/**
* 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.framework.recipes.locks;
import com.google.common.base.Preconditions;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.utils.CloseableScheduledExecutorService;
import org.apache.curator.utils.ThreadUtils;
import org.apache.curator.utils.ZKPaths;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
/**
* Utility to reap empty child nodes of a parent node. Periodically calls getChildren on
* the node and adds empty nodes to an internally managed {@link Reaper}
*/
public class ChildReaper implements Closeable
{
private final Logger log = LoggerFactory.getLogger(getClass());
private final Reaper reaper;
private final AtomicReference<State> state = new AtomicReference<State>(State.LATENT);
private final CuratorFramework client;
private final String path;
private final Reaper.Mode mode;
private final CloseableScheduledExecutorService executor;
private final int reapingThresholdMs;
private volatile Future<?> task;
private enum State
{
LATENT,
STARTED,
CLOSED
}
/**
* @param client the client
* @param path path to reap children from
* @param mode reaping mode
*/
public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode)
{
this(client, path, mode, newExecutorService(), Reaper.DEFAULT_REAPING_THRESHOLD_MS);
}
/**
* @param client the client
* @param path path to reap children from
* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
* @param mode reaping mode
*/
public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode, int reapingThresholdMs)
{
this(client, path, mode, newExecutorService(), reapingThresholdMs);
}
/**
* @param client the client
* @param path path to reap children from
* @param executor executor to use for background tasks
* @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
* @param mode reaping mode
*/
public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode, ScheduledExecutorService executor, int reapingThresholdMs)
{
this.client = client;
this.path = path;
this.mode = mode;
this.executor = new CloseableScheduledExecutorService(executor);
this.reapingThresholdMs = reapingThresholdMs;
this.reaper = new Reaper(client, executor, reapingThresholdMs);
}
/**
* The reaper must be started
*
* @throws Exception errors
*/
public void start() throws Exception
{
Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED), "Cannot be started more than once");
task = executor.scheduleWithFixedDelay
(
new Runnable()
{
@Override
public void run()
{
doWork();
}
},
reapingThresholdMs,
reapingThresholdMs,
TimeUnit.MILLISECONDS
);
reaper.start();
}
@Override
public void close() throws IOException
{
if ( state.compareAndSet(State.STARTED, State.CLOSED) )
{
CloseableUtils.closeQuietly(reaper);
task.cancel(true);
}
}
private static ScheduledExecutorService newExecutorService()
{
return ThreadUtils.newFixedThreadScheduledPool(2, "ChildReaper");
}
private void doWork()
{
try
{
List<String> children = client.getChildren().forPath(path);
for ( String name : children )
{
String thisPath = ZKPaths.makePath(path, name);
Stat stat = client.checkExists().forPath(thisPath);
if ( (stat != null) && (stat.getNumChildren() == 0) )
{
reaper.addPath(thisPath, mode);
}
}
}
catch ( Exception e )
{
log.error("Could not get children for path: " + path, e);
}
}
}