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 <[email protected]> / iWeb Technologies
Spécialiste de l'Architecture TI
/ IT Architecture Specialist
=================================================
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