[openstack-dev] [neutron][nova][oslo] Common backoff & timeout utils

Joshua Harlow harlowja at fastmail.com
Thu Apr 21 19:38:54 UTC 2016

Boden Russell wrote:
> I haven't spent much time on this, so the answers below are a first
> approximation based on a quick visual inspection (e.g. subject to change
> when I get a chance to hack on some code).
> On 4/21/16 12:10 PM, Salvatore Orlando wrote:
>> Can you share more details on the "few things we need" that
>> retrying is lacking?
> (a) Some of our existing code uses a 'stepping' scheme (fist N attempts
> with timeout T, next M attempts with timeout U, etc.). For example [1].
> This could also be tackled using chaining.

This might be harder in retrying, but I think I can help u make 
something that will work, since retrying has a way to provide a custom 
delay function.

> (b) It doesn't appear retrying supports capping (ceiling) exponential
> sleep times as we do in [2].



>> Do you think oslo_messaging would be a good target? Or do you think it
>> should go somewhere else?
> My initial thought was to implement it as a subclass of oslo_messaging's
> RPCClient [3] with a nice way for consumers to configure the
> backoff/retry magic. If consumers want a backing off client, then they
> use the new subclass.
> [1] https://github.com/openstack/nova/blob/master/nova/conductor/api.py#L147
> [2] https://review.openstack.org/#/c/280595/
> [3]
> https://github.com/openstack/oslo.messaging/blob/master/oslo_messaging/rpc/client.py#L208
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