参考资料
第一篇配合第二篇阅读，讲解一些基本概念。若已了解可跳过。
推荐阅读第三篇，因为本文是基于第三篇的笔记。
DEMO
一个DEMO，每3秒输出helloworld
public class MyJob implements Job {
@Override
public void execute(JobExecutionContext context) throws JobExecutionException {
JobDataMap jobDataMap = context.getMergedJobDataMap();
String say = jobDataMap.getString("say");
System.out.println(say);
}
}
public class Demo {
public static void main(String[] args) {
JobDetail jd = JobBuilder.newJob(MyJob.class)
.withIdentity("myJob","jobGroup1")
.withDescription("a demo jobDetail")
.usingJobData("say","helloworld")
.build();
CronTrigger cronTrigger = TriggerBuilder.newTrigger()
.withIdentity("myCronTrigger","triggerGroup1")
.withSchedule(CronScheduleBuilder.cronSchedule("0/3 * * * * ?"))
.forJob(jd)
.build();
try {
Scheduler scheduler = new StdSchedulerFactory().getScheduler();
scheduler.scheduleJob(jd,cronTrigger);
scheduler.start();//本文要讲的部分
} catch (SchedulerException e) {
e.printStackTrace();
}
}
}
启动scheduler
- QuartzScheduler.start()
public void start() throws SchedulerException {
if (shuttingDown|| closed) {
throw new SchedulerException(
"The Scheduler cannot be restarted after shutdown() has been called.");
}
// QTZ-212 : calling new schedulerStarting() method on the listeners
// right after entering start()
notifySchedulerListenersStarting();
if (initialStart == null) {
initialStart = new Date();
this.resources.getJobStore().schedulerStarted();//RAMJobStore什么都不做，JobStoreSupport会判断是否集群并尝试恢复Job
startPlugins();
} else {
resources.getJobStore().schedulerResumed();
}
schedThread.togglePause(false); //核心代码
getLog().info(
"Scheduler " + resources.getUniqueIdentifier() + " started.");
notifySchedulerListenersStarted();
}
- QuartzSchedulerThread.togglePause(boolean pause)
void togglePause(boolean pause) {
synchronized (sigLock) {
paused = pause;
if (paused) {
signalSchedulingChange(0);
} else {
sigLock.notifyAll();//唤醒sigLock的等待线程
}
}
}
这里有两个疑问，QuartzSchedulerThread是什么时候创建并启动的？谁在等待sigLock？
QuartzSchedulerThread的创建和启动
StdSchedulerFacotry.instantiate()会创建一个QuartzScheduler实例，QuartzSchedulerThread就是在QuartzScheduler的构造方法中创建并启动的。
public QuartzScheduler(QuartzSchedulerResources resources, long idleWaitTime, @Deprecated long dbRetryInterval)
throws SchedulerException {
this.resources = resources;
if (resources.getJobStore() instanceof JobListener) {
addInternalJobListener((JobListener)resources.getJobStore());
}
this.schedThread = new QuartzSchedulerThread(this, resources);//创建QuartzSchedulerThread
ThreadExecutor schedThreadExecutor = resources.getThreadExecutor();
schedThreadExecutor.execute(this.schedThread);//启动QuartzSchedulerThread
if (idleWaitTime > 0) {
this.schedThread.setIdleWaitTime(idleWaitTime);
}
jobMgr = new ExecutingJobsManager();
addInternalJobListener(jobMgr);
errLogger = new ErrorLogger();
addInternalSchedulerListener(errLogger);
signaler = new SchedulerSignalerImpl(this, this.schedThread);
getLog().info("Quartz Scheduler v." + getVersion() + " created.");
}
通过sigLock控制QuartzSchedulerThread.run()
sigLock是QuartzSchedulerThread的一个final成员，且sigLock.wait()集中在QuartzSchedulerThread.run()中，可见sigLock是用来控制QuartzSchedulerThread的运行。
QuartzSchedulerThread.run()找出可用的Trigger和JobDetail
当ThreadPool有空闲线程时
找一批即将触发的Trigger
等待一段时间，直到最紧急的Trigger触发的前一刻
让Trigger触发，并找到对应的JobDetail
创建JobRunShell，JobDetail放入其中
JobRunShell带着JobDetail在ThreadPool中运行
public void run() {
int acquiresFailed = 0;
while (!halted.get()) {
try {
// check if we're supposed to pause...
synchronized (sigLock) {
while (paused && !halted.get()) {
try {
// wait until togglePause(false) is called...
// 等待 togglePause(false)将其唤醒
sigLock.wait(1000L);
} catch (InterruptedException ignore) {
}
// reset failure counter when paused, so that we don't
// wait again after unpausing
acquiresFailed = 0;
}
if (halted.get()) {
break;
}
}
// wait a bit, if reading from job store is consistently
// failing (e.g. DB is down or restarting)..
if (acquiresFailed > 1) {
try {
long delay = computeDelayForRepeatedErrors(qsRsrcs.getJobStore(), acquiresFailed);
Thread.sleep(delay);
} catch (Exception ignore) {
}
}
//阻塞，直到ThreadPool有空闲的线程
int availThreadCount = qsRsrcs.getThreadPool().blockForAvailableThreads();
if(availThreadCount > 0) { // will always be true, due to semantics of blockForAvailableThreads...
List<OperableTrigger> triggers;
long now = System.currentTimeMillis();
clearSignaledSchedulingChange();
try {
//得到一批即将触发的Trigger
triggers = qsRsrcs.getJobStore().acquireNextTriggers(
now + idleWaitTime, Math.min(availThreadCount, qsRsrcs.getMaxBatchSize()), qsRsrcs.getBatchTimeWindow());
acquiresFailed = 0;
if (log.isDebugEnabled())
log.debug("batch acquisition of " + (triggers == null ? 0 : triggers.size()) + " triggers");
} catch (JobPersistenceException jpe) {
if (acquiresFailed == 0) {
qs.notifySchedulerListenersError(
"An error occurred while scanning for the next triggers to fire.",
jpe);
}
if (acquiresFailed < Integer.MAX_VALUE)
acquiresFailed++;
continue;
} catch (RuntimeException e) {
if (acquiresFailed == 0) {
getLog().error("quartzSchedulerThreadLoop: RuntimeException "
+e.getMessage(), e);
}
if (acquiresFailed < Integer.MAX_VALUE)
acquiresFailed++;
continue;
}
if (triggers != null && !triggers.isEmpty()) {
now = System.currentTimeMillis();
long triggerTime = triggers.get(0).getNextFireTime().getTime();
long timeUntilTrigger = triggerTime - now;
while(timeUntilTrigger > 2) {
synchronized (sigLock) {
if (halted.get()) {
break;
}
if (!isCandidateNewTimeEarlierWithinReason(triggerTime, false)) {
try {
// we could have blocked a long while
// on 'synchronize', so we must recompute
now = System.currentTimeMillis();
timeUntilTrigger = triggerTime - now;
if(timeUntilTrigger >= 1)
sigLock.wait(timeUntilTrigger);//Trigger还没到触发时间，先等会
} catch (InterruptedException ignore) {
}
}
}
if(releaseIfScheduleChangedSignificantly(triggers, triggerTime)) {
break;
}
now = System.currentTimeMillis();
timeUntilTrigger = triggerTime - now;
}
// this happens if releaseIfScheduleChangedSignificantly decided to release triggers
if(triggers.isEmpty())
continue;
// set triggers to 'executing'
List<TriggerFiredResult> bndles = new ArrayList<TriggerFiredResult>();
boolean goAhead = true;
synchronized(sigLock) {
goAhead = !halted.get();
}
if(goAhead) {
try {
List<TriggerFiredResult> res = qsRsrcs.getJobStore().triggersFired(triggers);
if(res != null)
bndles = res;
} catch (SchedulerException se) {
qs.notifySchedulerListenersError(
"An error occurred while firing triggers '"
+ triggers + "'", se);
//QTZ-179 : a problem occurred interacting with the triggers from the db
//we release them and loop again
for (int i = 0; i < triggers.size(); i++) {
qsRsrcs.getJobStore().releaseAcquiredTrigger(triggers.get(i));
}
continue;
}
}
for (int i = 0; i < bndles.size(); i++) {
TriggerFiredResult result = bndles.get(i);
TriggerFiredBundle bndle = result.getTriggerFiredBundle();//bndle里面有JobDetail
Exception exception = result.getException();
if (exception instanceof RuntimeException) {
getLog().error("RuntimeException while firing trigger " + triggers.get(i), exception);
qsRsrcs.getJobStore().releaseAcquiredTrigger(triggers.get(i));
continue;
}
// it's possible to get 'null' if the triggers was paused,
// blocked, or other similar occurrences that prevent it being
// fired at this time... or if the scheduler was shutdown (halted)
if (bndle == null) {
qsRsrcs.getJobStore().releaseAcquiredTrigger(triggers.get(i));
continue;
}
JobRunShell shell = null;
try {
shell = qsRsrcs.getJobRunShellFactory().createJobRunShell(bndle);
shell.initialize(qs);
} catch (SchedulerException se) {
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
continue;
}
if (qsRsrcs.getThreadPool().runInThread(shell) == false) {//让shell在ThreadPool中运行
// this case should never happen, as it is indicative of the
// scheduler being shutdown or a bug in the thread pool or
// a thread pool being used concurrently - which the docs
// say not to do...
getLog().error("ThreadPool.runInThread() return false!");
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
}
}
continue; // while (!halted)
}
} else { // if(availThreadCount > 0)
// should never happen, if threadPool.blockForAvailableThreads() follows contract
continue; // while (!halted)
}
long now = System.currentTimeMillis();
long waitTime = now + getRandomizedIdleWaitTime();
long timeUntilContinue = waitTime - now;
synchronized(sigLock) {
try {
if(!halted.get()) {
// QTZ-336 A job might have been completed in the mean time and we might have
// missed the scheduled changed signal by not waiting for the notify() yet
// Check that before waiting for too long in case this very job needs to be
// scheduled very soon
if (!isScheduleChanged()) {
sigLock.wait(timeUntilContinue);
}
}
} catch (InterruptedException ignore) {
}
}
} catch(RuntimeException re) {
getLog().error("Runtime error occurred in main trigger firing loop.", re);
}
} // while (!halted)
// drop references to scheduler stuff to aid garbage collection...
qs = null;
qsRsrcs = null;
}
ThreadPool
ThreadPool，Job运行的地方，主要关注这几个接口方法
public interface ThreadPool {
void initialize() throws SchedulerConfigException;// 初始化ThreadPool
int blockForAvailableThreads();// 阻塞，直到有空闲线程，然后返回空闲线程的数量
boolean runInThread(Runnable runnable); //在ThreadPool中运行一个任务
/*
*其他接口
*/
}
以SimpleThreadPool为例
public class SimpleThreadPool implements ThreadPool {
//三个List维护WorkerThread的信息
private List<WorkerThread> workers;
private LinkedList<WorkerThread> availWorkers = new LinkedList<WorkerThread>();
private LinkedList<WorkerThread> busyWorkers = new LinkedList<WorkerThread>();
/*
*其他成员
*/
}
WorkerThread在ThreadPool初始化的时候就已经启动。如果你还记得的话，ThreadPool.initialize()被StdSchedulerFactory.instantiate()调用。
- SimpleThreadPool.initialize()
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();
}
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(); // 启动工作线程
availWorkers.add(wt);
}
}
- SimpleThreadPool.runInThread(Runnable runnable)
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) {
}
}
if (!isShutdown) {
WorkerThread wt = (WorkerThread)availWorkers.removeFirst();
busyWorkers.add(wt);
wt.run(runnable); //运行JobRunShell
} 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;
}
JobRunShell调用JobDetail方法
关键代码在job.execute(jec);处
- JobRunShell.run()
public void run() {
qs.addInternalSchedulerListener(this);
try {
OperableTrigger trigger = (OperableTrigger) jec.getTrigger();
JobDetail jobDetail = jec.getJobDetail();
do {
JobExecutionException jobExEx = null;
Job job = jec.getJobInstance();
try {
begin();
} catch (SchedulerException se) {
qs.notifySchedulerListenersError("Error executing Job ("
+ jec.getJobDetail().getKey()
+ ": couldn't begin execution.", se);
break;
}
// notify job & trigger listeners...
try {
if (!notifyListenersBeginning(jec)) {
break;
}
} catch(VetoedException ve) {
try {
CompletedExecutionInstruction instCode = trigger.executionComplete(jec, null);
qs.notifyJobStoreJobVetoed(trigger, jobDetail, instCode);
// QTZ-205
// Even if trigger got vetoed, we still needs to check to see if it's the trigger's finalized run or not.
if (jec.getTrigger().getNextFireTime() == null) {
qs.notifySchedulerListenersFinalized(jec.getTrigger());
}
complete(true);
} catch (SchedulerException se) {
qs.notifySchedulerListenersError("Error during veto of Job ("
+ jec.getJobDetail().getKey()
+ ": couldn't finalize execution.", se);
}
break;
}
long startTime = System.currentTimeMillis();
long endTime = startTime;
// execute the job
try {
log.debug("Calling execute on job " + jobDetail.getKey());
job.execute(jec);//关键代码，直接直接调用Job.execute
endTime = System.currentTimeMillis();
} catch (JobExecutionException jee) {
endTime = System.currentTimeMillis();
jobExEx = jee;
getLog().info("Job " + jobDetail.getKey() +
" threw a JobExecutionException: ", jobExEx);
} catch (Throwable e) {
endTime = System.currentTimeMillis();
getLog().error("Job " + jobDetail.getKey() +
" threw an unhandled Exception: ", e);
SchedulerException se = new SchedulerException(
"Job threw an unhandled exception.", e);
qs.notifySchedulerListenersError("Job ("
+ jec.getJobDetail().getKey()
+ " threw an exception.", se);
jobExEx = new JobExecutionException(se, false);
}
jec.setJobRunTime(endTime - startTime);
// notify all job listeners
if (!notifyJobListenersComplete(jec, jobExEx)) {
break;
}
CompletedExecutionInstruction instCode = CompletedExecutionInstruction.NOOP;
// update the trigger
try {
instCode = trigger.executionComplete(jec, jobExEx);
} catch (Exception e) {
// If this happens, there's a bug in the trigger...
SchedulerException se = new SchedulerException(
"Trigger threw an unhandled exception.", e);
qs.notifySchedulerListenersError(
"Please report this error to the Quartz developers.",
se);
}
// notify all trigger listeners
if (!notifyTriggerListenersComplete(jec, instCode)) {
break;
}
// update job/trigger or re-execute job
if (instCode == CompletedExecutionInstruction.RE_EXECUTE_JOB) {
jec.incrementRefireCount();
try {
complete(false);
} catch (SchedulerException se) {
qs.notifySchedulerListenersError("Error executing Job ("
+ jec.getJobDetail().getKey()
+ ": couldn't finalize execution.", se);
}
continue;
}
try {
complete(true);
} catch (SchedulerException se) {
qs.notifySchedulerListenersError("Error executing Job ("
+ jec.getJobDetail().getKey()
+ ": couldn't finalize execution.", se);
continue;
}
qs.notifyJobStoreJobComplete(trigger, jobDetail, instCode);
break;
} while (true);
} finally {
qs.removeInternalSchedulerListener(this);
}
}
