Open Stack

On Thu, Oct 16, 2014 at 7:03 PM, Adam Lawson <alawson at aqorn.com> wrote:
>
> Be forewarned; here's my two cents before I've had my morning coffee.
>
> It would seem to me that if we were seeking some level of resiliency against host failures (if a host fails, evacuate the instances that were hosted on it to a host that isn't broken), it would seem that host HA is a good approach. The ultimate goal of course is instance HA but the task of monitoring individual instances and determining what constitutes "down" seems like a much more complex task than detecting when a compute node is down. I know that requiring the presence of agents should probably need some more brain-cycles since we can't expect additional bytes consuming memory on each individual VM.

What Russell is suggesting, though, is actually a very feasible
approach for compute node HA today and per-instance HA tomorrow.

> Additionally, I'm not really hung up on the 'how' as we all realize there several ways to skin that cat, so long as that 'how' is leveraged via tools over which we have control and direct influence. Reason being, we may not want to leverage features as important as this on tools that change outside our control and subsequently shifts the foundation of the feature we implemented that was based on how the product USED to work. Basically if Pacemaker does what we need then cool but it seems that implementing a feature should be built upon a bedrock of programs over which we have a direct influence.

That almost sounds a bit like "let's always build a better wheel,
because control". I'm not sure if that's indeed the intention, but if
it is then that seems like a bad idea to me.

> This is why Nagios may be able to do it but it's a hack at best. I'm not saying Nagios isn't good or ythe hack doesn't work but in the context of an Openstack solution, we can't require a single external tool for a feature like host or VM HA. Are we suggesting that we tell people who want HA - "go use Nagios"? Call me a purist but if we're going to implement a feature, it should be our community implementing it because we have some of the best minds on staff. ; )

Anyone who thinks that having a monitoring solution to page people and
then waking up a human to restart the service constitutes HA needs to
be doused in a bucket of ice water. :)

Cheers,
Florian