A lot of warnings from Neutron about "Dictionary resource_versions is invalid"

[Sergey Arkhipov]

Detailed bug description:
During execution of longevity test on MOS 9.0, I've found a lot of warnings from Neutron about resource_versions dictionary:

neutron-server.log:2016-04-27T02:46:09.627497+00:00 warning: 2016-04-27 02:46:09.624 27817 WARNING neutron.db.agents_db [req-f7f2b2c6-4ef4-45c9-bd9d-9f43c7961658 - - - - -] Dictionary resource_versions for agent L3 agent on host node-59.domain.tld is invalid.
neutron-server.log:2016-04-27T02:46:09.627558+00:00 warning: 2016-04-27 02:46:09.624 27817 WARNING neutron.db.agents_db [req-f7f2b2c6-4ef4-45c9-bd9d-9f43c7961658 - - - - -] Dictionary resource_versions for agent L3 agent on host node-59.domain.tld is invalid.
neutron-server.log:2016-04-27T02:46:09.628482+00:00 warning: 2016-04-27 02:46:09.625 27817 WARNING neutron.db.agents_db [req-f7f2b2c6-4ef4-45c9-bd9d-9f43c7961658 - - - - -] Dictionary resource_versions for agent Metadata agent on host node-60.domain.tld is invalid.
neutron-server.log:2016-04-27T02:46:09.628510+00:00 warning: 2016-04-27 02:46:09.625 27817 WARNING neutron.db.agents_db [req-f7f2b2c6-4ef4-45c9-bd9d-9f43c7961658 - - - - -] Dictionary resource_versions for agent Metadata agent on host node-60.domain.tld is invalid.
neutron-server.log:2016-04-27T02:46:09.628903+00:00 warning: 2016-04-27 02:46:09.626 27817 WARNING neutron.db.agents_db [req-f7f2b2c6-4ef4-45c9-bd9d-9f43c7961658 - - - - -] Dictionary resource_versions for agent Metadata agent on host node-57.domain.tld is invalid.

Steps to reproduce:
1. Start any activity on cluster (run Neutron rally)

Actual result:
1. A lot of traces during execution

Reproducibility:
100%

Workaround:
N/A

Impact:
Unknown. I do not know how Neutron use this dictionary.

Description of the environment:
* MOS 9.0, build 227
* 10 baremetal nodes (12 CPU, 32GB RAM)
* Compute: KVM
* Network: Neutron with VLAN segmentation
* Ceph RBD for volumes (Cinder)
* Ceph RadosGW for objects (Swift API)
* Ceph RBD for ephemeral volumes (Nova)
* Ceph RBD for images (Glance)

Please check diagnostic snapshot:
https://drive.google.com/open?id=0B9tzODpFABxkQnhhS2d2SHNSNG8

Upstream bug: https://bugs.launchpad.net/neutron/+bug/1571544

[Bug Checker Bot (bug-checker)]

(This check performed automatically)
Please, make sure that bug description contains the following sections filled in with the appropriate data related to the bug you are describing:

expected result

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[Roman Podoliaka (rpodolyaka)]

MOS Neutron, please take a closer look and try to understand the impact of this.

[Eugene Nikanorov (enikanorov)]

The following backport is resolving the issue: https://review.openstack.org/#/c/312244/1

[Eugene Nikanorov (enikanorov)]

While the issue is not any kind of functional failure, setting priority to high due to increased visibility to operators.
Logs should not be flooded with warnings. It's suspicious and will create questions.

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/20797
Submitter: Pkgs Jenkins <email address hidden>
Branch: 9.0/mitaka

Commit: 7a3b99f6f9783953c61101fd0d2813cb0ddea09c
Author: Jenkins <email address hidden>
Date: Thu May 19 10:07:27 2016

Merge the tip of origin/stable/mitaka into origin/9.0/mitaka

ca690cc DVR: Fix TypeError in arp update with allowed_address_pairs
41e0fcd DVR: Handle unbound allowed_address_pair port with FIP
30a849e Fix SR-IOV binding when two NICs mapped to one physnet
65bb2d5 Fix test failure against latest oslo.* from master
3ab2ada Add exponential back-off RPC client
8825166 Use correct session in update_allocation_pools
a88b41c Don't log warning for missing resource_versions

Closes-Bug: #1576185
Closes-Bug: #1575554
Change-Id: I95d3e0fc16624d23ddf442723921b5153d898b0a

[Oleksiy Molchanov (omolchanov)]

Verified on #465.