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1   /**
2    * Copyright 2011 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.util;
21  
22  import java.util.concurrent.TimeUnit;
23  
24  import org.apache.commons.logging.Log;
25  import org.apache.commons.logging.LogFactory;
26  
27  public class RetryCounter {
28    private static final Log LOG = LogFactory.getLog(RetryCounter.class);
29    private final int maxRetries;
30    private int retriesRemaining;
31    private final int retryIntervalMillis;
32    private final TimeUnit timeUnit;
33  
34    public RetryCounter(int maxRetries, 
35    int retryIntervalMillis, TimeUnit timeUnit) {
36      this.maxRetries = maxRetries;
37      this.retriesRemaining = maxRetries;
38      this.retryIntervalMillis = retryIntervalMillis;
39      this.timeUnit = timeUnit;
40    }
41  
42    public int getMaxRetries() {
43      return maxRetries;
44    }
45  
46    /**
47     * Sleep for a exponentially back off time
48     * @throws InterruptedException
49     */
50    public void sleepUntilNextRetry() throws InterruptedException {
51      int attempts = getAttemptTimes();
52      long sleepTime = (long) (retryIntervalMillis * Math.pow(2, attempts));
53      LOG.info("Sleeping " + sleepTime + "ms before retry #" + attempts + "...");
54      timeUnit.sleep(sleepTime);
55    }
56  
57    public boolean shouldRetry() {
58      return retriesRemaining > 0;
59    }
60  
61    public void useRetry() {
62      retriesRemaining--;
63    }
64    
65    public int getAttemptTimes() {
66      return maxRetries-retriesRemaining+1;
67    }
68  }