Comment 4 for bug 1531241

At the same time the snippet http://paste.openstack.org/show/483057/ looks interesting. I think it's neutron-openvswitch-agent which creates an OVS integration bridge - br-int. Looks like in your case neutron agent started after nova-compute and by the time the latter tried to plug a VM's VIF into br-int the bridge didn't exist.

I checked the upstart config of nova-compute and looks like we don't have an explicit dependency on neutron-openvswitch-agent, so upstart *may* start the agent later. I guess, we could try to tweak upstart scripts here, although a started neutron agent process would not actually mean all the initialization steps have been performed (e.g. in our case - br-int has been created).