[Openstack-operators] VM status keeps ACTIVE after its nova-compute host is powered off
arahal at iweb.com
Wed Aug 7 18:32:55 UTC 2013
Le 2013-08-07 07:34, Robert Collins a écrit :
> On 7 August 2013 21:16, matt <matt at nycresistor.com> wrote:
>> That is certainly a potential problem.
> So I think we should separate out 'observed state' from 'intended state'.
This is interesting but the more I think of it the more I understand the
initial choice of state 'reporting'.
As soon as you start adding the 'observed state' you'd need to add some
kind of timestamp to make sure you're not relying on an 'old' observed
state. Moreover, you'll need to make sure the state gets updated
properly (sensible time frame) as you now guarantee the status'
coherence in (near) real-time.
If a node goes down, the VM state is the best thing to use to know if
you need to evacuate them to another node for instance. So, unless you
come up with another state for this peculiar situation, you're stuck
with 'active'. This is the desired state according to user request, not
a real-time status report on what is actually running on the nodes.
I guess that (near) real-time updates would also have performance
impacts as of the 'state updating' in a DB that's aimed at management.
Somehow, if you want to guarantee the information, you could check
instance and node status, but still may need to come up with other
checks to avoid corner cases ...
Ultimately, the one and best way to make sure your VM is up, is trying
to 'ping' it in some way (all this points back to full monitoring).
Looking at collectd or parameters from ceilometer may help here.
All this is how I understand it for now.
Ahmed Rahal <arahal at iweb.com> / iWeb Technologies
Spécialiste de l'Architecture TI
/ IT Architecture Specialist
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