Open Stack

Today we attempted to branch devstack and grenade for liberty, and are
currently blocked because in liberty with openstack client and
novaclient, it's not possible to boot a server from volume using just
the volume id.

That's because of this change in novaclient -
https://review.openstack.org/#/c/221525/

That was done to resolve the issue that strong schema validation in Nova
started rejecting the kinds of calls that novaclient was making for boot
from volume, because the bdm 1 and 2 code was sharing common code and
got a bit tangled up. So 3 bdm 2 params were being sent on every request.

However, https://review.openstack.org/#/c/221525/ removed the ==1 code
path. If you pass in just {"vda": "$volume_id"} the code falls through,
volume id is lost, and nothing is booted. This is how the devstack
exercises and osc recommends booting from volume. I expect other people
might be doing that as well.

There seem to be a few options going forward:

1) fix the client without a revert

This would bring back a ==1 code path, which is basically just setting
volume_id, and move on. This means that until people upgrade their
client they loose access to this function on the server.

2) revert the client and loose up schema validation

If we revert the client to the old code, we also need to accept the fact
that novaclient has been sending 3 extra parameters to this API call
since as long as people can remember. We'd need a nova schema relax to
let those in and just accept that people are going to pass those.

3) fix osc and novaclient cli to not use this code path. This will also
require everyone upgrades both of those to not explode in the common
case of specifying boot from volume on the command line.

I slightly lean towards #2 on a compatibility front, but it's a chunk of
change at this point in the cycle, so I don't think there is a clear win
path. It would be good to collect opinions here. The bug tracking this
is - https://bugs.launchpad.net/python-openstackclient/+bug/1501435

	-Sean

-- 
Sean Dague
http://dague.net