xenapi's check_can_live_migrate_destination should not return None

[Senhua Huang]

check_can_live_migration_destination should return a dictionary, which is used by check_can_live_migration_source in nova/compute/manager.py (line 3002 and 3023). But nova/virt/xenapi/vomps.py (line 1668) returns None if the block_migration is set to false. This will raise a NoneType exception.

[Chuck Short (zulcss)]

Can attach the traceback please?

[Senhua Huang (senhuang)]

Hi Chuck,

I don't have a traceback. But here is my analysis.
nova.compute.manager.ComputeManager's check_can_live_migrate_destination method will first call nova.virt.driver.check_can_live_migrate_destination method, and store the returned data in dest_check_data. For xenapi, if the block_migrate is set to be false, this method call will return None to dest_check_data. Then, it will call nova.compute.rpcapi.check_can_live_migrate_source method. If this method call invokes nova.compute.manager.ComputeManager's check_can_live_migrate_source, it will pase None as the dest_check_data to check_can_live_migrate_source. On line 3023 of nova/compute/manager.py, this check_can_live_migrate_source will try the following:
        dest_check_data['is_volume_backed'] = is_volume_backed
If my understanding of the API call flow is correct, this will raise a NoneType exception if dest_check_data is None. But I could be totally wrong.. Please let me know. Thanks!

[Hans Lindgren (hanlind)]

The same was reported for Hyper-V a while ago.
See https://bugs.launchpad.net/nova/+bug/1129091.

This should be fixed in ComputeManager instead of requiring drivers to return an empty dict.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/25284

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/25284
Committed: http://github.com/openstack/nova/commit/56252f4d7e8fbc481b6382a657dac659b6582fe0
Submitter: Jenkins
Branch: master

commit 56252f4d7e8fbc481b6382a657dac659b6582fe0
Author: Hans Lindgren <email address hidden>
Date: Mon Mar 25 15:53:12 2013 +0100

    NoneType exception thrown if driver live-migration check returns None

    XenAPI driver live-migration checks must return dicts as required by
    the virt api interface.

    Resolves bug 1158603.

    Change-Id: I0db364a17e3069b0b7e3f19030afc35283edecfb