Control different relation sequence

[Kapil Thangavelu]

The missing command here is relation-ids to list the relation ids of a
given relation name. JUJU_RELATION_ID gives the current relation be
executed for, to trigger/inspect state on other relations, the relation-ids
command can be used to find their id, which can be passed to
relation-get/set with -r. Any mutations of the other relation state via
relation-set will trigger change hooks on remote related units.

cheers,
Kapil


On Tue, Sep 3, 2013 at 10:33 PM, Gustavo Niemeyer <
gustavo.niemeyer at canonical.com> wrote:

> The relation-set command accepts a "-r" parameter which takes the relation
> id
> to act upon. You can pick the relation id of an executing hook from
> the JUJU_RELATION_ID environment variable. This way you can act across
> relations.
>
> Hopefully this will be better documented at some point.
>
> On Tue, Sep 3, 2013 at 11:23 PM, Mike Sam <mikesam460 at gmail.com> wrote:
> > Thanks Gustavo but I did not quite get your point. The problem is that
> for
> > the new unit for service A, the dependent hooks are on two different
> > independent relationships. I mean I can control when the new unit of
> Service
> > A has properly established a relation with all the units of service B on
> say
> > relation x_relation_changed, but how do I make all the units of service
> C to
> > now trigger the y_relation_changed hook of the Service A unit because the
> > unit is ready to process them? How do I make y_relation_changed hook to
> get
> > triggered AGAIN (in case it has already been triggered but ignored
> because
> > relation with service B was not done setting up) when x_relation_changed
> see
> > fit? Would you please explain your point is the Service A, B, C context
> of
> > my example?
> >
> >
> >
> >
> > On Tue, Sep 3, 2013 at 6:38 PM, Gustavo Niemeyer
> > <gustavo.niemeyer at canonical.com> wrote:
> >>
> >> Hi Mike,
> >>
> >> You cannot control the sequence in which the hooks are executed, but
> >> you have full control of what you do when the hooks do execute. You
> >> can choose to send nothing to the other side of the relation until its
> >> time to report that a connection may now be established, and when you
> >> do change the relation, the remote hook will run again to report the
> >> change.
> >>
> >> On Tue, Sep 3, 2013 at 10:17 PM, Mike Sam <mikesam460 at gmail.com> wrote:
> >> > Imagine a unit needs to be added to an existing service like service
> A.
> >> > Service A is already in relations with other services like Service B
> and
> >> > Service C on different "requires".
> >> >
> >> > For the new unit on Service A to work, it needs to first process the
> >> > relation_joined and relation_changed with the units of service B
> before
> >> > it
> >> > could process  relation_joined and relation_changed with the units of
> >> > service C.
> >> >
> >> > Is there a way to enforce such desired sequence relationship
> >> > establishment
> >> > at the charm level? In other words, I do not think we can control the
> >> > hook
> >> > execution sequence of different relationships officially but then I am
> >> > wondering how can we do a situation like above nicely?
> >> >
> >> > Thanks,
> >> > Mike
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Juju-dev mailing list
> >> > Juju-dev at lists.ubuntu.com
> >> > Modify settings or unsubscribe at:
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> >> >
> >>
> >> --
> >> gustavo @ http://niemeyer.net
> >
> >
>
>
>
> --
> gustavo @ http://niemeyer.net
>
> --
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