[openstack-dev] [Ironic] [Oslo] Question about Futurist executors (was: NoFreeConductorWorker going away with move to Futurist?)

Dmitry Tantsur dtantsur at redhat.com
Thu Jul 23 12:25:04 UTC 2015


I'm redirecting your question to oslo folks, as I'm afraid my answer can 
be wrong.

On 07/23/2015 01:55 PM, Jim Rollenhagen wrote:
> On Wed, Jul 22, 2015 at 02:40:47PM +0200, Dmitry Tantsur wrote:
>> Hi all!
>> Currently _spawn_worker in the conductor manager raises
>> NoFreeConductorWorker if pool is already full. That's not very user friendly
>> (potential source of retries in client) and does not map well on common
>> async worker patterns.
>> My understanding is that it was done to prevent the conductor thread from
>> waiting on pool to become free. If this is true, we no longer need it after
>> switch to Futurist, as Futurist maintains internal queue for its green
>> executor, just like thread and process executors in stdlib do. Instead of
>> blocking the conductor the request will be queued, and a user won't have to
>> retry vague (and rare!) HTTP 503 error.
>> WDYT about me dropping this exception with move to Futurist?
> I kind of like this, but with my operator hat on this is a bit scary.
> Does Futurist just queue all requests indefinitely? Is it configurable?
> Am I able to get any insight into the current state of that queue?

I believe answer is no, and the reason IIUC is that Futurist executors 
are modeled after stdlib executors, but I may be wrong.

> Just indefinitely queueing up everything seems like it could end with a
> system that's backlogged to death, with no way to determine if that's
> actually the problem or not.
> // jim
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