/**
*
* 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 java.io.IOException;
import java.util.List;
import org.apache.hadoop.hbase.CellScanner;
import org.apache.hadoop.hbase.Coprocessor;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.MetaMutationAnnotation;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.hbase.shaded.protobuf.generated.AdminProtos.WALEntry;
import org.apache.hadoop.hbase.regionserver.Region;
import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
/**
* Defines coprocessor hooks for interacting with operations on the
* {@link org.apache.hadoop.hbase.regionserver.HRegionServer} process.
*
* Since most implementations will be interested in only a subset of hooks, this class uses
* 'default' functions to avoid having to add unnecessary overrides. When the functions are
* non-empty, it's simply to satisfy the compiler by returning value of expected (non-void) type.
* It is done in a way that these default definitions act as no-op. So our suggestion to
* implementation would be to not call these 'default' methods from overrides.
* <br><br>
*
* <h3>Exception Handling</h3>
* For all functions, exception handling is done as follows:
* <ul>
* <li>Exceptions of type {@link IOException} are reported back to client.</li>
* <li>For any other kind of exception:
* <ul>
* <li>If the configuration {@link CoprocessorHost#ABORT_ON_ERROR_KEY} is set to true, then
* the server aborts.</li>
* <li>Otherwise, coprocessor is removed from the server and
* {@link org.apache.hadoop.hbase.DoNotRetryIOException} is returned to the client.</li>
* </ul>
* </li>
* </ul>
*/
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving
public interface RegionServerObserver extends Coprocessor {
/**
* Called before stopping region server.
* @param ctx the environment to interact with the framework and region server.
*/
default void preStopRegionServer(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx) throws IOException {}
/**
* Called before the regions merge.
* Call {@link org.apache.hadoop.hbase.coprocessor.ObserverContext#bypass()} to skip the merge.
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
*/
default void preMerge(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB) throws IOException {}
/**
* called after the regions merge.
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
*/
default void postMerge(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB, final Region mergedRegion) throws IOException {}
/**
* This will be called before PONR step as part of regions merge transaction. Calling
* {@link org.apache.hadoop.hbase.coprocessor.ObserverContext#bypass()} rollback the merge
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
* @param metaEntries mutations to execute on hbase:meta atomically with regions merge updates.
* Any puts or deletes to execute on hbase:meta can be added to the mutations.
*/
default void preMergeCommit(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB,
@MetaMutationAnnotation List<Mutation> metaEntries) throws IOException {}
/**
* This will be called after PONR step as part of regions merge transaction.
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
*/
default void postMergeCommit(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB, final Region mergedRegion) throws IOException {}
/**
* This will be called before the roll back of the regions merge.
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
*/
default void preRollBackMerge(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB) throws IOException {}
/**
* This will be called after the roll back of the regions merge.
* @param ctx the environment to interact with the framework and region server.
* @param regionA region being merged.
* @param regionB region being merged.
*/
default void postRollBackMerge(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
final Region regionA, final Region regionB) throws IOException {}
/**
* This will be called before executing user request to roll a region server WAL.
* @param ctx the environment to interact with the framework and region server.
*/
default void preRollWALWriterRequest(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx)
throws IOException {}
/**
* This will be called after executing user request to roll a region server WAL.
* @param ctx the environment to interact with the framework and region server.
*/
default void postRollWALWriterRequest(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx)
throws IOException {}
/**
* This will be called after the replication endpoint is instantiated.
* @param ctx the environment to interact with the framework and region server.
* @param endpoint - the base endpoint for replication
* @return the endpoint to use during replication.
*/
default ReplicationEndpoint postCreateReplicationEndPoint(
ObserverContext<RegionServerCoprocessorEnvironment> ctx, ReplicationEndpoint endpoint) {
return endpoint;
}
/**
* This will be called before executing replication request to shipping log entries.
* @param ctx the environment to interact with the framework and region server.
* @param entries list of WALEntries to replicate
* @param cells Cells that the WALEntries refer to (if cells is non-null)
*/
default void preReplicateLogEntries(final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
List<WALEntry> entries, CellScanner cells) throws IOException {}
/**
* This will be called after executing replication request to shipping log entries.
* @param ctx the environment to interact with the framework and region server.
* @param entries list of WALEntries to replicate
* @param cells Cells that the WALEntries refer to (if cells is non-null)
*/
default void postReplicateLogEntries(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx,
List<WALEntry> entries, CellScanner cells) throws IOException {}
/**
* This will be called before clearing compaction queues
* @param ctx the environment to interact with the framework and region server.
*/
default void preClearCompactionQueues(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx)
throws IOException {}
/**
* This will be called after clearing compaction queues
* @param ctx the environment to interact with the framework and region server.
*/
default void postClearCompactionQueues(
final ObserverContext<RegionServerCoprocessorEnvironment> ctx)
throws IOException {}
}