Quartz源码——Quartz调度器的Misfire处理规则（四）

Quartz调度器的Misfire处理规则

调度器的启动和恢复中使用的misfire机制，还需细化！

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SimpleTrigger的misfire机制 默认的 Trigger.MISFIRE_INSTRUCTION_SMART_POLICY !!!

trig.updateAfterMisfire(cal);
getMisfireInstruction() ----> misfireInstruction == 0
——以当前时间为触发频率立即触发执行

SimpleScheduleBuilder ssb = SimpleScheduleBuilder.simpleSchedule();

ssb.withMisfireHandlingInstructionFireNow();//1
ssb.withMisfireHandlingInstructionIgnoreMisfires();//2
ssb.withMisfireHandlingInstructionNextWithExistingCount();//3
ssb.withMisfireHandlingInstructionNextWithRemainingCount();//4
ssb.withMisfireHandlingInstructionNowWithExistingCount();//5
ssb.withMisfireHandlingInstructionNowWithRemainingCount();//6

//1
withMisfireHandlingInstructionFireNow  ---> misfireInstruction == 1
——以当前时间为触发频率立即触发执行
——执行至FinalTIme的剩余周期次数
——以调度或恢复调度的时刻为基准的周期频率，FinalTime根据剩余次数和当前时间计算得到
——调整后的FinalTime会略大于根据starttime计算的到的FinalTime值

//2
withMisfireHandlingInstructionIgnoreMisfires ---> misfireInstruction == -1
—以错过的第一个频率时间立刻开始执行
——重做错过的所有频率周期
——当下一次触发频率发生时间大于当前时间以后，按照Interval的依次执行剩下的频率
——共执行RepeatCount+1次

//3
withMisfireHandlingInstructionNextWithExistingCount ---> misfireInstruction == 5
——不触发立即执行
——等待下次触发频率周期时刻，执行至FinalTime的剩余周期次数
——以startTime为基准计算周期频率，并得到FinalTime
——即使中间出现pause，resume以后保持FinalTime时间不变

//4
withMisfireHandlingInstructionNextWithRemainingCount ---> misfireInstruction = 4
——不触发立即执行
——等待下次触发频率周期时刻，执行至FinalTime的剩余周期次数
——以startTime为基准计算周期频率，并得到FinalTime
——即使中间出现pause，resume以后保持FinalTime时间不变

//5
withMisfireHandlingInstructionNowWithExistingCount ---> misfireInstruction = 2
——以当前时间为触发频率立即触发执行
——执行至FinalTIme的剩余周期次数
——以调度或恢复调度的时刻为基准的周期频率，FinalTime根据剩余次数和当前时间计算得到
——调整后的FinalTime会略大于根据starttime计算的到的FinalTime值

//6
withMisfireHandlingInstructionNowWithRemainingCount --- >misfireInstruction = 3
——以当前时间为触发频率立即触发执行
——执行至FinalTIme的剩余周期次数
——以调度或恢复调度的时刻为基准的周期频率，FinalTime根据剩余次数和当前时间计算得到
——调整后的FinalTime会略大于根据starttime计算的到的FinalTime值


MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_REMAINING_REPEAT_COUNT 值为 3
——此指令导致trigger忘记原始设置的starttime和repeat-count
——触发器的repeat-count将被设置为剩余的次数
——这样会导致后面无法获得原始设定的starttime和repeat-count值

updateAfterMisfire 方法源码：

 /**
     * <p>
     * Updates the <code>SimpleTrigger</code>'s state based on the
     * MISFIRE_INSTRUCTION_XXX that was selected when the <code>SimpleTrigger</code>
     * was created.
     * </p>
     * 
     * <p>
     * If the misfire instruction is set to MISFIRE_INSTRUCTION_SMART_POLICY,
     * then the following scheme will be used: <br>
     * <ul>
     * <li>If the Repeat Count is <code>0</code>, then the instruction will
     * be interpreted as <code>MISFIRE_INSTRUCTION_FIRE_NOW</code>.</li>
     * <li>If the Repeat Count is <code>REPEAT_INDEFINITELY</code>, then
     * the instruction will be interpreted as <code>MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT</code>.
     * <b>WARNING:</b> using MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT 
     * with a trigger that has a non-null end-time may cause the trigger to 
     * never fire again if the end-time arrived during the misfire time span. 
     * </li>
     * <li>If the Repeat Count is <code>&gt; 0</code>, then the instruction
     * will be interpreted as <code>MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_EXISTING_REPEAT_COUNT</code>.
     * </li>
     * </ul>
     * </p>
     * */
/*
基于在创建SimpleTrigger时选择的MISFIRE_INSTRUCTION_XXX更新SimpleTrigger的状态。
如果失火指令设置为MISFIRE_INSTRUCTION_SMART_POLICY，则将使用以下方案：

•如果重复计数为0，则指令将解释为MISFIRE_INSTRUCTION_FIRE_NOW。
•如果重复计数为REPEAT_INDEFINITELY，则指令将解释为MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT。 警告：如果触发器具有非空的结束时间，则使用MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT可能会导致触发器在失火时间范围内到达结束时，不会再次触发。
•如果重复计数大于0，则指令将解释为MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_EXISTING_REPEAT_COUNT。
*/
    @Override
    public void updateAfterMisfire(Calendar cal) {
        int instr = getMisfireInstruction();//获取misfire的值，默认为0
        
        if(instr == Trigger.MISFIRE_INSTRUCTION_IGNORE_MISFIRE_POLICY)//instr == -1
            return;
        
        if (instr == Trigger.MISFIRE_INSTRUCTION_SMART_POLICY) { //instr == 1
            if (getRepeatCount() == 0) {
                instr = MISFIRE_INSTRUCTION_FIRE_NOW; //instr = 1
            } else if (getRepeatCount() == REPEAT_INDEFINITELY) {//getRe..Count == -1
	            //instr = 4
                instr = MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT;
            } else {
                // if (getRepeatCount() > 0)
                instr = MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_EXISTING_REPEAT_COUNT;//instr == 2
            }
		            //instr  == 1
        } else if (instr == MISFIRE_INSTRUCTION_FIRE_NOW && getRepeatCount() != 0) {
	        //instr  == 3
            instr = MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_REMAINING_REPEAT_COUNT;
        }

        if (instr == MISFIRE_INSTRUCTION_FIRE_NOW) { //instr  == 1
            setNextFireTime(new Date());
			            //instr  == 5
        } else if (instr == MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_EXISTING_COUNT) {
            Date newFireTime = getFireTimeAfter(new Date());
            while (newFireTime != null && cal != null
                    && !cal.isTimeIncluded(newFireTime.getTime())) {
                newFireTime = getFireTimeAfter(newFireTime);

                if(newFireTime == null)
                    break;
                
                //avoid infinite loop
                java.util.Calendar c = java.util.Calendar.getInstance();
                c.setTime(newFireTime);
                if (c.get(java.util.Calendar.YEAR) > YEAR_TO_GIVEUP_SCHEDULING_AT) {
                    newFireTime = null;
                }
            }
            setNextFireTime(newFireTime);
             //instr  == 4
        } else if (instr == MISFIRE_INSTRUCTION_RESCHEDULE_NEXT_WITH_REMAINING_COUNT) {
            Date newFireTime = getFireTimeAfter(new Date());
            while (newFireTime != null && cal != null
                    && !cal.isTimeIncluded(newFireTime.getTime())) {
                newFireTime = getFireTimeAfter(newFireTime);

                if(newFireTime == null)
                    break;
                
                //avoid infinite loop
                java.util.Calendar c = java.util.Calendar.getInstance();
                c.setTime(newFireTime);
                if (c.get(java.util.Calendar.YEAR) > YEAR_TO_GIVEUP_SCHEDULING_AT) {
                    newFireTime = null;
                }
            }
            if (newFireTime != null) {
                int timesMissed = computeNumTimesFiredBetween(nextFireTime,
                        newFireTime);
                setTimesTriggered(getTimesTriggered() + timesMissed);
            }

            setNextFireTime(newFireTime);
        } else if (instr == MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_EXISTING_REPEAT_COUNT) { //instr  == 2
            Date newFireTime = new Date();
            if (repeatCount != 0 && repeatCount != REPEAT_INDEFINITELY) {
                setRepeatCount(getRepeatCount() - getTimesTriggered());
                setTimesTriggered(0);
            }
            
            if (getEndTime() != null && getEndTime().before(newFireTime)) {
                setNextFireTime(null); // We are past the end time
            } else {
                setStartTime(newFireTime);
                setNextFireTime(newFireTime);
            } 
        } else if (instr == MISFIRE_INSTRUCTION_RESCHEDULE_NOW_WITH_REMAINING_REPEAT_COUNT) { //instr  == 3
            Date newFireTime = new Date();

            int timesMissed = computeNumTimesFiredBetween(nextFireTime,
                    newFireTime);

            if (repeatCount != 0 && repeatCount != REPEAT_INDEFINITELY) { //repeatCount == -1
                int remainingCount = getRepeatCount()
                        - (getTimesTriggered() + timesMissed);
                if (remainingCount <= 0) { 
                    remainingCount = 0;
                }
                setRepeatCount(remainingCount);
                setTimesTriggered(0);
            }

            if (getEndTime() != null && getEndTime().before(newFireTime)) {
                setNextFireTime(null); // We are past the end time
            } else {
                setStartTime(newFireTime);
                setNextFireTime(newFireTime);
            } 
        }

    }

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CronTrigger的misfire机制----默认的 Trigger.MISFIRE_INSTRUCTION_SMART_POLICY !!!
trig.updateAfterMisfire(cal);
getMisfireInstruction() ----> misfireInstruction == 0

CronScheduleBuilder csb = CronScheduleBuilder.cronSchedule("0/5 * * * * ?");
				
csb.withMisfireHandlingInstructionDoNothing();
csb.withMisfireHandlingInstructionFireAndProceed();
csb.withMisfireHandlingInstructionIgnoreMisfires();

withMisfireHandlingInstructionDoNothing ---> misfireInstruction = 2
——不触发立即执行
——等待下次Cron触发频率到达时刻开始按照Cron频率依次执行

withMisfireHandlingInstructionFireAndProceed ---> misfireInstruction = 1
——以当前时间为触发频率立刻触发一次执行
——然后按照Cron频率依次执行

withMisfireHandlingInstructionIgnoreMisfires ---> misfireInstruction = -1
——以错过的第一个频率时间立刻开始执行
——重做错过的所有频率周期后
——当下一次触发频率发生时间大于当前时间后，再按照正常的Cron频率依次执行

updateAfterMisfire 方法源码：

/**
     * <p>
     * Updates the <code>CronTrigger</code>'s state based on the
     * MISFIRE_INSTRUCTION_XXX that was selected when the <code>CronTrigger</code>
     * was created.
     * </p>
     * 
     * <p>
     * If the misfire instruction is set to MISFIRE_INSTRUCTION_SMART_POLICY,
     * then the following scheme will be used: <br>
     * <ul>
     * <li>The instruction will be interpreted as <code>MISFIRE_INSTRUCTION_FIRE_ONCE_NOW</code>
     * </ul>
     * </p>
     */
/*
	根据创建CronTrigger时选择的MISFIRE_INSTRUCTION_XXX更新CronTrigger的状态。

如果失火指令设置为MISFIRE_INSTRUCTION_SMART_POLICY，则将使用以下方案：

•指令将解释为MISFIRE_INSTRUCTION_FIRE_ONCE_NOW
*/
     
    @Override
    public void updateAfterMisfire(org.quartz.Calendar cal) {
        int instr = getMisfireInstruction();//获取misfire的值，默认为0

        if(instr == Trigger.MISFIRE_INSTRUCTION_IGNORE_MISFIRE_POLICY)//instr  == -1
            return;

        if (instr == MISFIRE_INSTRUCTION_SMART_POLICY) {//instr  == 0
            instr = MISFIRE_INSTRUCTION_FIRE_ONCE_NOW;//instr = 1
        }

        if (instr == MISFIRE_INSTRUCTION_DO_NOTHING) {//instr  == 2
            Date newFireTime = getFireTimeAfter(new Date());
            while (newFireTime != null && cal != null
                    && !cal.isTimeIncluded(newFireTime.getTime())) {
                newFireTime = getFireTimeAfter(newFireTime);
            }
            setNextFireTime(newFireTime);
        } else if (instr == MISFIRE_INSTRUCTION_FIRE_ONCE_NOW) {//instr  == 1
            setNextFireTime(new Date());
        }
    }

参考文章：https://my.oschina.net/chenleijava/blog/109904

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