[nova][ops] Trying to get per-instance live migration timeout action spec unstuck

Matt Riedemann mriedemos at gmail.com
Thu Jan 3 23:23:21 UTC 2019

On 1/3/2019 4:37 PM, Dan Smith wrote:
> Because in nova[0] we currently only switch to post-copy after we decide
> we're not making progress right? 

If you're referring to the "live_migration_progress_timeout" option that 
has been deprecated and was replaced in Stein with the 
live_migration_timeout_action option, which was a pre-requisite for the 
per-instance timeout + action spec.

In Stein, we only switch to post-copy if we hit 
live_migration_completion_timeout and 
live_migration_timeout_action=force_complete and 
live_migration_permit_post_copy=True (and libvirt/qemu are new enough 
for post-copy), otherwise we pause the guest.

So I don't think the stalled progress stuff has applied for awhile (OSIC 
found problems with it in Ocata and disabled/deprecated it).

> If we later allow a configuration where
> post-copy is the default from the start (as I believe is the actual
> current recommendation from the virt people[1]), and someone triggers a
> migration with a short timeout and abort action, we'll not be able to
> actually do the abort.

Sorry but I don't understand this, how does "post-copy from the start" 
apply? If I specify a short timeout and abort action in the API, and the 
timeout is reached before the migration is complete, it should abort, 
just like if I abort it via the API. As noted above, post-copy should 
only be triggered once we reach the timeout, and if you overwrite that 
action to abort (per instance, in the API), it should abort rather than 
switch to post-copy.




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