/*
* Copyright 2001-2009 Terracotta, 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 org.quartz.simpl;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.quartz.SchedulerConfigException;
import org.quartz.spi.ThreadPool;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* <p>
* This is class is a simple implementation of a thread pool, based on the
* <code>{@link org.quartz.spi.ThreadPool}</code> interface.
* </p>
*
* <p>
* <CODE>Runnable</CODE> objects are sent to the pool with the <code>{@link #runInThread(Runnable)}</code>
* method, which blocks until a <code>Thread</code> becomes available.
* </p>
*
* <p>
* The pool has a fixed number of <code>Thread</code>s, and does not grow or
* shrink based on demand.
* </p>
*
* @author James House
* @author Juergen Donnerstag
*/
public class SimpleThreadPool implements ThreadPool {
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Data members.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
private int count = -1;
private int prio = Thread.NORM_PRIORITY;
private boolean isShutdown = false;
private boolean handoffPending = false;
private boolean inheritLoader = false;
private boolean inheritGroup = true;
private boolean makeThreadsDaemons = false;
private ThreadGroup threadGroup;
private final Object nextRunnableLock = new Object(); //锁
private List<WorkerThread> workers; <span style="font-family: Arial, Helvetica, sans-serif;">//工作线程</span>
private LinkedList<WorkerThread> availWorkers = new LinkedList<WorkerThread>(); <span style="font-family: Arial, Helvetica, sans-serif;">//可用线程</span>
private LinkedList<WorkerThread> busyWorkers = new LinkedList<WorkerThread>();//已用线程
private String threadNamePrefix; //名字前缀
private final Logger log = LoggerFactory.getLogger(getClass());
private String schedulerInstanceName;
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Constructors.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
/**
* <p>
* Create a new (unconfigured) <code>SimpleThreadPool</code>.
* </p>
*
* @see #setThreadCount(int)
* @see #setThreadPriority(int)
*/
public SimpleThreadPool() {
}
/**
* <p>
* Create a new <code>SimpleThreadPool</code> with the specified number
* of <code>Thread</code> s that have the given priority.
* </p>
*
* @param threadCount
* the number of worker <code>Threads</code> in the pool, must
* be > 0.
* @param threadPriority
* the thread priority for the worker threads.
*
* @see java.lang.Thread
*/
public SimpleThreadPool(int threadCount, int threadPriority) {
setThreadCount(threadCount);
setThreadPriority(threadPriority);
}
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Interface.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
public Logger getLog() {
return log;
}
public int getPoolSize() {
return getThreadCount();
}
/**
* <p>
* Set the number of worker threads in the pool - has no effect after
* <code>initialize()</code> has been called.
* </p>
*/
public void setThreadCount(int count) {
this.count = count;
}
/**
* <p>
* Get the number of worker threads in the pool.
* </p>
*/
public int getThreadCount() {
return count;
}
/**
* <p>
* Set the thread priority of worker threads in the pool - has no effect
* after <code>initialize()</code> has been called.
* </p>
*/
public void setThreadPriority(int prio) {
this.prio = prio;
}
/**
* <p>
* Get the thread priority of worker threads in the pool.
* </p>
*/
public int getThreadPriority() {
return prio;
}
public void setThreadNamePrefix(String prfx) {
this.threadNamePrefix = prfx;
}
public String getThreadNamePrefix() {
return threadNamePrefix;
}
/**
* @return Returns the
* threadsInheritContextClassLoaderOfInitializingThread.
*/
public boolean isThreadsInheritContextClassLoaderOfInitializingThread() {
return inheritLoader;
}
/**
* @param inheritLoader
* The threadsInheritContextClassLoaderOfInitializingThread to
* set.
*/
public void setThreadsInheritContextClassLoaderOfInitializingThread(
boolean inheritLoader) {
this.inheritLoader = inheritLoader;
}
public boolean isThreadsInheritGroupOfInitializingThread() {
return inheritGroup;
}
public void setThreadsInheritGroupOfInitializingThread(
boolean inheritGroup) {
this.inheritGroup = inheritGroup;
}
/**
* @return Returns the value of makeThreadsDaemons.
*/
public boolean isMakeThreadsDaemons() {
return makeThreadsDaemons;
}
/**
* @param makeThreadsDaemons
* The value of makeThreadsDaemons to set.
*/
public void setMakeThreadsDaemons(boolean makeThreadsDaemons) {
this.makeThreadsDaemons = makeThreadsDaemons;
}
public void setInstanceId(String schedInstId) {
}
public void setInstanceName(String schedName) {
schedulerInstanceName = schedName;
}
//初始化线程池
public void initialize() throws SchedulerConfigException {
if(workers != null && workers.size() > 0) // already initialized...
return;
if (count <= 0) {
throw new SchedulerConfigException(
"Thread count must be > 0");
}
if (prio <= 0 || prio > 9) {
throw new SchedulerConfigException(
"Thread priority must be > 0 and <= 9");
}
if(isThreadsInheritGroupOfInitializingThread()) {
threadGroup = Thread.currentThread().getThreadGroup();
} else {
// follow the threadGroup tree to the root thread group.
threadGroup = Thread.currentThread().getThreadGroup();
ThreadGroup parent = threadGroup;
while ( !parent.getName().equals("main") ) {
threadGroup = parent;
parent = threadGroup.getParent();//直到parent是main线程
}
threadGroup = new ThreadGroup(parent, schedulerInstanceName + "-SimpleThreadPool");
if (isMakeThreadsDaemons()) {
threadGroup.setDaemon(true);
}
}
if (isThreadsInheritContextClassLoaderOfInitializingThread()) {
getLog().info(
"Job execution threads will use class loader of thread: "
+ Thread.currentThread().getName());
}
// create the worker threads and start them
Iterator<WorkerThread> workerThreads = createWorkerThreads(count).iterator();
while(workerThreads.hasNext()) {
WorkerThread wt = workerThreads.next();
wt.start();
availWorkers.add(wt);//初始化工作线程
}
}
protected List<WorkerThread> createWorkerThreads(int createCount) {
workers = new LinkedList<WorkerThread>();
for (int i = 1; i<= createCount; ++i) {
String threadPrefix = getThreadNamePrefix();
if (threadPrefix == null) {
threadPrefix = schedulerInstanceName + "_Worker";
}
WorkerThread wt = new WorkerThread(this, threadGroup,
threadPrefix + "-" + i,
getThreadPriority(),
isMakeThreadsDaemons());
if (isThreadsInheritContextClassLoaderOfInitializingThread()) {
wt.setContextClassLoader(Thread.currentThread()
.getContextClassLoader());
}
workers.add(wt);
}
return workers;
}
/**
* <p>
* Terminate any worker threads in this thread group.
* </p>
*
* <p>
* Jobs currently in progress will complete.
* </p>
*/
public void shutdown() {
shutdown(true);
}
/**
* <p>
* Terminate any worker threads in this thread group.
* </p>
*
* <p>
* Jobs currently in progress will complete.
* </p>
*/
public void shutdown(boolean waitForJobsToComplete) {
synchronized (nextRunnableLock) {
getLog().debug("Shutting down threadpool...");
isShutdown = true;
if(workers == null) // case where the pool wasn't even initialize()ed
return;
// signal each worker thread to shut down
Iterator<WorkerThread> workerThreads = workers.iterator();
while(workerThreads.hasNext()) {
WorkerThread wt = workerThreads.next();
wt.shutdown();
availWorkers.remove(wt);
}
// Give waiting (wait(1000)) worker threads a chance to shut down.
// Active worker threads will shut down after finishing their
// current job.
nextRunnableLock.notifyAll();//让wait（1000）的线程有时间去停止
//等待工作线程完成任务后停止
if (waitForJobsToComplete == true) {
boolean interrupted = false;
try {
// wait for hand-off in runInThread to complete...
while(handoffPending) {
try {
nextRunnableLock.wait(100);
} catch(InterruptedException _) {
interrupted = true;
}
}
// Wait until all worker threads are shut down
while (busyWorkers.size() > 0) {
WorkerThread wt = (WorkerThread) busyWorkers.getFirst();
try {
getLog().debug(
"Waiting for thread " + wt.getName()
+ " to shut down");
// note: with waiting infinite time the
// application may appear to 'hang'.
//无限等待可能出现整个应用挂起的情况
nextRunnableLock.wait(2000);
} catch (InterruptedException _) {
interrupted = true;
}
}
workerThreads = workers.iterator();
while(workerThreads.hasNext()) {
WorkerThread wt = (WorkerThread) workerThreads.next();
try {
wt.join();
workerThreads.remove();
} catch (InterruptedException _) {
interrupted = true;
}
}
} finally {
if (interrupted) {
Thread.currentThread().interrupt();
}
}
getLog().debug("No executing jobs remaining, all threads stopped.");
}
getLog().debug("Shutdown of threadpool complete.");
}
}
/**
* <p>
* Run the given <code>Runnable</code> object in the next available
* <code>Thread</code>. If while waiting the thread pool is asked to
* shut down, the Runnable is executed immediately within a new additional
* thread.
* </p>
*
* @param runnable
* the <code>Runnable</code> to be added.
*/
public boolean runInThread(Runnable runnable) {
if (runnable == null) {
return false;
}
synchronized (nextRunnableLock) {
handoffPending = true;
// Wait until a worker thread is available
while ((availWorkers.size() < 1) && !isShutdown) {
try {
nextRunnableLock.wait(500);
} catch (InterruptedException ignore) {
}
}
//从线程池获得新的worker，如果线程池被shutdown了，那就新建线程。
if (!isShutdown) {
WorkerThread wt = (WorkerThread)availWorkers.removeFirst();
busyWorkers.add(wt);
wt.run(runnable);
} else {
// If the thread pool is going down, execute the Runnable
// within a new additional worker thread (no thread from the pool).
WorkerThread wt = new WorkerThread(this, threadGroup,
"WorkerThread-LastJob", prio, isMakeThreadsDaemons(), runnable);
busyWorkers.add(wt);
workers.add(wt);
wt.start();
}
nextRunnableLock.notifyAll();
handoffPending = false;
}
return true;
}
public int blockForAvailableThreads() {
synchronized(nextRunnableLock) {
while((availWorkers.size() < 1 || handoffPending) && !isShutdown) {
try {
nextRunnableLock.wait(500);
} catch (InterruptedException ignore) {
}
}
return availWorkers.size();
}
}
protected void makeAvailable(WorkerThread wt) {
synchronized(nextRunnableLock) {
if(!isShutdown) {
availWorkers.add(wt);
}
busyWorkers.remove(wt);
nextRunnableLock.notifyAll();
}
}
protected void clearFromBusyWorkersList(WorkerThread wt) {
synchronized(nextRunnableLock) {
busyWorkers.remove(wt);
nextRunnableLock.notifyAll();
}
}
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* WorkerThread Class.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
/**
* <p>
* A Worker loops, waiting to execute tasks.
* </p>
*/
class WorkerThread extends Thread {
private final Object lock = new Object();
// A flag that signals the WorkerThread to terminate.
private AtomicBoolean run = new AtomicBoolean(true);
private SimpleThreadPool tp;
private Runnable runnable = null;
private boolean runOnce = false;
/**
* <p>
* Create a worker thread and start it. Waiting for the next Runnable,
* executing it, and waiting for the next Runnable, until the shutdown
* flag is set.
* </p>
*/
WorkerThread(SimpleThreadPool tp, ThreadGroup threadGroup, String name,
int prio, boolean isDaemon) {
this(tp, threadGroup, name, prio, isDaemon, null);
}
/**
* <p>
* Create a worker thread, start it, execute the runnable and terminate
* the thread (one time execution).
* </p>
*/
WorkerThread(SimpleThreadPool tp, ThreadGroup threadGroup, String name,
int prio, boolean isDaemon, Runnable runnable) {
super(threadGroup, name);
this.tp = tp;
this.runnable = runnable;
if(runnable != null)
runOnce = true;
setPriority(prio);
setDaemon(isDaemon);
}
/**
* <p>
* Signal the thread that it should terminate.
* </p>
*/
void shutdown() {
run.set(false);
}
public void run(Runnable newRunnable) {
synchronized(lock) {
if(runnable != null) {
throw new IllegalStateException("Already running a Runnable!");
}
runnable = newRunnable;
lock.notifyAll();
}
}
/**
* <p>
* Loop, executing targets as they are received.
* </p>
*/
@Override
public void run() {
boolean ran = false;
while (run.get()) {
try {
synchronized(lock) {
while (runnable == null && run.get()) {
lock.wait(500);
}
if (runnable != null) {
ran = true;
runnable.run();
}
}
} catch (InterruptedException unblock) {
// do nothing (loop will terminate if shutdown() was called
try {
getLog().error("Worker thread was interrupt()'ed.", unblock);
} catch(Exception e) {
// ignore to help with a tomcat glitch
}
} catch (Throwable exceptionInRunnable) {
try {
getLog().error("Error while executing the Runnable: ",
exceptionInRunnable);
} catch(Exception e) {
// ignore to help with a tomcat glitch
}
} finally {
synchronized(lock) {
runnable = null;
}
// repair the thread in case the runnable mucked it up...
if(getPriority() != tp.getThreadPriority()) {
setPriority(tp.getThreadPriority());
}
if (runOnce) {
run.set(false);
clearFromBusyWorkersList(this);
} else if(ran) {
ran = false;
makeAvailable(this);
}
}
}
//if (log.isDebugEnabled())
try {
getLog().debug("WorkerThread is shut down.");
} catch(Exception e) {
// ignore to help with a tomcat glitch
}
}
}
}
