Is there a universal interface I can use?

Stuart Bishop stuart.bishop at
Mon Nov 27 23:38:11 UTC 2017

On 23 November 2017 at 21:37, Tilman Baumann
<tilman.baumann at> wrote:
> On 22.11.2017 23:26, Haw Loeung wrote:
>> Hi Tilman,
>> On Wed, Nov 22, 2017 at 04:02:08PM +0100, Tilman Baumann wrote:
>>> However, that doesn't seem to work. Juju complains the relation doesn't
>>> exist.
>>> $ juju add-relation cassandra-backup:database cassandra:database
>>> ERROR no relations found
>>> So, is there a interface that I can (ab-)use in a similar way?
>>> I don't  want to build a full blown cassandra interface and at it to the
>>> list.
>> Not sure if you've seen this, but I did some work recently with
>> something similar to backup Cassandra DBs:
>> |
> I didn't want to talk about it before it's usable. I think I might be
> working on something similar.
> It seems to only use "nodetool snapshot"
> I'm integrating this for a 3rd party so I don't quite know what is going
> on there. But looks like the intent is pretty much the same.

I think this charm needs to remain a subordinate, because 'nodetool
snapshot' requires a JMX connection and that should be blocked
(because it is not secured).

I'd be happy to have actions on the main Cassandra charm to manage
snapshots, and cronned snapshots would also be a feature suitable for
the main charm. But you would still need some way to ship the
snapshots to your backup host which should be a subordinate.

Ideally the Cassandra charm would support multiple DCs, which would
allow you to backup only a subset of your nodes to get a complete copy
of your data, but that is going to need to wait until a
charms.reactive rewrite.

Stuart Bishop <stuart.bishop at>

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