Instance.refresh() sends new info_cache objects

[Dan Smith]

If an older node does an Instance.refresh() it will fail because conductor will overwrite the info_cache field with a new InstanceInfoCache object. This happens during the LifecycleEvent handler in nova-compute.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/64721

[Dan Smith (danms)]

Here is the error that shows up in the log:

2014-01-07 06:43:52.519 ERROR nova.virt.driver [-] Exception dispatching event <nova.virt.event.LifecycleEvent object at 0x35e9d50>: Version 1.5 of InstanceInfoCache is not supported

It's pretty muted because it's just a lifecycle event, but it means that the refresh() action prevents those from going out. While it's buried pretty deep, the call to _sync_instance_power_state() from handle_lifecycle_event() is where this gets triggered:

https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L4811

The refresh ends up with a new InstanceInfoCache attached to the Instance, which fails to deserialize on the older client.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/64721
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e73072e76c2aedfc52cd2de480b2f41b60769acc
Submitter: Jenkins
Branch: master

commit e73072e76c2aedfc52cd2de480b2f41b60769acc
Author: Dan Smith <email address hidden>
Date: Thu Jan 2 10:18:03 2014 -0800

    Prevent Instance.refresh() from returning a new info cache

    If an older node does a refresh() on an instance, conductor will
    return a new copy of the InstanceInfoCache, which the client
    will balk at. Instead, add a refresh() method to info_cache and
    call it from Instance.refresh().

    Closes-bug: #1265607
    Change-Id: I6a4787a23cd851cf56958c61f8b0559a79847ca0