content: /**
   *
   * 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 com.alibaba.wasp.master;
  
  import com.alibaba.wasp.Server;
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  import org.apache.hadoop.classification.InterfaceAudience;
  
  import java.io.IOException;
  import java.lang.Thread.UncaughtExceptionHandler;
  import java.util.concurrent.Executors;
  
  /**
   * Base class used bulk assigning and unassigning entityGroups.
   * Encapsulates a fixed size thread pool of executors to run assignment/unassignment.
   * Implement {@link #populatePool(java.util.concurrent.ExecutorService)} and
   * {@link #waitUntilDone(long)}.  The default implementation of
   * the {@link #getUncaughtExceptionHandler()} is to abort the hosting
   * Server.
   */
  @InterfaceAudience.Private
  public abstract class BulkAssigner {
    protected final Server server;
  
    /**
     * @param server An instance of Server
     */
    public BulkAssigner(final Server server) {
      this.server = server;
    }
  
    /**
     * @return What to use for a thread prefix when executor runs.
     */
    protected String getThreadNamePrefix() {
      return this.server.getServerName() + "-" + this.getClass().getName(); 
    }
  
    protected UncaughtExceptionHandler getUncaughtExceptionHandler() {
      return new UncaughtExceptionHandler() {
        @Override
        public void uncaughtException(Thread t, Throwable e) {
          // Abort if exception of any kind.
          server.abort("Uncaught exception in " + t.getName(), e);
        }
      };
    }
  
    protected int getThreadCount() {
      return this.server.getConfiguration().getInt(
          "wasp.bulk.assignment.threadpool.size", 20);
    }
  
    protected long getTimeoutOnRIT() {
      return this.server.getConfiguration().getLong(
          "wasp.bulk.assignment.waiton.empty.rit", 5 * 60 * 1000);
    }
  
    protected abstract void populatePool(
        final java.util.concurrent.ExecutorService pool) throws IOException;
  
    public boolean bulkAssign() throws InterruptedException, IOException {
      return bulkAssign(true);
    }
  
    /**
     * Run the bulk assign.
     * 
     * @param sync
     *          Whether to assign synchronously.
     * @throws InterruptedException
     * @return True if done.
     * @throws java.io.IOException
     */
    public boolean bulkAssign(boolean sync) throws InterruptedException,
        IOException {
      boolean result = false;
      ThreadFactoryBuilder builder = new ThreadFactoryBuilder();
      builder.setDaemon(true);
      builder.setNameFormat(getThreadNamePrefix() + "-%1$d");
      builder.setUncaughtExceptionHandler(getUncaughtExceptionHandler());
      int threadCount = getThreadCount();
      java.util.concurrent.ExecutorService pool =
        Executors.newFixedThreadPool(threadCount, builder.build());
      try {
        populatePool(pool);
        // How long to wait on empty entityGroups-in-transition.  If we timeout, the
        // RIT monitor should do fixup.
        if (sync) result = waitUntilDone(getTimeoutOnRIT());
      } finally {
        // We're done with the pool.  It'll exit when its done all in queue.
        pool.shutdown();
      }
      return result;
    }
  
    /**
     * Wait until bulk assign is done.
     * @param timeout How long to wait.
     * @throws InterruptedException
     * @return True if the condition we were waiting on happened.
     */
    protected abstract boolean waitUntilDone(final long timeout)
    throws InterruptedException;
  }
  