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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  package org.apache.hadoop.hbase.client;
19  
20  import org.apache.hadoop.hbase.HConstants;
21  
22  import java.util.Random;
23  
24  /**
25   * Utility used by client connections such as {@link HConnection} and
26   * {@link ServerCallable}
27   */
28  public class ConnectionUtils {
29  
30    private static final Random RANDOM = new Random();
31    /**
32     * Calculate pause time.
33     * Built on {@link HConstants#RETRY_BACKOFF}.
34     * @param pause
35     * @param tries
36     * @return How long to wait after <code>tries</code> retries
37     */
38    public static long getPauseTime(final long pause, final int tries) {
39      int ntries = tries;
40      if (ntries >= HConstants.RETRY_BACKOFF.length) {
41        ntries = HConstants.RETRY_BACKOFF.length - 1;
42      }
43  
44      long normalPause = pause * HConstants.RETRY_BACKOFF[ntries];
45      long jitter =  (long)(normalPause * RANDOM.nextFloat() * 0.01f); // 1% possible jitter
46      return normalPause + jitter;
47    }
48  }