[openstack-dev] [nova] Should we make rebuild + new image on a volume-backed instance fail fast?

Sean Dague sean at dague.net
Fri Oct 6 18:08:25 UTC 2017

On 10/06/2017 01:22 PM, Matt Riedemann wrote:
> So with all of this in mind, should we at least consider, until at least
> someone owns supporting this, that the API should fail with a 400
> response if you're trying to rebuild with a new image on a volume-backed
> instance? That way it's a fast failure in the API, similar to trying to
> backup a volume-backed instance fails fast.
> If we did, that would change the API response from a 202 today to a 400,
> which is something we normally don't do. I don't think a microversion
> would be necessary if we did this, however, because essentially what the
> user is asking for isn't what we're actually giving them, so it's a
> failure in an unexpected way even if there is no fault recorded, it's
> not what the user asked for. I might not be thinking of something here
> though, like interoperability for example - a cloud without this change
> would blissfully return 202 but a cloud with the change would return a
> 400...so that should be considered.

Yes, and this is the kind of thing I think we'd backport to all stable
branches as well. Right now this is effectively a silent 500 (giving a
202 that we know will never actually do what is asked).


Sean Dague

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