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From Shubham Gupta <>
Subject Re: Failover in apache 1.8.0
Date Fri, 20 Jul 2018 20:42:07 GMT
Hi Ruiqin Yang,

Can you please elaborate on what is meant by "and the scheduler lost track
of it"  in your second paragraph? When can this happen? Also, what is the
default state when the scheduler restarts? Is it not* None*?

Thanks for your quick reply.

Shubham Gupta

On Fri, Jul 20, 2018 at 1:04 AM Ruiqin Yang <> wrote:

> Hi Shubham,
> Worker running actual airflow task will regularly heartbeat, which updates
> the task instance entry in the DB. Scheduler will kill task instance w/o
> heartbeat for a long time, called zombie tasks, and if the task has retry
> left it will try to reschedule it( given all trigger rules are satisfied).
> If workers have heavy load, the scheduler will still be able to schedule
> tasks( putting tasks into worker queue). And you will just wait for workers
> to pick up the tasks from the queue. If the tasks never get picked up and
> the scheduler lost track of it, their state will be reset to NONE when
> scheduler restarts, they are called orphan tasks.
> FYI, inside Airbnb, Alex Guziel( @saguziel <>)
> has a patch that will requeue tasks if they don't get picked up by workers
> for a long time and he has plan to open source it.
> Cheers,
> Kevin Y
> On Fri, Jul 20, 2018 at 12:40 AM Shubham Gupta <
> >
> wrote:
> > Hi,
> >
> > I would like to know what happens if a Celery worker running one of the
> > tasks crashes. Will the job be rescheduled?
> >
> > Also, if the scheduler is not able to schedule a task on time due to
> heavy
> > load on all workers, what will happen to the task?
> >
> > Regards
> > Shubham Gupta
> >

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