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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.util;
20  
21  import java.util.concurrent.TimeUnit;
22  
23  import org.apache.commons.logging.Log;
24  import org.apache.commons.logging.LogFactory;
25  import org.apache.hadoop.classification.InterfaceAudience;
26  
27  @InterfaceAudience.Private
28  public class RetryCounter {
29    private static final Log LOG = LogFactory.getLog(RetryCounter.class);
30    private final int maxRetries;
31    private int retriesRemaining;
32    private final int retryIntervalMillis;
33    private final TimeUnit timeUnit;
34  
35    public RetryCounter(int maxRetries, 
36    int retryIntervalMillis, TimeUnit timeUnit) {
37      this.maxRetries = maxRetries;
38      this.retriesRemaining = maxRetries;
39      this.retryIntervalMillis = retryIntervalMillis;
40      this.timeUnit = timeUnit;
41    }
42  
43    public int getMaxRetries() {
44      return maxRetries;
45    }
46  
47    /**
48     * Sleep for a exponentially back off time
49     * @throws InterruptedException
50     */
51    public void sleepUntilNextRetry() throws InterruptedException {
52      int attempts = getAttemptTimes();
53      long sleepTime = (long) (retryIntervalMillis * Math.pow(2, attempts));
54      LOG.info("Sleeping " + sleepTime + "ms before retry #" + attempts + "...");
55      timeUnit.sleep(sleepTime);
56    }
57  
58    public boolean shouldRetry() {
59      return retriesRemaining > 0;
60    }
61  
62    public void useRetry() {
63      retriesRemaining--;
64    }
65    
66    public int getAttemptTimes() {
67      return maxRetries-retriesRemaining+1;
68    }
69  }