<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Jan 28, 2013, at 3:54 PM, Vishvananda Ishaya <<a href="mailto:vishvananda@gmail.com">vishvananda@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><meta http-equiv="Content-Type" content="text/html charset=windows-1252"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Jan 28, 2013, at 12:58 PM, Alex Glikson <<a href="mailto:GLIKSON@il.ibm.com">GLIKSON@il.ibm.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><font size="2" face="sans-serif">Hi all,</font>
<br>
<br><font size="2" face="sans-serif">As (some of) you know, a host can be
put into maintenance mode by invoking "host_update <host-xx>
–maintenance enable/disable", which would disable future provisioning
on this host, and would trigger migration of guest VMs to other hosts (e.g.,
within a host aggregate). Such requests are currently routed directly to
the nova-compute on the corresponding node. The only implementation is
available for Xen, delegating to XenAPI pool operations. </font>
<br><font size="2" face="sans-serif">We have recently submitted a small patch
directing the host maintenance requests to scheduler instead of nova-compute,
aiming to enable wider range of implementations. A rather straightforward
implementation that we had in mind could leverage the scheduler capabilities
to find placement for VMs, and live migration capabilities to evacuate
them.</font>
<br><font size="2" face="sans-serif">During the review, an interesting perspective
has been brought up, suggesting that such an orchestration is better to
be implemented in the recently introduced nova-conductor, rather than in
scheduler.</font>
<br><font size="2" face="sans-serif">While I personally agree that scheduler
might not be the best place for orchestration, I wonder whether nova-conductor
is the right place, whether people think that it is mature enough to start
becoming an orchestration component, and what would make most sense in
the short term, to enable a more flexible host evacuation (in Grizzly,
hopefully). I am aware of many use-cases where such capability would be
of great value.</font>
<br>
<br><a href="https://review.openstack.org/#/c/19636/"><font size="2" face="sans-serif">https://review.openstack.org/#/c/19636/</font></a>
<br>
<br><font size="2" face="sans-serif">Would appreciate your thoughts.</font> </blockquote><br></div><div>I agree that it might not be the right long-term place for functionality like this but we haven't yet added any top-down calls to the conductor (everything is from the compute-node up), and until we move live-migration logic into the conductor I don't see any reason to put this functionality there. This seems closely tied with the migration code and I think both should be in the same place wherever they end up.</div></div></blockquote><div><br></div><div>I don't think that "we haven't yet added any top-down calls to the conductor" is a good reason not to look at it for this. :) I'd prefer to see us start moving in the correct direction here. Fair point about being close to the live migration code… although I don't know how close it really needs to be. If this is just going to fire off a bunch of live migrations for instances, I don't think it needs to be near. If it's going to be more involved, I can see it making sense to put it near by. However, I'd rather not see a bunch of orchestration logic added to the scheduler. I'd work on things in a different order and start moving things to nova-conductor where I feel like they now belong.</div><div><br></div><div>- Chris</div><div><br></div><div><br></div></div></body></html>