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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.metrics2.lib;
20  
21  import java.util.concurrent.ScheduledExecutorService;
22  import java.util.concurrent.ScheduledThreadPoolExecutor;
23  import java.util.concurrent.ThreadFactory;
24  import java.util.concurrent.atomic.AtomicInteger;
25  
26  import org.apache.hadoop.classification.InterfaceAudience;
27  import org.apache.hadoop.metrics2.MetricsExecutor;
28  
29  /**
30   *  Class to handle the ScheduledExecutorService{@link ScheduledExecutorService} used by MetricMutableQuantiles{@link MetricMutableQuantiles}
31   */
32  @InterfaceAudience.Private
33  public class MetricsExecutorImpl implements MetricsExecutor {
34  
35    @Override
36    public ScheduledExecutorService getExecutor() {
37      return ExecutorSingleton.INSTANCE.scheduler;
38    }
39  
40    @Override
41    public void stop() {
42      if (!getExecutor().isShutdown()) {
43        getExecutor().shutdown();
44      }
45    }
46  
47    private enum ExecutorSingleton {
48      INSTANCE;
49  
50      private final ScheduledExecutorService scheduler = new ScheduledThreadPoolExecutor(1, new ThreadPoolExecutorThreadFactory("HBase-Metrics2-"));
51    }
52  
53    private static class ThreadPoolExecutorThreadFactory implements ThreadFactory {
54      private final String name;
55      private final AtomicInteger threadNumber = new AtomicInteger(1);
56  
57      private ThreadPoolExecutorThreadFactory(String name) {
58        this.name = name;
59      }
60  
61      @Override
62      public Thread newThread(Runnable runnable) {
63        Thread t = new Thread(runnable, name + threadNumber.getAndIncrement());
64        t.setDaemon(true);
65        return t;
66      }
67    }
68  }