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

Matt Riedemann mriedemos at gmail.com
Wed Jul 18 20:14:55 UTC 2018

On 7/18/2018 1:13 PM, melanie witt wrote:
>> 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 
> microversion.

Correct, we can't just remove it since that's a backward incompatible 
microversion change. Plus, NFV people *love* it.

>>> 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. 

Yes, I agree RequestSpec.num_instances is something we shouldn't persist 
since it's only applicable to the initial server create (you can't 
multi-migrate a group of instances, for example - but I'm sure people 
have asked for that at some point), and it should be set per call to the 
scheduler, but that's a wider-ranging change since it would touch 
several parts of conductor, plus the request spec, plus the 

Honestly I'm OK with doing either, and I don't think they are mutually 
exclusive things, so we could make num_instances a per-request thing in 
the future for sanity reasons.




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