| /** |
| * 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.curator; |
| |
| import org.apache.curator.drivers.TracerDriver; |
| import org.apache.curator.utils.DebugUtils; |
| import org.apache.zookeeper.KeeperException; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.atomic.AtomicReference; |
| |
| /** |
| * <p>Mechanism to perform an operation on Zookeeper that is safe against |
| * disconnections and "recoverable" errors.</p> |
| * |
| * <p> |
| * If an exception occurs during the operation, the RetryLoop will process it, |
| * check with the current retry policy and either attempt to reconnect or re-throw |
| * the exception |
| * </p> |
| * |
| * Canonical usage:<br/> |
| * <code><pre> |
| * RetryLoop retryLoop = client.newRetryLoop(); |
| * while ( retryLoop.shouldContinue() ) |
| * { |
| * try |
| * { |
| * // do your work |
| * ZooKeeper zk = client.getZooKeeper(); // it's important to re-get the ZK instance in case there was an error and the instance was re-created |
| * |
| * retryLoop.markComplete(); |
| * } |
| * catch ( Exception e ) |
| * { |
| * retryLoop.takeException(e); |
| * } |
| * } |
| * </pre></code> |
| */ |
| public class RetryLoop |
| { |
| private boolean isDone = false; |
| private int retryCount = 0; |
| |
| private final Logger log = LoggerFactory.getLogger(getClass()); |
| private final long startTimeMs = System.currentTimeMillis(); |
| private final RetryPolicy retryPolicy; |
| private final AtomicReference<TracerDriver> tracer; |
| |
| private static final RetrySleeper sleeper = new RetrySleeper() |
| { |
| @Override |
| public void sleepFor(long time, TimeUnit unit) throws InterruptedException |
| { |
| unit.sleep(time); |
| } |
| }; |
| |
| /** |
| * Returns the default retry sleeper |
| * |
| * @return sleeper |
| */ |
| public static RetrySleeper getDefaultRetrySleeper() |
| { |
| return sleeper; |
| } |
| |
| /** |
| * Convenience utility: creates a retry loop calling the given proc and retrying if needed |
| * |
| * @param client Zookeeper |
| * @param proc procedure to call with retry |
| * @param <T> return type |
| * @return procedure result |
| * @throws Exception any non-retriable errors |
| */ |
| public static<T> T callWithRetry(CuratorZookeeperClient client, Callable<T> proc) throws Exception |
| { |
| T result = null; |
| RetryLoop retryLoop = client.newRetryLoop(); |
| while ( retryLoop.shouldContinue() ) |
| { |
| try |
| { |
| client.internalBlockUntilConnectedOrTimedOut(); |
| |
| result = proc.call(); |
| retryLoop.markComplete(); |
| } |
| catch ( Exception e ) |
| { |
| retryLoop.takeException(e); |
| } |
| } |
| return result; |
| } |
| |
| RetryLoop(RetryPolicy retryPolicy, AtomicReference<TracerDriver> tracer) |
| { |
| this.retryPolicy = retryPolicy; |
| this.tracer = tracer; |
| } |
| |
| /** |
| * If true is returned, make an attempt at the operation |
| * |
| * @return true/false |
| */ |
| public boolean shouldContinue() |
| { |
| return !isDone; |
| } |
| |
| /** |
| * Call this when your operation has successfully completed |
| */ |
| public void markComplete() |
| { |
| isDone = true; |
| } |
| |
| /** |
| * Utility - return true if the given Zookeeper result code is retry-able |
| * |
| * @param rc result code |
| * @return true/false |
| */ |
| public static boolean shouldRetry(int rc) |
| { |
| return (rc == KeeperException.Code.CONNECTIONLOSS.intValue()) || |
| (rc == KeeperException.Code.OPERATIONTIMEOUT.intValue()) || |
| (rc == KeeperException.Code.SESSIONMOVED.intValue()) || |
| (rc == KeeperException.Code.SESSIONEXPIRED.intValue()); |
| } |
| |
| /** |
| * Utility - return true if the given exception is retry-able |
| * |
| * @param exception exception to check |
| * @return true/false |
| */ |
| public static boolean isRetryException(Throwable exception) |
| { |
| if ( exception instanceof KeeperException ) |
| { |
| KeeperException keeperException = (KeeperException)exception; |
| return shouldRetry(keeperException.code().intValue()); |
| } |
| return false; |
| } |
| |
| /** |
| * Pass any caught exceptions here |
| * |
| * @param exception the exception |
| * @throws Exception if not retry-able or the retry policy returned negative |
| */ |
| public void takeException(Exception exception) throws Exception |
| { |
| boolean rethrow = true; |
| if ( isRetryException(exception) ) |
| { |
| if ( !Boolean.getBoolean(DebugUtils.PROPERTY_DONT_LOG_CONNECTION_ISSUES) ) |
| { |
| log.debug("Retry-able exception received", exception); |
| } |
| |
| if ( retryPolicy.allowRetry(retryCount++, System.currentTimeMillis() - startTimeMs, sleeper) ) |
| { |
| tracer.get().addCount("retries-allowed", 1); |
| if ( !Boolean.getBoolean(DebugUtils.PROPERTY_DONT_LOG_CONNECTION_ISSUES) ) |
| { |
| log.debug("Retrying operation"); |
| } |
| rethrow = false; |
| } |
| else |
| { |
| tracer.get().addCount("retries-disallowed", 1); |
| if ( !Boolean.getBoolean(DebugUtils.PROPERTY_DONT_LOG_CONNECTION_ISSUES) ) |
| { |
| log.debug("Retry policy not allowing retry"); |
| } |
| } |
| } |
| |
| if ( rethrow ) |
| { |
| throw exception; |
| } |
| } |
| } |