[Openstack-operators] [nova] Usability question for the server migrations API

Matt Riedemann mriedemos at gmail.com
Fri Apr 14 20:27:42 UTC 2017

The GET /servers/{server_id}/migrations API only lists in-progress live 
migrations. This is an artifact of when it was originally introduced as 
the os-migrations API which was tightly coupled with the API operation 
to cancel a live migration.

There is a spec [1] which is now approved which proposes to expand that 
to also return other types of in-progress migrations, like cold 
migrations, resizes and evacuations.

What I don't like about the proposal is that it still filters out 
completed migrations from being returned. I never liked the original 
design where only in-progress live migrations would be returned. I 
understand why it was done that way, as a convenience for using those 
results to then cancel a live migration, but seriously that's something 
that can be filtered out properly.

So what I'd propose is that in a new microversion, we'd return all 
migration records for a server, regardless of status. We could provide a 
status filter query parameter if desired to just see in-progress 
migrations, or completed migrations, etc. And the live migration cancel 
action API would still validate that the requested migration to cancel 
is indeed in progress first, else it's a 400 error.

The actual migration entries in the response are quite detailed, so if 
that's a problem, we could change listing to just show some short info 
(id, status, source and target host), and then leave the actual details 
for the show API.

What do operators think about this? Is this used at all? Would you like 
to get all migrations and not just in-progress migrations, with the 
ability to filter as necessary?

[1] https://review.openstack.org/#/c/407237/




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