[nova][dev][ops] server status when compute host is down

Matt Riedemann mriedemos at gmail.com
Thu May 23 18:53:43 UTC 2019

On 5/23/2019 1:47 PM, Dan Smith wrote:
> It also avoids the case where a script is polling for an instance's
> state, and if it becomes anything other than ACTIVE, it takes action or
> wakes someone up. If you've just taken the compute service down for an
> upgrade (or rabbit took a dump) you don't end up freaking out because
> "the instance has changed state" which is what that looks like from the
> outside. If you_want_  to take action based on the host's state, then
> you look at that attribute (if allowed) and make decisions thusly.

This raises another concern - if the UNKNOWN status is not baked into 
the instance.vm_state itself, then what do you do about notifications 
that nova is sending out? Would those also be checking the host status 
and changing the instance status in the notification payload to UNKNOWN?

Anyway, it's stuff like this that requires a lot more thought than just 
deciding on a whim that we'd like some behavior change in the API (note 
the original email nor any of the people agreeing with it in this thread 
said anything about a new microversion).

Rather than deal with all of these side effects, just explain to people 
that need this information how to configure their cloud to expose it and 
how to write their client side tooling to get it.




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