Open Stack

On 10/15/2014 03:16 PM, Florian Haas wrote:
> On Wed, Oct 15, 2014 at 7:20 PM, Russell Bryant <rbryant at redhat.com> wrote:
> (4) Per-guest HA.
> 
> This is the idea of just doing "nova boot --keep-this running", i.e.
> setting a per-guest flag that still means the machine is to be kept up
> at all times. Again, not supported in Nova right now, and probably
> even more complex to implement generically than (3), at the same or
> greater cost.
> 
> I have a suggestion to tackle this that I *think* is reasonably
> user-friendly while still bearable in terms of Nova development
> effort:
> 
> (a) Define a well-known metadata key for a host aggregate, say "ha".
> Define that any host aggregate that represents a highly available
> group of compute nodes should have this metadata key set.
> 
> (b) Then define a flavor that sets extra_specs "ha=true".
> 
> Granted, this places an additional burden on distro vendors to
> integrate highly-available compute nodes into their deployment
> infrastructure. But since practically all of them already include
> Pacemaker, the additional scaffolding required is actually rather
> limited.
> 
> Am I making sense?

Yep, the downside is just that you need to provide a new set of flavors
for "ha" vs "non-ha".  A benefit though is that it's a way to support it
today without *any* changes to OpenStack.

This seems like the kind of thing we should also figure out how to offer
on a per-guest basis without needing a new set of flavors.  That's why I
also listed the server tagging functionality as another possible solution.

-- 
Russell Bryant