Why is unit id mandatory in config-changed context?

[Andreas Hasenack]

On Sun, Jun 2, 2013 at 3:54 PM, Gustavo Niemeyer <gustavo at niemeyer.net>wrote:

> On Sat, Jun 1, 2013 at 3:20 PM, Andreas Hasenack <andreas at canonical.com>
> wrote:
> > On Fri, May 31, 2013 at 8:42 PM, Gustavo Niemeyer <gustavo at niemeyer.net>
> > wrote:
> >>
> >> On Fri, May 31, 2013 at 8:14 PM, Andreas Hasenack <
> andreas at canonical.com>
> >> wrote:
> >> > But aren't the key-value pairs that I set in the relation the same for
> >> > all
> >> > units?
> >>
> >> Yes, because it is associated with the local unit. It's similar to the
> >> following scheme:
> >>
> >> relation R1:
> >>     unit U1:
> >>           setting S1=V1
> >>           setting S2=V2
> >>     unit U2:
> >>           setting S1=V3
> >>           setting S2=V4
> >>           setting S3=V5
> >>     unit U3:
> >>           setting S1=V6
> >>
> >> If U1 does relation-set S1=V1, it sets its own S1 setting to V1. If it
> >
> >
> > I think I have a basic misunderstanding of "scope". I didn't know the
> > relation "variables" (let me call S1..S3 that) could be local and
> specific
> > to a unit.
>
> s/could be/are always/
>
>
My thinking was that the variables are attributes of the relation, and the
relation is between services, not between units, so all units have a copy
of the relation.

> I thought all changes would eventually be propagated to all
> > units, meaning these "variables" are "global" in the relation. Let's take
> > your example above:
> >
> > U1 does relation-set S1=V1 in a hook relation, for example. When this
> hook
> > finishes successfully, this change (S1=V1) is committed and the
> > relation-changed hook is fired in U2 and U3, right?
> >
> > If U2 or U3 do relation-get S1 without specifying a unit, they will get
> V1 I
> > suppose. But what if U2 does "relation-get -r R1 S1 U3"? Will it get V6
> or
> > V1? "Depends"?
>
> It'll get S1 of U3, which is V6 until U3 changes it. Only U3 can ever
> change it.
>
>
This changes things, I'll rethink my concepts. Thanks!
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