Hi Sandor On Fri, 26 Jan 2018 at 13:32 Sandor Zeestraten <zando...@gmail.com> wrote:
> 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 > > Questions: > 1. Is there a preferred way to migrate OpenStack services deployed by > charms? > I think your approach above is how I've always envisioned deployments would migrate services between machines. > 2. Does the plan above look somewhat sane? > Yes - esp the bit about increasing the cluster_count on the hacluster applications *prior* to adding the new units to the cluster. Failure todo this results in some confused behaviour from corosync. > 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.launchpad.net/charm-hacluster/+bug/1424048 > Set cluster_count before adding the units (I remember that bug). > 4. Anything to keep in mind for scaling up and down the rabbitmq and > percona clusters? > For PXC bear in mind that if you have a large amount of data in your database, its going to take a bit of time and generate some load in terms of disk IO and network IO whilst the new unit receive a full state transfer. I'd also recommend testing your migration process first - this does mean having some spare kit around to standup a second cloud and then testing the migration. I believe the above should work fine, but I'd not want you to trip over the edge case/bug we've not seen during testing in your production environment. Cheers James
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