| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.ratis.retry; |
| |
| import org.apache.ratis.util.Preconditions; |
| import org.apache.ratis.util.TimeDuration; |
| |
| import java.util.concurrent.ThreadLocalRandom; |
| |
| /** |
| * Retry Policy exponentially increases sleep time with randomness on successive |
| * retries. The sleep time is a geometric progression b*2, b*4, b*8, b*16... |
| * bounded by maximum configured duration. |
| * |
| * If sleep time calculated using the progression is s then randomness is added |
| * in the range [s*0.5, s*1.5). |
| */ |
| public final class ExponentialBackoffRetry implements RetryPolicy { |
| |
| public static final class Builder { |
| |
| private Builder() {} |
| |
| private TimeDuration baseSleepTime; |
| private TimeDuration maxSleepTime = null; |
| private int maxAttempts = Integer.MAX_VALUE; |
| |
| public Builder setMaxAttempts(int maxAttempts) { |
| this.maxAttempts = maxAttempts; |
| return this; |
| } |
| |
| public Builder setBaseSleepTime(TimeDuration baseSleepTime) { |
| this.baseSleepTime = baseSleepTime; |
| return this; |
| } |
| |
| public Builder setMaxSleepTime(TimeDuration maxSleepTime) { |
| this.maxSleepTime = maxSleepTime; |
| return this; |
| } |
| |
| public ExponentialBackoffRetry build() { |
| Preconditions.assertNotNull(baseSleepTime, "baseSleepTime"); |
| return new ExponentialBackoffRetry(baseSleepTime, maxSleepTime, |
| maxAttempts); |
| } |
| } |
| |
| private final TimeDuration baseSleepTime; |
| private final TimeDuration maxSleepTime; |
| private final int maxAttempts; |
| |
| private ExponentialBackoffRetry(TimeDuration baseSleepTime, TimeDuration maxSleepTime, int maxAttempts) { |
| this.baseSleepTime = baseSleepTime; |
| this.maxSleepTime = maxSleepTime; |
| this.maxAttempts = maxAttempts; |
| } |
| |
| public static Builder newBuilder() { |
| return new Builder(); |
| } |
| |
| private TimeDuration getSleepTime(int attemptCount) { |
| TimeDuration sleepTime = baseSleepTime.multiply(Math.pow(2, attemptCount)); |
| sleepTime = maxSleepTime != null && sleepTime.compareTo(maxSleepTime) > 0 ? maxSleepTime : sleepTime; |
| return sleepTime.multiply(ThreadLocalRandom.current().nextDouble() + 0.5); |
| } |
| |
| @Override |
| public Action handleAttemptFailure(Event event) { |
| TimeDuration sleepTime = getSleepTime(event.getAttemptCount()); |
| return event.getAttemptCount() < maxAttempts ? () -> sleepTime : NO_RETRY_ACTION; |
| } |
| } |