Add RelationUnit type

Add RelationUnit type

This is kinda like the original RelationUnit proposed a few days ago, but
exposes its various bits of functionality separately rather than being a
magical watch-and-join chimera.

Notably, RelationUnitsWatcher is now exported, so the internal tests have
been dropped.

https://code.launchpad.net/~fwereade/juju-core/relation-unit-methods/+merge/115924

(do not edit description out of merge proposal)

[fwereade, 2012-07-20 09:52:06]

Please take a look.

[fwereade, 2012-07-20 16:01:06]

Please take a look.

[niemeyer, 2012-07-23 11:10:44]

This is awesome. Just needs thinking around errors.

https://codereview.appspot.com/6430055/diff/5001/state/relation.go
File state/relation.go (right):

https://codereview.appspot.com/6430055/diff/5001/state/relation.go#newcode174
state/relation.go:174: if err := ru.scope.prepareJoin(ru.st.zk, ru.role); err !=
nil {
Can you please check whether the error messages coming out of prepareJoin are
sensible enough to have context when returned from Join?

https://codereview.appspot.com/6430055/diff/5001/state/relation.go#newcode182
state/relation.go:182: settings, err := readConfigNode(ru.st.zk,
ru.scope.settingsPath(ru.unit.key))
Ditto. I'm not sure this will have enough context.

https://codereview.appspot.com/6430055/diff/5001/state/relation.go#newcode187
state/relation.go:187: if _, err := settings.Write(); err != nil {
Same.

https://codereview.appspot.com/6430055/diff/5001/state/relation.go#newcode191
state/relation.go:191: return presence.StartPinger(ru.st.zk, presencePath,
agentPingerPeriod)
Same.

https://codereview.appspot.com/6430055/diff/5001/state/relation.go#newcode194
state/relation.go:194: // Watch returns a RelationUnitsWatcher which notifies of
relevant changes to
// Watch returns a watcher that notifies when any other unit in
// the relation joins, departs, or has its settings changed.

?

[fwereade, 2012-07-23 13:18:27]

Please take a look.

[niemeyer, 2012-07-23 17:10:35]

LGTM, thanks.

[fwereade, 2012-07-23 18:16:09]

*** Submitted:

Add RelationUnit type

This is kinda like the original RelationUnit proposed a few days ago, but
exposes its various bits of functionality separately rather than being a
magical watch-and-join chimera.

Notably, RelationUnitsWatcher is now exported, so the internal tests have
been dropped.

R=niemeyer
CC=
https://codereview.appspot.com/6430055