allow_resize_to_same_host is not handled properly in the resize() api

[Kanagaraj Manickam]

allow_resize_to_same_host is used to direct the 'resize' action to the same node where the instance was running now. But the nova.compute.api. resize() method is not taking care of this condition as of now when this flag is set to TRUE.

Following code set the force_nodes to make sure that, the instance is resized to the same node again.

        if not CONF.allow_resize_to_same_host:
            filter_properties['ignore_hosts'].append(instance['host'])
        else:
            filter_properties['force_nodes'] = [instance['node']]

[Jay Pipes (jaypipes)]

Not sure this is a bug. AFAICT, the behaviour of the logic is correct...

[Kanagaraj Manickam (kanagaraj-manickam)]

When there are more than one host, and when this flag is set, request has to be routed to the same host where the VM is created before resize request. But now that is not happening.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/117116

[melanie witt (melwitt)]

I also see this as not a bug -- and it has been raised before [0]. The option allow_resize_to_same_host means "consider the same host as an option for resize" not "force the same host for resize."

I interpret the meaning from the code [1]:

    cfg.BoolOpt('allow_resize_to_same_host',
                default=False,
                help='Allow destination machine to match source for resize. '
                     'Useful when testing in single-host environments.'),

[0] https://bugs.launchpad.net/nova/+bug/1323578
[1] https://github.com/openstack/nova/blob/96ddc3e/nova/compute/api.py#L77

[Kanagaraj Manickam (kanagaraj-manickam)]

I agree that description provided for the allow_resize_to_same_host says for single host environment. But this flag is very much useful in multi host envrionment as well when cloud admin wants the resize to happen on the same host and is valid expectation as well. Nova is perfectly working in multi host environment with the fix provided. so could you reconsider on enabling it. Thank you.

[melanie witt (melwitt)]

@Kanagaraj The thing is that the option says "allow" same host, not "force" same host. So by default, the same host is not included in the pool of possible destinations. When allow_resize_to_same_host is True, the same host *is* included in the pool of possible destinations. It doesn't mean the same host will be the only choice.

To me it sounds like you desire a new feature, maybe a new option like "force_resize_to_same_host."

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sean Dague (<email address hidden>) on branch: master
Review: https://review.openstack.org/117116
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.