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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.master.procedure;

import java.io.IOException;

import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.procedure2.FailedRemoteDispatchException;
import org.apache.hadoop.hbase.procedure2.Procedure;
import org.apache.hadoop.hbase.procedure2.ProcedureEvent;
import org.apache.hadoop.hbase.procedure2.ProcedureSuspendedException;
import org.apache.hadoop.hbase.procedure2.ProcedureYieldException;
import org.apache.hadoop.hbase.procedure2.RemoteProcedureDispatcher;
import org.apache.hadoop.hbase.procedure2.RemoteProcedureException;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@InterfaceAudience.Private
/**
 * The base class for Procedures that run {@link java.util.concurrent.Callable}s on a (remote)
 * RegionServer; e.g. asking a RegionServer to split a WAL file as a sub-procedure of
 * the ServerCrashProcedure recovery process.
 *
 * 

To implement a new Procedure type, extend this class and override remoteCallBuild() and * complete(). The dispatch and callback will be handled for you here, internally. * *

The Procedure works as follows. It uses {@link RSProcedureDispatcher}, the same system * used dispatching Region OPEN and CLOSE RPCs, to pass a Callable to a RegionServer. Examples * include {@link org.apache.hadoop.hbase.regionserver.SplitWALCallable} and * {@link org.apache.hadoop.hbase.replication.regionserver.RefreshPeerCallable}. Rather than * assign/unassign, the Master calls #executeProcedures against the remote RegionServer wrapping * a Callable in a {@link ExecuteProceduresRequest}. Upon successful dispatch, * the Procedure then suspends itself on the Master-side and relinqushes its executor worker. * On receipt, the RegionServer submits the Callable to its executor service. When the Callable * completes, it adds itself to a queue on the RegionServer side for processing by a background * thread, the {@link RemoteProcedureResultReporter}. It picks up the completed Callable from the * queue and RPCs the master at #reportProcedureDone with the procedure id and whether success or * failure. The master calls complete() setting success or failure state and then reschedules the * suspended Procedure so it can finish. * *

Here are some details on operation: *

If adding the operation to the dispatcher fails, addOperationToNode will throw * FailedRemoteDispatchException, and this Procedure will return 'null'. The Procedure Executor * will then mark this procedure as 'complete' (though we failed to dispatch our task). In this * case, the upper layer of this procedure must have a way to check if this Procedure really * succeeded or not and have appropriate handling. * *

If sending the operation to remote RS failed, dispatcher will call remoteCallFailed() to * handle this which calls remoteOperationDone with the exception. If the targetServer crashed but * this procedure has no response, than dispatcher will call remoteOperationFailed() which also * calls remoteOperationDone with the exception. If the operation is successful, then * remoteOperationCompleted will be called and actually calls the remoteOperationDone without * exception. * * In remoteOperationDone, we'll check if the procedure is already get wake up by others. Then * developer could implement complete() based on their own purpose. * * But basic logic is that if operation succeed, set succ to true and do the clean work. * * If operation failed and require to resend it to the same server, leave the succ as false. * * If operation failed and require to resend it to another server, set succ to true and upper layer * should be able to find out this operation not work and send a operation to another server. */ public abstract class ServerRemoteProcedure extends Procedure implements RemoteProcedureDispatcher.RemoteProcedure { protected static final Logger LOG = LoggerFactory.getLogger(ServerRemoteProcedure.class); protected ProcedureEvent event; protected ServerName targetServer; protected boolean dispatched; protected boolean succ; protected abstract void complete(MasterProcedureEnv env, Throwable error); @Override protected synchronized Procedure[] execute(MasterProcedureEnv env) throws ProcedureYieldException, ProcedureSuspendedException, InterruptedException { if (dispatched) { if (succ) { return null; } dispatched = false; } try { env.getRemoteDispatcher().addOperationToNode(targetServer, this); } catch (FailedRemoteDispatchException frde) { LOG.warn("Can not send remote operation {} to {}, this operation will " + "be retried to send to another server", this.getProcId(), targetServer); return null; } dispatched = true; event = new ProcedureEvent<>(this); event.suspendIfNotReady(this); throw new ProcedureSuspendedException(); } @Override protected synchronized void completionCleanup(MasterProcedureEnv env) { env.getRemoteDispatcher().removeCompletedOperation(targetServer, this); } @Override public synchronized void remoteCallFailed(MasterProcedureEnv env, ServerName serverName, IOException exception) { remoteOperationDone(env, exception); } @Override public synchronized void remoteOperationCompleted(MasterProcedureEnv env) { remoteOperationDone(env, null); } @Override public synchronized void remoteOperationFailed(MasterProcedureEnv env, RemoteProcedureException error) { remoteOperationDone(env, error); } synchronized void remoteOperationDone(MasterProcedureEnv env, Throwable error) { if (this.isFinished()) { LOG.info("This procedure {} is already finished, skip the rest processes", this.getProcId()); return; } if (event == null) { LOG.warn("procedure event for {} is null, maybe the procedure is created when recovery", getProcId()); return; } complete(env, error); event.wake(env.getProcedureScheduler()); event = null; } }





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