Horizontal scaling between clouds?


Recently I just spun up a postgresql machine in my MAAS cloud on one side of the country.
I then scaled the application using a tag in MAAS and had the replica come up in a different AZ on the other side of the country. It’s a pretty neat solution if say; Datacentre A blows up, at least I have a copy in Datacentre B.
I’ve been wondering would it be possible to further scale that application into Google cloud for example?
I thought I could do this using the -m and --to flags but that just seems to scale things within the same model and controller.

I tried to do it using:

juju add-unit -n 1 awx-postgres -m juju-controller:awx-ansible --to 0

Is it possible to do something like:

juju add-unit -n 1 awx-postgres -m maascontroller:awx-ansible --to googlecontroller:awx-ansible:0

Or am I just being a f@#$tard


No, it’s not currently possible to do that. What we’d suggest is that charms that want to really support geographic fail over do it across relations. So you’d have your production HA setup say in us-east1 and then deploy a second HA cluster in eu-west1 and then use a cross model relation that’s setup for that purpose on the charms. Doing failover on that scale involves a bit more complex logic than the normal “I lost one of the local cluster” and so I think this setup would be the more explicit and clear way to go about it.


The Juju Show #42 - 18:00UTC - Nov 14th