[openstack-dev] [nova] Rocky PTG summary - cells

Chris Dent cdent+os at anticdent.org
Wed Mar 14 18:26:07 UTC 2018

On Wed, 14 Mar 2018, melanie witt wrote:

> I’ve created a summary etherpad [0] for the nova cells session from the PTG and included a plain text export of it on this email.

Nice summary. Apparently I wasn't there or paying attention when
something was decided:

>  * An attempt to delete an instance in a "down" cell should result in a 500 or 503 error.

Depending on how we look at it, this doesn't really align with what
500 or 503 are supposed to be used. They are supposed to indicate
that the web server is broken in some fashion: 500 being an
unexpected and uncaught exception in the web server, 503 that the
web server is either overloaded or down for maintenance.

So, you could argue that 409 is the right thing here (as seems to
always happen when we discuss these things). You send a DELETE to
kill the instance, but the current state of the instance is "on a
cell that can't be reached" which is in "conflict" with the state
required to do a DELETE.

If a 5xx is really necessary, for whatever reason, then 503 is a
better choice than 500 because it at least signals that the broken
thing is sort of "over there somewhere" rather than the web server
having an error (which is what 500 is supposed to mean).

Chris Dent                       ٩◔̯◔۶           https://anticdent.org/
freenode: cdent                                         tw: @anticdent

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