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Greetings,

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.

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.

This is something I would like to discuss here and at the PTG, feel free to
bring questions/concerns,
Thanks!
-- 
Emilien Macchi
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