Add service relations watcher

Add service relations watcher



https://code.launchpad.net/~fwereade/juju-core/watch-service-relations/+merge/111832

(do not edit description out of merge proposal)

[fwereade, 2012-06-25 12:53:36]

Please take a look.

[fwereade, 2012-06-28 14:09:42]

Please take a look.

[niemeyer, 2012-07-03 01:19:56]

LGTM with doc suggestions only. So much easier to review watchers now.

https://codereview.appspot.com/6338059/diff/3001/state/watcher.go
File state/watcher.go (right):

https://codereview.appspot.com/6338059/diff/3001/state/watcher.go#newcode525
state/watcher.go:525: // ServiceRelationsWatcher notifies of changes to a
service's relations.
// ServiceRelationsWatcher sends notifications when a relation
// that includes the service is added or removed.

https://codereview.appspot.com/6338059/diff/3001/state/watcher.go#newcode550
state/watcher.go:550: // the service enters and leaves relations.
This is not bad at all, but I guess we could just reproduce the comment:

// Changes returns a channel that will receive changes when
// a relation that includes the service is added or removed.

https://codereview.appspot.com/6338059/diff/3001/state/watcher.go#newcode552
state/watcher.go:552: // state, corresponding to that returned by
service.Relations.
While we're here, this is something I've been meaning to suggest for some time
on all watches. I suspect this would read better as:

s/that/what would be/

Because there's a matter of timing that is lost on the original comment. If we
call the given method, it may not return the same value, whether we call it
before or after (IOW, it's just a hypothesis).

[fwereade, 2012-07-03 22:27:19]

*** Submitted:

Add service relations watcher

R=niemeyer
CC=
https://codereview.appspot.com/6338059