frankgh commented on code in PR #45: URL: https://github.com/apache/cassandra-sidecar/pull/45#discussion_r1192872529
########## client/src/main/java/org/apache/cassandra/sidecar/client/retry/ExponentialBackoffRetryPolicy.java: ########## @@ -0,0 +1,90 @@ +/* + * 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.cassandra.sidecar.client.retry; + +/** + * A retry policy that will perform an exponential backoff. The backoff period increases for each retry attempt. + * + * <p>Example: For a configured {@code maxRetries} of {@code 10}, {@code retryDelayMillis} of {@code 200} + * milliseconds, and {@code maxRetryDelayMillis} of {@code 20,000} milliseconds, the sequence is as follows: + * + * <pre> + * request backoff + * + * 1 200 + * 2 400 + * 3 800 + * 4 1600 + * 5 3200 + * 6 6400 + * 7 12800 + * 8 20000 + * 9 20000 + * 10 20000 + * </pre> + */ +public class ExponentialBackoffRetryPolicy extends BasicRetryPolicy +{ + private final long maxRetryDelayMillis; + + /** + * Constructs an exponential backoff retry policy unlimited number of retries and no delay between retries. + */ + public ExponentialBackoffRetryPolicy() + { + super(); + this.maxRetryDelayMillis = 0; + } + + /** + * Constructs an exponential backoff retry policy with {@code maxRetries} number of retries, + * {@code retryDelayMillis} delay between retries, and {@code maxRetryDelayMillis} maximum delay for the + * exponential backoff. + * + * @param maxRetries the maximum number of retries + * @param retryDelayMillis the delay between retries in milliseconds + * @param maxRetryDelayMillis the maximum retry delay in milliseconds + */ + public ExponentialBackoffRetryPolicy(int maxRetries, long retryDelayMillis, long maxRetryDelayMillis) + { + super(maxRetries, retryDelayMillis); + this.maxRetryDelayMillis = maxRetryDelayMillis; + } + + /** + * Returns the number of milliseconds to wait before attempting the next request. This value is upper-bounded + * by {@code maxRetryDelayMillis} if configured. The delay increases exponentially based on the number of + * attempts already performed. + * + * @param attempts the number of attempts already performed for this request + * @return the number of milliseconds to wait before attempting the next request + */ + @Override + protected long retryDelayMillis(int attempts) + { + long exponentialValue = (long) Math.pow(2, attempts - 1); + // do not multiply times retryDelayMillis, if we've reached the Long.MAX_VALUE already to avoid overflows + long retryDelay = exponentialValue == Long.MAX_VALUE ? exponentialValue : exponentialValue * retryDelayMillis; Review Comment: this check here is so it doesn't overflow. Math.pow will return Long.MAX_VALUE if it will overflow. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
