[openstack-dev] [TripleO] Move redis out of Pacemaker

Pradeep Kilambi prad at redhat.com
Mon Dec 12 22:08:59 UTC 2016

On Mon, Dec 12, 2016 at 3:48 PM, Michele Baldessari <michele at acksyn.org>

> Hi Pradeep,
> On Mon, Dec 12, 2016 at 02:51:59PM +0100, Giulio Fidente wrote:
> > On 12/09/2016 04:49 PM, Pradeep Kilambi wrote:
> > >I would like to get some thoughts on $Subject. This came up when i was
> > >discussing the standalone roles for telemetry. Currently when we deploy
> > >redis in tripleo, its a pacemaker managed service. So if we were to
> > >deploy telemetry services on a dedicated node we could. But redis will
> > >have to be on a another node? (assuming we dont want to pull in
> > >pacemaker on to telemetry nodes).
> Ok so with the composable HA work [1] you should be able to split out
> the redis service on to dedicated nodes and these nodes can be either
> full pacemaker cluster members or only have the pacemaker-remote
> service.
> > currently redis instances are not configured as a redis cluster but use
> the
> > master/slave replication model instead and pacemaker is taking care of
> > electing/relocating the redis master as needed
> >
> > there shouldn't be any dependency on the redis profile for the telemetry
> > roles, they should instead just point at the redis_vip
> >
> > the redis_vip is always guaranteed (by haproxy) to point to the redis
> master
> >
> > >With most services moved out of pacemaker in Newton, I think its time to
> > >move redis as well? Are there any constraints in moving redis to be
> > >managed by systemd? Looking at how we do it, It should be easily movable
> > >to systemd? Can we consider doing this for Ocata?
> >
> > I think we could look at using the redis cluster which allows multiple
> > masters, but I am not sure this can happen in Ocata ... yet again, there
> > shouldn't be in the telemetry roles any dependency on redis itself
> >
> > if we were to use the cluster mode the only difference would probably be
> > that the redis_vip will start balancing requests across the nodes
> In general I am in favour to split out redis from pacemaker. There is
> the question that in theory we'd have two potentially separate quorums,
> but I think that with redis this should not be a big problem.
> Maybe let's start with a prototype and see how things look and iterate
> from there? I think it is a bit late for ocata, but we could at least
> start the work without changing the defaults (i.e. let the operator
> override the tripleo::service with a redis base profile instead of the
> pacemaker one)

Makes sense. I understand it might be too late for ocata. We don't really
any urgency so long as we can split out redis like you say we can with
composable HA.
I was more curious what the long term plan was and what you said makes

~ Prad

> Does that make sense,
> Michele
> [1] https://review.openstack.org/#/q/topic:bp/composable-ha
> --
> Michele Baldessari            <michele at acksyn.org>
> C2A5 9DA3 9961 4FFB E01B  D0BC DDD4 DCCB 7515 5C6D
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