[openstack-dev] [nova] Bug 1781710 killing the check queue

melanie witt melwittt at gmail.com
Wed Jul 18 18:13:58 UTC 2018

On Wed, 18 Jul 2018 12:05:13 -0600, Chris Friesen wrote:
> On 07/18/2018 10:14 AM, Matt Riedemann wrote:
>> As can be seen from logstash [1] this bug is hurting us pretty bad in the check
>> queue.
>> I thought I originally had this fixed with [2] but that turned out to only be
>> part of the issue.
>> I think I've identified the problem but I have failed to write a recreate
>> regression test [3] because (I think) it's due to random ordering of which
>> request spec we select to send to the scheduler during a multi-create request
>> (and I tried making that predictable by sorting the instances by uuid in both
>> conductor and the scheduler but that didn't make a difference in my test).
> Can we get rid of multi-create?  It keeps causing complications, and it already
> has weird behaviour if you ask for min_count=X and max_count=Y and only X
> instances can be scheduled.  (Currently it fails with NoValidHost, but it should
> arguably start up X instances.)

We've discussed that before but I think users do use it and appreciate 
the ability to boot instances in batches (one request). The behavior you 
describe could be changed with a microversion, though I'm not sure if 
that would mean we have to preserve old behavior with the previous 

>> After talking with Sean Mooney, we have another fix which is self-contained to
>> the scheduler [5] so we wouldn't need to make any changes to the RequestSpec
>> handling in conductor. It's admittedly a bit hairy, so I'm asking for some eyes
>> on it since either way we go, we should get going soon before we hit the FF and
>> RC1 rush which *always* kills the gate.
> One of your options mentioned using RequestSpec.num_instances to decide if it's
> in a multi-create.  Is there any reason to persist RequestSpec.num_instances?
> It seems like it's only applicable to the initial request, since after that each
> instance is managed individually.
> Chris
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