[openstack-dev] [nova] should we have a stale data indication in "nova list/show"?

Belmiro Moreira moreira.belmiro.email.lists at gmail.com
Wed Jun 25 08:28:31 UTC 2014

I like the current behavior of not changing the VM state if nova-compute
goes down.

The cloud operators can identify the issue in the compute node and try to
fix it without users noticing. Depending in the problem I can inform users
if instances are affected and change the state if necessary.

I wouldn't like is to expose any failure in nova-compute to users and be
contacted because VM state changed.


On Wed, Jun 25, 2014 at 4:49 AM, Ahmed RAHAL <arahal at iweb.com> wrote:

> Hi,
> Le 2014-06-24 20:12, Joe Gordon a écrit :
>>     Finally, assuming the customer had access to this 'unknown' state
>>     information, what would he be able to do with it ? Usually he has no
>>     lever to 'evacuate' or 'recover' the VM. All he could do is spawn
>>     another instance to replace the lost one. But only if the VM really
>>     is currently unavailable, an information he must get from other
>> sources.
>> If I was a user, and my instance went to an 'UNKNOWN' state, I would
>> check if its still operating, and if not delete it and start another
>> instance.
> If I was a user and polled nova list/show on a regular basis just in case
> the management pane indicates a failure, I should have no expectation
> whatsoever. If service availability is my concern, I should monitor the
> service, nothing else. From there, once the service has failed, I can
> imagine checking if VM management is telling me something. However, if my
> service is down and I have no longer access to the VM ... simple case:
> destroy and respawn.
> My point is that we should not make the nova state an expected source of
> truth regarding service availability in the VM, as there is no way to tell
> such a thing. If my VM is being DDOSed, nova would still say everything is
> fine, while my service is really down. In that situation, console access
> would help me determine if the VM management is wrong by stating everything
> is ok or if there is another root cause.
> Similarly, should nova show a state change if load in the VM is through
> the roof and the service is not responsive ? or if OOM is killing all my
> processes because of a memory shortage ?
> As stated before, providing such a state information is misleading because
> there are cases where node unavailability is not service disruptive, thus
> it would indicate a false positive while the opposite (everything is ok) is
> not at all indicative of a healthy status of the service.
> Maybe am I overseeing a use case here where you absolutely need the user
> of the service to know a potential problem with his hosting platform.
> Ahmed.
> --
> =================================================
> Ahmed Rahal <arahal at iweb.com> / iWeb Technologies
> Spécialiste de l'Architecture TI
> / IT Architecture Specialist
> =================================================
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