCallback =
  *     new BlockingRpcCallback&lt;BulkDeleteResponse&gt;();
  *
  *   public BulkDeleteResponse call(BulkDeleteService service) throws IOException {
@@ -95,16 +95,15 @@ import com.google.protobuf.Service;
  * }
  * </code></pre>
  */
-public class BulkDeleteEndpoint extends BulkDeleteService implements CoprocessorService,
-    Coprocessor {
+public class BulkDeleteEndpoint extends BulkDeleteService implements RegionCoprocessor {
   private static final String NO_OF_VERSIONS_TO_DELETE = "noOfVersionsToDelete";
   private static final Log LOG = LogFactory.getLog(BulkDeleteEndpoint.class);
 
   private RegionCoprocessorEnvironment env;
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ExampleMasterObserverWithMetrics.java

@@ -19,6 +19,7 @@
 package org.apache.hadoop.hbase.coprocessor.example;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -26,6 +27,7 @@ import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.TableDescriptor;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -45,7 +47,11 @@ import org.apache.hadoop.hbase.metrics.Timer;
  * </p>
  * @see ExampleRegionObserverWithMetrics
  */
-public class ExampleMasterObserverWithMetrics implements MasterObserver {
+public class ExampleMasterObserverWithMetrics implements MasterCoprocessor, MasterObserver {
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
+  }
 
   private static final Log LOG = LogFactory.getLog(ExampleMasterObserverWithMetrics.class);
 
@@ -133,4 +139,4 @@ public class ExampleMasterObserverWithMetrics implements MasterObserver {
       registry.register("maxMemory", this::getMaxMemory);
     }
   }
-}
+}

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ExampleRegionObserverWithMetrics.java

@@ -22,12 +22,14 @@ package org.apache.hadoop.hbase.coprocessor.example;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.ThreadLocalRandom;
 
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.client.Get;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.metrics.Counter;
@@ -45,36 +47,49 @@ import org.apache.hadoop.hbase.metrics.Timer;
  *
  * @see ExampleMasterObserverWithMetrics
  */
-public class ExampleRegionObserverWithMetrics implements RegionObserver {
+public class ExampleRegionObserverWithMetrics implements RegionCoprocessor {
 
   private Counter preGetCounter;
   private Timer costlyOperationTimer;
+  private ExampleRegionObserver observer;
 
-  @Override
-  public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get, List<Cell> results)
-      throws IOException {
-    // Increment the Counter whenever the coprocessor is called
-    preGetCounter.increment();
-  }
+  class ExampleRegionObserver implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
-  @Override
-  public void postGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get,
-                        List<Cell> results) throws IOException {
-    // do a costly (high latency) operation which we want to measure how long it takes by
-    // using a Timer (which is a Meter and a Histogram).
-    long start = System.nanoTime();
-    try {
-      performCostlyOperation();
-    } finally {
-      costlyOperationTimer.updateNanos(System.nanoTime() - start);
+    @Override
+    public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get,
+        List<Cell> results) throws IOException {
+      // Increment the Counter whenever the coprocessor is called
+      preGetCounter.increment();
+    }
+
+    @Override
+    public void postGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get,
+        List<Cell> results) throws IOException {
+      // do a costly (high latency) operation which we want to measure how long it takes by
+      // using a Timer (which is a Meter and a Histogram).
+      long start = System.nanoTime();
+      try {
+        performCostlyOperation();
+      } finally {
+        costlyOperationTimer.updateNanos(System.nanoTime() - start);
+      }
+    }
+
+    private void performCostlyOperation() {
+      try {
+        // simulate the operation by sleeping.
+        Thread.sleep(ThreadLocalRandom.current().nextLong(100));
+      } catch (InterruptedException ignore) {
+      }
     }
   }
 
-  private void performCostlyOperation() {
-    try {
-      // simulate the operation by sleeping.
-      Thread.sleep(ThreadLocalRandom.current().nextLong(100));
-    } catch (InterruptedException ignore) {}
+  @Override public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(observer);
   }
 
   @Override
@@ -88,6 +103,7 @@ public class ExampleRegionObserverWithMetrics implements RegionObserver {
       // at the region server level per-regionserver.
       MetricRegistry registry =
           ((RegionCoprocessorEnvironment) env).getMetricRegistryForRegionServer();
+      observer = new ExampleRegionObserver();
 
       if (preGetCounter == null) {
         // Create a new Counter, or get the already registered counter.

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/RefreshHFilesEndpoint.java

@@ -23,16 +23,16 @@ import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.protobuf.generated.RefreshHFilesProtos;
 import org.apache.hadoop.hbase.regionserver.Store;
 
 import java.io.IOException;
+import java.util.Optional;
 
 /**
  * Coprocessor endpoint to refresh HFiles on replica.
@@ -43,7 +43,7 @@ import java.io.IOException;
  * </p>
  */
 public class RefreshHFilesEndpoint extends RefreshHFilesProtos.RefreshHFilesService
-  implements Coprocessor, CoprocessorService {
+  implements RegionCoprocessor {
   protected static final Log LOG = LogFactory.getLog(RefreshHFilesEndpoint.class);
   private RegionCoprocessorEnvironment env;
 
@@ -51,8 +51,8 @@ public class RefreshHFilesEndpoint extends RefreshHFilesProtos.RefreshHFilesServ
   }
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   @Override

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/RowCountEndpoint.java

@@ -21,14 +21,14 @@ package org.apache.hadoop.hbase.coprocessor.example;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.example.generated.ExampleProtos;
 import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
@@ -48,8 +48,7 @@ import com.google.protobuf.Service;
  * hbase-examples/src/main/protobuf/Examples.proto.
  * </p>
  */
-public class RowCountEndpoint extends ExampleProtos.RowCountService
-    implements Coprocessor, CoprocessorService {
+public class RowCountEndpoint extends ExampleProtos.RowCountService implements RegionCoprocessor {
   private RegionCoprocessorEnvironment env;
 
   public RowCountEndpoint() {
@@ -59,8 +58,8 @@ public class RowCountEndpoint extends ExampleProtos.RowCountService
    * Just returns a reference to this object, which implements the RowCounterService interface.
    */
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   /**

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ZooKeeperScanPolicyObserver.java

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.coprocessor.example;
 import java.io.IOException;
 import java.util.List;
 import java.util.NavigableSet;
+import java.util.Optional;
 import java.util.OptionalInt;
 
 import org.apache.commons.logging.Log;
@@ -30,6 +31,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.client.IsolationLevel;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.regionserver.HStore;
@@ -51,20 +53,25 @@ import org.apache.zookeeper.ZooKeeper;
  * This is an example showing how a RegionObserver could configured
  * via ZooKeeper in order to control a Region compaction, flush, and scan policy.
  *
- * This also demonstrated the use of shared 
+ * This also demonstrated the use of shared
  * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} state.
  * See {@link RegionCoprocessorEnvironment#getSharedData()}.
  *
  * This would be useful for an incremental backup tool, which would indicate the last
  * time of a successful backup via ZK and instruct HBase to not delete data that was
- * inserted since (based on wall clock time). 
+ * inserted since (based on wall clock time).
  *
  * This implements org.apache.zookeeper.Watcher directly instead of using
- * {@link org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher}, 
+ * {@link org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher},
  * because RegionObservers come and go and currently
  * listeners registered with ZooKeeperWatcher cannot be removed.
  */
-public class ZooKeeperScanPolicyObserver implements RegionObserver {
+public class ZooKeeperScanPolicyObserver implements RegionCoprocessor, RegionObserver {
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   // The zk ensemble info is put in hbase config xml with given custom key.
   public static final String ZK_ENSEMBLE_KEY = "ZooKeeperScanPolicyObserver.zookeeper.ensemble";
   public static final String ZK_SESSION_TIMEOUT_KEY =
@@ -243,4 +250,4 @@ public class ZooKeeperScanPolicyObserver implements RegionObserver {
     return new StoreScanner((HStore) store, scanInfo, scan, targetCols,
         ((HStore) store).getHRegion().getReadPoint(IsolationLevel.READ_COMMITTED));
   }
-}
+}

hbase-it/src/test/java/org/apache/hadoop/hbase/mapreduce/IntegrationTestBulkLoad.java

@@ -27,6 +27,7 @@ import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Random;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicLong;
@@ -56,6 +57,7 @@ import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
@@ -155,12 +157,18 @@ public class IntegrationTestBulkLoad extends IntegrationTestBase {
   private boolean load = false;
   private boolean check = false;
 
-  public static class SlowMeCoproScanOperations implements RegionObserver {
+  public static class SlowMeCoproScanOperations implements RegionCoprocessor, RegionObserver {
     static final AtomicLong sleepTime = new AtomicLong(2000);
     Random r = new Random();
     AtomicLong countOfNext = new AtomicLong(0);
     AtomicLong countOfOpen = new AtomicLong(0);
     public SlowMeCoproScanOperations() {}
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public RegionScanner preScannerOpen(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Scan scan, final RegionScanner s) throws IOException {

hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapreduce/TestImportTSVWithOperationAttributes.java

@@ -24,6 +24,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.UUID;
 
 import org.apache.commons.logging.Log;
@@ -41,6 +42,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.client.Connection;
 import org.apache.hadoop.hbase.client.ConnectionFactory;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.testclassification.LargeTests;
 import org.apache.hadoop.hbase.testclassification.MapReduceTests;
@@ -247,7 +249,13 @@ public class TestImportTSVWithOperationAttributes implements Configurable {
     assertTrue(verified);
   }
 
-  public static class OperationAttributesTestController implements RegionObserver {
+  public static class OperationAttributesTestController
+      implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public void prePut(ObserverContext<RegionCoprocessorEnvironment> e, Put put, WALEdit edit,

hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapreduce/TestImportTSVWithTTLs.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.UUID;
 
 import org.apache.commons.logging.Log;
@@ -34,6 +35,7 @@ import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.testclassification.LargeTests;
 import org.apache.hadoop.hbase.testclassification.MapReduceTests;
@@ -156,7 +158,12 @@ public class TestImportTSVWithTTLs implements Configurable {
     return tool;
   }
 
-  public static class TTLCheckingObserver implements RegionObserver {
+  public static class TTLCheckingObserver implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public void prePut(ObserverContext<RegionCoprocessorEnvironment> e, Put put, WALEdit edit,

hbase-rsgroup/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupAdminEndpoint.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hbase.rsgroup;
 
 import java.io.IOException;
 import java.util.HashSet;
+import java.util.Optional;
 import java.util.Set;
 
 import com.google.protobuf.RpcCallback;
@@ -35,7 +36,7 @@ import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.SnapshotDescription;
 import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.constraint.ConstraintException;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -70,8 +71,9 @@ import org.apache.hadoop.hbase.protobuf.generated.TableProtos;
 import org.apache.hadoop.hbase.shaded.com.google.common.collect.Sets;
 import org.apache.yetus.audience.InterfaceAudience;
 
+// TODO: Encapsulate MasterObserver functions into separate subclass.
 @InterfaceAudience.Private
-public class RSGroupAdminEndpoint implements MasterObserver, CoprocessorService {
+public class RSGroupAdminEndpoint implements MasterCoprocessor, MasterObserver {
   private static final Log LOG = LogFactory.getLog(RSGroupAdminEndpoint.class);
 
   private MasterServices master = null;
@@ -94,8 +96,13 @@ public class RSGroupAdminEndpoint implements MasterObserver, CoprocessorService
   }
 
   @Override
-  public Service getService() {
-    return groupAdminService;
+  public Optional<Service> getService() {
+    return Optional.of(groupAdminService);
+  }
+
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
   }
 
   RSGroupInfoManager getGroupInfoManager() {
@@ -107,12 +114,6 @@ public class RSGroupAdminEndpoint implements MasterObserver, CoprocessorService
    * This class calls {@link RSGroupAdminServer} for actual work, converts result to protocol
    * buffer response, handles exceptions if any occurred and then calls the {@code RpcCallback} with
    * the response.
-   * Since our CoprocessorHost asks the Coprocessor for a Service
-   * ({@link CoprocessorService#getService()}) instead of doing "coproc instanceOf Service"
-   * and requiring Coprocessor itself to be Service (something we do with our observers),
-   * we can use composition instead of inheritance here. That makes it easy to manage
-   * functionalities in concise classes (sometimes inner classes) instead of single class doing
-   * many different things.
    */
   private class RSGroupAdminServiceImpl extends RSGroupAdminProtos.RSGroupAdminService {
     @Override

hbase-rsgroup/src/test/java/org/apache/hadoop/hbase/rsgroup/TestRSGroups.java

@@ -97,8 +97,8 @@ public class TestRSGroups extends TestRSGroupsBase {
     admin.setBalancerRunning(false,true);
     rsGroupAdmin = new VerifyingRSGroupAdminClient(
         new RSGroupAdminClient(TEST_UTIL.getConnection()), TEST_UTIL.getConfiguration());
-    rsGroupAdminEndpoint =
-        master.getMasterCoprocessorHost().findCoprocessors(RSGroupAdminEndpoint.class).get(0);
+    rsGroupAdminEndpoint = (RSGroupAdminEndpoint)
+        master.getMasterCoprocessorHost().findCoprocessor(RSGroupAdminEndpoint.class.getName());
   }
 
   @AfterClass

hbase-rsgroup/src/test/java/org/apache/hadoop/hbase/rsgroup/TestRSGroupsOfflineMode.java

@@ -161,7 +161,7 @@ public class TestRSGroupsOfflineMode {
 
     // Get groupInfoManager from the new active master.
     RSGroupInfoManager groupMgr = ((MiniHBaseCluster)cluster).getMaster().getMasterCoprocessorHost()
-            .findCoprocessors(RSGroupAdminEndpoint.class).get(0).getGroupInfoManager();
+            .findCoprocessor(RSGroupAdminEndpoint.class).getGroupInfoManager();
     // Make sure balancer is in offline mode, since this is what we're testing.
     assertFalse(groupMgr.isOnline());
     // Verify the group affiliation that's loaded from ZK instead of tables.

hbase-server/src/main/java/org/apache/hadoop/hbase/JMXListener.java

@@ -18,6 +18,7 @@
  */
 package org.apache.hadoop.hbase;
 
+import com.google.protobuf.Service;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
@@ -32,6 +33,7 @@ import java.rmi.server.RMIClientSocketFactory;
 import java.rmi.server.RMIServerSocketFactory;
 import java.rmi.server.UnicastRemoteObject;
 import java.util.HashMap;
+import java.util.Optional;
 
 import javax.management.MBeanServer;
 import javax.management.remote.JMXConnectorServer;
@@ -46,8 +48,7 @@ import javax.management.remote.rmi.RMIConnectorServer;
  * 2)support password authentication
  * 3)support subset of SSL (with default configuration)
  */
-public class JMXListener implements Coprocessor {
-
+public class JMXListener implements MasterCoprocessor, RegionServerCoprocessor {
   private static final Log LOG = LogFactory.getLog(JMXListener.class);
   public static final String RMI_REGISTRY_PORT_CONF_KEY = ".rmi.registry.port";
   public static final String RMI_CONNECTOR_PORT_CONF_KEY = ".rmi.connector.port";

hbase-server/src/main/java/org/apache/hadoop/hbase/client/HTableWrapper.java

@@ -38,7 +38,7 @@ import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.yetus.audience.InterfaceStability;
 import org.apache.hadoop.hbase.client.coprocessor.Batch;
 import org.apache.hadoop.hbase.client.coprocessor.Batch.Callback;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorHost.Environment;
+import org.apache.hadoop.hbase.coprocessor.BaseEnvironment;
 import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcChannel;
 import org.apache.hadoop.io.MultipleIOException;
@@ -70,7 +70,7 @@ public final class HTableWrapper implements Table {
    * @throws IOException
    */
   public static Table createWrapper(List<Table> openTables,
-      TableName tableName, Environment env, ExecutorService pool) throws IOException {
+      TableName tableName, BaseEnvironment env, ExecutorService pool) throws IOException {
     return new HTableWrapper(openTables, tableName,
         CoprocessorHConnection.getConnectionForEnvironment(env), pool);
   }

hbase-server/src/main/java/org/apache/hadoop/hbase/constraint/ConstraintProcessor.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hbase.constraint;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -30,6 +31,7 @@ import org.apache.hadoop.hbase.client.Put;
 import org.apache.hadoop.hbase.client.Durability;
 import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.regionserver.InternalScanner;
@@ -42,7 +44,7 @@ import org.apache.hadoop.hbase.wal.WALEdit;
  * implemented on any given system by a coprocessor.
  */
 @InterfaceAudience.Private
-public class ConstraintProcessor implements RegionObserver {
+public class ConstraintProcessor implements RegionCoprocessor, RegionObserver {
 
   private static final Log LOG = LogFactory.getLog(ConstraintProcessor.class);
 
@@ -50,6 +52,11 @@ public class ConstraintProcessor implements RegionObserver {
 
   private List<? extends Constraint> constraints = new ArrayList<>();
 
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   /**
    * Create the constraint processor.
    * <p>

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/BaseEnvironment.java

@@ -0,0 +1,187 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.CoprocessorEnvironment;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.HTableWrapper;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.util.VersionInfo;
+import org.apache.yetus.audience.InterfaceAudience;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+
+/**
+ * Encapsulation of the environment of each coprocessor
+ */
+@InterfaceAudience.Private
+public class BaseEnvironment<C extends Coprocessor> implements CoprocessorEnvironment<C> {
+  private static final Log LOG = LogFactory.getLog(BaseEnvironment.class);
+
+  /** The coprocessor */
+  public C impl;
+  /** Chaining priority */
+  protected int priority = Coprocessor.PRIORITY_USER;
+  /** Current coprocessor state */
+  Coprocessor.State state = Coprocessor.State.UNINSTALLED;
+  /** Accounting for tables opened by the coprocessor */
+  protected List<Table> openTables =
+    Collections.synchronizedList(new ArrayList<Table>());
+  private int seq;
+  private Configuration conf;
+  private ClassLoader classLoader;
+
+  /**
+   * Constructor
+   * @param impl the coprocessor instance
+   * @param priority chaining priority
+   */
+  public BaseEnvironment(final C impl, final int priority,
+      final int seq, final Configuration conf) {
+    this.impl = impl;
+    this.classLoader = impl.getClass().getClassLoader();
+    this.priority = priority;
+    this.state = Coprocessor.State.INSTALLED;
+    this.seq = seq;
+    this.conf = conf;
+  }
+
+  /** Initialize the environment */
+  @Override
+  public void startup() throws IOException {
+    if (state == Coprocessor.State.INSTALLED ||
+        state == Coprocessor.State.STOPPED) {
+      state = Coprocessor.State.STARTING;
+      Thread currentThread = Thread.currentThread();
+      ClassLoader hostClassLoader = currentThread.getContextClassLoader();
+      try {
+        currentThread.setContextClassLoader(this.getClassLoader());
+        impl.start(this);
+        state = Coprocessor.State.ACTIVE;
+      } finally {
+        currentThread.setContextClassLoader(hostClassLoader);
+      }
+    } else {
+      LOG.warn("Not starting coprocessor " + impl.getClass().getName() +
+          " because not inactive (state=" + state.toString() + ")");
+    }
+  }
+
+  /** Clean up the environment */
+  @Override
+  public void shutdown() {
+    if (state == Coprocessor.State.ACTIVE) {
+      state = Coprocessor.State.STOPPING;
+      Thread currentThread = Thread.currentThread();
+      ClassLoader hostClassLoader = currentThread.getContextClassLoader();
+      try {
+        currentThread.setContextClassLoader(this.getClassLoader());
+        impl.stop(this);
+        state = Coprocessor.State.STOPPED;
+      } catch (IOException ioe) {
+        LOG.error("Error stopping coprocessor "+impl.getClass().getName(), ioe);
+      } finally {
+        currentThread.setContextClassLoader(hostClassLoader);
+      }
+    } else {
+      LOG.warn("Not stopping coprocessor "+impl.getClass().getName()+
+          " because not active (state="+state.toString()+")");
+    }
+    synchronized (openTables) {
+      // clean up any table references
+      for (Table table: openTables) {
+        try {
+          ((HTableWrapper)table).internalClose();
+        } catch (IOException e) {
+          // nothing can be done here
+          LOG.warn("Failed to close " +
+              table.getName(), e);
+        }
+      }
+    }
+  }
+
+  @Override
+  public C getInstance() {
+    return impl;
+  }
+
+  @Override
+  public ClassLoader getClassLoader() {
+    return classLoader;
+  }
+
+  @Override
+  public int getPriority() {
+    return priority;
+  }
+
+  @Override
+  public int getLoadSequence() {
+    return seq;
+  }
+
+  /** @return the coprocessor environment version */
+  @Override
+  public int getVersion() {
+    return Coprocessor.VERSION;
+  }
+
+  /** @return the HBase release */
+  @Override
+  public String getHBaseVersion() {
+    return VersionInfo.getVersion();
+  }
+
+  @Override
+  public Configuration getConfiguration() {
+    return conf;
+  }
+
+  /**
+   * Open a table from within the Coprocessor environment
+   * @param tableName the table name
+   * @return an interface for manipulating the table
+   * @exception IOException Exception
+   */
+  @Override
+  public Table getTable(TableName tableName) throws IOException {
+    return this.getTable(tableName, null);
+  }
+
+  /**
+   * Open a table from within the Coprocessor environment
+   * @param tableName the table name
+   * @return an interface for manipulating the table
+   * @exception IOException Exception
+   */
+  @Override
+  public Table getTable(TableName tableName, ExecutorService pool) throws IOException {
+    return HTableWrapper.createWrapper(openTables, tableName, this, pool);
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/BaseRowProcessorEndpoint.java

@@ -20,11 +20,11 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.Optional;
 
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.yetus.audience.InterfaceStability;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 import org.apache.hadoop.hbase.HConstants;
@@ -46,19 +46,19 @@ import com.google.protobuf.Service;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public abstract class BaseRowProcessorEndpoint<S extends Message, T extends Message> 
-extends RowProcessorService implements CoprocessorService, Coprocessor {
+public abstract class BaseRowProcessorEndpoint<S extends Message, T extends Message>
+extends RowProcessorService implements RegionCoprocessor {
   private RegionCoprocessorEnvironment env;
   /**
    * Pass a processor to region to process multiple rows atomically.
-   * 
+   *
    * The RowProcessor implementations should be the inner classes of your
    * RowProcessorEndpoint. This way the RowProcessor can be class-loaded with
    * the Coprocessor endpoint together.
    *
    * See {@code TestRowProcessorEndpoint} for example.
    *
-   * The request contains information for constructing processor 
+   * The request contains information for constructing processor
    * (see {@link #constructRowProcessorFromRequest}. The processor object defines
    * the read-modify-write procedure.
    */
@@ -83,8 +83,8 @@ extends RowProcessorService implements CoprocessorService, Coprocessor {
   }
 
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   /**

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/BulkLoadObserver.java

@@ -49,7 +49,7 @@ import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos.CleanupBul
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface BulkLoadObserver extends Coprocessor {
+public interface BulkLoadObserver {
     /**
       * Called as part of SecureBulkLoadEndpoint.prepareBulkLoad() RPC call.
       * It can't bypass the default action, e.g., ctx.bypass() won't have effect.

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/CoprocessorHost.java

@@ -25,12 +25,13 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeSet;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentSkipListSet;
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -44,22 +45,22 @@ import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.DoNotRetryIOException;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 import org.apache.hadoop.hbase.HConstants;
-import org.apache.hadoop.hbase.TableName;
-import org.apache.hadoop.hbase.client.HTableWrapper;
-import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.ipc.RpcServer;
+import org.apache.hadoop.hbase.security.User;
+import org.apache.hadoop.hbase.shaded.com.google.common.annotations.VisibleForTesting;
 import org.apache.hadoop.hbase.util.CoprocessorClassLoader;
 import org.apache.hadoop.hbase.util.SortedList;
-import org.apache.hadoop.hbase.util.VersionInfo;
 
 /**
  * Provides the common setup framework and runtime services for coprocessor
  * invocation from HBase services.
- * @param <E> the specific environment extension that a concrete implementation
+ * @param <C> type of specific coprocessor this host will handle
+ * @param <E> type of specific coprocessor environment this host requires.
  * provides
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
+public abstract class CoprocessorHost<C extends Coprocessor, E extends CoprocessorEnvironment<C>> {
   public static final String REGION_COPROCESSOR_CONF_KEY =
       "hbase.coprocessor.region.classes";
   public static final String REGIONSERVER_COPROCESSOR_CONF_KEY =
@@ -81,7 +82,8 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
   private static final Log LOG = LogFactory.getLog(CoprocessorHost.class);
   protected Abortable abortable;
   /** Ordered set of loaded coprocessors with lock */
-  protected SortedList<E> coprocessors = new SortedList<>(new EnvironmentPriorityComparator());
+  protected final SortedList<E> coprocEnvironments =
+      new SortedList<>(new EnvironmentPriorityComparator());
   protected Configuration conf;
   // unique file prefix to use for local copies of jars when classloading
   protected String pathPrefix;
@@ -96,7 +98,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
    * Not to be confused with the per-object _coprocessors_ (above),
    * coprocessorNames is static and stores the set of all coprocessors ever
    * loaded by any thread in this JVM. It is strictly additive: coprocessors are
-   * added to coprocessorNames, by loadInstance() but are never removed, since
+   * added to coprocessorNames, by checkAndLoadInstance() but are never removed, since
    * the intention is to preserve a history of all loaded coprocessors for
    * diagnosis in case of server crash (HBASE-4014).
    */
@@ -118,7 +120,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
    */
   public Set<String> getCoprocessors() {
     Set<String> returnValue = new TreeSet<>();
-    for (CoprocessorEnvironment e: coprocessors) {
+    for (E e: coprocEnvironments) {
       returnValue.add(e.getInstance().getClass().getSimpleName());
     }
     return returnValue;
@@ -135,7 +137,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
       return;
     }
 
-    Class<?> implClass = null;
+    Class<?> implClass;
 
     // load default coprocessors from configure file
     String[] defaultCPClasses = conf.getStrings(confKey);
@@ -156,10 +158,13 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
         implClass = cl.loadClass(className);
         // Add coprocessors as we go to guard against case where a coprocessor is specified twice
         // in the configuration
-        this.coprocessors.add(loadInstance(implClass, priority, conf));
-        LOG.info("System coprocessor " + className + " was loaded " +
-            "successfully with priority (" + priority + ").");
-        ++priority;
+        E env = checkAndLoadInstance(implClass, priority, conf);
+        if (env != null) {
+          this.coprocEnvironments.add(env);
+          LOG.info(
+              "System coprocessor " + className + " was loaded " + "successfully with priority (" + priority + ").");
+          ++priority;
+        }
       } catch (Throwable t) {
         // We always abort if system coprocessors cannot be loaded
         abortServer(className, t);
@@ -196,7 +201,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
    */
   public E load(Path path, String className, int priority,
       Configuration conf, String[] includedClassPrefixes) throws IOException {
-    Class<?> implClass = null;
+    Class<?> implClass;
     LOG.debug("Loading coprocessor class " + className + " with path " +
         path + " and priority " + priority);
 
@@ -223,7 +228,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
     try{
       // switch temporarily to the thread classloader for custom CP
       currentThread.setContextClassLoader(cl);
-      E cpInstance = loadInstance(implClass, priority, conf);
+      E cpInstance = checkAndLoadInstance(implClass, priority, conf);
       return cpInstance;
     } finally {
       // restore the fresh (host) classloader
@@ -231,16 +236,11 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
     }
   }
 
-  /**
-   * @param implClass Implementation class
-   * @param priority priority
-   * @param conf configuration
-   * @throws java.io.IOException Exception
-   */
-  public void load(Class<?> implClass, int priority, Configuration conf)
+  @VisibleForTesting
+  public void load(Class<? extends C> implClass, int priority, Configuration conf)
       throws IOException {
-    E env = loadInstance(implClass, priority, conf);
-    coprocessors.add(env);
+    E env = checkAndLoadInstance(implClass, priority, conf);
+    coprocEnvironments.add(env);
   }
 
   /**
@@ -249,29 +249,22 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
    * @param conf configuration
    * @throws java.io.IOException Exception
    */
-  public E loadInstance(Class<?> implClass, int priority, Configuration conf)
+  public E checkAndLoadInstance(Class<?> implClass, int priority, Configuration conf)
       throws IOException {
-    if (!Coprocessor.class.isAssignableFrom(implClass)) {
-      throw new IOException("Configured class " + implClass.getName() + " must implement "
-          + Coprocessor.class.getName() + " interface ");
-    }
-
     // create the instance
-    Coprocessor impl;
-    Object o = null;
+    C impl;
     try {
-      o = implClass.newInstance();
-      impl = (Coprocessor)o;
-    } catch (InstantiationException e) {
-      throw new IOException(e);
-    } catch (IllegalAccessException e) {
+      impl = checkAndGetInstance(implClass);
+      if (impl == null) {
+        LOG.error("Cannot load coprocessor " + implClass.getSimpleName());
+        return null;
+      }
+    } catch (InstantiationException|IllegalAccessException e) {
       throw new IOException(e);
     }
     // create the environment
-    E env = createEnvironment(implClass, impl, priority, loadSequence.incrementAndGet(), conf);
-    if (env instanceof Environment) {
-      ((Environment)env).startup();
-    }
+    E env = createEnvironment(impl, priority, loadSequence.incrementAndGet(), conf);
+    env.startup();
     // HBASE-4014: maintain list of loaded coprocessors for later crash analysis
     // if server (master or regionserver) aborts.
     coprocessorNames.add(implClass.getName());
@@ -281,28 +274,30 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
   /**
    * Called when a new Coprocessor class is loaded
    */
-  public abstract E createEnvironment(Class<?> implClass, Coprocessor instance,
-      int priority, int sequence, Configuration conf);
+  public abstract E createEnvironment(C instance, int priority, int sequence, Configuration conf);
 
-  public void shutdown(CoprocessorEnvironment e) {
-    if (e instanceof Environment) {
-      if (LOG.isDebugEnabled()) {
-        LOG.debug("Stop coprocessor " + e.getInstance().getClass().getName());
-      }
-      ((Environment)e).shutdown();
-    } else {
-      LOG.warn("Shutdown called on unknown environment: "+
-          e.getClass().getName());
+  /**
+   * Called when a new Coprocessor class needs to be loaded. Checks if type of the given class
+   * is what the corresponding host implementation expects. If it is of correct type, returns an
+   * instance of the coprocessor to be loaded. If not, returns null.
+   * If an exception occurs when trying to create instance of a coprocessor, it's passed up and
+   * eventually results into server aborting.
+   */
+  public abstract C checkAndGetInstance(Class<?> implClass)
+      throws InstantiationException, IllegalAccessException;
+
+  public void shutdown(E e) {
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Stop coprocessor " + e.getInstance().getClass().getName());
     }
+    e.shutdown();
   }
 
   /**
-   * Find a coprocessor implementation by class name
-   * @param className the class name
-   * @return the coprocessor, or null if not found
+   * Find coprocessors by full class name or simple name.
    */
-  public Coprocessor findCoprocessor(String className) {
-    for (E env: coprocessors) {
+  public C findCoprocessor(String className) {
+    for (E env: coprocEnvironments) {
       if (env.getInstance().getClass().getName().equals(className) ||
           env.getInstance().getClass().getSimpleName().equals(className)) {
         return env.getInstance();
@@ -311,16 +306,26 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
     return null;
   }
 
+  @VisibleForTesting
+  public <T extends C> T findCoprocessor(Class<T> cls) {
+    for (E env: coprocEnvironments) {
+      if (cls.isAssignableFrom(env.getInstance().getClass())) {
+        return (T) env.getInstance();
+      }
+    }
+    return null;
+  }
+
   /**
    * Find list of coprocessors that extend/implement the given class/interface
    * @param cls the class/interface to look for
    * @return the list of coprocessors, or null if not found
    */
-  public <T extends Coprocessor> List<T> findCoprocessors(Class<T> cls) {
+  public <T extends C> List<T> findCoprocessors(Class<T> cls) {
     ArrayList<T> ret = new ArrayList<>();
 
-    for (E env: coprocessors) {
-      Coprocessor cp = env.getInstance();
+    for (E env: coprocEnvironments) {
+      C cp = env.getInstance();
 
       if(cp != null) {
         if (cls.isAssignableFrom(cp.getClass())) {
@@ -331,33 +336,14 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
     return ret;
   }
 
-  /**
-   * Find list of CoprocessorEnvironment that extend/implement the given class/interface
-   * @param cls the class/interface to look for
-   * @return the list of CoprocessorEnvironment, or null if not found
-   */
-  public List<CoprocessorEnvironment> findCoprocessorEnvironment(Class<?> cls) {
-    ArrayList<CoprocessorEnvironment> ret = new ArrayList<>();
-
-    for (E env: coprocessors) {
-      Coprocessor cp = env.getInstance();
-
-      if(cp != null) {
-        if (cls.isAssignableFrom(cp.getClass())) {
-          ret.add(env);
-        }
-      }
-    }
-    return ret;
-  }
-
   /**
    * Find a coprocessor environment by class name
    * @param className the class name
    * @return the coprocessor, or null if not found
    */
-  public CoprocessorEnvironment findCoprocessorEnvironment(String className) {
-    for (E env: coprocessors) {
+  @VisibleForTesting
+  public E findCoprocessorEnvironment(String className) {
+    for (E env: coprocEnvironments) {
       if (env.getInstance().getClass().getName().equals(className) ||
           env.getInstance().getClass().getSimpleName().equals(className)) {
         return env;
@@ -374,7 +360,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
   Set<ClassLoader> getExternalClassLoaders() {
     Set<ClassLoader> externalClassLoaders = new HashSet<>();
     final ClassLoader systemClassLoader = this.getClass().getClassLoader();
-    for (E env : coprocessors) {
+    for (E env : coprocEnvironments) {
       ClassLoader cl = env.getInstance().getClass().getClassLoader();
       if (cl != systemClassLoader){
         //do not include system classloader
@@ -388,8 +374,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
    * Environment priority comparator.
    * Coprocessors are chained in sorted order.
    */
-  static class EnvironmentPriorityComparator
-      implements Comparator<CoprocessorEnvironment> {
+  static class EnvironmentPriorityComparator implements Comparator<CoprocessorEnvironment> {
     @Override
     public int compare(final CoprocessorEnvironment env1,
         final CoprocessorEnvironment env2) {
@@ -407,153 +392,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
     }
   }
 
-  /**
-   * Encapsulation of the environment of each coprocessor
-   */
-  public static class Environment implements CoprocessorEnvironment {
-
-    /** The coprocessor */
-    public Coprocessor impl;
-    /** Chaining priority */
-    protected int priority = Coprocessor.PRIORITY_USER;
-    /** Current coprocessor state */
-    Coprocessor.State state = Coprocessor.State.UNINSTALLED;
-    /** Accounting for tables opened by the coprocessor */
-    protected List<Table> openTables =
-      Collections.synchronizedList(new ArrayList<Table>());
-    private int seq;
-    private Configuration conf;
-    private ClassLoader classLoader;
-
-    /**
-     * Constructor
-     * @param impl the coprocessor instance
-     * @param priority chaining priority
-     */
-    public Environment(final Coprocessor impl, final int priority,
-        final int seq, final Configuration conf) {
-      this.impl = impl;
-      this.classLoader = impl.getClass().getClassLoader();
-      this.priority = priority;
-      this.state = Coprocessor.State.INSTALLED;
-      this.seq = seq;
-      this.conf = conf;
-    }
-
-    /** Initialize the environment */
-    public void startup() throws IOException {
-      if (state == Coprocessor.State.INSTALLED ||
-          state == Coprocessor.State.STOPPED) {
-        state = Coprocessor.State.STARTING;
-        Thread currentThread = Thread.currentThread();
-        ClassLoader hostClassLoader = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(this.getClassLoader());
-          impl.start(this);
-          state = Coprocessor.State.ACTIVE;
-        } finally {
-          currentThread.setContextClassLoader(hostClassLoader);
-        }
-      } else {
-        LOG.warn("Not starting coprocessor "+impl.getClass().getName()+
-            " because not inactive (state="+state.toString()+")");
-      }
-    }
-
-    /** Clean up the environment */
-    protected void shutdown() {
-      if (state == Coprocessor.State.ACTIVE) {
-        state = Coprocessor.State.STOPPING;
-        Thread currentThread = Thread.currentThread();
-        ClassLoader hostClassLoader = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(this.getClassLoader());
-          impl.stop(this);
-          state = Coprocessor.State.STOPPED;
-        } catch (IOException ioe) {
-          LOG.error("Error stopping coprocessor "+impl.getClass().getName(), ioe);
-        } finally {
-          currentThread.setContextClassLoader(hostClassLoader);
-        }
-      } else {
-        LOG.warn("Not stopping coprocessor "+impl.getClass().getName()+
-            " because not active (state="+state.toString()+")");
-      }
-      synchronized (openTables) {
-        // clean up any table references
-        for (Table table: openTables) {
-          try {
-            ((HTableWrapper)table).internalClose();
-          } catch (IOException e) {
-            // nothing can be done here
-            LOG.warn("Failed to close " +
-                table.getName(), e);
-          }
-        }
-      }
-    }
-
-    @Override
-    public Coprocessor getInstance() {
-      return impl;
-    }
-
-    @Override
-    public ClassLoader getClassLoader() {
-      return classLoader;
-    }
-
-    @Override
-    public int getPriority() {
-      return priority;
-    }
-
-    @Override
-    public int getLoadSequence() {
-      return seq;
-    }
-
-    /** @return the coprocessor environment version */
-    @Override
-    public int getVersion() {
-      return Coprocessor.VERSION;
-    }
-
-    /** @return the HBase release */
-    @Override
-    public String getHBaseVersion() {
-      return VersionInfo.getVersion();
-    }
-
-    @Override
-    public Configuration getConfiguration() {
-      return conf;
-    }
-
-    /**
-     * Open a table from within the Coprocessor environment
-     * @param tableName the table name
-     * @return an interface for manipulating the table
-     * @exception java.io.IOException Exception
-     */
-    @Override
-    public Table getTable(TableName tableName) throws IOException {
-      return this.getTable(tableName, null);
-    }
-
-    /**
-     * Open a table from within the Coprocessor environment
-     * @param tableName the table name
-     * @return an interface for manipulating the table
-     * @exception java.io.IOException Exception
-     */
-    @Override
-    public Table getTable(TableName tableName, ExecutorService pool) throws IOException {
-      return HTableWrapper.createWrapper(openTables, tableName, this, pool);
-    }
-  }
-
-  protected void abortServer(final CoprocessorEnvironment environment, final Throwable e) {
+  protected void abortServer(final E environment, final Throwable e) {
     abortServer(environment.getInstance().getClass().getName(), e);
   }
 
@@ -586,8 +425,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
   // etc) mention this nuance of our exception handling so that coprocessor can throw appropriate
   // exceptions depending on situation. If any changes are made to this logic, make sure to
   // update all classes' comments.
-  protected void handleCoprocessorThrowable(final CoprocessorEnvironment env, final Throwable e)
-      throws IOException {
+  protected void handleCoprocessorThrowable(final E env, final Throwable e) throws IOException {
     if (e instanceof IOException) {
       throw (IOException)e;
     }
@@ -610,7 +448,7 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
                 "environment",e);
       }
 
-      coprocessors.remove(env);
+      coprocEnvironments.remove(env);
       try {
         shutdown(env);
       } catch (Exception x) {
@@ -695,4 +533,192 @@ public abstract class CoprocessorHost<E extends CoprocessorEnvironment> {
           "'. Details of the problem: " + message);
     }
   }
+
+  /**
+   * Implementations defined function to get an observer of type {@code O} from a coprocessor of
+   * type {@code C}. Concrete implementations of CoprocessorHost define one getter for each
+   * observer they can handle. For e.g. RegionCoprocessorHost will use 3 getters, one for
+   * each of RegionObserver, EndpointObserver and BulkLoadObserver.
+   * These getters are used by {@code ObserverOperation} to get appropriate observer from the
+   * coprocessor.
+   */
+  @FunctionalInterface
+  public interface ObserverGetter<C, O> extends Function<C, Optional<O>> {}
+
+  private abstract class ObserverOperation<O> extends ObserverContext<E> {
+    ObserverGetter<C, O> observerGetter;
+
+    ObserverOperation(ObserverGetter<C, O> observerGetter) {
+      this(observerGetter, RpcServer.getRequestUser());
+    }
+
+    ObserverOperation(ObserverGetter<C, O> observerGetter, User user) {
+      super(user);
+      this.observerGetter = observerGetter;
+    }
+
+    abstract void callObserver() throws IOException;
+    protected void postEnvCall() {}
+  }
+
+  // Can't derive ObserverOperation from ObserverOperationWithResult (R = Void) because then all
+  // ObserverCaller implementations will have to have a return statement.
+  // O = observer, E = environment, C = coprocessor, R=result type
+  public abstract class ObserverOperationWithoutResult<O> extends ObserverOperation<O> {
+    protected abstract void call(O observer) throws IOException;
+
+    public ObserverOperationWithoutResult(ObserverGetter<C, O> observerGetter) {
+      super(observerGetter);
+    }
+
+    public ObserverOperationWithoutResult(ObserverGetter<C, O> observerGetter, User user) {
+      super(observerGetter, user);
+    }
+
+    /**
+     * In case of coprocessors which have many kinds of observers (for eg, {@link RegionCoprocessor}
+     * has BulkLoadObserver, RegionObserver, etc), some implementations may not need all
+     * observers, in which case they will return null for that observer's getter.
+     * We simply ignore such cases.
+     */
+    @Override
+    void callObserver() throws IOException {
+      Optional<O> observer = observerGetter.apply(getEnvironment().getInstance());
+      if (observer.isPresent()) {
+        call(observer.get());
+      }
+    }
+  }
+
+  public abstract class ObserverOperationWithResult<O, R> extends ObserverOperation<O> {
+    protected abstract R call(O observer) throws IOException;
+
+    private R result;
+
+    public ObserverOperationWithResult(ObserverGetter<C, O> observerGetter) {
+      super(observerGetter);
+    }
+
+    public ObserverOperationWithResult(ObserverGetter<C, O> observerGetter, User user) {
+      super(observerGetter, user);
+    }
+
+    void setResult(final R result) {
+      this.result = result;
+    }
+
+    protected R getResult() {
+      return this.result;
+    }
+
+    void callObserver() throws IOException {
+      Optional<O> observer = observerGetter.apply(getEnvironment().getInstance());
+      if (observer.isPresent()) {
+        result = call(observer.get());
+      }
+    }
+  }
+
+  //////////////////////////////////////////////////////////////////////////////////////////
+  // Functions to execute observer hooks and handle results (if any)
+  //////////////////////////////////////////////////////////////////////////////////////////
+  protected <O, R> R execOperationWithResult(final R defaultValue,
+      final ObserverOperationWithResult<O, R> observerOperation) throws IOException {
+    if (observerOperation == null) {
+      return defaultValue;
+    }
+    observerOperation.setResult(defaultValue);
+    execOperation(observerOperation);
+    return observerOperation.getResult();
+  }
+
+  // what does bypass mean?
+  protected <O, R> R execOperationWithResult(final boolean ifBypass, final R defaultValue,
+      final ObserverOperationWithResult<O, R> observerOperation) throws IOException {
+    if (observerOperation == null) {
+      return ifBypass ? null : defaultValue;
+    } else {
+      observerOperation.setResult(defaultValue);
+      boolean bypass = execOperation(true, observerOperation);
+      R result = observerOperation.getResult();
+      return bypass == ifBypass ? result : null;
+    }
+  }
+
+  protected <O> boolean execOperation(final ObserverOperation<O> observerOperation)
+      throws IOException {
+    return execOperation(true, observerOperation);
+  }
+
+  protected <O> boolean execOperation(final boolean earlyExit,
+      final ObserverOperation<O> observerOperation) throws IOException {
+    if (observerOperation == null) return false;
+    boolean bypass = false;
+    List<E> envs = coprocEnvironments.get();
+    for (E env : envs) {
+      observerOperation.prepare(env);
+      Thread currentThread = Thread.currentThread();
+      ClassLoader cl = currentThread.getContextClassLoader();
+      try {
+        currentThread.setContextClassLoader(env.getClassLoader());
+        observerOperation.callObserver();
+      } catch (Throwable e) {
+        handleCoprocessorThrowable(env, e);
+      } finally {
+        currentThread.setContextClassLoader(cl);
+      }
+      bypass |= observerOperation.shouldBypass();
+      if (earlyExit && observerOperation.shouldComplete()) {
+        break;
+      }
+      observerOperation.postEnvCall();
+    }
+    return bypass;
+  }
+
+
+  /**
+   * Coprocessor classes can be configured in any order, based on that priority is set and
+   * chained in a sorted order. Should be used preStop*() hooks i.e. when master/regionserver is
+   * going down. This function first calls coprocessor methods (using ObserverOperation.call())
+   * and then shutdowns the environment in postEnvCall(). <br>
+   * Need to execute all coprocessor methods first then postEnvCall(), otherwise some coprocessors
+   * may remain shutdown if any exception occurs during next coprocessor execution which prevent
+   * master/regionserver stop or cluster shutdown. (Refer:
+   * <a href="https://issues.apache.org/jira/browse/HBASE-16663">HBASE-16663</a>
+   * @return true if bypaas coprocessor execution, false if not.
+   * @throws IOException
+   */
+  protected <O> boolean execShutdown(final ObserverOperation<O> observerOperation)
+      throws IOException {
+    if (observerOperation == null) return false;
+    boolean bypass = false;
+    List<E> envs = coprocEnvironments.get();
+    // Iterate the coprocessors and execute ObserverOperation's call()
+    for (E env : envs) {
+      observerOperation.prepare(env);
+      Thread currentThread = Thread.currentThread();
+      ClassLoader cl = currentThread.getContextClassLoader();
+      try {
+        currentThread.setContextClassLoader(env.getClassLoader());
+        observerOperation.callObserver();
+      } catch (Throwable e) {
+        handleCoprocessorThrowable(env, e);
+      } finally {
+        currentThread.setContextClassLoader(cl);
+      }
+      bypass |= observerOperation.shouldBypass();
+      if (observerOperation.shouldComplete()) {
+        break;
+      }
+    }
+
+    // Iterate the coprocessors and execute ObserverOperation's postEnvCall()
+    for (E env : envs) {
+      observerOperation.prepare(env);
+      observerOperation.postEnvCall();
+    }
+    return bypass;
+  }
+
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/CoprocessorService.java

@@ -26,7 +26,9 @@ import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 /**
  * Coprocessor endpoints providing protobuf services should implement this
  * interface and return the {@link Service} instance via {@link #getService()}.
+ * @deprecated Since 2.0. Will be removed in 3.0
  */
+@Deprecated
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
 public interface CoprocessorService {

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/CoprocessorServiceBackwardCompatiblity.java

@@ -0,0 +1,86 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import com.google.protobuf.Service;
+import org.apache.yetus.audience.InterfaceAudience;
+
+import java.util.Optional;
+
+/**
+ * Classes to help maintain backward compatibility with now deprecated {@link CoprocessorService}
+ * and {@link SingletonCoprocessorService}.
+ * From 2.0 onwards, implementors of coprocessor service should also implement the relevant
+ * coprocessor class (For eg {@link MasterCoprocessor} for coprocessor service in master), and
+ * override get*Service() method to return the {@link com.google.protobuf.Service} object.
+ * To maintain backward compatibility with 1.0 implementation, we'll wrap implementation of
+ * CoprocessorService/SingletonCoprocessorService in the new
+ * {Master, Region, RegionServer}Coprocessor class.
+ * Since there is no backward compatibility guarantee for Observers, we leave get*Observer() to
+ * default which returns null.
+ * This approach to maintain backward compatibility seems cleaner and more explicit.
+ */
+@InterfaceAudience.Private
+@Deprecated
+public class CoprocessorServiceBackwardCompatiblity {
+
+  static public class MasterCoprocessorService implements MasterCoprocessor {
+
+    CoprocessorService service;
+
+    public MasterCoprocessorService(CoprocessorService service) {
+      this.service = service;
+    }
+
+    @Override
+    public Optional<Service> getService() {
+      return Optional.of(service.getService());
+    }
+  }
+
+  static public class RegionCoprocessorService implements RegionCoprocessor {
+
+    CoprocessorService service;
+
+    public RegionCoprocessorService(CoprocessorService service) {
+      this.service = service;
+    }
+
+    @Override
+    public Optional<Service> getService() {
+      return Optional.of(service.getService());
+    }
+  }
+
+  static public class RegionServerCoprocessorService implements RegionServerCoprocessor {
+
+    SingletonCoprocessorService service;
+
+    public RegionServerCoprocessorService(SingletonCoprocessorService service) {
+      this.service = service;
+    }
+
+    @Override
+    public Optional<Service> getService() {
+      return Optional.of(service.getService());
+    }
+  }
+}
+

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/EndpointObserver.java

@@ -50,7 +50,7 @@ import com.google.protobuf.Service;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface EndpointObserver extends Coprocessor {
+public interface EndpointObserver {
 
   /**
    * Called before an Endpoint service method is invoked.

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterCoprocessor.java

@@ -0,0 +1,34 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+
+import java.util.Optional;
+
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
+@InterfaceStability.Evolving
+public interface MasterCoprocessor extends Coprocessor {
+  default Optional<MasterObserver> getMasterObserver() {
+    return Optional.empty();
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterCoprocessorEnvironment.java

@@ -28,7 +28,7 @@ import org.apache.hadoop.hbase.metrics.MetricRegistry;
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface MasterCoprocessorEnvironment extends CoprocessorEnvironment {
+public interface MasterCoprocessorEnvironment extends CoprocessorEnvironment<MasterCoprocessor> {
   /** @return reference to the HMaster services */
   MasterServices getMasterServices();
 

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterObserver.java

@@ -77,7 +77,7 @@ import org.apache.yetus.audience.InterfaceStability;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface MasterObserver extends Coprocessor {
+public interface MasterObserver {
   /**
    * Called before a new table is created by
    * {@link org.apache.hadoop.hbase.master.HMaster}.  Called as part of create

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MultiRowMutationEndpoint.java

@@ -20,12 +20,12 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 import java.util.SortedSet;
 import java.util.TreeSet;
 
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.yetus.audience.InterfaceStability;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 import org.apache.hadoop.hbase.HConstants;
@@ -77,8 +77,7 @@ import com.google.protobuf.Service;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public class MultiRowMutationEndpoint extends MultiRowMutationService implements
-CoprocessorService, Coprocessor {
+public class MultiRowMutationEndpoint extends MultiRowMutationService implements RegionCoprocessor {
   private RegionCoprocessorEnvironment env;
   @Override
   public void mutateRows(RpcController controller, MutateRowsRequest request,
@@ -120,10 +119,9 @@ CoprocessorService, Coprocessor {
     done.run(response);
   }
 
-
   @Override
-  public Service getService() {
-    return this;
+  public Optional<Service> getService() {
+    return Optional.of(this);
   }
 
   /**

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/ObserverContext.java

@@ -116,13 +116,13 @@ public class ObserverContext<E extends CoprocessorEnvironment> {
    * @param env The coprocessor environment to set
    * @param context An existing ObserverContext instance to use, or <code>null</code>
    *     to create a new instance
-   * @param <T> The environment type for the context
+   * @param <E> The environment type for the context
    * @return An instance of <code>ObserverContext</code> with the environment set
    */
   @Deprecated
   // TODO: Remove this method, ObserverContext should not depend on RpcServer
-  public static <T extends CoprocessorEnvironment> ObserverContext<T> createAndPrepare(
-      T env, ObserverContext<T> context) {
+  public static <E extends CoprocessorEnvironment> ObserverContext<E> createAndPrepare(
+      E env, ObserverContext< E> context) {
     if (context == null) {
       context = new ObserverContext<>(RpcServer.getRequestUser());
     }
@@ -140,11 +140,11 @@ public class ObserverContext<E extends CoprocessorEnvironment> {
    * @param context An existing ObserverContext instance to use, or <code>null</code>
    *     to create a new instance
    * @param user The requesting caller for the execution context
-   * @param <T> The environment type for the context
+   * @param <E> The environment type for the context
    * @return An instance of <code>ObserverContext</code> with the environment set
    */
-  public static <T extends CoprocessorEnvironment> ObserverContext<T> createAndPrepare(
-      T env, ObserverContext<T> context, User user) {
+  public static <E extends CoprocessorEnvironment> ObserverContext<E> createAndPrepare(
+      E env, ObserverContext<E> context, User user) {
     if (context == null) {
       context = new ObserverContext<>(user);
     }

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionCoprocessor.java

@@ -0,0 +1,43 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+
+import java.util.Optional;
+
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
+@InterfaceStability.Evolving
+public interface RegionCoprocessor extends Coprocessor {
+
+  default Optional<RegionObserver> getRegionObserver() {
+    return Optional.empty();
+  }
+
+  default Optional<EndpointObserver> getEndpointObserver() {
+    return Optional.empty();
+  }
+
+  default Optional<BulkLoadObserver> getBulkLoadObserver() {
+    return Optional.empty();
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionCoprocessorEnvironment.java

@@ -32,7 +32,7 @@ import org.apache.yetus.audience.InterfaceStability;
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface RegionCoprocessorEnvironment extends CoprocessorEnvironment {
+public interface RegionCoprocessorEnvironment extends CoprocessorEnvironment<RegionCoprocessor> {
   /** @return the region associated with this coprocessor */
   Region getRegion();
 
@@ -61,6 +61,4 @@ public interface RegionCoprocessorEnvironment extends CoprocessorEnvironment {
   // so we do not want to allow coprocessors to export metrics at the region level. We can allow
   // getMetricRegistryForTable() to allow coprocessors to track metrics per-table, per-regionserver.
   MetricRegistry getMetricRegistryForRegionServer();
-
-
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionObserver.java

@@ -99,7 +99,7 @@ import org.apache.yetus.audience.InterfaceStability;
 // TODO as method signatures need to break, update to
 // ObserverContext<? extends RegionCoprocessorEnvironment>
 // so we can use additional environment state that isn't exposed to coprocessors.
-public interface RegionObserver extends Coprocessor {
+public interface RegionObserver {
   /** Mutation type for postMutationBeforeWAL hook */
   enum MutationType {
     APPEND, INCREMENT

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionServerCoprocessor.java

@@ -0,0 +1,34 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+
+import java.util.Optional;
+
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
+@InterfaceStability.Evolving
+public interface RegionServerCoprocessor extends Coprocessor {
+  default Optional<RegionServerObserver> getRegionServerObserver() {
+    return Optional.empty();
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionServerCoprocessorEnvironment.java

@@ -27,7 +27,8 @@ import org.apache.yetus.audience.InterfaceStability;
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface RegionServerCoprocessorEnvironment extends CoprocessorEnvironment {
+public interface RegionServerCoprocessorEnvironment
+    extends CoprocessorEnvironment<RegionServerCoprocessor> {
   /**
    * Gets the region server services.
    *

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionServerObserver.java

@@ -53,7 +53,7 @@ import org.apache.yetus.audience.InterfaceStability;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface RegionServerObserver extends Coprocessor {
+public interface RegionServerObserver {
   /**
    * Called before stopping region server.
    * @param ctx the environment to interact with the framework and region server.

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/SingletonCoprocessorService.java

@@ -26,7 +26,9 @@ import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 /**
  * Coprocessor endpoints registered once per server and providing protobuf services should implement
  * this interface and return the {@link Service} instance via {@link #getService()}.
+ * @deprecated Since 2.0. Will be removed in 3.0
  */
+@Deprecated
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
 public interface SingletonCoprocessorService {

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/WALCoprocessor.java

@@ -0,0 +1,36 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.coprocessor;
+
+import org.apache.hadoop.hbase.Coprocessor;
+import org.apache.hadoop.hbase.HBaseInterfaceAudience;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+
+import java.util.Optional;
+
+/**
+ * WALCoprocessor don't support loading services using {@link #getService()}.
+ */
+@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
+@InterfaceStability.Evolving
+public interface WALCoprocessor extends Coprocessor {
+  Optional<WALObserver> getWALObserver();
+
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/WALCoprocessorEnvironment.java

@@ -28,7 +28,7 @@ import org.apache.hadoop.hbase.wal.WAL;
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface WALCoprocessorEnvironment extends CoprocessorEnvironment {
+public interface WALCoprocessorEnvironment extends CoprocessorEnvironment<WALCoprocessor> {
   /** @return reference to the region server's WAL */
   WAL getWAL();
 

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/WALObserver.java

@@ -66,7 +66,7 @@ import org.apache.yetus.audience.InterfaceStability;
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
-public interface WALObserver extends Coprocessor {
+public interface WALObserver {
   /**
    * Called before a {@link WALEdit}
    * is writen to WAL.

hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/package-info.java

@@ -181,9 +181,8 @@ To implement an Endpoint, you need to:
  <a href="https://developers.google.com/protocol-buffers/docs/proto#services">protocol buffer guide</a>
  for more details on defining services.</li>
  <li>Generate the Service and Message code using the protoc compiler</li>
- <li>Implement the generated Service interface in your coprocessor class and implement the
- <code>CoprocessorService</code> interface.  The <code>CoprocessorService.getService()</code>
- method should return a reference to the Endpoint's protocol buffer Service instance.
+ <li>Implement the generated Service interface and override get*Service() method in
+ relevant Coprocessor to return a reference to the Endpoint's protocol buffer Service instance.
 </ul>
 <p>
 For a more detailed discussion of how to implement a coprocessor Endpoint, along with some sample

hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/MasterSpaceQuotaObserver.java

@@ -17,6 +17,7 @@
 package org.apache.hadoop.hbase.quotas;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
@@ -24,6 +25,7 @@ import org.apache.hadoop.hbase.TableName;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.hadoop.hbase.client.Admin;
 import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -35,7 +37,7 @@ import org.apache.hadoop.hbase.shaded.protobuf.generated.QuotaProtos.Quotas;
  * are deleted.
  */
 @InterfaceAudience.Private
-public class MasterSpaceQuotaObserver implements MasterObserver {
+public class MasterSpaceQuotaObserver implements MasterCoprocessor, MasterObserver {
   public static final String REMOVE_QUOTA_ON_TABLE_DELETE = "hbase.quota.remove.on.table.delete";
   public static final boolean REMOVE_QUOTA_ON_TABLE_DELETE_DEFAULT = true;
 
@@ -43,6 +45,11 @@ public class MasterSpaceQuotaObserver implements MasterObserver {
   private Configuration conf;
   private boolean quotasEnabled = false;
 
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public void start(CoprocessorEnvironment ctx) throws IOException {
     this.cpEnv = ctx;

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionServerCoprocessorHost.java

@@ -19,33 +19,29 @@
 package org.apache.hadoop.hbase.regionserver;
 
 import java.io.IOException;
-import java.util.Comparator;
-import java.util.List;
 
-import org.apache.commons.lang3.ClassUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hbase.Coprocessor;
-import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.yetus.audience.InterfaceStability;
+import org.apache.hadoop.hbase.coprocessor.BaseEnvironment;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
+import org.apache.hadoop.hbase.coprocessor.CoprocessorServiceBackwardCompatiblity;
 import org.apache.hadoop.hbase.coprocessor.MetricsCoprocessor;
-import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionServerObserver;
 import org.apache.hadoop.hbase.coprocessor.SingletonCoprocessorService;
-import org.apache.hadoop.hbase.ipc.RpcServer;
 import org.apache.hadoop.hbase.metrics.MetricRegistry;
 import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
 import org.apache.hadoop.hbase.security.User;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
 public class RegionServerCoprocessorHost extends
-    CoprocessorHost<RegionServerCoprocessorHost.RegionServerEnvironment> {
+    CoprocessorHost<RegionServerCoprocessor, RegionServerCoprocessorEnvironment> {
 
   private static final Log LOG = LogFactory.getLog(RegionServerCoprocessorHost.class);
 
@@ -70,242 +66,149 @@ public class RegionServerCoprocessorHost extends
   }
 
   @Override
-  public RegionServerEnvironment createEnvironment(Class<?> implClass,
-      Coprocessor instance, int priority, int sequence, Configuration conf) {
-    return new RegionServerEnvironment(implClass, instance, priority,
-      sequence, conf, this.rsServices);
+  public RegionServerEnvironment createEnvironment(
+      RegionServerCoprocessor instance, int priority, int sequence, Configuration conf) {
+    return new RegionServerEnvironment(instance, priority, sequence, conf, this.rsServices);
   }
 
+  @Override
+  public RegionServerCoprocessor checkAndGetInstance(Class<?> implClass)
+      throws InstantiationException, IllegalAccessException {
+    if (RegionServerCoprocessor.class.isAssignableFrom(implClass)) {
+      return (RegionServerCoprocessor)implClass.newInstance();
+    } else if (SingletonCoprocessorService.class.isAssignableFrom(implClass)) {
+      // For backward compatibility with old CoprocessorService impl which don't extend
+      // RegionCoprocessor.
+      return new CoprocessorServiceBackwardCompatiblity.RegionServerCoprocessorService(
+          (SingletonCoprocessorService)implClass.newInstance());
+    } else {
+      LOG.error(implClass.getName() + " is not of type RegionServerCoprocessor. Check the "
+          + "configuration " + CoprocessorHost.REGIONSERVER_COPROCESSOR_CONF_KEY);
+      return null;
+    }
+  }
+
+  private ObserverGetter<RegionServerCoprocessor, RegionServerObserver> rsObserverGetter =
+      RegionServerCoprocessor::getRegionServerObserver;
+
+  abstract class RegionServerObserverOperation extends
+      ObserverOperationWithoutResult<RegionServerObserver> {
+    public RegionServerObserverOperation() {
+      super(rsObserverGetter);
+    }
+
+    public RegionServerObserverOperation(User user) {
+      super(rsObserverGetter, user);
+    }
+  }
+
+  //////////////////////////////////////////////////////////////////////////////////////////////////
+  // RegionServerObserver operations
+  //////////////////////////////////////////////////////////////////////////////////////////////////
+
   public void preStop(String message, User user) throws IOException {
     // While stopping the region server all coprocessors method should be executed first then the
     // coprocessor should be cleaned up.
-    execShutdown(coprocessors.isEmpty() ? null : new CoprocessorOperation(user) {
+    execShutdown(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation(user) {
       @Override
-      public void call(RegionServerObserver oserver,
-          ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.preStopRegionServer(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.preStopRegionServer(this);
       }
+
       @Override
-      public void postEnvCall(RegionServerEnvironment env) {
+      public void postEnvCall() {
         // invoke coprocessor stop method
-        shutdown(env);
+        shutdown(this.getEnvironment());
       }
     });
   }
 
   public void preRollWALWriterRequest() throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-          ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.preRollWALWriterRequest(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.preRollWALWriterRequest(this);
       }
     });
   }
 
   public void postRollWALWriterRequest() throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-          ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.postRollWALWriterRequest(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.postRollWALWriterRequest(this);
       }
     });
   }
 
   public void preReplicateLogEntries()
       throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-          ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.preReplicateLogEntries(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.preReplicateLogEntries(this);
       }
     });
   }
 
   public void postReplicateLogEntries()
       throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-          ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.postReplicateLogEntries(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.postReplicateLogEntries(this);
       }
     });
   }
 
   public ReplicationEndpoint postCreateReplicationEndPoint(final ReplicationEndpoint endpoint)
       throws IOException {
-    return execOperationWithResult(endpoint, coprocessors.isEmpty() ? null
-        : new CoprocessOperationWithResult<ReplicationEndpoint>() {
-          @Override
-          public void call(RegionServerObserver oserver,
-              ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-            setResult(oserver.postCreateReplicationEndPoint(ctx, getResult()));
-          }
-        });
+    return execOperationWithResult(endpoint, coprocEnvironments.isEmpty() ? null :
+        new ObserverOperationWithResult<RegionServerObserver, ReplicationEndpoint>(
+            rsObserverGetter) {
+      @Override
+      public ReplicationEndpoint call(RegionServerObserver observer) throws IOException {
+        return observer.postCreateReplicationEndPoint(this, getResult());
+      }
+    });
   }
 
   public void preClearCompactionQueues() throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-                       ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.preClearCompactionQueues(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.preClearCompactionQueues(this);
       }
     });
   }
 
   public void postClearCompactionQueues() throws IOException {
-    execOperation(coprocessors.isEmpty() ? null : new CoprocessorOperation() {
+    execOperation(coprocEnvironments.isEmpty() ? null : new RegionServerObserverOperation() {
       @Override
-      public void call(RegionServerObserver oserver,
-                       ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {
-        oserver.postClearCompactionQueues(ctx);
+      public void call(RegionServerObserver observer) throws IOException {
+        observer.postClearCompactionQueues(this);
       }
     });
   }
 
-  private <T> T execOperationWithResult(final T defaultValue,
-      final CoprocessOperationWithResult<T> ctx) throws IOException {
-    if (ctx == null)
-      return defaultValue;
-    ctx.setResult(defaultValue);
-    execOperation(ctx);
-    return ctx.getResult();
-  }
-
-  private static abstract class CoprocessorOperation
-      extends ObserverContext<RegionServerCoprocessorEnvironment> {
-    public CoprocessorOperation() {
-      this(RpcServer.getRequestUser());
-    }
-
-    public CoprocessorOperation(User user) {
-      super(user);
-    }
-
-    public abstract void call(RegionServerObserver oserver,
-        ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException;
-
-    public void postEnvCall(RegionServerEnvironment env) {
-    }
-  }
-
-  private static abstract class CoprocessOperationWithResult<T> extends CoprocessorOperation {
-    private T result = null;
-
-    public void setResult(final T result) {
-      this.result = result;
-    }
-
-    public T getResult() {
-      return this.result;
-    }
-  }
-
-  private boolean execOperation(final CoprocessorOperation ctx) throws IOException {
-    if (ctx == null) return false;
-    boolean bypass = false;
-    List<RegionServerEnvironment> envs = coprocessors.get();
-    for (int i = 0; i < envs.size(); i++) {
-      RegionServerEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof RegionServerObserver) {
-        ctx.prepare(env);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          ctx.call((RegionServerObserver)env.getInstance(), ctx);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        bypass |= ctx.shouldBypass();
-        if (ctx.shouldComplete()) {
-          break;
-        }
-      }
-      ctx.postEnvCall(env);
-    }
-    return bypass;
-  }
-
-  /**
-   * RegionServer coprocessor classes can be configured in any order, based on that priority is set
-   * and chained in a sorted order. For preStop(), coprocessor methods are invoked in call() and
-   * environment is shutdown in postEnvCall(). <br>
-   * Need to execute all coprocessor methods first then postEnvCall(), otherwise some coprocessors
-   * may remain shutdown if any exception occurs during next coprocessor execution which prevent
-   * RegionServer stop. (Refer:
-   * <a href="https://issues.apache.org/jira/browse/HBASE-16663">HBASE-16663</a>
-   * @param ctx CoprocessorOperation
-   * @return true if bypaas coprocessor execution, false if not.
-   * @throws IOException
-   */
-  private boolean execShutdown(final CoprocessorOperation ctx) throws IOException {
-    if (ctx == null) return false;
-    boolean bypass = false;
-    List<RegionServerEnvironment> envs = coprocessors.get();
-    int envsSize = envs.size();
-    // Iterate the coprocessors and execute CoprocessorOperation's call()
-    for (int i = 0; i < envsSize; i++) {
-      RegionServerEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof RegionServerObserver) {
-        ctx.prepare(env);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          ctx.call((RegionServerObserver) env.getInstance(), ctx);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        bypass |= ctx.shouldBypass();
-        if (ctx.shouldComplete()) {
-          break;
-        }
-      }
-    }
-
-    // Iterate the coprocessors and execute CoprocessorOperation's postEnvCall()
-    for (int i = 0; i < envsSize; i++) {
-      RegionServerEnvironment env = envs.get(i);
-      ctx.postEnvCall(env);
-    }
-    return bypass;
-  }
-
   /**
    * Coprocessor environment extension providing access to region server
    * related services.
    */
-  static class RegionServerEnvironment extends CoprocessorHost.Environment
+  private static class RegionServerEnvironment extends BaseEnvironment<RegionServerCoprocessor>
       implements RegionServerCoprocessorEnvironment {
     private final RegionServerServices regionServerServices;
     private final MetricRegistry metricRegistry;
 
     @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="BC_UNCONFIRMED_CAST",
         justification="Intentional; FB has trouble detecting isAssignableFrom")
-    public RegionServerEnvironment(final Class<?> implClass,
-        final Coprocessor impl, final int priority, final int seq,
-        final Configuration conf, final RegionServerServices services) {
+    public RegionServerEnvironment(final RegionServerCoprocessor impl, final int priority,
+        final int seq, final Configuration conf, final RegionServerServices services) {
       super(impl, priority, seq, conf);
       this.regionServerServices = services;
-      for (Object itf : ClassUtils.getAllInterfaces(implClass)) {
-        Class<?> c = (Class<?>) itf;
-        if (SingletonCoprocessorService.class.isAssignableFrom(c)) {// FindBugs: BC_UNCONFIRMED_CAST
-          this.regionServerServices.registerService(
-            ((SingletonCoprocessorService) impl).getService());
-          break;
-        }
-      }
+      impl.getService().ifPresent(regionServerServices::registerService);
       this.metricRegistry =
-          MetricsCoprocessor.createRegistryForRSCoprocessor(implClass.getName());
+          MetricsCoprocessor.createRegistryForRSCoprocessor(impl.getClass().getName());
     }
 
     @Override
@@ -319,32 +222,9 @@ public class RegionServerCoprocessorHost extends
     }
 
     @Override
-    protected void shutdown() {
+    public void shutdown() {
       super.shutdown();
       MetricsCoprocessor.removeRegistry(metricRegistry);
     }
   }
-
-  /**
-   * Environment priority comparator. Coprocessors are chained in sorted
-   * order.
-   */
-  static class EnvironmentPriorityComparator implements
-      Comparator<CoprocessorEnvironment> {
-    @Override
-    public int compare(final CoprocessorEnvironment env1,
-        final CoprocessorEnvironment env2) {
-      if (env1.getPriority() < env2.getPriority()) {
-        return -1;
-      } else if (env1.getPriority() > env2.getPriority()) {
-        return 1;
-      }
-      if (env1.getLoadSequence() < env2.getLoadSequence()) {
-        return -1;
-      } else if (env1.getLoadSequence() > env2.getLoadSequence()) {
-        return 1;
-      }
-      return 0;
-    }
-  }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/SecureBulkLoadManager.java

@@ -33,7 +33,9 @@ import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.hadoop.hbase.client.Connection;
 import org.apache.hadoop.hbase.coprocessor.BulkLoadObserver;
+import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.ipc.RpcServer;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos;
@@ -138,38 +140,17 @@ public class SecureBulkLoadManager {
 
   public String prepareBulkLoad(final Region region, final PrepareBulkLoadRequest request)
       throws IOException {
-    List<BulkLoadObserver> bulkLoadObservers = getBulkLoadObservers(region);
+    region.getCoprocessorHost().prePrepareBulkLoad(getActiveUser());
 
-    if (bulkLoadObservers != null && bulkLoadObservers.size() != 0) {
-      ObserverContext<RegionCoprocessorEnvironment> ctx = new ObserverContext<>(getActiveUser());
-      ctx.prepare((RegionCoprocessorEnvironment) region.getCoprocessorHost()
-          .findCoprocessorEnvironment(BulkLoadObserver.class).get(0));
-
-      for (BulkLoadObserver bulkLoadObserver : bulkLoadObservers) {
-        bulkLoadObserver.prePrepareBulkLoad(ctx);
-      }
-    }
-
-    String bulkToken =
-        createStagingDir(baseStagingDir, getActiveUser(), region.getTableDescriptor().getTableName())
-            .toString();
+    String bulkToken = createStagingDir(baseStagingDir, getActiveUser(),
+        region.getTableDescriptor().getTableName()).toString();
 
     return bulkToken;
   }
 
   public void cleanupBulkLoad(final Region region, final CleanupBulkLoadRequest request)
       throws IOException {
-    List<BulkLoadObserver> bulkLoadObservers = getBulkLoadObservers(region);
-
-    if (bulkLoadObservers != null && bulkLoadObservers.size() != 0) {
-      ObserverContext<RegionCoprocessorEnvironment> ctx = new ObserverContext<>(getActiveUser());
-      ctx.prepare((RegionCoprocessorEnvironment) region.getCoprocessorHost()
-        .findCoprocessorEnvironment(BulkLoadObserver.class).get(0));
-
-      for (BulkLoadObserver bulkLoadObserver : bulkLoadObservers) {
-        bulkLoadObserver.preCleanupBulkLoad(ctx);
-      }
-    }
+    region.getCoprocessorHost().preCleanupBulkLoad(getActiveUser());
 
     Path path = new Path(request.getBulkToken());
     if (!fs.delete(path, true)) {
@@ -275,13 +256,6 @@ public class SecureBulkLoadManager {
     return map;
   }
 
-  private List<BulkLoadObserver> getBulkLoadObservers(Region region) {
-    List<BulkLoadObserver> coprocessorList =
-        region.getCoprocessorHost().findCoprocessors(BulkLoadObserver.class);
-
-    return coprocessorList;
-  }
-
   private Path createStagingDir(Path baseDir,
                                 User user,
                                 TableName tableName) throws IOException {

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALCoprocessorHost.java

@@ -21,22 +21,23 @@
 package org.apache.hadoop.hbase.regionserver.wal;
 
 import java.io.IOException;
-import java.util.List;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.HRegionInfo;
-import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.hadoop.hbase.coprocessor.BaseEnvironment;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.MetricsCoprocessor;
-import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.WALCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.WALCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.WALObserver;
 import org.apache.hadoop.hbase.metrics.MetricRegistry;
 import org.apache.hadoop.hbase.wal.WAL;
 import org.apache.hadoop.hbase.wal.WALEdit;
 import org.apache.hadoop.hbase.wal.WALKey;
+import org.apache.yetus.audience.InterfaceAudience;
 
 /**
  * Implements the coprocessor environment and runtime support for coprocessors
@@ -44,12 +45,13 @@ import org.apache.hadoop.hbase.wal.WALKey;
  */
 @InterfaceAudience.Private
 public class WALCoprocessorHost
-    extends CoprocessorHost<WALCoprocessorHost.WALEnvironment> {
+    extends CoprocessorHost<WALCoprocessor, WALCoprocessorEnvironment> {
+  private static final Log LOG = LogFactory.getLog(WALCoprocessorHost.class);
 
   /**
    * Encapsulation of the environment of each coprocessor
    */
-  static class WALEnvironment extends CoprocessorHost.Environment
+  static class WALEnvironment extends BaseEnvironment<WALCoprocessor>
     implements WALCoprocessorEnvironment {
 
     private final WAL wal;
@@ -63,19 +65,18 @@ public class WALCoprocessorHost
 
     /**
      * Constructor
-     * @param implClass - not used
      * @param impl the coprocessor instance
      * @param priority chaining priority
      * @param seq load sequence
      * @param conf configuration
      * @param wal WAL
      */
-    public WALEnvironment(Class<?> implClass, final Coprocessor impl,
-        final int priority, final int seq, final Configuration conf,
-        final WAL wal) {
+    private WALEnvironment(final WALCoprocessor impl, final int priority, final int seq,
+        final Configuration conf, final WAL wal) {
       super(impl, priority, seq, conf);
       this.wal = wal;
-      this.metricRegistry = MetricsCoprocessor.createRegistryForWALCoprocessor(implClass.getName());
+      this.metricRegistry = MetricsCoprocessor.createRegistryForWALCoprocessor(
+          impl.getClass().getName());
     }
 
     @Override
@@ -84,7 +85,7 @@ public class WALCoprocessorHost
     }
 
     @Override
-    protected void shutdown() {
+    public void shutdown() {
       super.shutdown();
       MetricsCoprocessor.removeRegistry(this.metricRegistry);
     }
@@ -111,13 +112,34 @@ public class WALCoprocessorHost
   }
 
   @Override
-  public WALEnvironment createEnvironment(final Class<?> implClass,
-      final Coprocessor instance, final int priority, final int seq,
-      final Configuration conf) {
-    return new WALEnvironment(implClass, instance, priority, seq, conf,
-        this.wal);
+  public WALEnvironment createEnvironment(final WALCoprocessor instance, final int priority,
+      final int seq, final Configuration conf) {
+    return new WALEnvironment(instance, priority, seq, conf, this.wal);
   }
 
+  @Override
+  public WALCoprocessor checkAndGetInstance(Class<?> implClass)
+      throws InstantiationException, IllegalAccessException {
+    if (WALCoprocessor.class.isAssignableFrom(implClass)) {
+      return (WALCoprocessor)implClass.newInstance();
+    } else {
+      LOG.error(implClass.getName() + " is not of type WALCoprocessor. Check the "
+          + "configuration " + CoprocessorHost.WAL_COPROCESSOR_CONF_KEY);
+      return null;
+    }
+  }
+
+  private ObserverGetter<WALCoprocessor, WALObserver> walObserverGetter =
+      WALCoprocessor::getWALObserver;
+
+  abstract class WALObserverOperation extends
+      ObserverOperationWithoutResult<WALObserver> {
+    public WALObserverOperation() {
+      super(walObserverGetter);
+    }
+  }
+
+
   /**
    * @param info
    * @param logKey
@@ -127,32 +149,13 @@ public class WALCoprocessorHost
    */
   public boolean preWALWrite(final HRegionInfo info, final WALKey logKey, final WALEdit logEdit)
       throws IOException {
-    boolean bypass = false;
-    if (this.coprocessors == null || this.coprocessors.isEmpty()) return bypass;
-    ObserverContext<WALCoprocessorEnvironment> ctx = null;
-    List<WALEnvironment> envs = coprocessors.get();
-    for (int i = 0; i < envs.size(); i++) {
-      WALEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof WALObserver) {
-        final WALObserver observer = (WALObserver)env.getInstance();
-        ctx = ObserverContext.createAndPrepare(env, ctx);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          observer.preWALWrite(ctx, info, logKey, logEdit);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        bypass |= ctx.shouldBypass();
-        if (ctx.shouldComplete()) {
-          break;
-        }
+    return execOperationWithResult(false, coprocEnvironments.isEmpty() ? null :
+        new ObserverOperationWithResult<WALObserver, Boolean>(walObserverGetter) {
+      @Override
+      public Boolean call(WALObserver oserver) throws IOException {
+        return oserver.preWALWrite(this, info, logKey, logEdit);
       }
-    }
-    return bypass;
+    });
   }
 
   /**
@@ -163,29 +166,12 @@ public class WALCoprocessorHost
    */
   public void postWALWrite(final HRegionInfo info, final WALKey logKey, final WALEdit logEdit)
       throws IOException {
-    if (this.coprocessors == null || this.coprocessors.isEmpty()) return;
-    ObserverContext<WALCoprocessorEnvironment> ctx = null;
-    List<WALEnvironment> envs = coprocessors.get();
-    for (int i = 0; i < envs.size(); i++) {
-      WALEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof WALObserver) {
-        final WALObserver observer = (WALObserver)env.getInstance();
-        ctx = ObserverContext.createAndPrepare(env, ctx);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          observer.postWALWrite(ctx, info, logKey, logEdit);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        if (ctx.shouldComplete()) {
-          break;
-        }
+    execOperation(coprocEnvironments.isEmpty() ? null : new WALObserverOperation() {
+      @Override
+      protected void call(WALObserver observer) throws IOException {
+        observer.postWALWrite(this, info, logKey, logEdit);
       }
-    }
+    });
   }
 
   /**
@@ -194,29 +180,12 @@ public class WALCoprocessorHost
    * @param newPath the path of the wal we are going to create
    */
   public void preWALRoll(Path oldPath, Path newPath) throws IOException {
-    if (this.coprocessors == null || this.coprocessors.isEmpty()) return;
-    ObserverContext<WALCoprocessorEnvironment> ctx = null;
-    List<WALEnvironment> envs = coprocessors.get();
-    for (int i = 0; i < envs.size(); i++) {
-      WALEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof WALObserver) {
-        final WALObserver observer = (WALObserver)env.getInstance();
-        ctx = ObserverContext.createAndPrepare(env, ctx);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          observer.preWALRoll(ctx, oldPath, newPath);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        if (ctx.shouldComplete()) {
-          break;
-        }
+    execOperation(coprocEnvironments.isEmpty() ? null : new WALObserverOperation() {
+      @Override
+      protected void call(WALObserver observer) throws IOException {
+        observer.preWALRoll(this, oldPath, newPath);
       }
-    }
+    });
   }
 
   /**
@@ -225,28 +194,11 @@ public class WALCoprocessorHost
    * @param newPath the path of the wal we have created and now is the current
    */
   public void postWALRoll(Path oldPath, Path newPath) throws IOException {
-    if (this.coprocessors == null || this.coprocessors.isEmpty()) return;
-    ObserverContext<WALCoprocessorEnvironment> ctx = null;
-    List<WALEnvironment> envs = coprocessors.get();
-    for (int i = 0; i < envs.size(); i++) {
-      WALEnvironment env = envs.get(i);
-      if (env.getInstance() instanceof WALObserver) {
-        final WALObserver observer = (WALObserver)env.getInstance();
-        ctx = ObserverContext.createAndPrepare(env, ctx);
-        Thread currentThread = Thread.currentThread();
-        ClassLoader cl = currentThread.getContextClassLoader();
-        try {
-          currentThread.setContextClassLoader(env.getClassLoader());
-          observer.postWALRoll(ctx, oldPath, newPath);
-        } catch (Throwable e) {
-          handleCoprocessorThrowable(env, e);
-        } finally {
-          currentThread.setContextClassLoader(cl);
-        }
-        if (ctx.shouldComplete()) {
-          break;
-        }
+    execOperation(coprocEnvironments.isEmpty() ? null : new WALObserverOperation() {
+      @Override
+      protected void call(WALObserver observer) throws IOException {
+        observer.postWALRoll(this, oldPath, newPath);
       }
-    }
+    });
   }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationObserver.java

@@ -21,11 +21,13 @@ package org.apache.hadoop.hbase.replication.regionserver;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
 import org.apache.hadoop.hbase.HConstants;
@@ -40,9 +42,14 @@ import org.apache.hadoop.hbase.util.Pair;
  */
 
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
-public class ReplicationObserver implements RegionObserver {
+public class ReplicationObserver implements RegionCoprocessor, RegionObserver {
   private static final Log LOG = LogFactory.getLog(ReplicationObserver.class);
 
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public void preCommitStoreFile(final ObserverContext<RegionCoprocessorEnvironment> ctx,
       final byte[] family, final List<Pair<Path, Path>> pairs) throws IOException {

hbase-server/src/main/java/org/apache/hadoop/hbase/security/access/AccessController.java

@@ -28,6 +28,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.TreeSet;
@@ -74,13 +75,15 @@ import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.coprocessor.BulkLoadObserver;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
 import org.apache.hadoop.hbase.coprocessor.EndpointObserver;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
+import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionServerObserver;
 import org.apache.hadoop.hbase.filter.ByteArrayComparable;
@@ -169,8 +172,10 @@ import org.apache.yetus.audience.InterfaceAudience;
  * </p>
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
-public class AccessController implements MasterObserver, RegionObserver, RegionServerObserver,
-      AccessControlService.Interface, CoprocessorService, EndpointObserver, BulkLoadObserver {
+public class AccessController implements MasterCoprocessor, RegionCoprocessor,
+    RegionServerCoprocessor, AccessControlService.Interface,
+    MasterObserver, RegionObserver, RegionServerObserver, EndpointObserver, BulkLoadObserver {
+  // TODO: encapsulate observer functions into separate class/sub-class.
 
   private static final Log LOG = LogFactory.getLog(AccessController.class);
 
@@ -987,6 +992,39 @@ public class AccessController implements MasterObserver, RegionObserver, RegionS
     }
   }
 
+  /*********************************** Observer/Service Getters ***********************************/
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<EndpointObserver> getEndpointObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<BulkLoadObserver> getBulkLoadObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<RegionServerObserver> getRegionServerObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<Service> getService() {
+    return Optional.of(AccessControlProtos.AccessControlService.newReflectiveService(this));
+  }
+
+  /*********************************** Observer implementations ***********************************/
+
   @Override
   public void preCreateTable(ObserverContext<MasterCoprocessorEnvironment> c,
       TableDescriptor desc, RegionInfo[] regions) throws IOException {
@@ -2448,11 +2486,6 @@ public class AccessController implements MasterObserver, RegionObserver, RegionS
     done.run(response);
   }
 
-  @Override
-  public Service getService() {
-    return AccessControlProtos.AccessControlService.newReflectiveService(this);
-  }
-
   private Region getRegion(RegionCoprocessorEnvironment e) {
     return e.getRegion();
   }

hbase-server/src/main/java/org/apache/hadoop/hbase/security/access/CoprocessorWhitelistMasterObserver.java

@@ -20,6 +20,7 @@ package org.apache.hadoop.hbase.security.access;
 
 import java.io.IOException;
 import java.util.Collection;
+import java.util.Optional;
 import java.util.regex.Matcher;
 
 import org.apache.commons.io.FilenameUtils;
@@ -32,6 +33,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.TableDescriptor;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -43,7 +45,7 @@ import org.apache.yetus.audience.InterfaceAudience;
  * Master observer for restricting coprocessor assignments.
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
-public class CoprocessorWhitelistMasterObserver implements MasterObserver {
+public class CoprocessorWhitelistMasterObserver implements MasterCoprocessor, MasterObserver {
 
   public static final String CP_COPROCESSOR_WHITELIST_PATHS_KEY =
       "hbase.coprocessor.region.whitelist.paths";
@@ -51,6 +53,11 @@ public class CoprocessorWhitelistMasterObserver implements MasterObserver {
   private static final Log LOG = LogFactory
       .getLog(CoprocessorWhitelistMasterObserver.class);
 
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public void preModifyTable(ObserverContext<MasterCoprocessorEnvironment> ctx,
       TableName tableName, TableDescriptor htd) throws IOException {

hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/TokenProvider.java

@@ -19,13 +19,12 @@
 package org.apache.hadoop.hbase.security.token;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.ipc.RpcServer;
@@ -42,6 +41,7 @@ import org.apache.hadoop.security.token.Token;
 import com.google.protobuf.RpcCallback;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.Service;
+import org.apache.yetus.audience.InterfaceAudience;
 
 /**
  * Provides a service for obtaining authentication tokens via the
@@ -49,7 +49,7 @@ import com.google.protobuf.Service;
  */
 @InterfaceAudience.Private
 public class TokenProvider implements AuthenticationProtos.AuthenticationService.Interface,
-    Coprocessor, CoprocessorService {
+    RegionCoprocessor {
 
   private static final Log LOG = LogFactory.getLog(TokenProvider.class);
 
@@ -96,8 +96,8 @@ public class TokenProvider implements AuthenticationProtos.AuthenticationService
   // AuthenticationService implementation
 
   @Override
-  public Service getService() {
-    return AuthenticationProtos.AuthenticationService.newReflectiveService(this);
+  public Optional<Service> getService() {
+    return Optional.of(AuthenticationProtos.AuthenticationService.newReflectiveService(this));
   }
 
   @Override

hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityController.java

@@ -30,6 +30,7 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -64,14 +65,13 @@ import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.constraint.ConstraintException;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorException;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
-import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
-import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment;
-import org.apache.hadoop.hbase.coprocessor.RegionServerObserver;
 import org.apache.hadoop.hbase.exceptions.DeserializationException;
 import org.apache.hadoop.hbase.exceptions.FailedSanityCheckException;
 import org.apache.hadoop.hbase.filter.Filter;
@@ -101,7 +101,6 @@ import org.apache.hadoop.hbase.regionserver.OperationStatus;
 import org.apache.hadoop.hbase.regionserver.Region;
 import org.apache.hadoop.hbase.regionserver.RegionScanner;
 import org.apache.hadoop.hbase.regionserver.querymatcher.DeleteTracker;
-import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
 import org.apache.hadoop.hbase.security.AccessDeniedException;
 import org.apache.hadoop.hbase.security.Superusers;
 import org.apache.hadoop.hbase.security.User;
@@ -122,8 +121,9 @@ import com.google.protobuf.Service;
  * visibility labels
  */
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
-public class VisibilityController implements MasterObserver, RegionObserver,
-    VisibilityLabelsService.Interface, CoprocessorService {
+// TODO: break out Observer functions into separate class/sub-class.
+public class VisibilityController implements MasterCoprocessor, RegionCoprocessor,
+    VisibilityLabelsService.Interface, MasterObserver, RegionObserver {
 
   private static final Log LOG = LogFactory.getLog(VisibilityController.class);
   private static final Log AUDITLOG = LogFactory.getLog("SecurityLogger."
@@ -176,10 +176,6 @@ public class VisibilityController implements MasterObserver, RegionObserver,
         + " accordingly.");
     }
 
-    if (env instanceof RegionServerCoprocessorEnvironment) {
-      throw new RuntimeException("Visibility controller should not be configured as "
-          + "'hbase.coprocessor.regionserver.classes'.");
-    }
     // Do not create for master CPs
     if (!(env instanceof MasterCoprocessorEnvironment)) {
       visibilityLabelService = VisibilityLabelServiceManager.getInstance()
@@ -192,6 +188,22 @@ public class VisibilityController implements MasterObserver, RegionObserver,
 
   }
 
+  /**************************** Observer/Service Getters ************************************/
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<MasterObserver> getMasterObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<Service> getService() {
+    return Optional.of(VisibilityLabelsProtos.VisibilityLabelsService.newReflectiveService(this));
+  }
+
   /********************************* Master related hooks **********************************/
 
   @Override
@@ -760,11 +772,6 @@ public class VisibilityController implements MasterObserver, RegionObserver,
     return rewriteCell;
   }
 
-  @Override
-  public Service getService() {
-    return VisibilityLabelsProtos.VisibilityLabelsService.newReflectiveService(this);
-  }
-
   @Override
   public boolean postScannerFilterRow(final ObserverContext<RegionCoprocessorEnvironment> e,
       final InternalScanner s, final Cell curRowCell, final boolean hasMore) throws IOException {
@@ -1086,35 +1093,6 @@ public class VisibilityController implements MasterObserver, RegionObserver,
     }
   }
 
-  /**
-   * A RegionServerObserver impl that provides the custom
-   * VisibilityReplicationEndpoint. This class should be configured as the
-   * 'hbase.coprocessor.regionserver.classes' for the visibility tags to be
-   * replicated as string.  The value for the configuration should be
-   * 'org.apache.hadoop.hbase.security.visibility.VisibilityController$VisibilityReplication'.
-   */
-  public static class VisibilityReplication implements RegionServerObserver {
-    private Configuration conf;
-    private VisibilityLabelService visibilityLabelService;
-
-    @Override
-    public void start(CoprocessorEnvironment env) throws IOException {
-      this.conf = env.getConfiguration();
-      visibilityLabelService = VisibilityLabelServiceManager.getInstance()
-          .getVisibilityLabelService(this.conf);
-    }
-
-    @Override
-    public void stop(CoprocessorEnvironment env) throws IOException {
-    }
-
-    @Override
-    public ReplicationEndpoint postCreateReplicationEndPoint(
-        ObserverContext<RegionServerCoprocessorEnvironment> ctx, ReplicationEndpoint endpoint) {
-      return new VisibilityReplicationEndpoint(endpoint, visibilityLabelService);
-    }
-  }
-
   /**
    * @param t
    * @return NameValuePair of the exception name to stringified version os exception.

hbase-server/src/main/java/org/apache/hadoop/hbase/security/visibility/VisibilityReplication.java

@@ -0,0 +1,64 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hbase.security.visibility;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.CoprocessorEnvironment;
+import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessor;
+import org.apache.hadoop.hbase.coprocessor.RegionServerCoprocessorEnvironment;
+import org.apache.hadoop.hbase.coprocessor.RegionServerObserver;
+import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
+
+import java.io.IOException;
+import java.util.Optional;
+
+/**
+ * A RegionServerObserver impl that provides the custom
+ * VisibilityReplicationEndpoint. This class should be configured as the
+ * 'hbase.coprocessor.regionserver.classes' for the visibility tags to be
+ * replicated as string.  The value for the configuration should be
+ * 'org.apache.hadoop.hbase.security.visibility.VisibilityController$VisibilityReplication'.
+ */
+public class VisibilityReplication implements RegionServerCoprocessor, RegionServerObserver {
+  private Configuration conf;
+  private VisibilityLabelService visibilityLabelService;
+
+  @Override
+  public void start(CoprocessorEnvironment env) throws IOException {
+    this.conf = env.getConfiguration();
+    visibilityLabelService = VisibilityLabelServiceManager.getInstance()
+        .getVisibilityLabelService(this.conf);
+  }
+
+  @Override
+  public void stop(CoprocessorEnvironment env) throws IOException {
+  }
+
+  @Override public Optional<RegionServerObserver> getRegionServerObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public ReplicationEndpoint postCreateReplicationEndPoint(
+      ObserverContext<RegionServerCoprocessorEnvironment> ctx, ReplicationEndpoint endpoint) {
+    return new VisibilityReplicationEndpoint(endpoint, visibilityLabelService);
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/tool/WriteSinkCoprocessor.java

@@ -23,12 +23,14 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.client.Mutation;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.regionserver.MiniBatchOperationInProgress;
 import org.apache.hadoop.hbase.regionserver.OperationStatus;
 
 import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
 
 /**
@@ -58,9 +60,15 @@ import java.util.concurrent.atomic.AtomicLong;
  * 0 row(s) in 0.0050 seconds
  * </p>
  */
-public class WriteSinkCoprocessor implements RegionObserver {
+public class WriteSinkCoprocessor implements RegionCoprocessor, RegionObserver {
   private static final Log LOG = LogFactory.getLog(WriteSinkCoprocessor.class);
   private final AtomicLong ops = new AtomicLong();
+
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   private String regionName;
 
   @Override
@@ -68,7 +76,6 @@ public class WriteSinkCoprocessor implements RegionObserver {
     regionName = e.getEnvironment().getRegion().getRegionInfo().getRegionNameAsString();
   }
 
-
   @Override
   public void preBatchMutate(final ObserverContext<RegionCoprocessorEnvironment> c,
                              final MiniBatchOperationInProgress<Mutation> miniBatchOp)

hbase-server/src/test/java/org/apache/hadoop/hbase/client/HConnectionTestingUtility.java

@@ -18,6 +18,7 @@
 package org.apache.hadoop.hbase.client;
 
 import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.hadoop.conf.Configuration;
@@ -27,6 +28,7 @@ import org.apache.hadoop.hbase.HRegionInfo;
 import org.apache.hadoop.hbase.HRegionLocation;
 import org.apache.hadoop.hbase.ServerName;
 import org.apache.hadoop.hbase.ZooKeeperConnectionException;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.AdminProtos;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.ClientProtos;
@@ -159,13 +161,18 @@ public class HConnectionTestingUtility {
   /**
    * This coproceesor sleep 2s at first increment/append rpc call.
    */
-  public static class SleepAtFirstRpcCall implements RegionObserver {
+  public static class SleepAtFirstRpcCall implements RegionCoprocessor, RegionObserver {
     static final AtomicLong ct = new AtomicLong(0);
     static final String SLEEP_TIME_CONF_KEY =
         "hbase.coprocessor.SleepAtFirstRpcCall.sleepTime";
     static final long DEFAULT_SLEEP_TIME = 2000;
     static final AtomicLong sleepTime = new AtomicLong(DEFAULT_SLEEP_TIME);
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     public SleepAtFirstRpcCall() {
     }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncAdminBuilder.java

@@ -24,6 +24,7 @@ import static org.junit.Assert.fail;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.ForkJoinPool;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
@@ -35,6 +36,7 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -170,10 +172,15 @@ public class TestAsyncAdminBuilder {
     }
   }
 
-  public static class TestRpcTimeoutCoprocessor implements MasterObserver {
+  public static class TestRpcTimeoutCoprocessor implements MasterCoprocessor, MasterObserver {
     public TestRpcTimeoutCoprocessor() {
     }
 
+
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
     @Override
     public void preGetNamespaceDescriptor(ObserverContext<MasterCoprocessorEnvironment> ctx,
         String namespace) throws IOException {
@@ -181,12 +188,17 @@ public class TestAsyncAdminBuilder {
     }
   }
 
-  public static class TestOperationTimeoutCoprocessor implements MasterObserver {
+  public static class TestOperationTimeoutCoprocessor implements MasterCoprocessor, MasterObserver {
     AtomicLong sleepTime = new AtomicLong(0);
 
     public TestOperationTimeoutCoprocessor() {
     }
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetNamespaceDescriptor(ObserverContext<MasterCoprocessorEnvironment> ctx,
         String namespace) throws IOException {
@@ -197,12 +209,17 @@ public class TestAsyncAdminBuilder {
     }
   }
 
-  public static class TestMaxRetriesCoprocessor implements MasterObserver {
+  public static class TestMaxRetriesCoprocessor implements MasterCoprocessor, MasterObserver {
     AtomicLong retryNum = new AtomicLong(0);
 
     public TestMaxRetriesCoprocessor() {
     }
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetNamespaceDescriptor(ObserverContext<MasterCoprocessorEnvironment> ctx,
         String namespace) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncNonMetaRegionLocatorConcurrenyLimit.java

@@ -27,6 +27,7 @@ import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -38,6 +39,7 @@ import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HRegionLocation;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.regionserver.InternalScanner;
@@ -73,7 +75,12 @@ public class TestAsyncNonMetaRegionLocatorConcurrenyLimit {
 
   private static AtomicInteger MAX_CONCURRENCY = new AtomicInteger(0);
 
-  public static final class CountingRegionObserver implements RegionObserver {
+  public static final class CountingRegionObserver implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public RegionScanner preScannerOpen(ObserverContext<RegionCoprocessorEnvironment> e, Scan scan,

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncRegionLocatorTimeout.java

@@ -27,6 +27,7 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 
@@ -36,6 +37,7 @@ import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HRegionLocation;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.exceptions.TimeoutIOException;
@@ -65,7 +67,11 @@ public class TestAsyncRegionLocatorTimeout {
 
   private static volatile long SLEEP_MS = 0L;
 
-  public static class SleepRegionObserver implements RegionObserver {
+  public static class SleepRegionObserver implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public RegionScanner preScannerOpen(ObserverContext<RegionCoprocessorEnvironment> e, Scan scan,

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncTableBatch.java

@@ -28,6 +28,7 @@ import java.io.UncheckedIOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ForkJoinPool;
@@ -40,6 +41,7 @@ import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HTableDescriptor;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
@@ -202,7 +204,12 @@ public class TestAsyncTableBatch {
     assertEquals(4, Bytes.toInt(appendValue, 8));
   }
 
-  public static final class ErrorInjectObserver implements RegionObserver {
+  public static final class ErrorInjectObserver implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get,

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAvoidCellReferencesIntoShippedBlocks.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -38,6 +39,7 @@ import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.MultiRowMutationEndpoint;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.io.hfile.BlockCache;
@@ -253,7 +255,12 @@ public class TestAvoidCellReferencesIntoShippedBlocks {
     }
   }
 
-  public static class CompactorRegionObserver implements RegionObserver {
+  public static class CompactorRegionObserver implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public InternalScanner preCompactScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c,

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestBlockEvictionFromClient.java

@@ -25,6 +25,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -43,6 +44,7 @@ import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.MultiRowMutationEndpoint;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.io.hfile.BlockCache;
@@ -1549,7 +1551,7 @@ public class TestBlockEvictionFromClient {
     }
   }
 
-  public static class CustomInnerRegionObserver implements RegionObserver {
+  public static class CustomInnerRegionObserver implements RegionCoprocessor, RegionObserver {
     static final AtomicLong sleepTime = new AtomicLong(0);
     static final AtomicBoolean slowDownNext = new AtomicBoolean(false);
     static final AtomicInteger countOfNext = new AtomicInteger(0);
@@ -1559,6 +1561,11 @@ public class TestBlockEvictionFromClient {
     private static final AtomicReference<CountDownLatch> cdl = new AtomicReference<>(
         new CountDownLatch(0));
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public boolean postScannerNext(ObserverContext<RegionCoprocessorEnvironment> e,
         InternalScanner s, List<Result> results, int limit, boolean hasMore) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestClientOperationInterrupt.java

@@ -28,6 +28,7 @@ import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
@@ -45,6 +46,7 @@ import java.io.InterruptedIOException;
 import java.net.SocketTimeoutException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicInteger;
 
 @Category({MediumTests.class, ClientTests.class})
@@ -58,7 +60,12 @@ public class TestClientOperationInterrupt {
   private static final byte[] test = Bytes.toBytes("test");
   private static Configuration conf;
 
-  public static class TestCoprocessor implements RegionObserver {
+  public static class TestCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
                          final Get get, final List<Cell> results) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestEnableTable.java

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.client;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CountDownLatch;
 
 import org.apache.commons.logging.Log;
@@ -34,6 +35,7 @@ import org.apache.hadoop.hbase.MetaTableAccessor;
 import org.apache.hadoop.hbase.MiniHBaseCluster;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
+import org.apache.hadoop.hbase.coprocessor.MasterCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.MasterCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.MasterObserver;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
@@ -189,10 +191,15 @@ public class TestEnableTable {
     }
   }
 
-  public  static class MasterSyncObserver implements MasterObserver {
+  public  static class MasterSyncObserver implements MasterCoprocessor, MasterObserver {
     volatile CountDownLatch tableCreationLatch = null;
     volatile CountDownLatch tableDeletionLatch = null;
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postCompletedCreateTableAction(
         final ObserverContext<MasterCoprocessorEnvironment> ctx,
@@ -222,8 +229,8 @@ public class TestEnableTable {
   throws Exception {
     // NOTE: We need a latch because admin is not sync,
     // so the postOp coprocessor method may be called after the admin operation returned.
-    MasterSyncObserver observer = (MasterSyncObserver)testUtil.getHBaseCluster().getMaster()
-      .getMasterCoprocessorHost().findCoprocessor(MasterSyncObserver.class.getName());
+    MasterSyncObserver observer = testUtil.getHBaseCluster().getMaster()
+      .getMasterCoprocessorHost().findCoprocessor(MasterSyncObserver.class);
     observer.tableCreationLatch = new CountDownLatch(1);
     Admin admin = testUtil.getAdmin();
     if (splitKeys != null) {
@@ -240,8 +247,8 @@ public class TestEnableTable {
   throws Exception {
     // NOTE: We need a latch because admin is not sync,
     // so the postOp coprocessor method may be called after the admin operation returned.
-    MasterSyncObserver observer = (MasterSyncObserver)testUtil.getHBaseCluster().getMaster()
-      .getMasterCoprocessorHost().findCoprocessor(MasterSyncObserver.class.getName());
+    MasterSyncObserver observer = testUtil.getHBaseCluster().getMaster()
+      .getMasterCoprocessorHost().findCoprocessor(MasterSyncObserver.class);
     observer.tableDeletionLatch = new CountDownLatch(1);
     Admin admin = testUtil.getAdmin();
     try {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide.java

@@ -40,6 +40,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.NavigableMap;
 import java.util.NavigableSet;
+import java.util.Optional;
 import java.util.UUID;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
@@ -74,6 +75,7 @@ import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
 import org.apache.hadoop.hbase.coprocessor.CoprocessorHost;
 import org.apache.hadoop.hbase.coprocessor.MultiRowMutationEndpoint;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.exceptions.ScannerResetException;
@@ -543,7 +545,7 @@ public class TestFromClientSide {
    * This is a coprocessor to inject a test failure so that a store scanner.reseek() call will
    * fail with an IOException() on the first call.
    */
-  public static class ExceptionInReseekRegionObserver implements RegionObserver {
+  public static class ExceptionInReseekRegionObserver implements RegionCoprocessor, RegionObserver {
     static AtomicLong reqCount = new AtomicLong(0);
     static AtomicBoolean isDoNotRetry = new AtomicBoolean(false); // whether to throw DNRIOE
     static AtomicBoolean throwOnce = new AtomicBoolean(true); // whether to only throw once
@@ -554,6 +556,11 @@ public class TestFromClientSide {
       throwOnce.set(true);
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     class MyStoreScanner extends StoreScanner {
       public MyStoreScanner(HStore store, ScanInfo scanInfo, Scan scan, NavigableSet<byte[]> columns,
           long readPt) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide3.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.Random;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
@@ -37,6 +38,7 @@ import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.regionserver.HRegionServer;
@@ -688,7 +690,7 @@ public class TestFromClientSide3 {
 
   private void testPreBatchMutate(TableName tableName, Runnable rn)throws Exception {
     HTableDescriptor desc = new HTableDescriptor(tableName);
-    desc.addCoprocessor(WatiingForScanObserver.class.getName());
+    desc.addCoprocessor(WaitingForScanObserver.class.getName());
     desc.addFamily(new HColumnDescriptor(FAMILY));
     TEST_UTIL.getAdmin().createTable(desc);
     ExecutorService service = Executors.newFixedThreadPool(2);
@@ -720,7 +722,7 @@ public class TestFromClientSide3 {
   public void testLockLeakWithDelta() throws Exception, Throwable {
     final TableName tableName = TableName.valueOf(name.getMethodName());
     HTableDescriptor desc = new HTableDescriptor(tableName);
-    desc.addCoprocessor(WatiingForMultiMutationsObserver.class.getName());
+    desc.addCoprocessor(WaitingForMultiMutationsObserver.class.getName());
     desc.setConfiguration("hbase.rowlock.wait.duration", String.valueOf(5000));
     desc.addFamily(new HColumnDescriptor(FAMILY));
     TEST_UTIL.getAdmin().createTable(desc);
@@ -735,7 +737,7 @@ public class TestFromClientSide3 {
         try (Table table = con.getTable(tableName)) {
           Put put = new Put(ROW);
           put.addColumn(FAMILY, QUALIFIER, VALUE);
-          // the put will be blocked by WatiingForMultiMutationsObserver.
+          // the put will be blocked by WaitingForMultiMutationsObserver.
           table.put(put);
         } catch (IOException ex) {
           throw new RuntimeException(ex);
@@ -753,7 +755,7 @@ public class TestFromClientSide3 {
       });
       appendService.shutdown();
       appendService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
-      WatiingForMultiMutationsObserver observer = find(tableName, WatiingForMultiMutationsObserver.class);
+      WaitingForMultiMutationsObserver observer = find(tableName, WaitingForMultiMutationsObserver.class);
       observer.latch.countDown();
       putService.shutdown();
       putService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
@@ -774,7 +776,7 @@ public class TestFromClientSide3 {
     final TableName tableName = TableName.valueOf(name.getMethodName());
     HTableDescriptor desc = new HTableDescriptor(tableName);
     desc.addCoprocessor(MultiRowMutationEndpoint.class.getName());
-    desc.addCoprocessor(WatiingForMultiMutationsObserver.class.getName());
+    desc.addCoprocessor(WaitingForMultiMutationsObserver.class.getName());
     desc.setConfiguration("hbase.rowlock.wait.duration", String.valueOf(5000));
     desc.addFamily(new HColumnDescriptor(FAMILY));
     TEST_UTIL.getAdmin().createTable(desc);
@@ -793,7 +795,7 @@ public class TestFromClientSide3 {
         try (Table table = con.getTable(tableName)) {
           Put put0 = new Put(rowLocked);
           put0.addColumn(FAMILY, QUALIFIER, value0);
-          // the put will be blocked by WatiingForMultiMutationsObserver.
+          // the put will be blocked by WaitingForMultiMutationsObserver.
           table.put(put0);
         } catch (IOException ex) {
           throw new RuntimeException(ex);
@@ -830,7 +832,7 @@ public class TestFromClientSide3 {
       });
       cpService.shutdown();
       cpService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
-      WatiingForMultiMutationsObserver observer = find(tableName, WatiingForMultiMutationsObserver.class);
+      WaitingForMultiMutationsObserver observer = find(tableName, WaitingForMultiMutationsObserver.class);
       observer.latch.countDown();
       putService.shutdown();
       putService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
@@ -975,8 +977,15 @@ public class TestFromClientSide3 {
     return clz.cast(cp);
   }
 
-  public static class WatiingForMultiMutationsObserver implements RegionObserver {
+  public static class WaitingForMultiMutationsObserver
+      implements RegionCoprocessor, RegionObserver {
     final CountDownLatch latch = new CountDownLatch(1);
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postBatchMutate(final ObserverContext<RegionCoprocessorEnvironment> c,
             final MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
@@ -988,8 +997,14 @@ public class TestFromClientSide3 {
     }
   }
 
-  public static class WatiingForScanObserver implements RegionObserver {
+  public static class WaitingForScanObserver implements RegionCoprocessor, RegionObserver {
     private final CountDownLatch latch = new CountDownLatch(1);
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postBatchMutate(final ObserverContext<RegionCoprocessorEnvironment> c,
             final MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestHCM.java

@@ -31,6 +31,7 @@ import java.lang.reflect.Modifier;
 import java.net.SocketTimeoutException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 import java.util.Random;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.SynchronousQueue;
@@ -55,6 +56,7 @@ import org.apache.hadoop.hbase.ServerName;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.Waiter;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.exceptions.ClientExceptionsUtil;
@@ -118,7 +120,7 @@ public class TestHCM {
 /**
 * This copro sleeps 20 second. The first call it fails. The second time, it works.
 */
-  public static class SleepAndFailFirstTime implements RegionObserver {
+  public static class SleepAndFailFirstTime implements RegionCoprocessor, RegionObserver {
     static final AtomicLong ct = new AtomicLong(0);
     static final String SLEEP_TIME_CONF_KEY =
         "hbase.coprocessor.SleepAndFailFirstTime.sleepTime";
@@ -128,6 +130,11 @@ public class TestHCM {
     public SleepAndFailFirstTime() {
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postOpen(ObserverContext<RegionCoprocessorEnvironment> c) {
       RegionCoprocessorEnvironment env = c.getEnvironment();
@@ -175,8 +182,14 @@ public class TestHCM {
 
   }
 
-  public static class SleepCoprocessor implements RegionObserver {
+  public static class SleepCoprocessor implements RegionCoprocessor, RegionObserver {
     public static final int SLEEP_TIME = 5000;
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {
@@ -204,9 +217,15 @@ public class TestHCM {
 
   }
 
-  public static class SleepLongerAtFirstCoprocessor implements RegionObserver {
+  public static class SleepLongerAtFirstCoprocessor implements RegionCoprocessor, RegionObserver {
     public static final int SLEEP_TIME = 2000;
     static final AtomicLong ct = new AtomicLong(0);
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestMobCloneSnapshotFromClient.java

@@ -21,6 +21,7 @@ import static org.junit.Assert.assertEquals;
 
 import java.io.IOException;
 import java.io.InterruptedIOException;
+import java.util.Optional;
 
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HColumnDescriptor;
@@ -28,6 +29,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HTableDescriptor;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.master.cleaner.TimeToLiveHFileCleaner;
@@ -137,7 +139,13 @@ public class TestMobCloneSnapshotFromClient extends TestCloneSnapshotFromClient
   /**
    * This coprocessor is used to delay the flush.
    */
-  public static class DelayFlushCoprocessor implements RegionObserver {
+  public static class DelayFlushCoprocessor implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preFlush(ObserverContext<RegionCoprocessorEnvironment> e) throws IOException {
       if (delayFlush) {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestReplicaWithCluster.java

@@ -24,6 +24,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
@@ -46,6 +47,7 @@ import org.apache.hadoop.hbase.Waiter;
 
 import org.apache.hadoop.hbase.client.replication.ReplicationAdmin;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
@@ -83,13 +85,18 @@ public class TestReplicaWithCluster {
   /**
    * This copro is used to synchronize the tests.
    */
-  public static class SlowMeCopro implements RegionObserver {
+  public static class SlowMeCopro implements RegionCoprocessor, RegionObserver {
     static final AtomicLong sleepTime = new AtomicLong(0);
     static final AtomicReference<CountDownLatch> cdl = new AtomicReference<>(new CountDownLatch(0));
 
     public SlowMeCopro() {
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
                          final Get get, final List<Cell> results) throws IOException {
@@ -119,11 +126,16 @@ public class TestReplicaWithCluster {
   /**
    * This copro is used to simulate region server down exception for Get and Scan
    */
-  public static class RegionServerStoppedCopro implements RegionObserver {
+  public static class RegionServerStoppedCopro implements RegionCoprocessor, RegionObserver {
 
     public RegionServerStoppedCopro() {
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {
@@ -164,10 +176,16 @@ public class TestReplicaWithCluster {
   /**
    * This copro is used to slow down the primary meta region scan a bit
    */
-  public static class RegionServerHostingPrimayMetaRegionSlowOrStopCopro implements RegionObserver {
+  public static class RegionServerHostingPrimayMetaRegionSlowOrStopCopro
+      implements RegionCoprocessor, RegionObserver {
     static boolean slowDownPrimaryMetaScan = false;
     static boolean throwException = false;
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestReplicasClient.java

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 import java.util.Random;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
@@ -47,6 +48,7 @@ import org.apache.hadoop.hbase.NotServingRegionException;
 import org.apache.hadoop.hbase.RegionLocations;
 import org.apache.hadoop.hbase.TableNotFoundException;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
@@ -98,7 +100,7 @@ public class TestReplicasClient {
   /**
    * This copro is used to synchronize the tests.
    */
-  public static class SlowMeCopro implements RegionObserver {
+  public static class SlowMeCopro implements RegionCoprocessor, RegionObserver {
     static final AtomicLong sleepTime = new AtomicLong(0);
     static final AtomicBoolean slowDownNext = new AtomicBoolean(false);
     static final AtomicInteger countOfNext = new AtomicInteger(0);
@@ -108,6 +110,11 @@ public class TestReplicasClient {
     public SlowMeCopro() {
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
                          final Get get, final List<Cell> results) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestResultFromCoprocessor.java

@@ -21,6 +21,8 @@ package org.apache.hadoop.hbase.client;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Optional;
+
 import static junit.framework.TestCase.assertTrue;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
@@ -29,6 +31,7 @@ import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.KeyValue;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
@@ -101,7 +104,11 @@ public class TestResultFromCoprocessor {
     }
   }
 
-  public static class MyObserver implements RegionObserver {
+  public static class MyObserver implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public Result postAppend(final ObserverContext<RegionCoprocessorEnvironment> c,

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestServerBusyException.java

@@ -22,6 +22,7 @@ import static org.junit.Assert.assertEquals;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.hadoop.conf.Configuration;
@@ -32,6 +33,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HTableDescriptor;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
+import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
 import org.apache.hadoop.hbase.ipc.ServerTooBusyException;
@@ -66,8 +68,13 @@ public class TestServerBusyException {
   @Rule
   public TestName name = new TestName();
 
-  public static class SleepCoprocessor implements RegionObserver {
+  public static class SleepCoprocessor implements RegionCoprocessor, RegionObserver {
     public static final int SLEEP_TIME = 5000;
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {
@@ -95,9 +102,15 @@ public class TestServerBusyException {
 
   }
 
-  public static class SleepLongerAtFirstCoprocessor implements RegionObserver {
+  public static class SleepLongerAtFirstCoprocessor implements RegionCoprocessor, RegionObserver {
     public static final int SLEEP_TIME = 2000;
     static final AtomicLong ct = new AtomicLong(0);
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Get get, final List<Cell> results) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SampleRegionWALCoprocessor.java

@@ -22,6 +22,7 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -39,9 +40,10 @@ import org.apache.hadoop.hbase.wal.WALKey;
  * passed-in WALEdit, i.e, ignore specified columns when writing, or add a KeyValue. On the other
  * side, it checks whether the ignored column is still in WAL when Restoreed at region reconstruct.
  */
-public class SampleRegionWALObserver implements WALObserver, RegionObserver {
+public class SampleRegionWALCoprocessor implements WALCoprocessor, RegionCoprocessor,
+    WALObserver, RegionObserver {
 
-  private static final Log LOG = LogFactory.getLog(SampleRegionWALObserver.class);
+  private static final Log LOG = LogFactory.getLog(SampleRegionWALCoprocessor.class);
 
   private byte[] tableName;
   private byte[] row;
@@ -81,6 +83,15 @@ public class SampleRegionWALObserver implements WALObserver, RegionObserver {
     postWALRollCalled = false;
   }
 
+  @Override public Optional<WALObserver> getWALObserver() {
+    return Optional.of(this);
+  }
+
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public void postWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> env,
       RegionInfo info, WALKey logKey, WALEdit logEdit) throws IOException {
@@ -167,13 +178,13 @@ public class SampleRegionWALObserver implements WALObserver, RegionObserver {
   }
 
   public boolean isPreWALRestoreCalled() {
-    LOG.debug(SampleRegionWALObserver.class.getName() +
+    LOG.debug(SampleRegionWALCoprocessor.class.getName() +
       ".isPreWALRestoreCalled is called.");
     return preWALRestoreCalled;
   }
 
   public boolean isPostWALRestoreCalled() {
-    LOG.debug(SampleRegionWALObserver.class.getName() +
+    LOG.debug(SampleRegionWALCoprocessor.class.getName() +
       ".isPostWALRestoreCalled is called.");
     return postWALRestoreCalled;
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SimpleRegionObserver.java

@@ -28,6 +28,7 @@ import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 import java.util.NavigableSet;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -72,7 +73,7 @@ import org.apache.hadoop.hbase.shaded.com.google.common.collect.ImmutableList;
  * A sample region observer that tests the RegionObserver interface.
  * It works with TestRegionObserverInterface to provide the test case.
  */
-public class SimpleRegionObserver implements RegionObserver {
+public class SimpleRegionObserver implements RegionCoprocessor, RegionObserver {
 
   final AtomicInteger ctBeforeDelete = new AtomicInteger(1);
   final AtomicInteger ctPreOpen = new AtomicInteger(0);
@@ -134,6 +135,11 @@ public class SimpleRegionObserver implements RegionObserver {
     throwOnPostFlush.set(val);
   }
 
+  @Override
+  public Optional<RegionObserver> getRegionObserver() {
+    return Optional.of(this);
+  }
+
   @Override
   public void start(CoprocessorEnvironment e) throws IOException {
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorConfiguration.java

@@ -20,13 +20,13 @@
 package org.apache.hadoop.hbase.coprocessor;
 
 import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.mockito.Mockito.*;
 import static org.junit.Assert.*;
 
 import org.apache.hadoop.conf.Configuration;
-import org.apache.hadoop.hbase.Coprocessor;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
 import org.apache.hadoop.hbase.HBaseConfiguration;
 import org.apache.hadoop.hbase.HRegionInfo;
@@ -74,7 +74,8 @@ public class TestCoprocessorConfiguration {
   private static final AtomicBoolean systemCoprocessorLoaded = new AtomicBoolean();
   private static final AtomicBoolean tableCoprocessorLoaded = new AtomicBoolean();
 
-  public static class SystemCoprocessor implements Coprocessor {
+  public static class SystemCoprocessor implements MasterCoprocessor, RegionCoprocessor,
+      RegionServerCoprocessor {
     @Override
     public void start(CoprocessorEnvironment env) throws IOException {
       systemCoprocessorLoaded.set(true);
@@ -84,7 +85,7 @@ public class TestCoprocessorConfiguration {
     public void stop(CoprocessorEnvironment env) throws IOException { }
   }
 
-  public static class TableCoprocessor implements Coprocessor {
+  public static class TableCoprocessor implements RegionCoprocessor {
     @Override
     public void start(CoprocessorEnvironment env) throws IOException {
       tableCoprocessorLoaded.set(true);
@@ -108,7 +109,7 @@ public class TestCoprocessorConfiguration {
       systemCoprocessorLoaded.get(),
       CoprocessorHost.DEFAULT_COPROCESSORS_ENABLED);
     assertEquals("Table coprocessors loading default was not honored",
-      tableCoprocessorLoaded.get(), 
+      tableCoprocessorLoaded.get(),
       CoprocessorHost.DEFAULT_COPROCESSORS_ENABLED &&
       CoprocessorHost.DEFAULT_USER_COPROCESSORS_ENABLED);
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorHost.java

@@ -39,7 +39,7 @@ public class TestCoprocessorHost {
   /**
    * An {@link Abortable} implementation for tests.
    */
-  class TestAbortable implements Abortable {
+  private class TestAbortable implements Abortable {
     private volatile boolean aborted = false;
 
     @Override
@@ -56,13 +56,23 @@ public class TestCoprocessorHost {
   @Test
   public void testDoubleLoadingAndPriorityValue() {
     final Configuration conf = HBaseConfiguration.create();
-    CoprocessorHost<CoprocessorEnvironment> host =
-        new CoprocessorHost<CoprocessorEnvironment>(new TestAbortable()) {
-      final Configuration cpHostConf = conf;
+    CoprocessorHost<RegionCoprocessor, CoprocessorEnvironment<RegionCoprocessor>> host =
+        new CoprocessorHost<RegionCoprocessor, CoprocessorEnvironment<RegionCoprocessor>>(
+            new TestAbortable()) {
+          @Override
+          public RegionCoprocessor checkAndGetInstance(Class<?> implClass)
+              throws InstantiationException, IllegalAccessException {
+            if(RegionCoprocessor.class.isAssignableFrom(implClass)) {
+              return (RegionCoprocessor)implClass.newInstance();
+            }
+            return null;
+          }
+
+          final Configuration cpHostConf = conf;
 
       @Override
-      public CoprocessorEnvironment createEnvironment(Class<?> implClass,
-          final Coprocessor instance, final int priority, int sequence, Configuration conf) {
+      public CoprocessorEnvironment createEnvironment(final RegionCoprocessor instance,
+          final int priority, int sequence, Configuration conf) {
         return new CoprocessorEnvironment() {
           final Coprocessor envInstance = instance;
 
@@ -106,6 +116,12 @@ public class TestCoprocessorHost {
             return null;
           }
 
+          @Override
+          public void startup() throws IOException {}
+
+          @Override
+          public void shutdown() {}
+
           @Override
           public ClassLoader getClassLoader() {
             return null;
@@ -116,13 +132,16 @@ public class TestCoprocessorHost {
     final String key = "KEY";
     final String coprocessor = "org.apache.hadoop.hbase.coprocessor.SimpleRegionObserver";
     // Try and load a coprocessor three times
-    conf.setStrings(key, coprocessor, coprocessor, coprocessor, SimpleRegionObserverV2.class.getName());
+    conf.setStrings(key, coprocessor, coprocessor, coprocessor,
+        SimpleRegionObserverV2.class.getName());
     host.loadSystemCoprocessors(conf, key);
     // Two coprocessors(SimpleRegionObserver and SimpleRegionObserverV2) loaded
-    Assert.assertEquals(2, host.coprocessors.size());
+    Assert.assertEquals(2, host.coprocEnvironments.size());
     // Check the priority value
-    CoprocessorEnvironment simpleEnv = host.findCoprocessorEnvironment(SimpleRegionObserver.class.getName());
-    CoprocessorEnvironment simpleEnv_v2 = host.findCoprocessorEnvironment(SimpleRegionObserverV2.class.getName());
+    CoprocessorEnvironment simpleEnv = host.findCoprocessorEnvironment(
+        SimpleRegionObserver.class.getName());
+    CoprocessorEnvironment simpleEnv_v2 = host.findCoprocessorEnvironment(
+        SimpleRegionObserverV2.class.getName());
     assertNotNull(simpleEnv);
     assertNotNull(simpleEnv_v2);
     assertEquals(Coprocessor.PRIORITY_SYSTEM, simpleEnv.getPriority());

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorInterface.java

@@ -32,6 +32,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.ConcurrentMap;
 
 import org.apache.commons.logging.Log;
@@ -62,7 +63,6 @@ import org.apache.hadoop.hbase.regionserver.ScannerContext;
 import org.apache.hadoop.hbase.regionserver.Store;
 import org.apache.hadoop.hbase.regionserver.StoreFile;
 import org.apache.hadoop.hbase.regionserver.compactions.CompactionLifeCycleTracker;
-import org.apache.hadoop.hbase.regionserver.compactions.CompactionRequest;
 import org.apache.hadoop.hbase.testclassification.CoprocessorTests;
 import org.apache.hadoop.hbase.testclassification.SmallTests;
 import org.junit.Rule;
@@ -149,7 +149,7 @@ public class TestCoprocessorInterface {
     }
   }
 
-  public static class CoprocessorImpl implements RegionObserver {
+  public static class CoprocessorImpl implements RegionCoprocessor, RegionObserver {
 
     private boolean startCalled;
     private boolean stopCalled;
@@ -177,6 +177,11 @@ public class TestCoprocessorInterface {
       stopCalled = true;
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preOpen(ObserverContext<RegionCoprocessorEnvironment> e) {
       preOpenCalled = true;
@@ -242,23 +247,31 @@ public class TestCoprocessorInterface {
     }
   }
 
-  public static class CoprocessorII implements RegionObserver {
+  public static class CoprocessorII implements RegionCoprocessor {
     private ConcurrentMap<String, Object> sharedData;
+
     @Override
     public void start(CoprocessorEnvironment e) {
       sharedData = ((RegionCoprocessorEnvironment)e).getSharedData();
       sharedData.putIfAbsent("test2", new Object());
     }
+
     @Override
     public void stop(CoprocessorEnvironment e) {
       sharedData = null;
     }
+
     @Override
-    public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
-        final Get get, final List<Cell> results) throws IOException {
-      if (1/0 == 1) {
-        e.complete();
-      }
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(new RegionObserver() {
+        @Override
+        public void preGetOp(final ObserverContext<RegionCoprocessorEnvironment> e,
+            final Get get, final List<Cell> results) throws IOException {
+          if (1/0 == 1) {
+            e.complete();
+          }
+        }
+      });
     }
 
     Map<String, Object> getSharedData() {
@@ -272,8 +285,7 @@ public class TestCoprocessorInterface {
     byte [][] families = { fam1, fam2, fam3 };
 
     Configuration hc = initConfig();
-    Region region = initHRegion(tableName, name.getMethodName(), hc,
-      new Class<?>[]{}, families);
+    Region region = initHRegion(tableName, name.getMethodName(), hc, new Class<?>[]{}, families);
 
     for (int i = 0; i < 3; i++) {
       HBaseTestCase.addContent(region, fam3);
@@ -284,18 +296,16 @@ public class TestCoprocessorInterface {
 
     region = reopenRegion(region, CoprocessorImpl.class, CoprocessorII.class);
 
-    Coprocessor c = region.getCoprocessorHost().
-        findCoprocessor(CoprocessorImpl.class.getName());
-    Coprocessor c2 = region.getCoprocessorHost().
-        findCoprocessor(CoprocessorII.class.getName());
+    Coprocessor c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class);
+    Coprocessor c2 = region.getCoprocessorHost().findCoprocessor(CoprocessorII.class);
     Object o = ((CoprocessorImpl)c).getSharedData().get("test1");
     Object o2 = ((CoprocessorII)c2).getSharedData().get("test2");
     assertNotNull(o);
     assertNotNull(o2);
     // to coprocessors get different sharedDatas
     assertFalse(((CoprocessorImpl)c).getSharedData() == ((CoprocessorII)c2).getSharedData());
-    c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class.getName());
-    c2 = region.getCoprocessorHost().findCoprocessor(CoprocessorII.class.getName());
+    c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class);
+    c2 = region.getCoprocessorHost().findCoprocessor(CoprocessorII.class);
     // make sure that all coprocessor of a class have identical sharedDatas
     assertTrue(((CoprocessorImpl)c).getSharedData().get("test1") == o);
     assertTrue(((CoprocessorII)c2).getSharedData().get("test2") == o2);
@@ -312,21 +322,18 @@ public class TestCoprocessorInterface {
       fail();
     } catch (org.apache.hadoop.hbase.DoNotRetryIOException xc) {
     }
-    assertNull(region.getCoprocessorHost().findCoprocessor(CoprocessorII.class.getName()));
-    c = region.getCoprocessorHost().
-        findCoprocessor(CoprocessorImpl.class.getName());
+    assertNull(region.getCoprocessorHost().findCoprocessor(CoprocessorII.class));
+    c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class);
     assertTrue(((CoprocessorImpl)c).getSharedData().get("test1") == o);
     c = c2 = null;
     // perform a GC
     System.gc();
     // reopen the region
     region = reopenRegion(region, CoprocessorImpl.class, CoprocessorII.class);
-    c = region.getCoprocessorHost().
-        findCoprocessor(CoprocessorImpl.class.getName());
+    c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class);
     // CPimpl is unaffected, still the same reference
     assertTrue(((CoprocessorImpl)c).getSharedData().get("test1") == o);
-    c2 = region.getCoprocessorHost().
-        findCoprocessor(CoprocessorII.class.getName());
+    c2 = region.getCoprocessorHost().findCoprocessor(CoprocessorII.class);
     // new map and object created, hence the reference is different
     // hence the old entry was indeed removed by the GC and new one has been created
     Object o3 = ((CoprocessorII)c2).getSharedData().get("test2");
@@ -357,8 +364,7 @@ public class TestCoprocessorInterface {
     scanner.next(new ArrayList<>());
 
     HBaseTestingUtility.closeRegionAndWAL(region);
-    Coprocessor c = region.getCoprocessorHost().
-      findCoprocessor(CoprocessorImpl.class.getName());
+    Coprocessor c = region.getCoprocessorHost().findCoprocessor(CoprocessorImpl.class);
 
     assertTrue("Coprocessor not started", ((CoprocessorImpl)c).wasStarted());
     assertTrue("Coprocessor not stopped", ((CoprocessorImpl)c).wasStopped());
@@ -382,7 +388,7 @@ public class TestCoprocessorInterface {
     ((HRegion)r).setCoprocessorHost(host);
 
     for (Class<?> implClass : implClasses) {
-      host.load(implClass, Coprocessor.PRIORITY_USER, conf);
+      host.load((Class<? extends RegionCoprocessor>) implClass, Coprocessor.PRIORITY_USER, conf);
     }
     // we need to manually call pre- and postOpen here since the
     // above load() is not the real case for CP loading. A CP is
@@ -412,7 +418,7 @@ public class TestCoprocessorInterface {
     ((HRegion)r).setCoprocessorHost(host);
 
     for (Class<?> implClass : implClasses) {
-      host.load(implClass, Coprocessor.PRIORITY_USER, conf);
+      host.load((Class<? extends RegionCoprocessor>) implClass, Coprocessor.PRIORITY_USER, conf);
       Coprocessor c = host.findCoprocessor(implClass.getName());
       assertNotNull(c);
     }

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorMetrics.java

@@ -95,7 +95,7 @@ public class TestCoprocessorMetrics {
   /**
    * MasterObserver that has a Timer metric for create table operation.
    */
-  public static class CustomMasterObserver implements MasterObserver {
+  public static class CustomMasterObserver implements MasterCoprocessor, MasterObserver {
     private Timer createTableTimer;
     private long start = Long.MIN_VALUE;
 
@@ -125,14 +125,25 @@ public class TestCoprocessorMetrics {
         createTableTimer  = registry.timer("CreateTable");
       }
     }
+
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
   }
 
   /**
    * RegionServerObserver that has a Counter for rollWAL requests.
    */
-  public static class CustomRegionServerObserver implements RegionServerObserver {
+  public static class CustomRegionServerObserver implements RegionServerCoprocessor,
+      RegionServerObserver {
     /** This is the Counter metric object to keep track of the current count across invocations */
     private Counter rollWALCounter;
+
+    @Override public Optional<RegionServerObserver> getRegionServerObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postRollWALWriterRequest(ObserverContext<RegionServerCoprocessorEnvironment> ctx)
         throws IOException {
@@ -156,7 +167,7 @@ public class TestCoprocessorMetrics {
   /**
    * WALObserver that has a Counter for walEdits written.
    */
-  public static class CustomWALObserver implements WALObserver {
+  public static class CustomWALObserver implements WALCoprocessor, WALObserver {
     private Counter walEditsCount;
 
     @Override
@@ -177,12 +188,16 @@ public class TestCoprocessorMetrics {
         }
       }
     }
+
+    @Override public Optional<WALObserver> getWALObserver() {
+      return Optional.of(this);
+    }
   }
 
   /**
    * RegionObserver that has a Counter for preGet()
    */
-  public static class CustomRegionObserver implements RegionObserver {
+  public static class CustomRegionObserver implements RegionCoprocessor, RegionObserver {
     private Counter preGetCounter;
 
     @Override
@@ -191,6 +206,11 @@ public class TestCoprocessorMetrics {
       preGetCounter.increment();
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void start(CoprocessorEnvironment env) throws IOException {
       if (env instanceof RegionCoprocessorEnvironment) {

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorStop.java

@@ -49,7 +49,7 @@ public class TestCoprocessorStop {
   private static final String REGIONSERVER_FILE =
                               "regionserver" + System.currentTimeMillis();
 
-  public static class FooCoprocessor implements Coprocessor {
+  public static class FooCoprocessor implements MasterCoprocessor, RegionServerCoprocessor {
     @Override
     public void start(CoprocessorEnvironment env) throws IOException {
       String where = null;

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestHTableWrapper.java

@@ -29,6 +29,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Coprocessor;
@@ -87,7 +88,11 @@ public class TestHTableWrapper {
   private static final byte[] bytes4 = Bytes.toBytes(4);
   private static final byte[] bytes5 = Bytes.toBytes(5);
 
-  static class DummyRegionObserver implements RegionObserver {
+  public static class DummyRegionObserver implements MasterCoprocessor, MasterObserver {
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
   }
 
   private Table hTableInterface;
@@ -135,14 +140,14 @@ public class TestHTableWrapper {
   public void testHTableInterfaceMethods() throws Exception {
     Configuration conf = util.getConfiguration();
     MasterCoprocessorHost cpHost = util.getMiniHBaseCluster().getMaster().getMasterCoprocessorHost();
-    Class<?> implClazz = DummyRegionObserver.class;
+    Class<? extends MasterCoprocessor> implClazz = DummyRegionObserver.class;
     cpHost.load(implClazz, Coprocessor.PRIORITY_HIGHEST, conf);
     CoprocessorEnvironment env = cpHost.findCoprocessorEnvironment(implClazz.getName());
     assertEquals(Coprocessor.VERSION, env.getVersion());
     assertEquals(VersionInfo.getVersion(), env.getHBaseVersion());
     hTableInterface = env.getTable(TEST_TABLE);
     checkHTableInterfaceMethods();
-    cpHost.shutdown(env);
+    cpHost.shutdown((MasterCoprocessorEnvironment) env);
   }
 
   private void checkHTableInterfaceMethods() throws Exception {

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestMasterCoprocessorExceptionWithAbort.java

@@ -20,6 +20,7 @@
 package org.apache.hadoop.hbase.coprocessor;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Abortable;
@@ -97,12 +98,17 @@ public class TestMasterCoprocessorExceptionWithAbort {
    }
   }
 
-  public static class BuggyMasterObserver implements MasterObserver {
+  public static class BuggyMasterObserver implements MasterCoprocessor, MasterObserver {
     private boolean preCreateTableCalled;
     private boolean postCreateTableCalled;
     private boolean startCalled;
     private boolean postStartMasterCalled;
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postCreateTable(ObserverContext<MasterCoprocessorEnvironment> env,
         TableDescriptor desc, RegionInfo[] regions) throws IOException {
@@ -163,8 +169,7 @@ public class TestMasterCoprocessorExceptionWithAbort {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    BuggyMasterObserver cp = (BuggyMasterObserver)host.findCoprocessor(
-        BuggyMasterObserver.class.getName());
+    BuggyMasterObserver cp = host.findCoprocessor(BuggyMasterObserver.class);
     assertFalse("No table created yet", cp.wasCreateTableCalled());
 
     // set a watch on the zookeeper /hbase/master node. If the master dies,

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestMasterCoprocessorExceptionWithRemove.java

@@ -20,6 +20,7 @@
 package org.apache.hadoop.hbase.coprocessor;
 
 import java.io.IOException;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Abortable;
@@ -73,12 +74,17 @@ public class TestMasterCoprocessorExceptionWithRemove {
     }
   }
 
-  public static class BuggyMasterObserver implements MasterObserver {
+  public static class BuggyMasterObserver implements MasterCoprocessor, MasterObserver {
     private boolean preCreateTableCalled;
     private boolean postCreateTableCalled;
     private boolean startCalled;
     private boolean postStartMasterCalled;
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @SuppressWarnings("null")
     @Override
     public void postCreateTable(ObserverContext<MasterCoprocessorEnvironment> env,
@@ -144,8 +150,7 @@ public class TestMasterCoprocessorExceptionWithRemove {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    BuggyMasterObserver cp = (BuggyMasterObserver)host.findCoprocessor(
-        BuggyMasterObserver.class.getName());
+    BuggyMasterObserver cp = host.findCoprocessor(BuggyMasterObserver.class);
     assertFalse("No table created yet", cp.wasCreateTableCalled());
 
     // Set a watch on the zookeeper /hbase/master node. If the master dies,

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestMasterObserver.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 
@@ -95,7 +96,7 @@ public class TestMasterObserver {
   public static CountDownLatch tableCreationLatch = new CountDownLatch(1);
   public static CountDownLatch tableDeletionLatch = new CountDownLatch(1);
 
-  public static class CPMasterObserver implements MasterObserver {
+  public static class CPMasterObserver implements MasterCoprocessor, MasterObserver {
 
     private boolean bypass = false;
     private boolean preCreateTableCalled;
@@ -282,6 +283,11 @@ public class TestMasterObserver {
       postLockHeartbeatCalled = false;
     }
 
+    @Override
+    public Optional<MasterObserver> getMasterObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preMergeRegions(
         final ObserverContext<MasterCoprocessorEnvironment> ctx,
@@ -1503,8 +1509,7 @@ public class TestMasterObserver {
     assertTrue("Master should be active", master.isActiveMaster());
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
     assertNotNull("CoprocessorHost should not be null", host);
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     assertNotNull("CPMasterObserver coprocessor not found or not installed!", cp);
 
     // check basic lifecycle
@@ -1521,8 +1526,7 @@ public class TestMasterObserver {
     final TableName tableName = TableName.valueOf(name.getMethodName());
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.enableBypass(true);
     cp.resetStates();
     assertFalse("No table created yet", cp.wasCreateTableCalled());
@@ -1698,8 +1702,7 @@ public class TestMasterObserver {
     MiniHBaseCluster cluster = UTIL.getHBaseCluster();
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     // create a table
@@ -1760,8 +1763,7 @@ public class TestMasterObserver {
     String testNamespace = "observed_ns";
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
 
     cp.enableBypass(false);
     cp.resetStates();
@@ -1866,8 +1868,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.enableBypass(false);
     cp.resetStates();
 
@@ -1955,8 +1956,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     GetTableDescriptorsRequest req =
@@ -1973,8 +1973,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     master.getMasterRpcServices().getTableNames(null,
@@ -1989,8 +1988,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     master.abortProcedure(1, true);
@@ -2005,8 +2003,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     master.getProcedures();
@@ -2021,8 +2018,7 @@ public class TestMasterObserver {
 
     HMaster master = cluster.getMaster();
     MasterCoprocessorHost host = master.getMasterCoprocessorHost();
-    CPMasterObserver cp = (CPMasterObserver)host.findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = host.findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     master.getLocks();
@@ -2043,8 +2039,7 @@ public class TestMasterObserver {
   @Test
   public void testQueueLockAndLockHeartbeatOperations() throws Exception {
     HMaster master = UTIL.getMiniHBaseCluster().getMaster();
-    CPMasterObserver cp = (CPMasterObserver)master.getMasterCoprocessorHost().findCoprocessor(
-        CPMasterObserver.class.getName());
+    CPMasterObserver cp = master.getMasterCoprocessorHost().findCoprocessor(CPMasterObserver.class);
     cp.resetStates();
 
     final TableName tableName = TableName.valueOf("testLockedTable");

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestOpenTableInCoprocessor.java

@@ -41,6 +41,7 @@ import org.junit.experimental.categories.Category;
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.Optional;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.SynchronousQueue;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -63,7 +64,12 @@ public class TestOpenTableInCoprocessor {
   /**
    * Custom coprocessor that just copies the write to another table.
    */
-  public static class SendToOtherTableCoprocessor implements RegionObserver {
+  public static class SendToOtherTableCoprocessor implements RegionCoprocessor, RegionObserver {
+
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
 
     @Override
     public void prePut(final ObserverContext<RegionCoprocessorEnvironment> e, final Put put,
@@ -80,7 +86,7 @@ public class TestOpenTableInCoprocessor {
   /**
    * Coprocessor that creates an HTable with a pool to write to another table
    */
-  public static class CustomThreadPoolCoprocessor implements RegionObserver {
+  public static class CustomThreadPoolCoprocessor implements RegionCoprocessor, RegionObserver {
 
     /**
      * Get a pool that has only ever one thread. A second action added to the pool (running
@@ -97,6 +103,11 @@ public class TestOpenTableInCoprocessor {
       return pool;
     }
 
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void prePut(final ObserverContext<RegionCoprocessorEnvironment> e, final Put put,
         final WALEdit edit, final Durability durability) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRegionObserverBypass.java

@@ -24,6 +24,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Cell;
@@ -204,7 +205,12 @@ public class TestRegionObserverBypass {
     t.delete(d);
   }
 
-  public static class TestCoprocessor implements RegionObserver {
+  public static class TestCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void prePut(final ObserverContext<RegionCoprocessorEnvironment> e,
         final Put put, final WALEdit edit, final Durability durability)

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRegionObserverForAddingMutationsFromCoprocessors.java

@@ -21,6 +21,7 @@ package org.apache.hadoop.hbase.coprocessor;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -194,7 +195,12 @@ public class TestRegionObserverForAddingMutationsFromCoprocessors {
     }
   }
 
-  public static class TestMultiMutationCoprocessor implements RegionObserver {
+  public static class TestMultiMutationCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preBatchMutate(ObserverContext<RegionCoprocessorEnvironment> c,
         MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
@@ -211,7 +217,12 @@ public class TestRegionObserverForAddingMutationsFromCoprocessors {
     }
   }
 
-  public static class TestDeleteCellCoprocessor implements RegionObserver {
+  public static class TestDeleteCellCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preBatchMutate(ObserverContext<RegionCoprocessorEnvironment> c,
         MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
@@ -230,7 +241,12 @@ public class TestRegionObserverForAddingMutationsFromCoprocessors {
     }
   }
 
-  public static class TestDeleteFamilyCoprocessor implements RegionObserver {
+  public static class TestDeleteFamilyCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preBatchMutate(ObserverContext<RegionCoprocessorEnvironment> c,
         MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
@@ -249,7 +265,12 @@ public class TestRegionObserverForAddingMutationsFromCoprocessors {
     }
   }
 
-  public static class TestDeleteRowCoprocessor implements RegionObserver {
+  public static class TestDeleteRowCoprocessor implements RegionCoprocessor, RegionObserver {
+    @Override
+    public Optional<RegionObserver> getRegionObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void preBatchMutate(ObserverContext<RegionCoprocessorEnvironment> c,
         MiniBatchOperationInProgress<Mutation> miniBatchOp) throws IOException {
@@ -268,8 +289,14 @@ public class TestRegionObserverForAddingMutationsFromCoprocessors {
     }
   }
 
-  public static class TestWALObserver implements WALObserver {
+  public static class TestWALObserver implements WALCoprocessor, WALObserver {
     static WALEdit savedEdit = null;
+
+    @Override
+    public Optional<WALObserver> getWALObserver() {
+      return Optional.of(this);
+    }
+
     @Override
     public void postWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx,
                              RegionInfo info, WALKey logKey, WALEdit logEdit) throws IOException {