add actions for osd reweight and osd crush reweight

[JuanJo Ciarlante]

It would be very useful to be able to have
ceph reweight ops framed inside actions.

Most used ones:
ceph osd reweight osd.N WEIGHT
ceph osd crush reweight osd.N WEIGHT
ceph osd reweight-by-utilization

It would be also useful to be able to have
something to reweight all OSDs at a particular
juju unit, something like e.g.:

juju run-action ceph-mon/0 reweight-osds-at-unit \
  unit=ceph-osd/42 weight=0.2

[Chris Holcombe (xfactor973)]

I've been trying to avoid creating actions on the ceph-mon charm that are a 1:1 mapping to the underlying ceph command. Any of the commands you mentioned could easily be run with a juju run command without having the additional overhead of the juju run-action interface. Anything that requires multiple steps is a great candidate for an action.

[James Troup (elmo)]

So, the reason I think an action is better than juju run:

 1) the charm knows which OSDs are on which node; I, as a human,
    don't. That makes at least two of the things jjo mentioned a
    multi-step process, which is better wrapped in an action

 2) putting it into an action means it can be tested and become part
    of the normal CI/QA process and won't break if (for example) ceph
    change their CLI

[Chris Holcombe (xfactor973)]

Yeah I agree with point 2. The juju action yaml file is expressive enough that we could lock down what is/isn't allowed to be passed to the command.

I don't follow what you mean in point 1. I think I see what you're getting at though. As a user of the charm all you see from the status output is x osds on some unit. While somewhat useful it's not very useful for figuring out for example that I want to reweight osd.2 on unit ceph-osd/0 because I don't actually know where osd.2 lives.

If however you did juju run ceph-mon/0 "ceph osd tree" to see where everything lives and you figured out the osd you want to reweight it would still be a single command run against any of the mon units.

Does that make sense? Running any of those commands against a ceph-osd unit would fail because they don't have admin keys and if they did it would just get redirected to one of the mon units.

[Xav Paice (xavpaice)]

Note https://review.openstack.org/#/c/459234/ and https://review.openstack.org/#/c/460000/ partially implement this.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Xav Paice (<email address hidden>) on branch: master
Review: https://review.openstack.org/459234
Reason: this action increases the total workload on the cluster which is the opposite of the intent.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Chris MacNaughton <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/charm-ceph-mon/+/665719
Reason: Closing this review as it has updates requested for over a year and no updates submitted.