Ken Giusti <kgiu...@gmail.com> wrote:
On Mon, Jul 31, 2017 at 10:01 AM, Adam Spiers <aspi...@suse.com> wrote:
I recently discovered a bug where barbican-worker would hang on
shutdown if queue.asynchronous_workers was changed from 1 to 2:
https://bugs.launchpad.net/barbican/+bug/1705543
resulting in a warning like this:
WARNING oslo_messaging.server [-] Possible hang: stop is waiting for
start to complete
I found a similar bug in Sahara:
https://bugs.launchpad.net/sahara/+bug/1546119
where the fix was to call start() on the RPC service before making the
launcher wait() on it, so I ported the fix to Barbican, and it seems
to work fine:
https://review.openstack.org/#/c/485755
I noticed that both projects use ProcessLauncher; barbican uses
oslo_service.service.launch() which has:
if workers is None or workers == 1:
launcher = ServiceLauncher(conf, restart_method=restart_method)
else:
launcher = ProcessLauncher(conf, restart_method=restart_method)
However, I'm not an expert in oslo.service or oslo.messaging, and one
of Barbican's core reviewers (thanks Kaitlin!) noted that not many
other projects start the task before calling wait() on the launcher,
so I thought I'd check here whether that is the correct fix, or
whether there's something else odd going on.
Any oslo gurus able to shed light on this?
As far as an oslo.messaging server is concerned, the order of operations is:
server.start()
# do stuff until ready to stop the server...
server.stop()
server.wait()
The final wait blocks until all requests that are in progress when stop()
is called finish and cleanup.
Thanks - that makes sense. So the question is, why would
barbican-worker only hang on shutdown when there are multiple workers?
Maybe the real bug is somewhere in oslo_service.service.ProcessLauncher
and it's not calling start() correctly?
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