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/*
*
* Copyright 2011 Netflix, 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.netflix.curator.utils;
import com.netflix.curator.CuratorZookeeperClient;
import com.netflix.curator.RetryLoop;
import org.apache.zookeeper.ZooKeeper;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicReference;
/**
*
* Utility to ensure that a particular path is created.
*
*
*
* The first time it is used, a synchronized call to {@link ZKPaths#mkdirs(ZooKeeper, String)} is made to
* ensure that the entire path has been created (with an empty byte array if needed). Subsequent
* calls with the instance are un-synchronized NOPs.
*
*
*
* Usage:
*
* EnsurePath ensurePath = new EnsurePath(aFullPathToEnsure);
* ...
* String nodePath = aFullPathToEnsure + "/foo";
* ensurePath.ensure(zk); // first time syncs and creates if needed
* zk.create(nodePath, ...);
* ...
* ensurePath.ensure(zk); // subsequent times are NOPs
* zk.create(nodePath, ...);
*
*/
public class EnsurePath
{
private final String path;
private final AtomicReference helper = new AtomicReference();
private static final Helper doNothingHelper = new Helper()
{
@Override
public void ensure(CuratorZookeeperClient client, String path) throws Exception
{
// NOP
}
};
private interface Helper
{
public void ensure(CuratorZookeeperClient client, String path) throws Exception;
}
/**
* @param path the full path to ensure
*/
public EnsurePath(String path)
{
this.path = path;
helper.set(new InitialHelper());
}
/**
* First time, synchronizes and makes sure all nodes in the path are created. Subsequent calls
* with this instance are NOPs.
*
* @param client ZK client
* @throws Exception ZK errors
*/
public void ensure(CuratorZookeeperClient client) throws Exception
{
Helper localHelper = helper.get();
localHelper.ensure(client, path);
}
private class InitialHelper implements Helper
{
private boolean isSet = false; // guarded by synchronization
@Override
public synchronized void ensure(final CuratorZookeeperClient client, final String path) throws Exception
{
if ( !isSet )
{
RetryLoop.callWithRetry
(
client,
new Callable