network-get can't get default "" binding

[Zachary Zehring]

If an application has no relations, the only way for network-get to return useful networking information about the application is specifying an extra-binding in the metadata.yaml. There currently doesn't appear to be a way for network-get to return the default "" endpoint-binding (the binding "" comes from a `juju show-application $app` command)

So is there a way for network-get to return the binding for ""? If not, I think it would be a valid feature request to add the ability to do so, as the default binding for an app could be useful.

[Pen Gale (pengale)]

Thank you for filing the bug!

Can you describe a specific case where a charm wants to get the default endpoint binding? We want to understand why this feature is being requested, so that we can determine how best to expose the information to the charm, and model it in Juju in general.

[John A Meinel (jameinel)]

What is the service that you want to be running such that it would have an
associated binding, but not actually declare the service as either
something to be related to, or something in 'extra-binding'.
Charms don't have the "default" binding exposed to them, because they are
meant to think in terms of objects that might be bound.

On Wed, Sep 23, 2020 at 3:15 PM Zachary Zehring <email address hidden>
wrote:

> Public bug reported:
>
> If an application has no relations, the only way for network-get to
> return useful networking information about the application is specifying
> an extra-binding in the metadata.yaml. There currently doesn't appear to
> be a way for network-get to return the default "" endpoint-binding (the
> binding "" comes from a `juju show-application $app` command)
>
> So is there a way for network-get to return the binding for ""? If not,
> I think it would be a valid feature request to add the ability to do so,
> as the default binding for an app could be useful.
>
> ** Affects: juju
> Importance: Undecided
> Status: New
>
> --
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> https://bugs.launchpad.net/bugs/1896821
>
> Title:
> network-get can't get default "" binding
>
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[Cory Johns (johnsca)]

One use-case I could think of is a dashboard deployed in an environment with both public and private NICs where the relations use the private network via spaces but the charm needs to know what bind-address to use for the publicly exposed dashboard URL.

FWIW, except for a short period in 2.8.7 due to https://bugs.launchpad.net/juju/+bug/1906174 you can actually use `network-get juju-info` to do this. It can even get that network info for a charm which has no relations or extra-bindings defined at all.