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/**
 *
 * 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 org.apache.hadoop.hbase.Coprocessor;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;

/**
 * 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.
 * 

* *

Exception Handling

* For all functions, exception handling is done as follows: *
    *
  • Exceptions of type {@link IOException} are reported back to client.
  • *
  • For any other kind of exception: *
      *
    • If the configuration {@link CoprocessorHost#ABORT_ON_ERROR_KEY} is set to true, then * the server aborts.
    • *
    • Otherwise, coprocessor is removed from the server and * {@link org.apache.hadoop.hbase.DoNotRetryIOException} is returned to the client.
    • *
    *
  • *
*/ @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC) @InterfaceStability.Evolving public interface RegionServerObserver { /** * Called before stopping region server. * @param ctx the environment to interact with the framework and region server. */ default void preStopRegionServer( final ObserverContext ctx) 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 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 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 ctx, ReplicationEndpoint endpoint) { return endpoint; } // TODO remove below 2 hooks when we implement AC as a core impl than a CP impl. /** * This will be called before executing replication request to shipping log entries. * @param ctx the environment to interact with the framework and region server. * @deprecated As of release 2.0.0 with out any replacement. This is maintained for internal * usage by AccessController. Do not use these hooks in custom co-processors. */ @Deprecated default void preReplicateLogEntries(final ObserverContext ctx) 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. * @deprecated As of release 2.0.0 with out any replacement. This is maintained for internal * usage by AccessController. Do not use these hooks in custom co-processors. */ @Deprecated default void postReplicateLogEntries( final ObserverContext ctx) 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 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 ctx) throws IOException {} }




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