Quartz_理解1

public class HelloWorldMain {
    Log log = LogFactory.getLog(HelloWorldMain.class);
     
    public void run() {
        try {
            //取得Schedule对象
            SchedulerFactory sf = new StdSchedulerFactory();
            Scheduler sch = sf.getScheduler(); 
             
            JobDetail jd = new JobDetail("HelloWorldJobDetail",Scheduler.DEFAULT_GROUP,HelloWorldJob.class);
            Trigger tg = TriggerUtils.makeMinutelyTrigger(1);
            tg.setName("HelloWorldTrigger");
             
            sch.scheduleJob(jd, tg);
            sch.start();
        } catch ( Exception e ) {
            e.printStackTrace();
             
        }
    }
    public static void main(String[] args) {
        HelloWorldMain hw = new HelloWorldMain();
        hw.run();
    }
}

public Scheduler getScheduler() throws SchedulerException {
        if (cfg == null) {
            initialize();
        }
        SchedulerRepository schedRep = SchedulerRepository.getInstance();
        //从"调度器仓库"中根据properties的SchedulerName配置获取一个调度器实例
        Scheduler sched = schedRep.lookup(getSchedulerName());
        if (sched != null) {
            if (sched.isShutdown()) {
                schedRep.remove(getSchedulerName());
            } else {
                return sched;
            }
        }
        //初始化调度器
        sched = instantiate();
        return sched;
    }

public void initialize(ClassLoadHelper loadHelper,
            SchedulerSignaler signaler) throws SchedulerConfigException {
        if (dsName == null) {
            throw new SchedulerConfigException("DataSource name not set.");
        }
        classLoadHelper = loadHelper;
        if(isThreadsInheritInitializersClassLoadContext()) {
            log.info("JDBCJobStore threads will inherit ContextClassLoader of thread: " + Thread.currentThread().getName());
            initializersLoader = Thread.currentThread().getContextClassLoader();
        }
         
        this.schedSignaler = signaler;
        // If the user hasn‘t specified an explicit lock handler, then
        // choose one based on CMT/Clustered/UseDBLocks.
        if (getLockHandler() == null) {
             
            // If the user hasn‘t specified an explicit lock handler,
            // then we *must* use DB locks with clustering
            if (isClustered()) {
                setUseDBLocks(true);
            }
             
            if (getUseDBLocks()) {
                if(getDriverDelegateClass() != null && getDriverDelegateClass().equals(MSSQLDelegate.class.getName())) {
                    if(getSelectWithLockSQL() == null) {
                        //读取数据库LOCKS表中对应当前调度器的锁信息
                        String msSqlDflt = "SELECT * FROM {0}LOCKS WITH (UPDLOCK,ROWLOCK) WHERE " + COL_SCHEDULER_NAME + " = {1} AND LOCK_NAME = ?";
                        getLog().info("Detected usage of MSSQLDelegate class - defaulting ‘selectWithLockSQL‘ to ‘" + msSqlDflt + "‘.");
                        setSelectWithLockSQL(msSqlDflt);
                    }
                }
                getLog().info("Using db table-based data access locking (synchronization).");
                setLockHandler(new StdRowLockSemaphore(getTablePrefix(), getInstanceName(), getSelectWithLockSQL()));
            } else {
                getLog().info(
                    "Using thread monitor-based data access locking (synchronization).");
                setLockHandler(new SimpleSemaphore());
            }
        }
    }

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()
        //通知该调度器的listener启动开始
        notifySchedulerListenersStarting();
        if (initialStart == null) {
            initialStart = new Date();
            //启动调度器的线程
            this.resources.getJobStore().schedulerStarted();            
            //启动plugins
            startPlugins();
        } else {
            resources.getJobStore().schedulerResumed();
        }
        schedThread.togglePause(false);
        getLog().info(
                "Scheduler " + resources.getUniqueIdentifier() + " started.");
        //通知该调度器的listener启动完成
        notifySchedulerListenersStarted();
    }

public void run() {
        boolean lastAcquireFailed = false;
        //
        while (!halted.get()) {
            try {
                // check if we‘re supposed to pause...
                synchronized (sigLock) {
                    while (paused && !halted.get()) {
                        try {
                            // wait until togglePause(false) is called...
                            sigLock.wait(1000L);
                        } catch (InterruptedException ignore) {
                        }
                    }
                    if (halted.get()) {
                        break;
                    }
                }
                /获取当前线程池中线程的数量
                int availThreadCount = qsRsrcs.getThreadPool().blockForAvailableThreads();
                if(availThreadCount > 0) { // will always be true, due to semantics of blockForAvailableThreads...
                    List<OperableTrigger> triggers = null;
                    long now = System.currentTimeMillis();
                    clearSignaledSchedulingChange();
                    try {
                        //调度器在trigger队列中寻找30秒内一定数目的trigger准备执行调度,
                        //参数1:nolaterthan = now+3000ms,参数2 最大获取数量,大小取线程池线程剩余量与定义值得较小者
                        //参数3 时间窗口 默认为0,程序会在nolaterthan后加上窗口大小来选择trigger
                        triggers = qsRsrcs.getJobStore().acquireNextTriggers(
                                now + idleWaitTime, Math.min(availThreadCount, qsRsrcs.getMaxBatchSize()), qsRsrcs.getBatchTimeWindow());
                        //上一步获取成功将失败标志置为false;
                        lastAcquireFailed = false;
                        if (log.isDebugEnabled())
                            log.debug("batch acquisition of " + (triggers == null ? 0 : triggers.size()) + " triggers");
                    } catch (JobPersistenceException jpe) {
                        if(!lastAcquireFailed) {
                            qs.notifySchedulerListenersError(
                                "An error occurred while scanning for the next triggers to fire.",
                                jpe);
                        }
                        //捕捉到异常则值标志为true,再次尝试获取
                        lastAcquireFailed = true;
                        continue;
                    } catch (RuntimeException e) {
                        if(!lastAcquireFailed) {
                            getLog().error("quartzSchedulerThreadLoop: RuntimeException "
                                    +e.getMessage(), e);
                        }
                        lastAcquireFailed = true;
                        continue;
                    }
                    if (triggers != null && !triggers.isEmpty()) {
                        now = System.currentTimeMillis();
                        long triggerTime = triggers.get(0).getNextFireTime().getTime();
                        long timeUntilTrigger = triggerTime - now;//计算距离trigger触发的时间
                        while(timeUntilTrigger > 2) {
                            synchronized (sigLock) {
                                if (halted.get()) {
                                    break;
                                }
                                //如果这时调度器发生了改变,新的trigger添加进来,那么有可能新添加的trigger比当前待执行的trigger
                                //更急迫,那么需要放弃当前trigger重新获取,然而,这里存在一个值不值得的问题,如果重新获取新trigger
                                //的时间要长于当前时间到新trigger出发的时间,那么即使放弃当前的trigger,仍然会导致xntrigger获取失败,
                                //但我们又不知道获取新的trigger需要多长时间,于是,我们做了一个主观的评判,若jobstore为RAM,那么
                                //假定获取时间需要7ms,若jobstore是持久化的,假定其需要70ms,当前时间与新trigger的触发时间之差小于
                                // 这个值的我们认为不值得重新获取,返回false
                                //这里判断是否有上述情况发生,值不值得放弃本次trigger,若判定不放弃,则线程直接等待至trigger触发的时刻
                                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) {
                                    }
                                }
                            }
                            //该方法调用了上面的判定方法,作为再次判定的逻辑
                            //到达这里有两种情况1.决定放弃当前trigger,那么再判定一次,如果仍然有放弃,那么清空triggers列表并
                            // 退出循环 2.不放弃当前trigger,且线程已经wait到trigger触发的时刻,那么什么也不做
                            if(releaseIfScheduleChangedSignificantly(triggers, triggerTime)) {
                                break;
                            }
                            now = System.currentTimeMillis();
                            timeUntilTrigger = triggerTime - now;
                            //这时触发器已经即将触发,值会<2
                        }
                        // 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 {
                                //触发triggers,结果付给bndles,注意,从这里返回后,trigger在数据库中已经经过了锁定,解除锁定,这一套过程
                                //所以说,quratz定不是等到job执行完才释放trigger资源的占有,而是读取完本次触发所需的信息后立即释放资源
                                //然后再执行jobs
                                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;
                            }
                        }
                        //迭代trigger的信息,分别跑job
                        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)
                            //在特殊情况下,bndle可能为null,看triggerFired方法可以看到,当从数据库获取trigger时,如果status不是
                            //STATE_ACQUIRED,那么会直接返回空.quratz这种情况下本调度器启动重试流程,重新获取4次,若仍有问题,
                            // 则抛出异常.
                            if (bndle == null) {
                                qsRsrcs.getJobStore().releaseAcquiredTrigger(triggers.get(i));
                                continue;
                            }
                            //执行job
                            JobRunShell shell = null;
                            try {
                                //创建一个job的Runshell
                                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;
                            }
                            //把runShell放在线程池里跑
                            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)
                }
                //保证负载平衡的方法,每次执行一轮触发后,本scheduler会等待一个随机的时间,这样就使得其他节点上的scheduler可以得到资源.
                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;
    }

public List<OperableTrigger> acquireNextTriggers(final long noLaterThan, final int maxCount, final long timeWindow)
        throws JobPersistenceException {
         
        String lockName;
        if(isAcquireTriggersWithinLock() || maxCount > 1) {
            lockName = LOCK_TRIGGER_ACCESS;
        } else {
            lockName = null;
        }
        return executeInNonManagedTXLock(lockName,
                new TransactionCallback<List<OperableTrigger>>() {
                    public List<OperableTrigger> execute(Connection conn) throws JobPersistenceException {
                        return acquireNextTrigger(conn, noLaterThan, maxCount, timeWindow);
                    }
                },
                new TransactionValidator<List<OperableTrigger>>() {
                    public Boolean validate(Connection conn, List<OperableTrigger> result) throws JobPersistenceException {
                        //...异常处理回调方法
                    }
                });
    }

public List<TriggerFiredResult> triggersFired(final List<OperableTrigger> triggers) throws JobPersistenceException {
        return executeInNonManagedTXLock(LOCK_TRIGGER_ACCESS,
                new TransactionCallback<List<TriggerFiredResult>>() {
                    public List<TriggerFiredResult> execute(Connection conn) throws JobPersistenceException {
                        List<TriggerFiredResult> results = new ArrayList<TriggerFiredResult>();
                        TriggerFiredResult result;
                        for (OperableTrigger trigger : triggers) {
                            try {
                              TriggerFiredBundle bundle = triggerFired(conn, trigger);
                              result = new TriggerFiredResult(bundle);
                            } catch (JobPersistenceException jpe) {
                                result = new TriggerFiredResult(jpe);
                            } catch(RuntimeException re) {
                                result = new TriggerFiredResult(re);
                            }
                            results.add(result);
                        }
                        return results;
                    }
                },
                new TransactionValidator<List<TriggerFiredResult>>() {
                    @Override
                    public Boolean validate(Connection conn, List<TriggerFiredResult> result) throws JobPersistenceException {
                        //...异常处理回调方法
                    }
                });
    }

protected TriggerFiredBundle triggerFired(Connection conn,
            OperableTrigger trigger)
        throws JobPersistenceException {
        JobDetail job;
        Calendar cal = null;
        // Make sure trigger wasn‘t deleted, paused, or completed...
        try { // if trigger was deleted, state will be STATE_DELETED
            String state = getDelegate().selectTriggerState(conn,
                    trigger.getKey());
            if (!state.equals(STATE_ACQUIRED)) {
                return null;
            }
        } catch (SQLException e) {
            throw new JobPersistenceException("Couldn‘t select trigger state: "
                    + e.getMessage(), e);
        }
        try {
            job = retrieveJob(conn, trigger.getJobKey());
            if (job == null) { return null; }
        } catch (JobPersistenceException jpe) {
            try {
                getLog().error("Error retrieving job, setting trigger state to ERROR.", jpe);
                getDelegate().updateTriggerState(conn, trigger.getKey(),
                        STATE_ERROR);
            } catch (SQLException sqle) {
                getLog().error("Unable to set trigger state to ERROR.", sqle);
            }
            throw jpe;
        }
        if (trigger.getCalendarName() != null) {
            cal = retrieveCalendar(conn, trigger.getCalendarName());
            if (cal == null) { return null; }
        }
        try {
            getDelegate().updateFiredTrigger(conn, trigger, STATE_EXECUTING, job);
        } catch (SQLException e) {
            throw new JobPersistenceException("Couldn‘t insert fired trigger: "
                    + e.getMessage(), e);
        }
        Date prevFireTime = trigger.getPreviousFireTime();
        // call triggered - to update the trigger‘s next-fire-time state...
        trigger.triggered(cal);
        String state = STATE_WAITING;
        boolean force = true;
         
        if (job.isConcurrentExectionDisallowed()) {
            state = STATE_BLOCKED;
            force = false;
            try {
                getDelegate().updateTriggerStatesForJobFromOtherState(conn, job.getKey(),
                        STATE_BLOCKED, STATE_WAITING);
                getDelegate().updateTriggerStatesForJobFromOtherState(conn, job.getKey(),
                        STATE_BLOCKED, STATE_ACQUIRED);
                getDelegate().updateTriggerStatesForJobFromOtherState(conn, job.getKey(),
                        STATE_PAUSED_BLOCKED, STATE_PAUSED);
            } catch (SQLException e) {
                throw new JobPersistenceException(
                        "Couldn‘t update states of blocked triggers: "
                                + e.getMessage(), e);
            }
        }
             
        if (trigger.getNextFireTime() == null) {
            state = STATE_COMPLETE;
            force = true;
        }
        storeTrigger(conn, trigger, job, true, state, force, false);
        job.getJobDataMap().clearDirtyFlag();
        return new TriggerFiredBundle(job, trigger, cal, trigger.getKey().getGroup()
                .equals(Scheduler.DEFAULT_RECOVERY_GROUP), new Date(), trigger
                .getPreviousFireTime(), prevFireTime, trigger.getNextFireTime());
    }

3.
select TRIGGER_ACCESS from QRTZ2_LOCKS for update
4.
SELECT TRIGGER_NAME,
TRIGGER_GROUP,
NEXT_FIRE_TIME,
PRIORITY
FROM QRTZ2_TRIGGERS
WHERE SCHEDULER_NAME = ‘CRMscheduler‘
AND TRIGGER_STATE = ‘ACQUIRED‘
AND NEXT_FIRE_TIME <= ‘{timekey 30s latter}‘
AND ( MISFIRE_INSTR = -1
OR ( MISFIRE_INSTR != -1
AND NEXT_FIRE_TIME >= ‘{timekey now}‘ ) )
ORDER BY NEXT_FIRE_TIME ASC,
PRIORITY DESC;
5.
SELECT *
FROM QRTZ2_JOB_DETAILS
WHERE SCHEDULER_NAME = CRMscheduler
AND JOB_NAME = ?
AND JOB_GROUP = ?;
6.
UPDATE TQRTZ2_TRIGGERS
SET TRIGGER_STATE = ‘ACQUIRED‘
WHERE SCHED_NAME = ‘CRMscheduler‘
AND TRIGGER_NAME = ‘{triggerName}‘
AND TRIGGER_GROUP = ‘{triggerGroup}‘
AND TRIGGER_STATE = ‘waiting‘;
7.
INSERT INTO QRTZ2_FIRED_TRIGGERS
(SCHEDULER_NAME,
ENTRY_ID,
TRIGGER_NAME,
TRIGGER_GROUP,
INSTANCE_NAME,
FIRED_TIME,
SCHED_TIME,
STATE,
JOB_NAME,
JOB_GROUP,
IS_NONCONCURRENT,
REQUESTS_RECOVERY,
PRIORITY)
VALUES( ‘CRMscheduler‘, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
8.
commit;
12.
select STAT_ACCESS from QRTZ2_LOCKS for update
13.
SELECT TRIGGER_STATE FROM QRTZ2_TRIGGERS WHERE SCHEDULER_NAME = ‘CRMscheduler‘ AND TRIGGER_NAME = ? AND TRIGGER_GROUP = ?;
14.
SELECT TRIGGER_STATE
FROM QRTZ2_TRIGGERS
WHERE SCHEDULER_NAME = ‘CRMscheduler‘
AND TRIGGER_NAME = ?
AND TRIGGER_GROUP = ?;
14.
SELECT *
FROM QRTZ2_JOB_DETAILS
WHERE SCHEDULER_NAME = CRMscheduler
AND JOB_NAME = ?
AND JOB_GROUP = ?;
15.
SELECT *
FROM QRTZ2_CALENDARS
WHERE SCHEDULER_NAME = ‘CRMscheduler‘
AND CALENDAR_NAME = ?;
16.
UPDATE QRTZ2_FIRED_TRIGGERS
SET INSTANCE_NAME = ?,
FIRED_TIME = ?,
SCHED_TIME = ?,
ENTRY_STATE = ?,
JOB_NAME = ?,
JOB_GROUP = ?,
IS_NONCONCURRENT = ?,
REQUESTS_RECOVERY = ?
WHERE SCHEDULER_NAME = ‘CRMscheduler‘
AND ENTRY_ID = ?;
17.
UPDATE TQRTZ2_TRIGGERS
SET TRIGGER_STATE = ?
WHERE SCHED_NAME = ‘CRMscheduler‘
AND TRIGGER_NAME = ‘{triggerName}‘
AND TRIGGER_GROUP = ‘{triggerGroup}‘
AND TRIGGER_STATE = ？;
18.
UPDATE QRTZ2_TRIGGERS
SET JOB_NAME = ?,
JOB_GROUP = ?,
DESCRIPTION = ?,
NEXT_FIRE_TIME = ?,
PREV_FIRE_TIME = ?,
TRIGGER_STATE = ?,
TRIGGER_TYPE = ?,
START_TIME = ?,
END_TIME = ?,
CALENDAR_NAME = ?,
MISFIRE_INSTRUCTION = ?,
PRIORITY = ?,
JOB_DATAMAP = ?
WHERE SCHEDULER_NAME = SCHED_NAME_SUBST
AND TRIGGER_NAME = ?
AND TRIGGER_GROUP = ?;
19.
commit;