Open Stack

In item #2 below the reboot is down via the guest and not the nova api's :)

From: Gary Kotton <gkotton at vmware.com<mailto:gkotton at vmware.com>>
Reply-To: OpenStack List <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Date: Monday, August 24, 2015 at 7:18 PM
To: OpenStack List <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Subject: [openstack-dev] [nova] periodic task

Hi,
A couple of months ago I posted a patch for bug https://launchpad.net/bugs/1463688. The issue is as follows: the periodic task detects that the instance state does not match the state on the hypervisor and it shuts down the running VM. There are a number of ways that this may happen and I will try and explain:

  1.  Vmware driver example: a host where the instances are running goes down. This could be a power outage, host failure, etc. The first iteration of the perdioc task will determine that the actual instacne is down. This will update the state of the instance to DOWN. The VC has the ability to do HA and it will start the instance up and running again. The next iteration of the periodic task will determine that the instance is up and the compute manager will stop the instance.
  2.  All drivers. The tenant decides to do a reboot of the instance and that coincides with the periodic task state validation. At this point in time the instance will not be up and the compute node will update the state of the instance as DWON. Next iteration the states will differ and the instance will be shutdown

Basically the issue hit us with our CI and there was no CI running for a couple of hours due to the fact that the compute node decided to shutdown the running instances. The hypervisor should be the source of truth and it should not be the compute node that decides to shutdown instances. I posted a patch to deal with this https://review.openstack.org/#/c/190047/. Which is the reason for this mail. The patch is backwards compatible so that the existing deployments and random shutdown continues as it works today and the admin now has an ability just to do a log if there is a inconsistency.

We do not want to disable the periodic task as knowing the current state of the instance is very important and has a ton of value, we just do not want the periodic to task to shut down a running instance.

Thanks
Gary
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