mojo should support setting options for juju services to match existing deploy phase configs

[Tom Haddon]

Currently if you run a deploy phase against an already deployed environment, and some of the config options have changed, juju-deployer won't sync the changes for you (see bug #1200663). We should add an option to mojo to support this. This should be available as a deploy phase option, as well as a standalone phase.

As an example:

deploy config=services local=services-secrets sync-config=True

Or a standalone phase:

sync-deploy-config config=services local=services-secrets

[Robin Winslow (nottrobin)]

We have code to do this in mojo-comms-maas-io.

https://bazaar.launchpad.net/~canonical-is/canonical-mojo-specs/mojo-comms-maas-io/view/head:/comms/shared/scripts/update-deployed-charms-golive.py
Which uses:
https://bazaar.launchpad.net/~canonical-is/canonical-mojo-specs/mojo-comms-maas-io/view/head:/comms/shared/scripts/lib/mojo_helpers.py#L109

In case it's any help.

[Robin Winslow (nottrobin)]

Apologies for the private link. Here's a public paste of the relevant part of that code - "update_deployed_services".

http://pastebin.ubuntu.com/14687410/

It does the following:

- Back-up existing local charms
- Go through each service and
  > Upgrade its charm if it changed
  > Update its settings if they've changed

It does the charm-upgrade (as mentioned in this bug: https://bugs.launchpad.net/mojo/+bug/1530831) and the settings-update together, because in some situations you may have new settings which only work with the new charm version and would break the old one - so updating the two as close to each other as possible is safest.