Is there a universal interface I can use?

Stuart Bishop stuart.bishop at canonical.com
Fri Dec 1 05:17:35 UTC 2017


On 28 November 2017 at 20:22, Tilman Baumann
<tilman.baumann at canonical.com> wrote:

> That would be quite nice actually. Backup and snapshot could be two
> different actions even.
> Snapshot is a little low-level as it is per-node. But it makes for fast
> recovery if a node hickups.
> Full backup like Haw Leoeung implemented in
> https://jujucharms.com/u/hloeung/cassandra-backup/ is probably even more
> useful for many scenarios.

There doesn't seem to be a standard backup mechanism, so backup
probably belongs in a subordinate. I currently have a subordinate that
rsyncs the files to a backup host on my smallest deployment (per
https://insights.ubuntu.com/2015/08/04/introducing-turku-cloud-friendly-backups-for-your-infrastructure/)


> I'm quite stumped right now with the odd combination of needing to be a
> subordinate and needing to connect to the database relation.
> I just can't get it to work. And I'm out of ideas.
> I would love to just finish it "to get it to work" but I don't know what
> else I could try at this point.

You just need to define the juju-info container scoped relation as
well as the standard cassandra relation.

subordinate: true
requires:
  cassandra:
    interface: cassandra
  juju-info:
    interface: juju-info
    scope: container

When you deploy, you need to connect both relations and you will have
them both become available, with the different scopes:

juju add-relation mysub:juju-info cassandra:juju-info
juju add-relation mysub:cassandra cassandra:database


> I'm not very familiar with the coding style used in the cassandra charm.
> But I think I could help you with adding those functionalities even.
> I will have a lot of distractions the next two weeks. But I can see what
> I can do...

I want to make time to rework it as a charms.reactive charm. But
adding an action shouldn't need that, as the actions.yaml and
actions/foo script don't need any dependencies on the rest of the
charm.


-- 
Stuart Bishop <stuart.bishop at canonical.com>



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