com.google.cloud.dataflow.sdk.util.IntervalBoundedExponentialBackOff Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.cloud.dataflow.sdk.util;
import com.google.api.client.util.BackOff;
import com.google.common.base.Preconditions;
/**
* Implementation of {@link BackOff} that increases the back off period for each retry attempt
* using a randomization function that grows exponentially.
*
* Example: The initial interval is .5 seconds and the maximum interval is 60 secs.
* For 14 tries the sequence will be (values in seconds):
*
*
retry# retry_interval randomized_interval
1 0.5 [0.25, 0.75]
2 0.75 [0.375, 1.125]
3 1.125 [0.562, 1.687]
4 1.687 [0.8435, 2.53]
5 2.53 [1.265, 3.795]
6 3.795 [1.897, 5.692]
7 5.692 [2.846, 8.538]
8 8.538 [4.269, 12.807]
9 12.807 [6.403, 19.210]
10 28.832 [14.416, 43.248]
11 43.248 [21.624, 64.873]
12 60.0 [30.0, 90.0]
13 60.0 [30.0, 90.0]
14 60.0 [30.0, 90.0]
*
*
*
* Implementation is not thread-safe.
*/
public class IntervalBoundedExponentialBackOff implements BackOff {
public static final double DEFAULT_MULTIPLIER = 1.5;
public static final double DEFAULT_RANDOMIZATION_FACTOR = 0.5;
private final long maximumIntervalMillis;
private final long initialIntervalMillis;
private int currentAttempt;
public IntervalBoundedExponentialBackOff(int maximumIntervalMillis, long initialIntervalMillis) {
Preconditions.checkArgument(
maximumIntervalMillis > 0, "Maximum interval must be greater than zero.");
Preconditions.checkArgument(
initialIntervalMillis > 0, "Initial interval must be greater than zero.");
this.maximumIntervalMillis = maximumIntervalMillis;
this.initialIntervalMillis = initialIntervalMillis;
reset();
}
@Override
public void reset() {
currentAttempt = 1;
}
@Override
public long nextBackOffMillis() {
double currentIntervalMillis =
Math.min(
initialIntervalMillis * Math.pow(DEFAULT_MULTIPLIER, currentAttempt - 1),
maximumIntervalMillis);
double randomOffset =
(Math.random() * 2 - 1) * DEFAULT_RANDOMIZATION_FACTOR * currentIntervalMillis;
currentAttempt += 1;
return Math.round(currentIntervalMillis + randomOffset);
}
public boolean atMaxInterval() {
return initialIntervalMillis * Math.pow(DEFAULT_MULTIPLIER, currentAttempt - 1)
>= maximumIntervalMillis;
}
}