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From "David P Grove" <gro...@us.ibm.com>
Subject Re: possible approaches for dynamic assignment of invoker ids
Date Thu, 07 Sep 2017 20:27:49 GMT

Thanks for the feedback on the PR.  I've revised it accordingly to support
optional external assignment of invokerUUIDs and a stable mapping of UUIDs
to assigned topics (invokerIds) to avoid churn on instance restarts.
Please take another look if you are interested.

--dave

"David P Grove" <groved@us.ibm.com> wrote on 09/02/2017 08:17:45 PM:
>
>    I prototyped one possible approach for supporting dynamic assignment
> of invoker instance ids in [1].  This approach adds a round of messaging
to
> invoker startup where the invoker communicates with the controller(s) to
be
> assigned an instance id.   It preserves the current dense numbering of
> invokers, but adds a little latency to system startup.
>    I think it would be possible (with marginally more work) to instead
> change invoker ids to be random UUIDs that the invokers could self
> generate.  This would eliminate the extra round of communication, but
would
> make invoker names more cumbersome to humans and would need some tweaks
in
> the load balancer to add a mapping between sparse UUIDs to a dense
> numbering to be used during the hash-based assignment of incoming work to
> invokers.
>
>    The motivation for dynamic assignment of invoker instance ids is (a)
> elasticity support (frequent resizing of invoker pool to match load) and
> (b) making it easy to use DaemonSets instead of StatefulSets for invokers
> when deploying openwhisk on kubernetes.
>
>    If people have thoughts on the merits of the two possible approaches
> or thoughts on other possible approaches, please comment on the PR or
> discuss here on the dev list
>
> thanks,
>
> --dave
>
> [1] https://github.com/apache/incubator-openwhisk/pull/2689

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