How to count relations?

Alex Kavanagh alex.kavanagh at
Wed Jun 7 15:38:30 UTC 2017


I'm assuming you are using charms.reactive; if not then look into
relation_ids command.

In your interface, count the number of conversations that have a scope set
to something other than None.  scope shouldn't be None, but I've had cases
where it has been (it may have been a bug):

So in the RelationBase derived class, something along the lines

num = len([c for c in self.conversations() if c.scope])

in a method would be a relatively simple way of doing it.

(There may be better ways of doing this!)


On Wed, Jun 7, 2017 at 4:22 PM, fengxia <fxia1 at> wrote:

> Hi Juju,
> I'm building two charms and linking them with one relation, one charm
> ("A") will provide and the other ("B") will require.
> The deployment will have one "A" and three "B"s. How do I know all three
> Bs have joined? I'm thinking to use a counter in A's relation, then at
> relation-joined hook by B to add this counter. But set_remote() and
> set_local() didn't work. Not sure what's the right way to achieve this?
> --
> Feng xia
> Engineer
> Lenovo USA
> Phone: 5088011794
> fxia1 at
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> 9
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Alex Kavanagh - Software Engineer
Cloud Dev Ops - Solutions & Product Engineering - Canonical Ltd
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