Do not retry INSERT task into metadata if max_allowed_packet limit is violated (#14271)

Changes
- Add a `DruidException` which contains a user-facing error message, HTTP response code
- Make `EntryExistsException` extend `DruidException`
- If metadata store max_allowed_packet limit is violated while inserting a new task, throw
`DruidException` with response code 400 (bad request) to prevent retries
- Add `SQLMetadataConnector.isRootCausePacketTooBigException` with impl for MySQL

extensions-core/kinesis-indexing-service/src/test/java/org/apache/druid/indexing/kinesis/supervisor/KinesisSupervisorTest.java

@@ -3465,7 +3465,7 @@ public class KinesisSupervisorTest extends EasyMockSupport
   }
 
   @Test
-  public void testSuspendedNoRunningTasks() throws Exception
+  public void testSuspendedNoRunningTasks()
   {
     supervisor = getTestableSupervisor(1, 1, true, "PT1H", null, null, true);
 

extensions-core/mysql-metadata-storage/src/main/java/org/apache/druid/metadata/storage/mysql/MySQLConnector.java

@@ -46,7 +46,12 @@ public class MySQLConnector extends SQLMetadataConnector
   private static final String SERIAL_TYPE = "BIGINT(20) AUTO_INCREMENT";
   private static final String QUOTE_STRING = "`";
   private static final String COLLATION = "CHARACTER SET utf8mb4 COLLATE utf8mb4_bin";
-  private static final String MYSQL_TRANSIENT_EXCEPTION_CLASS_NAME = "com.mysql.jdbc.exceptions.MySQLTransientException";
+  private static final String MYSQL_TRANSIENT_EXCEPTION_CLASS_NAME
+      = "com.mysql.jdbc.exceptions.MySQLTransientException";
+  private static final String MARIA_DB_PACKET_EXCEPTION_CLASS_NAME
+      = "org.mariadb.jdbc.internal.util.exceptions.MaxAllowedPacketException";
+  private static final String MYSQL_PACKET_EXCEPTION_CLASS_NAME
+      = "com.mysql.jdbc.PacketTooBigException";
 
   @Nullable
   private final Class<?> myTransientExceptionClass;
@@ -218,6 +223,19 @@ public class MySQLConnector extends SQLMetadataConnector
     return false;
   }
 
+  @Override
+  protected boolean isRootCausePacketTooBigException(Throwable t)
+  {
+    if (t == null) {
+      return false;
+    }
+
+    final String className = t.getClass().getName();
+    return MARIA_DB_PACKET_EXCEPTION_CLASS_NAME.equals(className)
+           || MYSQL_PACKET_EXCEPTION_CLASS_NAME.equals(className)
+           || isRootCausePacketTooBigException(t.getCause());
+  }
+
   @Override
   public Void insertOrUpdate(
       final String tableName,

extensions-core/mysql-metadata-storage/src/test/java/org/apache/druid/metadata/storage/mysql/MySQLConnectorTest.java

@@ -29,6 +29,7 @@ import org.junit.Test;
 
 import java.sql.SQLException;
 import java.sql.SQLTransientConnectionException;
+import java.sql.SQLTransientException;
 
 public class MySQLConnectorTest
 {
@@ -59,10 +60,10 @@ public class MySQLConnectorTest
     Assert.assertTrue(connector.connectorIsTransientException(new MySQLTransientException()));
     Assert.assertTrue(connector.connectorIsTransientException(new MySQLTransactionRollbackException()));
     Assert.assertTrue(
-        connector.connectorIsTransientException(new SQLException("some transient failure", "wtf", 1317))
+        connector.connectorIsTransientException(new SQLException("some transient failure", "s0", 1317))
     );
     Assert.assertFalse(
-        connector.connectorIsTransientException(new SQLException("totally realistic test data", "wtf", 1337))
+        connector.connectorIsTransientException(new SQLException("totally realistic test data", "s0", 1337))
     );
     // this method does not specially handle normal transient exceptions either, since it is not vendor specific
     Assert.assertFalse(
@@ -82,16 +83,43 @@ public class MySQLConnectorTest
     // no vendor specific for MariaDb, so should always be false
     Assert.assertFalse(connector.connectorIsTransientException(new MySQLTransientException()));
     Assert.assertFalse(
-        connector.connectorIsTransientException(new SQLException("some transient failure", "wtf", 1317))
+        connector.connectorIsTransientException(new SQLException("some transient failure", "s0", 1317))
     );
     Assert.assertFalse(
-        connector.connectorIsTransientException(new SQLException("totally realistic test data", "wtf", 1337))
+        connector.connectorIsTransientException(new SQLException("totally realistic test data", "s0", 1337))
     );
     Assert.assertFalse(
         connector.connectorIsTransientException(new SQLTransientConnectionException("transient"))
     );
   }
 
+  @Test
+  public void testIsRootCausePacketTooBigException()
+  {
+    MySQLConnector connector = new MySQLConnector(
+        CONNECTOR_CONFIG_SUPPLIER,
+        TABLES_CONFIG_SUPPLIER,
+        new MySQLConnectorSslConfig(),
+        MYSQL_DRIVER_CONFIG
+    );
+
+    // The test method should return true only for
+    // mariadb.MaxAllowedPacketException or mysql.PacketTooBigException.
+    // Verifying this requires creating a mock Class object, but Class is final
+    // and has only a private constructor. It would be overkill to try to mock it.
+
+    // Verify some of the false cases
+    Assert.assertFalse(
+        connector.isRootCausePacketTooBigException(new SQLException())
+    );
+    Assert.assertFalse(
+        connector.isRootCausePacketTooBigException(new SQLTransientException())
+    );
+    Assert.assertFalse(
+        connector.isRootCausePacketTooBigException(new MySQLTransientException())
+    );
+  }
+
   @Test
   public void testLimitClause()
   {

indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexPhaseRunner.java

@@ -242,7 +242,7 @@ public abstract class ParallelIndexPhaseRunner<SubTaskType extends Task, SubTask
       SubTaskSpec<SubTaskType> spec
   )
   {
-    LOG.info("Submit a new task for spec[%s]", spec.getId());
+    LOG.info("Submitting a new task for spec[%s]", spec.getId());
     final ListenableFuture<SubTaskCompleteEvent<SubTaskType>> future = taskMonitor.submit(spec);
     Futures.addCallback(
         future,

indexing-service/src/main/java/org/apache/druid/indexing/overlord/HeapMemoryTaskStorage.java

@@ -90,7 +90,7 @@ public class HeapMemoryTaskStorage implements TaskStorage
     TaskStuff newTaskStuff = new TaskStuff(task, status, DateTimes.nowUtc(), task.getDataSource());
     TaskStuff alreadyExisted = tasks.putIfAbsent(task.getId(), newTaskStuff);
     if (alreadyExisted != null) {
-      throw new EntryExistsException(task.getId());
+      throw new EntryExistsException("Task", task.getId());
     }
 
     log.info("Inserted task %s with status: %s", task.getId(), status);

indexing-service/src/main/java/org/apache/druid/indexing/overlord/MetadataTaskStorage.java

@@ -20,13 +20,13 @@
 package org.apache.druid.indexing.overlord;
 
 import com.fasterxml.jackson.core.type.TypeReference;
-import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import com.google.inject.Inject;
+import org.apache.druid.common.exception.DruidException;
 import org.apache.druid.indexer.TaskInfo;
 import org.apache.druid.indexer.TaskStatus;
 import org.apache.druid.indexer.TaskStatusPlus;
@@ -139,7 +139,7 @@ public class MetadataTaskStorage implements TaskStorage
         status.getId()
     );
 
-    log.info("Inserting task %s with status: %s", task.getId(), status);
+    log.info("Inserting task [%s] with status [%s].", task.getId(), status);
 
     try {
       handler.insert(
@@ -153,12 +153,11 @@ public class MetadataTaskStorage implements TaskStorage
           task.getGroupId()
       );
     }
+    catch (DruidException e) {
+      throw e;
+    }
     catch (Exception e) {
-      if (e instanceof EntryExistsException) {
+      throw new RuntimeException(e);
-        throw (EntryExistsException) e;
-      } else {
-        throw new RuntimeException(e);
-      }
     }
   }
 
@@ -167,15 +166,12 @@ public class MetadataTaskStorage implements TaskStorage
   {
     Preconditions.checkNotNull(status, "status");
 
-    log.info("Updating task %s to status: %s", status.getId(), status);
+    final String taskId = status.getId();
+    log.info("Updating status of task [%s] to [%s].", taskId, status);
 
-    final boolean set = handler.setStatus(
+    final boolean set = handler.setStatus(taskId, status.isRunnable(), status);
-        status.getId(),
-        status.isRunnable(),
-        status
-    );
     if (!set) {
-      throw new ISE("Active task not found: %s", status.getId());
+      throw new ISE("No active task for id [%s]", taskId);
     }
   }
 
@@ -279,10 +275,8 @@ public class MetadataTaskStorage implements TaskStorage
     Preconditions.checkNotNull(taskLock, "taskLock");
 
     log.info(
-        "Adding lock on interval[%s] version[%s] for task: %s",
+        "Adding lock on interval[%s] version[%s] for task [%s].",
-        taskLock.getInterval(),
+        taskLock.getInterval(), taskLock.getVersion(), taskid
-        taskLock.getVersion(),
-        taskid
     );
 
     handler.addLock(taskid, taskLock);
@@ -296,15 +290,13 @@ public class MetadataTaskStorage implements TaskStorage
     Preconditions.checkNotNull(newLock, "newLock");
 
     log.info(
-        "Replacing an existing lock[%s] with a new lock[%s] for task: %s",
+        "Replacing an existing lock[%s] with a new lock[%s] for task [%s].",
-        oldLock,
+        oldLock, newLock, taskid
-        newLock,
-        taskid
     );
 
     final Long oldLockId = handler.getLockId(taskid, oldLock);
     if (oldLockId == null) {
-      throw new ISE("Cannot find an existing lock[%s]", oldLock);
+      throw new ISE("Cannot find lock[%s] for task [%s]", oldLock, taskid);
     }
 
     handler.replaceLock(taskid, oldLockId, newLock);
@@ -336,14 +328,8 @@ public class MetadataTaskStorage implements TaskStorage
   {
     return ImmutableList.copyOf(
         Iterables.transform(
-            getLocksWithIds(taskid).entrySet(), new Function<Map.Entry<Long, TaskLock>, TaskLock>()
+            getLocksWithIds(taskid).entrySet(),
-            {
+            Entry::getValue
-              @Override
-              public TaskLock apply(Map.Entry<Long, TaskLock> e)
-              {
-                return e.getValue();
-              }
-            }
         )
     );
   }

indexing-service/src/main/java/org/apache/druid/indexing/overlord/TaskQueue.java

@@ -482,7 +482,7 @@ public class TaskQueue
     IdUtils.validateId("Task ID", task.getId());
 
     if (taskStorage.getTask(task.getId()).isPresent()) {
-      throw new EntryExistsException(StringUtils.format("Task %s already exists", task.getId()));
+      throw new EntryExistsException("Task", task.getId());
     }
 
     // Set forceTimeChunkLock before adding task spec to taskStorage, so that we can see always consistent task spec.

indexing-service/src/main/java/org/apache/druid/indexing/overlord/http/OverlordResource.java

@@ -36,6 +36,7 @@ import org.apache.druid.client.indexing.IndexingWorker;
 import org.apache.druid.client.indexing.IndexingWorkerInfo;
 import org.apache.druid.common.config.ConfigManager.SetResult;
 import org.apache.druid.common.config.JacksonConfigManager;
+import org.apache.druid.common.exception.DruidException;
 import org.apache.druid.indexer.RunnerTaskState;
 import org.apache.druid.indexer.TaskInfo;
 import org.apache.druid.indexer.TaskLocation;
@@ -64,7 +65,6 @@ import org.apache.druid.java.util.common.Intervals;
 import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.java.util.common.UOE;
 import org.apache.druid.java.util.common.logger.Logger;
-import org.apache.druid.metadata.EntryExistsException;
 import org.apache.druid.metadata.TaskLookup;
 import org.apache.druid.metadata.TaskLookup.ActiveTaskLookup;
 import org.apache.druid.metadata.TaskLookup.CompleteTaskLookup;
@@ -222,25 +222,15 @@ public class OverlordResource
 
     return asLeaderWith(
         taskMaster.getTaskQueue(),
-        new Function<TaskQueue, Response>()
+        taskQueue -> {
-        {
+          try {
-          @Override
+            taskQueue.add(task);
-          public Response apply(TaskQueue taskQueue)
+            return Response.ok(ImmutableMap.of("task", task.getId())).build();
-          {
+          }
-            try {
+          catch (DruidException e) {
-              taskQueue.add(task);
+            return Response.status(e.getResponseCode())
-              return Response.ok(ImmutableMap.of("task", task.getId())).build();
+                           .entity(ImmutableMap.of("error", e.getMessage()))
-            }
+                           .build();
-            catch (EntryExistsException e) {
-              return Response.status(Response.Status.BAD_REQUEST)
-                             .entity(
-                                 ImmutableMap.of(
-                                     "error",
-                                     StringUtils.format("Task[%s] already exists!", task.getId())
-                                 )
-                             )
-                             .build();
-            }
           }
         }
     );

indexing-service/src/test/java/org/apache/druid/indexing/overlord/TaskLockboxTest.java

@@ -149,7 +149,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testLock() throws Exception
+  public void testLock()
   {
     validator.expectLockCreated(
         TaskLockType.EXCLUSIVE,
@@ -176,7 +176,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testTrySharedLock() throws Exception
+  public void testTrySharedLock()
   {
     final Interval interval = Intervals.of("2017-01/2017-02");
 
@@ -427,7 +427,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testSyncWithUnknownTaskTypesFromModuleNotLoaded() throws Exception
+  public void testSyncWithUnknownTaskTypesFromModuleNotLoaded()
   {
     // ensure that if we don't know how to deserialize a task it won't explode the lockbox
     // (or anything else that uses taskStorage.getActiveTasks() and doesn't expect null which is most things)
@@ -1201,7 +1201,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testGetLockedIntervalsForLowPriorityTask() throws Exception
+  public void testGetLockedIntervalsForLowPriorityTask()
   {
     // Acquire lock for a low priority task
     final Task lowPriorityTask = NoopTask.create(5);
@@ -1221,7 +1221,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testGetLockedIntervalsForEqualPriorityTask() throws Exception
+  public void testGetLockedIntervalsForEqualPriorityTask()
   {
     // Acquire lock for a low priority task
     final Task task = NoopTask.create(5);
@@ -1245,7 +1245,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testExclusiveLockCompatibility() throws Exception
+  public void testExclusiveLockCompatibility()
   {
     final TaskLock theLock = validator.expectLockCreated(
         TaskLockType.EXCLUSIVE,
@@ -1282,7 +1282,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testExclusiveLockCanRevokeAllIncompatible() throws Exception
+  public void testExclusiveLockCanRevokeAllIncompatible()
   {
     final TaskLockboxValidator validator = new TaskLockboxValidator(lockbox, taskStorage);
 
@@ -1325,7 +1325,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testSharedLockCompatibility() throws Exception
+  public void testSharedLockCompatibility()
   {
     final TaskLock theLock = validator.expectLockCreated(
         TaskLockType.SHARED,
@@ -1374,7 +1374,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testSharedLockCanRevokeAllIncompatible() throws Exception
+  public void testSharedLockCanRevokeAllIncompatible()
   {
     final TaskLock exclusiveLock = validator.expectLockCreated(
         TaskLockType.EXCLUSIVE,
@@ -1415,7 +1415,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testAppendLockCompatibility() throws Exception
+  public void testAppendLockCompatibility()
   {
     final TaskLock theLock = validator.expectLockCreated(
         TaskLockType.APPEND,
@@ -1473,7 +1473,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testAppendLockCanRevokeAllIncompatible() throws Exception
+  public void testAppendLockCanRevokeAllIncompatible()
   {
     final TaskLock sharedLock = validator.expectLockCreated(
         TaskLockType.SHARED,
@@ -1521,7 +1521,7 @@ public class TaskLockboxTest
 
 
   @Test
-  public void testReplaceLockCompatibility() throws Exception
+  public void testReplaceLockCompatibility()
   {
     final TaskLock theLock = validator.expectLockCreated(
         TaskLockType.REPLACE,
@@ -1566,7 +1566,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testReplaceLockCanRevokeAllIncompatible() throws Exception
+  public void testReplaceLockCanRevokeAllIncompatible()
   {
     final TaskLock appendLock0 = validator.expectLockCreated(
         TaskLockType.APPEND,
@@ -1619,7 +1619,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testGetLockedIntervalsForRevokedLocks() throws Exception
+  public void testGetLockedIntervalsForRevokedLocks()
   {
     // Acquire lock for a low priority task
     final Task lowPriorityTask = NoopTask.create(5);
@@ -1663,7 +1663,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testFailedToReacquireTaskLock() throws Exception
+  public void testFailedToReacquireTaskLock()
   {
     // Tasks to be failed have a group id with the substring "FailingLockAcquisition"
     // Please refer to NullLockPosseTaskLockbox
@@ -1704,7 +1704,7 @@ public class TaskLockboxTest
   }
 
   @Test
-  public void testConflictsWithOverlappingSharedLocks() throws Exception
+  public void testConflictsWithOverlappingSharedLocks()
   {
     TaskLock conflictingLock = validator.expectLockCreated(
         TaskLockType.SHARED,
@@ -1744,7 +1744,7 @@ public class TaskLockboxTest
       this.taskStorage = taskStorage;
     }
 
-    public TaskLock expectLockCreated(TaskLockType type, Interval interval, int priority) throws Exception
+    public TaskLock expectLockCreated(TaskLockType type, Interval interval, int priority)
     {
       final TaskLock lock = tryTaskLock(type, interval, priority);
       Assert.assertNotNull(lock);
@@ -1757,7 +1757,7 @@ public class TaskLockboxTest
       lockbox.revokeLock(lockToTaskIdMap.get(lock), lock);
     }
 
-    public void expectLockNotGranted(TaskLockType type, Interval interval, int priority) throws Exception
+    public void expectLockNotGranted(TaskLockType type, Interval interval, int priority)
     {
       final TaskLock lock = tryTaskLock(type, interval, priority);
       Assert.assertNull(lock);
@@ -1785,7 +1785,7 @@ public class TaskLockboxTest
       }
     }
 
-    private TaskLock tryTaskLock(TaskLockType type, Interval interval, int priority) throws Exception
+    private TaskLock tryTaskLock(TaskLockType type, Interval interval, int priority)
     {
       final Task task = NoopTask.create(priority);
       tasks.add(task);

indexing-service/src/test/java/org/apache/druid/indexing/seekablestream/supervisor/SeekableStreamSupervisorStateTest.java

@@ -139,7 +139,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
     taskClientFactory = createMock(SeekableStreamIndexTaskClientFactory.class);
     spec = createMock(SeekableStreamSupervisorSpec.class);
     indexTaskClient = createMock(SeekableStreamIndexTaskClient.class);
-    recordSupplier = (RecordSupplier<String, String, ByteEntity>) createMock(RecordSupplier.class);
+    recordSupplier = createMock(RecordSupplier.class);
 
     rowIngestionMetersFactory = new TestUtils().getRowIngestionMetersFactory();
 
@@ -175,7 +175,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testRunning() throws Exception
+  public void testRunning()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();
@@ -214,7 +214,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testRunningStreamGetSequenceNumberReturnsNull() throws Exception
+  public void testRunningStreamGetSequenceNumberReturnsNull()
   {
     EasyMock.reset(recordSupplier);
     EasyMock.expect(recordSupplier.getAssignment()).andReturn(ImmutableSet.of(SHARD0_PARTITION)).anyTimes();
@@ -266,7 +266,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testConnectingToStreamFail() throws Exception
+  public void testConnectingToStreamFail()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM))
@@ -321,7 +321,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testConnectingToStreamFailRecoveryFailRecovery() throws Exception
+  public void testConnectingToStreamFailRecoveryFailRecovery()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM))
@@ -395,7 +395,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testDiscoveringInitialTasksFailRecoveryFail() throws Exception
+  public void testDiscoveringInitialTasksFailRecoveryFail()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();
@@ -560,7 +560,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testCreatingTasksFailRecoveryFail() throws Exception
+  public void testCreatingTasksFailRecoveryFail()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();
@@ -638,7 +638,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testSuspended() throws Exception
+  public void testSuspended()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(true).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();
@@ -677,7 +677,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testStopping() throws Exception
+  public void testStopping()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();
@@ -718,7 +718,7 @@ public class SeekableStreamSupervisorStateTest extends EasyMockSupport
   }
 
   @Test
-  public void testStoppingGracefully() throws Exception
+  public void testStoppingGracefully()
   {
     EasyMock.expect(spec.isSuspended()).andReturn(false).anyTimes();
     EasyMock.expect(recordSupplier.getPartitionIds(STREAM)).andReturn(ImmutableSet.of(SHARD_ID)).anyTimes();

processing/src/main/java/org/apache/druid/common/exception/DruidException.java

@@ -0,0 +1,53 @@
+/*
+ * 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.common.exception;
+
+/**
+ * A generic exception thrown by Druid.
+ */
+public class DruidException extends RuntimeException
+{
+  public static final int HTTP_CODE_SERVER_ERROR = 500;
+  public static final int HTTP_CODE_BAD_REQUEST = 400;
+
+  private final int responseCode;
+  private final boolean isTransient;
+
+  public DruidException(String message, int responseCode, Throwable cause, boolean isTransient)
+  {
+    super(message, cause);
+    this.responseCode = responseCode;
+    this.isTransient = isTransient;
+  }
+
+  public int getResponseCode()
+  {
+    return responseCode;
+  }
+
+  /**
+   * Returns true if this is a transient exception and might go away if the
+   * operation is retried.
+   */
+  public boolean isTransient()
+  {
+    return isTransient;
+  }
+}

processing/src/main/java/org/apache/druid/metadata/EntryExistsException.java

@@ -19,19 +19,26 @@
 
 package org.apache.druid.metadata;
 
+import org.apache.druid.common.exception.DruidException;
 import org.apache.druid.java.util.common.StringUtils;
 
-public class EntryExistsException extends Exception
+/**
+ * A non-transient Druid metadata exception thrown when trying to insert a
+ * duplicate entry in the metadata.
+ */
+public class EntryExistsException extends DruidException
 {
 
-  public EntryExistsException(String entryId, Throwable t)
+  private static final int HTTP_BAD_REQUEST = 400;
+
+  public EntryExistsException(String entryType, String entryId)
   {
-    super(StringUtils.format("Entry already exists: %s", entryId), t);
+    this(entryType, entryId, null);
   }
 
-  public EntryExistsException(String entryId)
+  public EntryExistsException(String entryType, String entryId, Throwable t)
   {
-    this(entryId, null);
+    super(StringUtils.format("%s [%s] already exists.", entryType, entryId), HTTP_BAD_REQUEST, t, false);
   }
 
 }

processing/src/main/java/org/apache/druid/metadata/MetadataStorageConnectorConfig.java

@@ -56,7 +56,7 @@ public class MetadataStorageConnectorConfig
       String connectUri,
       String user,
       String password,
-      Map<String, Object> properties
+      Map<String, String> properties
   )
   {
     MetadataStorageConnectorConfig config = new MetadataStorageConnectorConfig();

processing/src/test/java/org/apache/druid/common/exception/DruidExceptionTest.java

@@ -0,0 +1,40 @@
+/*
+ * 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.common.exception;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class DruidExceptionTest
+{
+  @Test
+  public void testExceptionMessageAndResponseCode()
+  {
+    DruidException exception = Assert.assertThrows(
+        DruidException.class,
+        () -> {
+          throw new DruidException("an error has occurred", 401, null, true);
+        }
+    );
+    Assert.assertEquals("an error has occurred", exception.getMessage());
+    Assert.assertEquals(401, exception.getResponseCode());
+    Assert.assertTrue(exception.isTransient());
+  }
+}

processing/src/test/java/org/apache/druid/metadata/EntryExistsExceptionTest.java

@@ -0,0 +1,40 @@
+/*
+ * 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.metadata;
+
+import org.apache.druid.common.exception.DruidException;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class EntryExistsExceptionTest
+{
+  @Test
+  public void testExceptionMessageAndResponseCode()
+  {
+    EntryExistsException exception = Assert.assertThrows(
+        EntryExistsException.class,
+        () -> {
+          throw new EntryExistsException("task", "100");
+        }
+    );
+    Assert.assertEquals("task [100] already exists.", exception.getMessage());
+    Assert.assertEquals(DruidException.HTTP_CODE_BAD_REQUEST, exception.getResponseCode());
+  }
+}

processing/src/test/java/org/apache/druid/metadata/MetadataStorageConnectorConfigTest.java

@@ -77,8 +77,8 @@ public class MetadataStorageConnectorConfigTest
         "user",
         "\"nothing\""
     );
-    Assert.assertTrue(metadataStorageConnectorConfig.equals(metadataStorageConnectorConfig2));
+    Assert.assertEquals(metadataStorageConnectorConfig, metadataStorageConnectorConfig2);
-    Assert.assertTrue(metadataStorageConnectorConfig.hashCode() == metadataStorageConnectorConfig2.hashCode());
+    Assert.assertEquals(metadataStorageConnectorConfig.hashCode(), metadataStorageConnectorConfig2.hashCode());
   }
 
   private static final ObjectMapper JSON_MAPPER = new ObjectMapper();
@@ -193,12 +193,9 @@ public class MetadataStorageConnectorConfigTest
   @Test
   public void testCreate()
   {
-    Map<String, Object> props = ImmutableMap.of("key", "value");
+    Map<String, String> props = ImmutableMap.of("key", "value");
-    MetadataStorageConnectorConfig config = MetadataStorageConnectorConfig.create(
+    MetadataStorageConnectorConfig config =
-        "connectURI",
+        MetadataStorageConnectorConfig.create("connectURI", "user", "pwd", props);
-        "user",
-        "pwd",
-        props);
     Assert.assertEquals("connectURI", config.getConnectURI());
     Assert.assertEquals("user", config.getUser());
     Assert.assertEquals("pwd", config.getPassword());

server/src/main/java/org/apache/druid/metadata/SQLMetadataConnector.java

@@ -169,7 +169,7 @@ public abstract class SQLMetadataConnector implements MetadataStorageConnector
                          || e instanceof SQLTransientException
                          || e instanceof SQLRecoverableException
                          || e instanceof UnableToObtainConnectionException
-                         || e instanceof UnableToExecuteStatementException
+                         || (e instanceof UnableToExecuteStatementException && isTransientException(e.getCause()))
                          || connectorIsTransientException(e)
                          || (e instanceof SQLException && isTransientException(e.getCause()))
                          || (e instanceof DBIException && isTransientException(e.getCause())));
@@ -183,6 +183,17 @@ public abstract class SQLMetadataConnector implements MetadataStorageConnector
     return false;
   }
 
+  /**
+   * Checks if the root cause of the given exception is a PacketTooBigException.
+   *
+   * @return false by default. Specific implementations should override this method
+   * to correctly classify their packet exceptions.
+   */
+  protected boolean isRootCausePacketTooBigException(Throwable t)
+  {
+    return false;
+  }
+
   public void createTable(final String tableName, final Iterable<String> sql)
   {
     try {
@@ -336,12 +347,7 @@ public abstract class SQLMetadataConnector implements MetadataStorageConnector
   {
     try {
       DatabaseMetaData databaseMetaData = handle.getConnection().getMetaData();
-      ResultSet columns = databaseMetaData.getColumns(
+      ResultSet columns = databaseMetaData.getColumns(null, null, table, column);
-          null,
-          null,
-          table,
-          column
-      );
       return columns.next();
     }
     catch (SQLException e) {

server/src/main/java/org/apache/druid/metadata/SQLMetadataStorageActionHandler.java

@@ -28,6 +28,7 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Optional;
 import com.google.common.base.Throwables;
 import com.google.common.collect.Maps;
+import org.apache.druid.common.exception.DruidException;
 import org.apache.druid.indexer.TaskIdentifier;
 import org.apache.druid.indexer.TaskInfo;
 import org.apache.druid.java.util.common.DateTimes;
@@ -165,34 +166,61 @@ public abstract class SQLMetadataStorageActionHandler<EntryType, StatusType, Log
   {
     try {
       getConnector().retryWithHandle(
-          (HandleCallback<Void>) handle -> {
+          handle -> insertEntryWithHandle(handle, id, timestamp, dataSource, entry, active, status, type, groupId),
-            final String sql = StringUtils.format(
+          this::isTransientDruidException
-                "INSERT INTO %s (id, created_date, datasource, payload, type, group_id, active, status_payload) "
-                + "VALUES (:id, :created_date, :datasource, :payload, :type, :group_id, :active, :status_payload)",
-                getEntryTable()
-            );
-            handle.createStatement(sql)
-                  .bind("id", id)
-                  .bind("created_date", timestamp.toString())
-                  .bind("datasource", dataSource)
-                  .bind("payload", jsonMapper.writeValueAsBytes(entry))
-                  .bind("type", type)
-                  .bind("group_id", groupId)
-                  .bind("active", active)
-                  .bind("status_payload", jsonMapper.writeValueAsBytes(status))
-                  .execute();
-            return null;
-          },
-          e -> getConnector().isTransientException(e) && !(isStatementException(e) && getEntry(id).isPresent())
       );
     }
+    catch (CallbackFailedException e) {
+      propagateAsRuntimeException(e.getCause());
+    }
     catch (Exception e) {
-      if (isStatementException(e) && getEntry(id).isPresent()) {
+      propagateAsRuntimeException(e);
-        throw new EntryExistsException(id, e);
+    }
-      } else {
+  }
-        Throwables.propagateIfPossible(e);
+
-        throw new RuntimeException(e);
+  private void propagateAsRuntimeException(Throwable t)
-      }
+  {
+    Throwables.propagateIfPossible(t);
+    throw new RuntimeException(t);
+  }
+
+  /**
+   * Inserts the given entry into the metadata store. This method wraps any
+   * exception thrown in a {@link DruidException}. When used in a HandleCallback,
+   * that exception is further wrapped in a {@link CallbackFailedException}.
+   */
+  private Void insertEntryWithHandle(
+      Handle handle,
+      String entryId,
+      DateTime timestamp,
+      String dataSource,
+      EntryType entry,
+      boolean active,
+      StatusType status,
+      String type,
+      String groupId
+  )
+  {
+    try {
+      final String sql = StringUtils.format(
+          "INSERT INTO %s (id, created_date, datasource, payload, type, group_id, active, status_payload) "
+          + "VALUES (:id, :created_date, :datasource, :payload, :type, :group_id, :active, :status_payload)",
+          getEntryTable()
+      );
+      handle.createStatement(sql)
+            .bind("id", entryId)
+            .bind("created_date", timestamp.toString())
+            .bind("datasource", dataSource)
+            .bind("payload", jsonMapper.writeValueAsBytes(entry))
+            .bind("type", type)
+            .bind("group_id", groupId)
+            .bind("active", active)
+            .bind("status_payload", jsonMapper.writeValueAsBytes(status))
+            .execute();
+      return null;
+    }
+    catch (Throwable t) {
+      throw wrapInDruidException(entryId, t);
     }
   }
 
@@ -202,6 +230,17 @@ public abstract class SQLMetadataStorageActionHandler<EntryType, StatusType, Log
            (e instanceof CallbackFailedException && e.getCause() instanceof StatementException);
   }
 
+  private boolean isTransientDruidException(Throwable t)
+  {
+    if (t instanceof CallbackFailedException) {
+      return isTransientDruidException(t.getCause());
+    } else if (t instanceof DruidException) {
+      return ((DruidException) t).isTransient();
+    } else {
+      return getConnector().isTransientException(t);
+    }
+  }
+
   @Override
   public boolean setStatus(final String entryId, final boolean active, final StatusType status)
   {
@@ -304,10 +343,7 @@ public abstract class SQLMetadataStorageActionHandler<EntryType, StatusType, Log
             final Query<Map<String, Object>> query;
             switch (entry.getKey()) {
               case ACTIVE:
-                query = createActiveTaskStreamingQuery(
+                query = createActiveTaskStreamingQuery(handle, dataSource);
-                    handle,
-                    dataSource
-                );
                 tasks.addAll(query.map(taskInfoMapper).list());
                 break;
               case COMPLETE:
@@ -390,6 +426,35 @@ public abstract class SQLMetadataStorageActionHandler<EntryType, StatusType, Log
     );
   }
 
+  /**
+   * Wraps the given error in a user friendly DruidException.
+   */
+  private DruidException wrapInDruidException(String taskId, Throwable t)
+  {
+    if (isStatementException(t) && getEntry(taskId).isPresent()) {
+      return new EntryExistsException("Task", taskId);
+    } else if (connector.isRootCausePacketTooBigException(t)) {
+      return new DruidException(
+          StringUtils.format(
+              "Payload for task [%s] exceeds the packet limit."
+              + " Update the max_allowed_packet on your metadata store"
+              + " server or in the connection properties.",
+              taskId
+          ),
+          DruidException.HTTP_CODE_BAD_REQUEST,
+          t,
+          false
+      );
+    } else {
+      return new DruidException(
+          StringUtils.format("Encountered metadata exception for task [%s]", taskId),
+          DruidException.HTTP_CODE_SERVER_ERROR,
+          t,
+          connector.isTransientException(t)
+      );
+    }
+  }
+
   /**
    * Fetches the columns needed to build TaskStatusPlus for completed tasks
    * Please note that this requires completion of data migration to avoid empty values for task type and groupId

server/src/test/java/org/apache/druid/metadata/SQLMetadataConnectorTest.java

@@ -19,9 +19,9 @@
 
 package org.apache.druid.metadata;
 
-import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Supplier;
 import com.google.common.base.Suppliers;
+import com.google.common.collect.ImmutableMap;
 import org.apache.commons.dbcp2.BasicDataSource;
 import org.apache.druid.java.util.common.StringUtils;
 import org.junit.Assert;
@@ -30,14 +30,19 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.skife.jdbi.v2.DBI;
 import org.skife.jdbi.v2.Handle;
-import org.skife.jdbi.v2.tweak.HandleCallback;
+import org.skife.jdbi.v2.exceptions.CallbackFailedException;
+import org.skife.jdbi.v2.exceptions.UnableToExecuteStatementException;
+import org.skife.jdbi.v2.exceptions.UnableToObtainConnectionException;
 
-import java.sql.ResultSet;
 import java.sql.SQLException;
-import java.sql.Statement;
+import java.sql.SQLRecoverableException;
+import java.sql.SQLTransientConnectionException;
+import java.sql.SQLTransientException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 
 
 public class SQLMetadataConnectorTest
@@ -47,7 +52,6 @@ public class SQLMetadataConnectorTest
 
   private TestDerbyConnector connector;
   private MetadataStorageTablesConfig tablesConfig;
-  private static final ObjectMapper JSON_MAPPER = new ObjectMapper();
 
   @Before
   public void setUp()
@@ -78,28 +82,23 @@ public class SQLMetadataConnectorTest
     connector.createSupervisorsTable();
 
     connector.getDBI().withHandle(
-        new HandleCallback<Void>()
+        handle -> {
-        {
+          for (String table : tables) {
-          @Override
+            Assert.assertTrue(
-          public Void withHandle(Handle handle)
+                StringUtils.format("table %s was not created!", table),
-          {
+                connector.tableExists(handle, table)
-            for (String table : tables) {
+            );
-              Assert.assertTrue(
-                  StringUtils.format("table %s was not created!", table),
-                  connector.tableExists(handle, table)
-              );
-            }
-
-            String taskTable = tablesConfig.getTasksTable();
-            for (String column : Arrays.asList("type", "group_id")) {
-              Assert.assertTrue(
-                  StringUtils.format("Tasks table column %s was not created!", column),
-                  connector.tableContainsColumn(handle, taskTable, column)
-              );
-            }
-
-            return null;
           }
+
+          String taskTable = tablesConfig.getTasksTable();
+          for (String column : Arrays.asList("type", "group_id")) {
+            Assert.assertTrue(
+                StringUtils.format("Tasks table column %s was not created!", column),
+                connector.tableContainsColumn(handle, taskTable, column)
+            );
+          }
+
+          return null;
         }
     );
 
@@ -147,16 +146,8 @@ public class SQLMetadataConnectorTest
   private void dropTable(final String tableName)
   {
     connector.getDBI().withHandle(
-        new HandleCallback<Void>()
+        handle -> handle.createStatement(StringUtils.format("DROP TABLE %s", tableName))
-        {
+                        .execute()
-          @Override
-          public Void withHandle(Handle handle)
-          {
-            handle.createStatement(StringUtils.format("DROP TABLE %s", tableName))
-                  .execute();
-            return null;
-          }
-        }
     );
   }
 
@@ -213,79 +204,74 @@ public class SQLMetadataConnectorTest
     }
   }
 
-  private MetadataStorageConnectorConfig getDbcpPropertiesFile(
-      boolean createTables,
-      String host,
-      int port,
-      String connectURI,
-      String user,
-      String pwdString,
-      String pwd
-  ) throws Exception
-  {
-    return JSON_MAPPER.readValue(
-        "{" +
-        "\"createTables\": \"" + createTables + "\"," +
-        "\"host\": \"" + host + "\"," +
-        "\"port\": \"" + port + "\"," +
-        "\"connectURI\": \"" + connectURI + "\"," +
-        "\"user\": \"" + user + "\"," +
-        "\"password\": " + pwdString + "," +
-        "\"dbcp\": {\n" +
-        "  \"maxConnLifetimeMillis\" : 1200000,\n" +
-        "  \"defaultQueryTimeout\" : \"30000\"\n" +
-        "}" +
-        "}",
-        MetadataStorageConnectorConfig.class
-    );
-  }
-
   @Test
-  public void testBasicDataSourceCreation() throws Exception
+  public void testBasicDataSourceCreation()
   {
-    MetadataStorageConnectorConfig config = getDbcpPropertiesFile(
+    Map<String, String> props = ImmutableMap.of(
-        true,
+        "maxConnLifetimeMillis", "1200000",
-        "host",
+        "defaultQueryTimeout", "30000"
-        1234,
-        "connectURI",
-        "user",
-        "{\"type\":\"default\",\"password\":\"nothing\"}",
-        "nothing"
     );
+    MetadataStorageConnectorConfig config =
+        MetadataStorageConnectorConfig.create("connectURI", "user", "password", props);
+
     TestSQLMetadataConnector testSQLMetadataConnector = new TestSQLMetadataConnector(
         Suppliers.ofInstance(config),
         Suppliers.ofInstance(tablesConfig)
     );
     BasicDataSource dataSource = testSQLMetadataConnector.getDatasource();
     Assert.assertEquals(dataSource.getMaxConnLifetimeMillis(), 1200000);
-    Assert.assertEquals((long) dataSource.getDefaultQueryTimeout(), 30000);
+    Assert.assertEquals(dataSource.getDefaultQueryTimeout().intValue(), 30000);
   }
 
-  private boolean verifyTaskTypeAndGroupId(String table, String id, String type, String groupId)
+  @Test
+  public void testIsTransientException()
   {
-    try {
+    MetadataStorageConnectorConfig config =
-      return connector.retryWithHandle(
+        MetadataStorageConnectorConfig.create("connectURI", "user", "password", Collections.emptyMap());
-          new HandleCallback<Boolean>()
+    TestSQLMetadataConnector metadataConnector = new TestSQLMetadataConnector(
-          {
+        Suppliers.ofInstance(config),
-            @Override
+        Suppliers.ofInstance(tablesConfig)
-            public Boolean withHandle(Handle handle) throws SQLException
+    );
-            {
+
-              Statement statement = handle.getConnection().createStatement();
+    // Transient exceptions
-              ResultSet resultSet = statement.executeQuery(
+    Assert.assertTrue(metadataConnector.isTransientException(new RetryTransactionException("")));
-                  StringUtils.format("SELECT * FROM %1$s WHERE id = '%2$s'", table, id)
+    Assert.assertTrue(metadataConnector.isTransientException(new SQLRecoverableException()));
-              );
+    Assert.assertTrue(metadataConnector.isTransientException(new SQLTransientException()));
-              resultSet.next();
+    Assert.assertTrue(metadataConnector.isTransientException(new SQLTransientConnectionException()));
-              boolean flag = type.equals(resultSet.getString("type"))
+
-                             && groupId.equals(resultSet.getString("group_id"));
+    // Non transient exceptions
-              statement.close();
+    Assert.assertFalse(metadataConnector.isTransientException(null));
-              return flag;
+    Assert.assertFalse(metadataConnector.isTransientException(new SQLException()));
-            }
+    Assert.assertFalse(metadataConnector.isTransientException(new UnableToExecuteStatementException("")));
-          }
+
-      );
+    // Nested transient exceptions
-    }
+    Assert.assertTrue(
-    catch (Exception e) {
+        metadataConnector.isTransientException(
-      e.printStackTrace();
+            new CallbackFailedException(new SQLTransientException())
-      return false;
+        )
-    }
+    );
+    Assert.assertTrue(
+        metadataConnector.isTransientException(
+            new UnableToObtainConnectionException(new SQLException())
+        )
+    );
+    Assert.assertTrue(
+        metadataConnector.isTransientException(
+            new UnableToExecuteStatementException(new SQLTransientException())
+        )
+    );
+
+    // Nested non-transient exceptions
+    Assert.assertFalse(
+        metadataConnector.isTransientException(
+            new CallbackFailedException(new SQLException())
+        )
+    );
+    Assert.assertFalse(
+        metadataConnector.isTransientException(
+            new UnableToExecuteStatementException(new SQLException())
+        )
+    );
+
   }
 }

server/src/test/java/org/apache/druid/metadata/SQLMetadataStorageActionHandlerTest.java

@@ -127,7 +127,7 @@ public class SQLMetadataStorageActionHandlerTest
   }
 
   @Test
-  public void testEntryAndStatus() throws Exception
+  public void testEntryAndStatus()
   {
     Map<String, Object> entry = ImmutableMap.of("numericId", 1234);
     Map<String, Object> status1 = ImmutableMap.of("count", 42);
@@ -256,7 +256,7 @@ public class SQLMetadataStorageActionHandlerTest
   }
 
   @Test(timeout = 60_000L)
-  public void testRepeatInsert() throws Exception
+  public void testRepeatInsert()
   {
     final String entryId = "abcd";
     Map<String, Object> entry = ImmutableMap.of("a", 1);
@@ -269,7 +269,7 @@ public class SQLMetadataStorageActionHandlerTest
   }
 
   @Test
-  public void testLogs() throws Exception
+  public void testLogs()
   {
     final String entryId = "abcd";
     Map<String, Object> entry = ImmutableMap.of("a", 1);
@@ -301,7 +301,7 @@ public class SQLMetadataStorageActionHandlerTest
 
 
   @Test
-  public void testLocks() throws Exception
+  public void testLocks()
   {
     final String entryId = "ABC123";
     Map<String, Object> entry = ImmutableMap.of("a", 1);
@@ -404,7 +404,7 @@ public class SQLMetadataStorageActionHandlerTest
   }
 
   @Test
-  public void testRemoveTasksOlderThan() throws Exception
+  public void testRemoveTasksOlderThan()
   {
     final String entryId1 = "1234";
     Map<String, Object> entry1 = ImmutableMap.of("numericId", 1234);