content: /*
   * Copyright (C) 2010-2101 Alibaba Group Holding Limited.
   *
   * Licensed 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.otter.shared.arbitrate.impl.zookeeper;
  
  import java.util.concurrent.ArrayBlockingQueue;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.zookeeper.WatchedEvent;
  import org.apache.zookeeper.Watcher;
  
  import com.alibaba.otter.shared.common.utils.thread.NamedThreadFactory;
  
  /**
   * 包装ZooKeeper的Watcher接口，支持Async的异步调用处理
   * 
   * <pre>
   * 说明：
   *  1. zookeeper针对watcher的调用是以单线程串行的方式进行处理，容易造成堵塞影响，monitor的数据同步及时性
   *  2. AsyncWatcher为采取的一种策略为当不超过acceptCount=60的任务时，会采用异步线程的方式处理。如果超过60任务，会变为原先的单线程串行的模式
   * </pre>
   * 
   * @author jianghang 2011-9-21 下午01:00:39
   * @version 4.0.0
   */
  public abstract class AsyncWatcher implements Watcher {
  
      private static final int       DEFAULT_POOL_SIZE    = 30;
      private static final int       DEFAULT_ACCEPT_COUNT = 60;
  
      private static ExecutorService executor             = new ThreadPoolExecutor(
                                                                                   DEFAULT_POOL_SIZE,
                                                                                   DEFAULT_POOL_SIZE,
                                                                                   0L,
                                                                                   TimeUnit.MILLISECONDS,
                                                                                   new ArrayBlockingQueue(
                                                                                                          DEFAULT_ACCEPT_COUNT),
                                                                                   new NamedThreadFactory(
                                                                                                          "Arbitrate-Async-Watcher"),
                                                                                   new ThreadPoolExecutor.CallerRunsPolicy());
  
      public void process(final WatchedEvent event) {
          executor.execute(new Runnable() {// 提交异步处理
  
              public void run() {
                  asyncProcess(event);
              }
          });
  
      }
  
      public abstract void asyncProcess(WatchedEvent event);
  
  }
  