[Bug 1506257] Re: [SRU] rpcapi version mismatch possible on upgrade

[Edward Hope-Morley]

** Tags added: ubuntu-sponsors

** Patch added: "lp1506257.debdiff"
   https://bugs.launchpad.net/ubuntu/trusty/+source/nova/+bug/1506257/+attachment/4496906/+files/lp1506257.debdiff

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https://bugs.launchpad.net/bugs/1506257

Title:
  [SRU] rpcapi version mismatch possible on upgrade

Status in nova package in Ubuntu:
  Fix Released
Status in nova source package in Trusty:
  In Progress

Bug description:
  [Impact]

  Resolves issue described below by making rpc client tolerant of incompatible
  remote agent for reserve_block_device_name() calls which can occur during upgrades if compute services are upgraded after clients e.g. nova-api. The proposed fix will cause the client to fallback to a known good/supported api version.

  [Test Case]

    * Deploy openstack with all nova services on the same version and test that
      volume operations, particularly attach and detach are working correctly.

    * Deploy Openstack with only Nova client services upgraded (i.e. don't
      upgrade nova-compute) and test that volume operations, particularly attach
      and detach are working correctly.

    * Perform same tests as for 1349888 to ensure the fix is still
  working.

  [Regression Potential]

    None.

  The SRU recently landed for
  https://bugs.launchpad.net/nova/+bug/1349888 introduced a potential
  upgrade regression if nova services are not upgraded all at once.

  2015-10-14 20:45:00.778 10909 TRACE nova.api.openstack RemoteError: Remote error: UnsupportedVersion Endpoint does not support RPC version 3.35
  2015-10-14 20:45:00.778 10909 TRACE nova.api.openstack [u'Traceback (most recent call last):\n', u'  File "/usr/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 133, in _dispatch_and_reply\n    incoming.message))\n', u'  File "/usr/lib/python2.7/dist-packages/oslo/messaging/rpc/dispatcher.py", line 185, in _dispatch\n    raise UnsupportedVersion(version)\n', u'UnsupportedVersion: Endpoint does not support RPC version 3.35\n'].

  Basically, if nova-compute services are updated after nova-api
  services you will hit this issue if you perform volume operations. A
  simple solution, if possible, is to upgrade nova-compute services so
  that they are all in sync but I still want to remove the possibility
  for regression while keeping the fix from 1349888. I will propose an
  SRU shortly to resolve this.

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