cross-model relations

[James Troup]

It's fairly well accepted best common practice to run services in
multiple regions in any given cloud (AWS or OpenStack) for maximum
availability.

Unfortunately juju doesn't support this model as relations can't span
across environments and each region is its own environment.

This also makes it hard to e.g. run a multi-DC swift as deployed by
MAAS and Juju.

[Clint Byrum (clint-fewbar)]

There are a number of workarounds, but none of them are attractive. Users will absolutely need a clear way to have service orchestration cross from one environment to another.

[Nick Moffitt (nick-moffitt)]

This remains a critical blocker for a large number of technical requirements we have. We are constantly required to write entire charms to get around this deficiency in juju-core. The power of juju is relations, and yet we're stuck manually setting configuration variables on services in multiple environments and hoping that the synchronisation issues won't bite us, or that we didn't make an error.

Please let us use juju relations to orchestrate our services in multiple environments!