org.apache.curator.RetryLoop Maven / Gradle / Ivy
/**
* 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.connection.ThreadLocalRetryLoop;
import org.apache.curator.utils.ThreadUtils;
import java.util.concurrent.Callable;
/**
* Mechanism to perform an operation on Zookeeper that is safe against
* disconnections and "recoverable" errors.
*
*
* 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
*
*
* Canonical usage:
*
* 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);
* }
* }
*
*
*
* Note: this an {@code abstract class} instead of an {@code interface} for historical reasons. It was originally a class
* and if it becomes an interface we risk {@link java.lang.IncompatibleClassChangeError}s with clients.
*
*/
public abstract class RetryLoop
{
/**
* Returns the default retry sleeper
*
* @return sleeper
*/
public static RetrySleeper getDefaultRetrySleeper()
{
return RetryLoopImpl.getRetrySleeper();
}
/**
* 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 return type
* @return procedure result
* @throws Exception any non-retriable errors
*/
public static T callWithRetry(CuratorZookeeperClient client, Callable proc) throws Exception
{
client.internalBlockUntilConnectedOrTimedOut();
T result = null;
ThreadLocalRetryLoop threadLocalRetryLoop = new ThreadLocalRetryLoop();
RetryLoop retryLoop = threadLocalRetryLoop.getRetryLoop(client::newRetryLoop);
try
{
while ( retryLoop.shouldContinue() )
{
try
{
result = proc.call();
retryLoop.markComplete();
}
catch ( Exception e )
{
ThreadUtils.checkInterrupted(e);
retryLoop.takeException(e);
}
}
}
finally
{
threadLocalRetryLoop.release();
}
return result;
}
/**
* If true is returned, make an attempt at the operation
*
* @return true/false
*/
public abstract boolean shouldContinue();
/**
* Call this when your operation has successfully completed
*/
public abstract void markComplete();
/**
* Pass any caught exceptions here
*
* @param exception the exception
* @throws Exception if not retry-able or the retry policy returned negative
*/
public abstract void takeException(Exception exception) throws Exception;
}