I should add to this if you don’t know what the FPCScheduler is or are
unsure about whether it’s in use, then you definitely are not using it. It
has not yet been released as a default deployment option of core Openwhisk.

On Mon, May 1, 2023 at 8:32 PM Brendan Doyle <bdoyle0...@gmail.com> wrote:

> Hi all,
>
> If you are not using the new fpc scheduler in a cluster that cannot handle
> zero downtime, you can stop reading here.
>
> I have two PR’s linked below that I will be merging in later this week.
> This is to allow getting the max instances per action within a namespace
> into master and to allow future changes to the CreateQueue message without
> another breaking change like this. With that said, it does not prevent an
> in place rolling cluster upgrade but it does require taking a certain
> order. So you have two options to continue on the latest master commit
> before we do an official release of the fpc scheduler:
>
> 1. Perform a blue / green deployment if capable which the new scheduler
> makes simple with the etcd cluster prefix config.
> 2.
> - To perform an in-place cluster change you should first update half of
> the schedulers. At this point the controller will not be able to send a
> CreateQueue message for actions without a queue running onto a scheduler
> that has been upgraded. However the controller should gracefully handle
> this and try to create queue on all schedules before failing the
> activation.
> - Once half of the schedulers have been upgraded, upgrade all of the
> controllers. Any action that already has a queue on a scheduler will work
> fine, any new action at this point will now be able to be created on any
> scheduler that has been upgraded but not the yet to be upgraded.
> - Finally upgrade the remaining schedulers.
>
> So to succinctly summarize the rolling upgrade order: upgrade half the
> schedulers, then all of the controllers, then finish the remaining
> schedulers.
>
> If you object to these changes, please respond by Thursday of this week
> which is when I plan to merge.
>
> https://github.com/apache/openwhisk/pull/5389
>
> https://github.com/apache/openwhisk/pull/5287
>
> Thanks,
> Brendan
>

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