snapshot action should pick a sane keys-version

Opened by kwmonroe on 2018-10-29 18:02:20+00:00 at https://github.com/juju-solutions/layer-etcd/issues/143

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When snapshotting/restoring etcd, it's important that you get the version right. We don't advertise this in the readme, but the snapshot action has a keys-version that should match the deployed version:
https://github.com/juju-solutions/layer-etcd/blob/master/actions.yaml#L22
I think we should update the action to default to an auto value that will set v2 or v3 based on the current channel configured in the charm:
https://github.com/juju-solutions/layer-etcd/blob/master/config.yaml#L12
if keys-version == auto:
    if channel startswith 2:
        keys-version=v2
    else:
        keys-version=v3

We should also update the readme to talk about this setting.

====================== COMMENTS ============================

Comment created by evilnick on 2018-10-30 11:17:25+00:00

This is a good idea. I think it would also help to include the version in the filename, e.g.

       etcd-v2-snapshot-2018-09-26-18.04.02.tar.gz