本章阅读收获:可了解Quartz框架中的正式开始运行部分源码
继上节内容
上面我们讲到了QuartzSchedulerThread中run方法的第一小部分，下面我们继续来进行分析。
QuartzSchedulerThread中run方法后续分析
if (triggers != null && !triggers.isEmpty()) {
now = System.currentTimeMillis();
//这里为什么triggers的第一个对象就是最早需要被执行的？
long triggerTime = triggers.get(0).getNextFireTime().getTime();
long timeUntilTrigger = triggerTime - now;
//如果第一条下次触发时间大于当前时间则进入等待
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);
} catch (InterruptedException ignore) {
}
}
}
//等待的过程中看看有没有收到调度信号
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 bndles = new ArrayList();
boolean goAhead = true;
synchronized(sigLock) {
goAhead = !halted.get();
}
if(goAhead) {
try {
List 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();
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;
}
// 下面是开始执行任务
JobRunShell shell = null;
try {
//构造执行对象，JobRunShell实现了Runnable
shell = qsRsrcs.getJobRunShellFactory().createJobRunShell(bndle);
//这个里面会用我们自定义的Job来new一个对象，并把相关执行Job是需要的数据传给JobExecutionContextImpl(这是我们自定义job的execute方法参数)
shell.initialize(qs);
} catch (SchedulerException se) {
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
continue;
}
// 这里是把任务放入到线程池中
if (qsRsrcs.getThreadPool().runInThread(shell) == false) {
// 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)
}
首先是判断trigger是否存在，不存在的话就continue，继续外层while循环，保证定时任务一直运行下去。
接下来分析triggers存在的情况下：
这里会获取trigger第一个触发器下次触发时间，这里值是指距离现在最近的触发时间，但是为什么trigger数组中第一个就是最快的呢？
这里不知大家还记得上一节中我们讲到的获取Trigger过程，它是存放在
protected TreeSet timeTriggers = new TreeSet(new TriggerWrapperComparator());
这个类的实现类就是根据Trigger的触发时间的远近来进行排序的，然后
OperableTrigger trig = (OperableTrigger) tw.trigger.clone();
if (result.isEmpty()) {
batchEnd = Math.max(tw.trigger.getNextFireTime().getTime(), System.currentTimeMillis()) + timeWindow;
}
result.add(trig);
通过克隆复制添加进去的，这个方法中返回的就是result。
接下来我们继续往下讲，我们会把根据距离触发时间的时间间隔，如果间隔大于2（这里为什么是2呢？我猜想主要是因为接下来的判断中有判断间隔大于1的，如果两个值相同就没有意思了，而且保证有足够的时间到下一步判断还能大于1）就继续往下走。
接下来的方法源码是：
/**
* 是否有更早的触发器
*/
private boolean isCandidateNewTimeEarlierWithinReason(long oldTime, boolean clearSignal) {
synchronized(sigLock) {
//看信号是否改变
if (!isScheduleChanged())
return false;
boolean earlier = false;
//如果信号发生改变了，则比较信号下次触发时间
if(getSignaledNextFireTime() == 0)
earlier = true;
else if(getSignaledNextFireTime() < oldTime )
earlier = true;
//下次触发时间可能比较早，但是如果本来执行时间快到了这个信号也不算
if(earlier) {
// so the new time is considered earlier, but is it enough earlier?
long diff = oldTime - System.currentTimeMillis();
if(diff < (qsRsrcs.getJobStore().supportsPersistence() ? 70L : 7L))
earlier = false;
}
//把本次的信号清除掉
if(clearSignal) {
clearSignaledSchedulingChange();
}
return earlier;
}
}
这个方法就是判断执行器有没有更早的触发器，如果没有的话则等待触发器触发的时间间隔时间。（至于这里的信号量改变，具体是哪里触发的现在还不太懂）。
接下来是releaseIfScheduleChangedSignificantly方法：
···
private boolean releaseIfScheduleChangedSignificantly(
List triggers, long triggerTime) {
if (isCandidateNewTimeEarlierWithinReason(triggerTime, true)) {
// above call does a clearSignaledSchedulingChange()
for (OperableTrigger trigger : triggers) {
qsRsrcs.getJobStore().releaseAcquiredTrigger(trigger);
}
triggers.clear();
return true;
}
return false;
}
···
这里面也调用了之前的isCandidateNewTimeEarlierWithinReason方法，为什么这里的Boolean参数就是true了呢？之前的是false。因为这里需要清空信号。
//把本次的信号清除掉
if(clearSignal) {
clearSignaledSchedulingChange();
}
之后就是把trigger这个列表都清空掉。
之后我们就进入了：
if(goAhead) {
try {
List 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;
}
}
就通知jobStore开始执行了，根据trigger获取其对应的JobDetail, 封装成TriggerFiredResult
/**
* 通知jobStore开始执行了，根据trigger获取其对应的JobDetail, 封装成TriggerFiredResult
*/
public List triggersFired(List firedTriggers) {
synchronized (lock) {
List results = new ArrayList();
for (OperableTrigger trigger : firedTriggers) {
TriggerWrapper tw = triggersByKey.get(trigger.getKey());
// was the trigger deleted since being acquired?
if (tw == null || tw.trigger == null) {
continue;
}
// was the trigger completed, paused, blocked, etc. since being acquired?
if (tw.state != TriggerWrapper.STATE_ACQUIRED) {
continue;
}
Calendar cal = null;
if (tw.trigger.getCalendarName() != null) {
cal = retrieveCalendar(tw.trigger.getCalendarName());
if(cal == null)
continue;
}
Date prevFireTime = trigger.getPreviousFireTime();
// in case trigger was replaced between acquiring and firing
timeTriggers.remove(tw);
// call triggered on our copy, and the scheduler's copy
tw.trigger.triggered(cal);
trigger.triggered(cal);
//tw.state = TriggerWrapper.STATE_EXECUTING;
tw.state = TriggerWrapper.STATE_WAITING;
TriggerFiredBundle bndle = new TriggerFiredBundle(retrieveJob(
tw.jobKey), trigger, cal,
false, new Date(), trigger.getPreviousFireTime(), prevFireTime,
trigger.getNextFireTime());
JobDetail job = bndle.getJobDetail();
if (job.isConcurrentExectionDisallowed()) {
ArrayList trigs = getTriggerWrappersForJob(job.getKey());
for (TriggerWrapper ttw : trigs) {
if (ttw.state == TriggerWrapper.STATE_WAITING) {
ttw.state = TriggerWrapper.STATE_BLOCKED;
}
if (ttw.state == TriggerWrapper.STATE_PAUSED) {
ttw.state = TriggerWrapper.STATE_PAUSED_BLOCKED;
}
timeTriggers.remove(ttw);
}
blockedJobs.add(job.getKey());
} else if (tw.trigger.getNextFireTime() != null) {
synchronized (lock) {
timeTriggers.add(tw);
}
}
results.add(new TriggerFiredResult(bndle));
}
return results;
}
}
获取到相应启动的TriggerFiredResult任务后，便是循环执行：
for (int i = 0; i < bndles.size(); i++) {
TriggerFiredResult result = bndles.get(i);
TriggerFiredBundle bndle = result.getTriggerFiredBundle();
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;
}
// 下面是开始执行任务
JobRunShell shell = null;
try {
//构造执行对象，JobRunShell实现了Runnable
shell = qsRsrcs.getJobRunShellFactory().createJobRunShell(bndle);
//这个里面会用我们自定义的Job来new一个对象，并把相关执行Job是需要的数据传给JobExecutionContextImpl(这是我们自定义job的execute方法参数)
shell.initialize(qs);
} catch (SchedulerException se) {
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
continue;
}
// 这里是把任务放入到线程池中
if (qsRsrcs.getThreadPool().runInThread(shell) == false) {
// 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);
}
}
我们会把任务封装成JobRunShell线程任务，然后放到线程池中跑动。
qsRsrcs.getThreadPool().runInThread(shell) 的源码是：
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);
} 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;
}
这里显示查询有没有空闲的线程，如果没有就等待。有的话，生成一个WorkerThread线程，去跑动
wt.run(runnable);这里的runnable就是JobRunShell。
那么至于JobRunShell里的run方法时怎样的呢？
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);
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);
}
}
我们这边就抓住关键点，就是Job job = jec.getJobInstance();
还有 job.execute(jec);去执行任务，这样子整个调度执行任务就串联起来啦。
结束语
本章结束了整个Quartz调度器整个调度任务，当然有很多细节，比如调度器状态、触发器状态、任务状态等等还没有理解透彻，但是我认为对于我现在来说不是特别的重要，如果有需要我再进去深入修改就好了。最主要的是知道了Quartz是怎么玩的。而且最近工作中也没有特别用Quartz的地方，倒是数据库路由这块需要用到，所以我又要开启阅读数据库路由的源码啦~~~~ 大家有兴趣的可以持续关注我哦~~~~