[Juju] Proxy Charm examples

[Cory Johns]

Stuart,

Excellent points.

Supporting separate different data for different services is exactly what I
was thinking of when I mentioned the actions, where calling the action
would register a service name (or pattern) and associated data.  Structured
data for the config value is another option there, as you mention.

Yes, the proxy charm could be a subordinate.  You could also simply deploy
it as a container on the bootstrap node with --to lxc:0 or similar.  That
would still take up some amount of resources, though, so a subordinate
would be a bit better there, but then you'd have a dangling (subordinate)
relation that muddies up the model a bit.  So I'm not sure which is better
in the end.

In the end, though, this was intended as a simple example of the general
idea of proxy charms, so I didn't bother making it more robust.  Perhaps it
would be worth filling it out, though, to show off all of these
considerations that one is faced with when using proxy charms that may not
be apparent at first.

On Fri, Aug 21, 2015 at 2:43 AM, Stuart Bishop <stuart.bishop at canonical.com>
wrote:

>
> On 21 August 2015 at 01:45, Cory Johns <cory.johns at canonical.com> wrote:
>
>
>
>> Even as a proxy charm, this could be improved (it could use actions to
>> enable per-service configuration, for example), but it should give you the
>> basic idea.
>>
>>
> The main limitation is that this approach only supports proxying a single
> unit service, or a service where each unit presents identical data. If you
> need a proxy like this, you may need to take these limitations into account
> when designing the relation interface (eg. present hostnames (plural - a
> list of all hosts) the same on each unit, rather than a individual hostname
> on each unit).
>
> Can the proxy be a subordinate to save spinning up the container?
>
> --
> Stuart Bishop <stuart.bishop at canonical.com>
>
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