Added LeaderClient interface and NoopDruidLeaderClient class

benchmarks/src/main/java/org/apache/druid/benchmark/query/SqlBenchmark.java

@@ -27,7 +27,8 @@ import org.apache.druid.benchmark.datagen.BenchmarkSchemas;
 import org.apache.druid.benchmark.datagen.SegmentGenerator;
 import org.apache.druid.client.TimelineServerView;
 import org.apache.druid.data.input.Row;
-import org.apache.druid.discovery.DruidLeaderClient;
+import org.apache.druid.discovery.LeaderClient;
+import org.apache.druid.discovery.NoopDruidLeaderClient;
 import org.apache.druid.java.util.common.Intervals;
 import org.apache.druid.java.util.common.Pair;
 import org.apache.druid.java.util.common.granularity.Granularities;
@@ -114,7 +115,7 @@ public class SqlBenchmark
         .createQueryRunnerFactoryConglomerate();
     final QueryRunnerFactoryConglomerate conglomerate = conglomerateCloserPair.lhs;
     final PlannerConfig plannerConfig = new PlannerConfig();
-    final DruidLeaderClient druidLeaderClient = EasyMock.createMock(DruidLeaderClient.class);
+    final LeaderClient druidLeaderClient = new NoopDruidLeaderClient();
 
     this.walker = new SpecificSegmentsQuerySegmentWalker(conglomerate).add(dataSegment, index);
     plannerFactory = new PlannerFactory(

server/src/main/java/org/apache/druid/discovery/DruidLeaderClient.java

@@ -59,7 +59,7 @@ import java.util.concurrent.atomic.AtomicReference;
  * request.setXXX(..)
  * FullResponseHolder responseHolder = druidLeaderClient.go(request)
  */
-public class DruidLeaderClient
+public class DruidLeaderClient implements LeaderClient
 {
   private final Logger log = new Logger(DruidLeaderClient.class);
 
@@ -93,6 +93,7 @@ public class DruidLeaderClient
     this.serverDiscoverySelector = serverDiscoverySelector;
   }
 
+  @Override
   @LifecycleStart
   public void start()
   {
@@ -110,6 +111,7 @@ public class DruidLeaderClient
     }
   }
 
+  @Override
   @LifecycleStop
   public void stop()
   {
@@ -123,6 +125,7 @@ public class DruidLeaderClient
   /**
    * Make a Request object aimed at the leader. Throws IOException if the leader cannot be located.
    */
+  @Override
   public Request makeRequest(HttpMethod httpMethod, String urlPath) throws IOException
   {
     Preconditions.checkState(lifecycleLock.awaitStarted(1, TimeUnit.MILLISECONDS));
@@ -137,6 +140,7 @@ public class DruidLeaderClient
   /**
    * Executes the request object aimed at the leader and process the response with given handler
    */
+  @Override
   public <Intermediate, Final> ListenableFuture<Final> goAsync(
       final Request request,
       final HttpResponseHandler<Intermediate, Final> handler
@@ -148,6 +152,7 @@ public class DruidLeaderClient
   /**
    * Executes a Request object aimed at the leader. Throws IOException if the leader cannot be located.
    */
+  @Override
   public FullResponseHolder go(
       Request request,
       HttpResponseHandler<FullResponseHolder, FullResponseHolder> responseHandler

server/src/main/java/org/apache/druid/discovery/LeaderClient.java

@@ -0,0 +1,59 @@
+/*
+ * 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.druid.discovery;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import org.apache.druid.java.util.http.client.Request;
+import org.apache.druid.java.util.http.client.response.FullResponseHolder;
+import org.apache.druid.java.util.http.client.response.HttpResponseHandler;
+import org.jboss.netty.handler.codec.http.HttpMethod;
+
+import java.io.IOException;
+
+/**
+ * This is used to facilitate interaction with Coordinator/Overlord leader nodes. Instance of this interface is injected
+ * via Guice with annotations @Coordinator or @IndexingService .
+ */
+public interface LeaderClient
+{
+
+  void start();
+
+  void stop();
+
+  /**
+   * Make a Request object aimed at the leader. Throws IOException if the leader cannot be located.
+   */
+  Request makeRequest(HttpMethod httpMethod, String urlPath) throws IOException;
+
+  /**
+   * Executes a Request object aimed at the leader. Throws IOException if the leader cannot be located.
+   */
+  FullResponseHolder go(Request request, HttpResponseHandler<FullResponseHolder, FullResponseHolder> responseHandler)
+      throws IOException, InterruptedException;
+
+  /**
+   * Executes the request object aimed at the leader and process the response with given handler
+   */
+  <Intermediate, Final> ListenableFuture<Final> goAsync(
+      Request request,
+      HttpResponseHandler<Intermediate, Final> handler
+  );
+
+}

server/src/main/java/org/apache/druid/discovery/NoopDruidLeaderClient.java

@@ -0,0 +1,66 @@
+/*
+ * 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.druid.discovery;
+
+import com.google.common.util.concurrent.ListenableFuture;
+import org.apache.druid.java.util.http.client.Request;
+import org.apache.druid.java.util.http.client.response.FullResponseHolder;
+import org.apache.druid.java.util.http.client.response.HttpResponseHandler;
+import org.jboss.netty.handler.codec.http.HttpMethod;
+
+public class NoopDruidLeaderClient implements LeaderClient
+{
+
+  @Override
+  public void start()
+  {
+    //Noop
+  }
+
+  @Override
+  public void stop()
+  {
+    //Noop
+  }
+
+  @Override
+  public Request makeRequest(
+      HttpMethod httpMethod, String urlPath
+  )
+  {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public FullResponseHolder go(
+      Request request, HttpResponseHandler<FullResponseHolder, FullResponseHolder> responseHandler
+  )
+  {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public <Intermediate, Final> ListenableFuture<Final> goAsync(
+      Request request, HttpResponseHandler<Intermediate, Final> handler
+  )
+  {
+    throw new UnsupportedOperationException();
+  }
+
+}

sql/src/main/java/org/apache/druid/sql/calcite/planner/Calcites.java

@@ -37,7 +37,7 @@ import org.apache.calcite.util.DateString;
 import org.apache.calcite.util.TimeString;
 import org.apache.calcite.util.TimestampString;
 import org.apache.druid.client.TimelineServerView;
-import org.apache.druid.discovery.DruidLeaderClient;
+import org.apache.druid.discovery.LeaderClient;
 import org.apache.druid.java.util.common.DateTimes;
 import org.apache.druid.java.util.common.IAE;
 import org.apache.druid.java.util.common.ISE;
@@ -105,8 +105,8 @@ public class Calcites
       final TimelineServerView serverView,
       final DruidSchema druidSchema,
       final AuthorizerMapper authorizerMapper,
-      final DruidLeaderClient coordinatorDruidLeaderClient,
-      final DruidLeaderClient overlordDruidLeaderClient,
+      final LeaderClient coordinatorDruidLeaderClient,
+      final LeaderClient overlordDruidLeaderClient,
       final ObjectMapper jsonMapper
   )
   {

sql/src/main/java/org/apache/druid/sql/calcite/planner/PlannerFactory.java

@@ -38,7 +38,7 @@ import org.apache.calcite.tools.Frameworks;
 import org.apache.druid.client.TimelineServerView;
 import org.apache.druid.client.coordinator.Coordinator;
 import org.apache.druid.client.indexing.IndexingService;
-import org.apache.druid.discovery.DruidLeaderClient;
+import org.apache.druid.discovery.LeaderClient;
 import org.apache.druid.guice.annotations.Json;
 import org.apache.druid.math.expr.ExprMacroTable;
 import org.apache.druid.server.QueryLifecycleFactory;
@@ -68,8 +68,8 @@ public class PlannerFactory
   private final PlannerConfig plannerConfig;
   private final ObjectMapper jsonMapper;
   private final AuthorizerMapper authorizerMapper;
-  private final DruidLeaderClient coordinatorDruidLeaderClient;
-  private final DruidLeaderClient overlordDruidLeaderClient;
+  private final LeaderClient coordinatorDruidLeaderClient;
+  private final LeaderClient overlordDruidLeaderClient;
 
   @Inject
   public PlannerFactory(
@@ -81,8 +81,8 @@ public class PlannerFactory
       final PlannerConfig plannerConfig,
       final AuthorizerMapper authorizerMapper,
       final @Json ObjectMapper jsonMapper,
-      final @Coordinator DruidLeaderClient coordinatorDruidLeaderClient,
-      final @IndexingService DruidLeaderClient overlordDruidLeaderClient
+      final @Coordinator LeaderClient coordinatorDruidLeaderClient,
+      final @IndexingService LeaderClient overlordDruidLeaderClient
   )
   {
     this.druidSchema = druidSchema;

sql/src/main/java/org/apache/druid/sql/calcite/schema/SystemSchema.java

@@ -25,7 +25,6 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Function;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.FluentIterable;
-import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Iterables;
 import com.google.common.util.concurrent.ListenableFuture;
@@ -46,7 +45,7 @@ import org.apache.druid.client.JsonParserIterator;
 import org.apache.druid.client.TimelineServerView;
 import org.apache.druid.client.coordinator.Coordinator;
 import org.apache.druid.client.indexing.IndexingService;
-import org.apache.druid.discovery.DruidLeaderClient;
+import org.apache.druid.discovery.LeaderClient;
 import org.apache.druid.indexer.TaskStatusPlus;
 import org.apache.druid.java.util.common.ISE;
 import org.apache.druid.java.util.common.StringUtils;
@@ -62,6 +61,7 @@ import org.apache.druid.server.security.Action;
 import org.apache.druid.server.security.AuthenticationResult;
 import org.apache.druid.server.security.AuthorizationUtils;
 import org.apache.druid.server.security.AuthorizerMapper;
+import org.apache.druid.server.security.ForbiddenException;
 import org.apache.druid.server.security.Resource;
 import org.apache.druid.server.security.ResourceAction;
 import org.apache.druid.server.security.ResourceType;
@@ -158,8 +158,8 @@ public class SystemSchema extends AbstractSchema
       final DruidSchema druidSchema,
       final TimelineServerView serverView,
       final AuthorizerMapper authorizerMapper,
-      final @Coordinator DruidLeaderClient coordinatorDruidLeaderClient,
-      final @IndexingService DruidLeaderClient overlordDruidLeaderClient,
+      final @Coordinator LeaderClient coordinatorDruidLeaderClient,
+      final @IndexingService LeaderClient overlordDruidLeaderClient,
       final ObjectMapper jsonMapper
   )
   {
@@ -182,14 +182,14 @@ public class SystemSchema extends AbstractSchema
   static class SegmentsTable extends AbstractTable implements ScannableTable
   {
     private final DruidSchema druidSchema;
-    private final DruidLeaderClient druidLeaderClient;
+    private final LeaderClient druidLeaderClient;
     private final ObjectMapper jsonMapper;
     private final BytesAccumulatingResponseHandler responseHandler;
     private final AuthorizerMapper authorizerMapper;
 
     public SegmentsTable(
         DruidSchema druidSchemna,
-        DruidLeaderClient druidLeaderClient,
+        LeaderClient druidLeaderClient,
         ObjectMapper jsonMapper,
         BytesAccumulatingResponseHandler responseHandler,
         AuthorizerMapper authorizerMapper
@@ -343,7 +343,7 @@ public class SystemSchema extends AbstractSchema
 
   // Note that coordinator must be up to get segments
   private static JsonParserIterator<DataSegment> getMetadataSegments(
-      DruidLeaderClient coordinatorClient,
+      LeaderClient coordinatorClient,
       ObjectMapper jsonMapper,
       BytesAccumulatingResponseHandler responseHandler
   )
@@ -424,7 +424,7 @@ public class SystemSchema extends AbstractSchema
           authorizerMapper
       );
       if (!access.isAllowed()) {
-        return Linq4j.asEnumerable(ImmutableList.of());
+        throw new ForbiddenException("Insufficient permission to view servers :" + access.toString());
       }
       final FluentIterable<Object[]> results = FluentIterable
           .from(druidServers)
@@ -486,13 +486,13 @@ public class SystemSchema extends AbstractSchema
 
   static class TasksTable extends AbstractTable implements ScannableTable
   {
-    private final DruidLeaderClient druidLeaderClient;
+    private final LeaderClient druidLeaderClient;
     private final ObjectMapper jsonMapper;
     private final BytesAccumulatingResponseHandler responseHandler;
     private final AuthorizerMapper authorizerMapper;
 
     public TasksTable(
-        DruidLeaderClient druidLeaderClient,
+        LeaderClient druidLeaderClient,
         ObjectMapper jsonMapper,
         BytesAccumulatingResponseHandler responseHandler,
         AuthorizerMapper authorizerMapper
@@ -609,7 +609,7 @@ public class SystemSchema extends AbstractSchema
 
   //Note that overlord must be up to get tasks
   private static JsonParserIterator<TaskStatusPlus> getTasks(
-      DruidLeaderClient indexingServiceClient,
+      LeaderClient indexingServiceClient,
       ObjectMapper jsonMapper,
       BytesAccumulatingResponseHandler responseHandler
   )