[Maas-devel] Cluster download tasks completely block other jobs :(
Raphaël Badin
raphael.badin at canonical.com
Thu Jun 12 07:11:25 UTC 2014
[...]
> I've filed a critical bug about this.
> https://bugs.launchpad.net/maas/+bug/1328351
Even if other tasks might take a long time to execute (powering up a
machine might for instance), the import task is a bit of a special case
in the sense that it can take a really long time to execute *and* it
doesn't make any sense to have two instances of this task running at the
same time. Plus it can be triggered both by a user and by a cron-like
mechanism.
We could change the import task so that it grabs a file-based lock when
it starts. Any import task started before the release of the lock would
just exit silently. Celery has provision to help us deal gracefully
with failure modes (task crashing without releasing the lock, etc.).
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