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From Bolke de Bruin <>
Subject Re: Multiple Schedulers - "scheduler_lock"
Date Fri, 01 Mar 2019 15:43:58 GMT
I have done quite some work on making it possible to run multiple schedulers at the same time.
 At the moment I don’t think there are real blockers actually to do so. We just don’t
actively test it.

Database locking is mostly in place (DagRuns and TaskInstances). And I think the worst that
can happen is that a task is scheduled twice. The task will detect this most of the time and
kill one off if concurrent if not sequential then I will run again in some occasions. Everyone
is having idempotent tasks right so no harm done? ;-)

Have you encountered issues? Maybe work those out?


Verstuurd vanaf mijn iPad

> Op 1 mrt. 2019 om 16:25 heeft Deng Xiaodong <> het volgende
> Hi Max,
> Following
I’m trying to prepare an AIP for supporting multiple-scheduler in Airflow (mainly for HA
and Higher scheduling performance).
> Along the process of code checking, I found that there is one attribute of DagModel,
“scheduler_lock”. It’s not used at all in current implementation, but it was introduced
long time back (2015) to allow multiple schedulers to work together (
> Since you were the original author of it, it would be very helpful if you can kindly
share why the multiple-schedulers implementation was removed eventually, and what challenges/complexity
there were.
> (You already shared a few valuable inputs in the earlier discussion
, mainly relating to hiccups around concurrency, cross DAG prioritisation & load on DB.
Other than these, anything else you would like to advise?)
> I will also dive into the git history further to understand it better.
> Thanks.
> XD

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