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Hi Emilien,

On Fri, Jul 13, 2018 at 02:33:02PM -0400, Emilien Macchi wrote:
> We have been supporting both Keepalived and Pacemaker to handle VIP
> management.  Keepalived is actually the tool used by the undercloud
> when SSL is enabled (for SSL termination).  While Pacemaker is used on
> the overcloud to handle VIPs but also services HA.
> 
> I see some benefits at removing support for keepalived and deploying
> Pacemaker by default:
> - pacemaker can be deployed on one node (we actually do it in CI), so can
> be deployed on the undercloud to handle VIPs and manage HA as well.
> - it'll allow to extend undercloud & standalone use cases to support
> multinode one day, with HA and SSL, like we already have on the overcloud.
> - it removes the complexity of managing two tools so we'll potentially
> removing code in TripleO.
> - of course since pacemaker features from overcloud would be usable in
> standalone environment, but also on the undercloud.
> 
> There is probably some downside, the first one is I think Keepalived is
> much more lightweight than Pacemaker, we probably need to run some
> benchmark here and make sure we don't make the undercloud heavier than it
> is now.

Right, I think the service startup of pacemaker/corosync + starting the
VIP will be a bit slower than a keepalived approach (seconds). But
after that there should not be a lot of difference.
Also, we're about to land proper support for updating pcmk resources
so in the future managing them will also be a bit simpler than it is
now.

> I went ahead and created this blueprint for Stein:
> https://blueprints.launchpad.net/tripleo/+spec/undercloud-pacemaker-default
> I also plan to prototype some basic code soon and provide an upgrade path
> if we accept this blueprint.

I like the approach for the reasons you mention above. I'll be happy to
chat about this at the PTG and help out in general with this.

thanks,
Michele
-- 
Michele Baldessari            <michele at acksyn.org>
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