/*
***************************************************************************************
* Copyright (C) 2006 EsperTech, Inc. All rights reserved. *
* http://www.espertech.com/esper *
* http://www.espertech.com *
* ---------------------------------------------------------------------------------- *
* The software in this package is published under the terms of the GPL license *
* a copy of which has been included with this distribution in the license.txt file. *
***************************************************************************************
*/
/***************************************************************************************
* Attribution Notice
*
* This file is imported from Metrics (https://github.com/codahale/metrics subproject metrics-core).
* Metrics is Copyright (c) 2010-2012 Coda Hale, Yammer.com
* Metrics is Published under Apache Software License 2.0, see LICENSE in root folder.
*
* Thank you for the Metrics developers efforts in making their library available under an Apache license.
* EsperTech incorporates Metrics version 0.2.2 in source code form since Metrics depends on SLF4J
* and this dependency is not possible to introduce for Esper.
* *************************************************************************************
*/
package com.espertech.esper.metrics.codahale_metrics.metrics.core;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A manager class for a set of named thread pools.
*/
class ThreadPools {
/**
* A simple named thread factory.
*/
private static class NamedThreadFactory implements ThreadFactory {
private final ThreadGroup group;
private final AtomicInteger threadNumber = new AtomicInteger(1);
private final String namePrefix;
/**
* Creates a new {@link ThreadPools.NamedThreadFactory} with the
* given name.
*
* @param name the name of the threads, to be used in the pattern {@code
* metrics-$NAME$-thread-$NUMBER$}
*/
NamedThreadFactory(String name) {
final SecurityManager s = System.getSecurityManager();
this.group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
this.namePrefix = "metrics-" + name + "-thread-";
}
@Override
public Thread newThread(Runnable r) {
final Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
t.setDaemon(true);
if (t.getPriority() != Thread.NORM_PRIORITY) {
t.setPriority(Thread.NORM_PRIORITY);
}
return t;
}
}
private final ConcurrentMap<String, ScheduledExecutorService> threadPools =
new ConcurrentHashMap<String, ScheduledExecutorService>(100);
/**
* Creates a new scheduled thread pool of a given size with the given name, or returns an
* existing thread pool if one was already created with the same name.
*
* @param poolSize the number of threads to create
* @param name the name of the pool
* @return a new {@link java.util.concurrent.ScheduledExecutorService}
*/
ScheduledExecutorService newScheduledThreadPool(int poolSize, String name) {
final ScheduledExecutorService existing = threadPools.get(name);
if (isValidExecutor(existing)) {
return existing;
} else {
// We lock here because executors are expensive to create. So
// instead of just doing the usual putIfAbsent dance, we lock the
// damn thing, check to see if anyone else put a thread pool in
// there while we weren't watching.
synchronized (this) {
final ScheduledExecutorService lastChance = threadPools.get(name);
if (isValidExecutor(lastChance)) {
return lastChance;
} else {
final ScheduledExecutorService service =
Executors.newScheduledThreadPool(poolSize, new NamedThreadFactory(name));
threadPools.put(name, service);
return service;
}
}
}
}
private static boolean isValidExecutor(ExecutorService executor) {
return executor != null && !executor.isShutdown() && !executor.isTerminated();
}
/**
* Shuts down all thread pools created by this class in an orderly fashion.
*/
void shutdown() {
synchronized (this) {
for (ExecutorService executor : threadPools.values()) {
executor.shutdown();
}
threadPools.clear();
}
}
}