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.classification.InterfaceAudience;
21 import org.apache.hadoop.classification.InterfaceStability;
22 import org.apache.hadoop.hbase.HConstants;
23
24 import java.util.Random;
25
26 /**
27 * Utility used by client connections.
28 */
29 @InterfaceAudience.Public
30 @InterfaceStability.Evolving
31 public class ConnectionUtils {
32
33 private static final Random RANDOM = new Random();
34 /**
35 * Calculate pause time.
36 * Built on {@link HConstants#RETRY_BACKOFF}.
37 * @param pause
38 * @param tries
39 * @return How long to wait after <code>tries</code> retries
40 */
41 public static long getPauseTime(final long pause, final int tries) {
42 int ntries = tries;
43 if (ntries >= HConstants.RETRY_BACKOFF.length) {
44 ntries = HConstants.RETRY_BACKOFF.length - 1;
45 }
46
47 long normalPause = pause * HConstants.RETRY_BACKOFF[ntries];
48 long jitter = (long)(normalPause * RANDOM.nextFloat() * 0.01f); // 1% possible jitter
49 return normalPause + jitter;
50 }
51
52
53 /**
54 * Adds / subs a 10% jitter to a pause time. Minimum is 1.
55 * @param pause the expected pause.
56 * @param jitter the jitter ratio, between 0 and 1, exclusive.
57 */
58 public static long addJitter(final long pause, final float jitter) {
59 float lag = pause * (RANDOM.nextFloat() - 0.5f) * jitter;
60 long newPause = pause + (long) lag;
61 if (newPause <= 0) {
62 return 1;
63 }
64 return newPause;
65 }
66 }