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From "Timothy Bish (JIRA)" <>
Subject [jira] [Commented] (AMQ-4683) Scheduler discards overdue messages on startup
Date Fri, 23 Aug 2013 16:05:51 GMT


Timothy Bish commented on AMQ-4683:

Case 1 analysis is incorrect.
Case 2 is true although the broker implementation doesn't currently use more than one listener
so it wouldn't happen this way. 

I've made some changes to make the start of dispatching separate from starting the store.
 Now the start of dispatch occurs when the SchedulerBroker is started and is stopped when
its stopped.  Any listener added after the broker could miss jobs but that's an inherent trait
in any event based model. 
> Scheduler discards overdue messages on startup
> ----------------------------------------------
>                 Key: AMQ-4683
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.8.0
>         Environment: Windows 7 64bit, JDK 1.6.0_26
>            Reporter: Andrey Zavodnik
>            Assignee: Timothy Bish
>            Priority: Critical
>              Labels: scheduler
>             Fix For: 5.9.0
>         Attachments:
> When message is scheduled for a delivery (using AMQ_SCHEDULED_PERIOD property) it is
not posted to the queue, but saved to the scheduler’s repository instead. If Broker instance
is shut down at the time for which the message is scheduled for a delivery, the scheduler
will try to process the message at the next time broker is started up. Due to a bug in the
scheduler implementation such messages may be dismissed rather than posted to the queue depending
on the racing conditions inside the JVM.
> Actual bug resides in
> This method first calls JobSchedulerStoreImpl. getJobScheduler(String name) method which
in turn creates an instance of runnable JobSchedulerImpl class and starts it.
> Then SchedulerBroker registers itselfas a listener of the newly created JobSchedulerImpl.
> Unfortunately this may happen after the JobSchedulerImpl have dismissed all the “missed”
tasks as “fired” as there were no listeners configured.

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