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Server functionality for HBase
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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
/**
 * This extract the common used methods of procedures which are send to remote servers. Developers
 * who extends this class only need to override remoteCallBuild() and complete(). This procedure
 * will help add the operation to {@link RSProcedureDispatcher}
 *
 * If adding the operation to dispatcher failed, addOperationToNode will throw
 * FailedRemoteDispatchException, and this procedure will return null which procedure Executor will
 * mark this procedure as complete. Thus the upper layer of this procedure must have a way to
 * check if this procedure really succeed and how to deal with it.
 *
 * If sending the operation to remote RS failed, dispatcher will call remoteCallFailed() to
 * handle this, which actually call remoteOperationDone with the exception.
 * If the targetServer crashed but this procedure has no response, than dispatcher will call
 * remoteOperationFailed() to handle this, 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;
  }
}