[openstack-dev] [Heat] Continue discussing multi-region orchestration

Mike Spreitzer mspreitz at us.ibm.com
Wed Nov 20 19:09:34 UTC 2013


Zane Bitter <zbitter at redhat.com> wrote on 11/15/2013 05:59:06 PM:
> On 15/11/13 22:17, Keith Bray wrote:
> > The way I view 2 vs. 4 is that 2 is more complicated and you don't 
gain
> > any benefit of availability.  If, in 2, your global heat endpoint is 
down,
> > you can't update the whole stack.  You have to work around it by 
talking
> > to Heat (or the individual service endpoints) in the region that is 
still
> > alive.
> 
> Not really, you still have the templates for all of the nested stacks 
> that are in the remaining region(s). You can manipulate those directly 
> and not risk getting things out of sync when the Heat master comes back.
> 
> If you really want a global stack, you can recreate it in a different 
> region and adopt the remaining parts.

If there were no dynamic data flowing between regions then the story would 
be this simple.  But we have not forbidden output from one regional 
template to be used in the input to another.  Maybe we should?  That would 
rule out some situations where a user can write something that looks valid 
but will simply not work (e.g., communicate cross region via wait 
condition).  That would only leave the problem of how the client keeps 
track of the outputs.

OTOH, the more we restrict what can be done, the less useful this really 
is.

Regards,
Mike
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