[Openstack-operators] [charms] Migrating HA control plane by scaling up and down

Sandor Zeestraten zandor.z at gmail.com
Fri Jan 26 13:29:59 UTC 2018

Hey OpenStack Charmers,

We have a Newton deployment on MAAS with 3 controller machines running all
the usual OpenStack controller services in 3x HA with the hacluster charm
in LXD containers. Now we'd like migrate some of those OpenStack services
to 3 larger controller machines. Downtime of the services during the
migration is not an issue.

My current plan is test something like this:
* Add the new controller machines to the model
* Increase the cluster_count from 3 to 6 on the hacluster charm of the
services in question
* Add units to the service to LXD containers on the new controller machine
* Wait for things to deploy and cluster
* Decrease the cluster_count from 6 to 3
* Remove units on the old controller

1. Is there a preferred way to migrate OpenStack services deployed by
2. Does the plan above look somewhat sane?
3. If yes to the above, does the order of changing the cluster_count and
adding/removing units matter? I've seen this bug for example: https://bugs.
4. Anything to keep in mind for scaling up and down the rabbitmq and
percona clusters?


Sandor Zeestraten
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