HBASE-21550 Add a new method preCreateTableRegionInfos for MasterObserver which allows CPs to modify the TableDescriptor

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

@@ -70,6 +70,21 @@ import org.apache.yetus.audience.InterfaceStability;
 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
 @InterfaceStability.Evolving
 public interface MasterObserver {
+
+  /**
+   * Called before we create the region infos for this table. Called as part of create table RPC
+   * call.
+   * @param ctx the environment to interact with the framework and master
+   * @param desc the TableDescriptor for the table
+   * @return the TableDescriptor used to create the table. Default is the one passed in. Return
+   *         {@code null} means cancel the creation.
+   */
+  default TableDescriptor preCreateTableRegionsInfos(
+      final ObserverContext<MasterCoprocessorEnvironment> ctx, TableDescriptor desc)
+      throws IOException {
+    return desc;
+  }
+
   /**
    * 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/master/HMaster.java

@@ -2030,26 +2030,26 @@ public class HMaster extends HRegionServer implements MasterServices {
   }
 
   @Override
-  public long createTable(
-      final TableDescriptor tableDescriptor,
-      final byte [][] splitKeys,
-      final long nonceGroup,
-      final long nonce) throws IOException {
+  public long createTable(final TableDescriptor tableDescriptor, final byte[][] splitKeys,
+      final long nonceGroup, final long nonce) throws IOException {
     checkInitialized();
-
-    String namespace = tableDescriptor.getTableName().getNamespaceAsString();
+    TableDescriptor desc = getMasterCoprocessorHost().preCreateTableRegionsInfos(tableDescriptor);
+    if (desc == null) {
+      throw new IOException("Creation for " + tableDescriptor + " is canceled by CP");
+    }
+    String namespace = desc.getTableName().getNamespaceAsString();
     this.clusterSchemaService.getNamespace(namespace);
 
-    RegionInfo[] newRegions = ModifyRegionUtils.createRegionInfos(tableDescriptor, splitKeys);
-    sanityCheckTableDescriptor(tableDescriptor);
+    RegionInfo[] newRegions = ModifyRegionUtils.createRegionInfos(desc, splitKeys);
+    sanityCheckTableDescriptor(desc);
 
-    return MasterProcedureUtil.submitProcedure(
-        new MasterProcedureUtil.NonceProcedureRunnable(this, nonceGroup, nonce) {
+    return MasterProcedureUtil
+      .submitProcedure(new MasterProcedureUtil.NonceProcedureRunnable(this, nonceGroup, nonce) {
         @Override
         protected void run() throws IOException {
-        getMaster().getMasterCoprocessorHost().preCreateTable(tableDescriptor, newRegions);
+          getMaster().getMasterCoprocessorHost().preCreateTable(desc, newRegions);
 
-        LOG.info(getClientIdAuditPrefix() + " create " + tableDescriptor);
+          LOG.info(getClientIdAuditPrefix() + " create " + desc);
 
           // TODO: We can handle/merge duplicate requests, and differentiate the case of
           // TableExistsException by saying if the schema is the same or not.
@@ -2057,11 +2057,11 @@ public class HMaster extends HRegionServer implements MasterServices {
           // We need to wait for the procedure to potentially fail due to "prepare" sanity
           // checks. This will block only the beginning of the procedure. See HBASE-19953.
           ProcedurePrepareLatch latch = ProcedurePrepareLatch.createBlockingLatch();
-        submitProcedure(new CreateTableProcedure(
-            procedureExecutor.getEnvironment(), tableDescriptor, newRegions, latch));
+          submitProcedure(
+            new CreateTableProcedure(procedureExecutor.getEnvironment(), desc, newRegions, latch));
           latch.await();
 
-        getMaster().getMasterCoprocessorHost().postCreateTable(tableDescriptor, newRegions);
+          getMaster().getMasterCoprocessorHost().postCreateTable(desc, newRegions);
         }
 
         @Override

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterCoprocessorHost.java

@@ -317,6 +317,20 @@ public class MasterCoprocessorHost
 
   /* Implementation of hooks for invoking MasterObservers */
 
+  public TableDescriptor preCreateTableRegionsInfos(TableDescriptor desc) throws IOException {
+    if (coprocEnvironments.isEmpty()) {
+      return desc;
+    }
+    return execOperationWithResult(
+      new ObserverOperationWithResult<MasterObserver, TableDescriptor>(masterObserverGetter, desc) {
+
+        @Override
+        protected TableDescriptor call(MasterObserver observer) throws IOException {
+          return observer.preCreateTableRegionsInfos(this, getResult());
+        }
+      });
+  }
+
   public void preCreateTable(final TableDescriptor htd, final RegionInfo[] regions)
       throws IOException {
     execOperation(coprocEnvironments.isEmpty() ? null : new MasterObserverOperation() {

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

@@ -94,6 +94,7 @@ public class TestMasterObserver {
 
   public static class CPMasterObserver implements MasterCoprocessor, MasterObserver {
 
+    private boolean preCreateTableRegionInfosCalled;
     private boolean preCreateTableCalled;
     private boolean postCreateTableCalled;
     private boolean preDeleteTableCalled;
@@ -186,6 +187,7 @@ public class TestMasterObserver {
     private boolean postLockHeartbeatCalled;
 
     public void resetStates() {
+      preCreateTableRegionInfosCalled = false;
       preCreateTableCalled = false;
       postCreateTableCalled = false;
       preDeleteTableCalled = false;
@@ -297,6 +299,14 @@ public class TestMasterObserver {
       return preMergeRegionsCalled && postMergeRegionsCalled;
     }
 
+    @Override
+    public TableDescriptor preCreateTableRegionsInfos(
+        ObserverContext<MasterCoprocessorEnvironment> ctx, TableDescriptor desc)
+        throws IOException {
+      preCreateTableRegionInfosCalled = true;
+      return desc;
+    }
+
     @Override
     public void preCreateTable(ObserverContext<MasterCoprocessorEnvironment> env,
         TableDescriptor desc, RegionInfo[] regions) throws IOException {
@@ -310,11 +320,11 @@ public class TestMasterObserver {
     }
 
     public boolean wasCreateTableCalled() {
-      return preCreateTableCalled && postCreateTableCalled;
+      return preCreateTableRegionInfosCalled && preCreateTableCalled && postCreateTableCalled;
     }
 
     public boolean preCreateTableCalledOnly() {
-      return preCreateTableCalled && !postCreateTableCalled;
+      return preCreateTableRegionInfosCalled && preCreateTableCalled && !postCreateTableCalled;
     }
 
     @Override