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