Code review comment for lp:~paulgear/charms/trusty/grafana/layer-grafana-reactive-states-fix

I've been thinking out loud a lot about this merge while in the office, and it boils down to basically one thing that's sorely needed when using the reactive model:

  Locking semantics.

The (now deprecated, I hope) only_once decorator is the most obvious example of this. Unfortunately the implementation doesn't fit our needs, but the desire it expresses is a good one. What you've gone through and done for a lot of this is to add "When not Y" to a lot of "When X" conditions. Again, this ensures that the non-idempotent steps are only run once.

I have always fought for idempotent state-enforcing changes, but accept that those aren't always possible. I'm not sure what the Right Thing is, but this change is definitely not Wrong!