/**
* 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.hadoop.util;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/*
* This class is a container of multiple thread pools, each for a volume,
* so that we can schedule async disk operations easily.
*
* Examples of async disk operations are deletion of files.
* We can move the files to a "TO_BE_DELETED" folder before asychronously
* deleting it, to make sure the caller can run it faster.
*/
public class AsyncDiskService {
public static final Log LOG = LogFactory.getLog(AsyncDiskService.class);
// ThreadPool core pool size
private static final int CORE_THREADS_PER_VOLUME = 1;
// ThreadPool maximum pool size
private static final int MAXIMUM_THREADS_PER_VOLUME = 4;
// ThreadPool keep-alive time for threads over core pool size
private static final long THREADS_KEEP_ALIVE_SECONDS = 60;
private final ThreadGroup threadGroup = new ThreadGroup("async disk service");
private ThreadFactory threadFactory;
private HashMap<String, ThreadPoolExecutor> executors
= new HashMap<String, ThreadPoolExecutor>();
/**
* Create a AsyncDiskServices with a set of volumes (specified by their
* root directories).
*
* The AsyncDiskServices uses one ThreadPool per volume to do the async
* disk operations.
*
* @param volumes The roots of the file system volumes.
*/
public AsyncDiskService(String[] volumes) throws IOException {
threadFactory = new ThreadFactory() {
public Thread newThread(Runnable r) {
return new Thread(threadGroup, r);
}
};
// Create one ThreadPool per volume
for (int v = 0 ; v < volumes.length; v++) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(
CORE_THREADS_PER_VOLUME, MAXIMUM_THREADS_PER_VOLUME,
THREADS_KEEP_ALIVE_SECONDS, TimeUnit.SECONDS,
new LinkedBlockingQueue<Runnable>(), threadFactory);
// This can reduce the number of running threads
executor.allowCoreThreadTimeOut(true);
executors.put(volumes[v], executor);
}
}
/**
* Execute the task sometime in the future, using ThreadPools.
*/
public synchronized void execute(String root, Runnable task) {
ThreadPoolExecutor executor = executors.get(root);
if (executor == null) {
throw new RuntimeException("Cannot find root " + root
+ " for execution of task " + task);
} else {
executor.execute(task);
}
}
/**
* Gracefully start the shut down of all ThreadPools.
*/
public synchronized void shutdown() {
LOG.info("Shutting down all AsyncDiskService threads...");
for (Map.Entry<String, ThreadPoolExecutor> e
: executors.entrySet()) {
e.getValue().shutdown();
}
}
/**
* Wait for the termination of the thread pools.
*
* @param milliseconds The number of milliseconds to wait
* @return true if all thread pools are terminated without time limit
* @throws InterruptedException
*/
public synchronized boolean awaitTermination(long milliseconds)
throws InterruptedException {
long end = System.currentTimeMillis() + milliseconds;
for (Map.Entry<String, ThreadPoolExecutor> e:
executors.entrySet()) {
ThreadPoolExecutor executor = e.getValue();
if (!executor.awaitTermination(
Math.max(end - System.currentTimeMillis(), 0),
TimeUnit.MILLISECONDS)) {
LOG.warn("AsyncDiskService awaitTermination timeout.");
return false;
}
}
LOG.info("All AsyncDiskService threads are terminated.");
return true;
}
/**
* Shut down all ThreadPools immediately.
*/
public synchronized List<Runnable> shutdownNow() {
LOG.info("Shutting down all AsyncDiskService threads immediately...");
List<Runnable> list = new ArrayList<Runnable>();
for (Map.Entry<String, ThreadPoolExecutor> e
: executors.entrySet()) {
list.addAll(e.getValue().shutdownNow());
}
return list;
}
}