** Description changed:

+ [Impact]
+ 
+ Requesting to backport to Mitaka since we are seeing this issue in
+ Mitaka clouds (and fix landed in Newton) whereby some compute nodes fail
+ to have their flows added to br-tun following restart of openvswitch-
+ switch.
+ 
+ [Test Case]
+ 
+ * Deploy Openstack Mitaka with one compute host
+ * Create an instance with overlay network (gre)
+ * Make a note of flows added to br-tun (ovs-vsctl dump-flows br-tun)
+ * systemctl restart openvswitch-switch
+ * Check that flows are re-added to br-tun (compare with previous output)
+ * Ensure you do not see "Interface monitor is not active" in 
/var/log/neutron/neutron-openvswitch-agent
+ 
+ NOTE: the root cause of this issue is that ovsdb monitor async process
+ that neutron-openvswitch-agent starts takes too long to start and is not
+ active by the time the rpc_loop tries to poll for updates. It is hard to
+ simulate this scenario and as such it is difficult to know whether it
+ has happened and resolved by this patch. Nevertheless this patch is
+ small and known to have resolved the issue for newer versions of
+ Openstack.
+ 
+ [Regression Potential]
+ 
+ 
+ ---------------
+ 
  I noticed this error message in neutron-ovs-agent log when start
  neutron-openvswitch-agent
  
  ERROR neutron.agent.linux.ovsdb_monitor [req-a7c7a398-a13b-490e-
  adf8-c5afb24b4b9c None None] Interface monitor is not active.
  
  ovs-agent will start ovsdb_monitor at [1], and first use it at [2].
  There is no guarantee that ovsdb_monitor is ready at [2]. So, I can see
  the error when start neutron-openvswitch-agent.
  
  We should block the start to wait for the process to be active, and then
  use it. Or else, the use of ovsdb_monitor will be meaningless.
  
- 
  [1]
  
https://github.com/openstack/neutron/blob/6da27a78f42db00c91a747861eafde7edc6f1fa7/neutron/agent/linux/polling.py#L35
  
  [2]
  
https://github.com/openstack/neutron/blob/6da27a78f42db00c91a747861eafde7edc6f1fa7/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_neutron_agent.py#L1994

** Summary changed:

- "Interface monitor is not active" can be observed at ovs-agent start
+ [SRU] "Interface monitor is not active" can be observed at ovs-agent start

** Tags added: sts sts-sru-needed

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https://bugs.launchpad.net/bugs/1584647

Title:
  [SRU] "Interface monitor is not active" can be observed at ovs-agent
  start

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