Check out the logs from http://logs.openstack.org/58/360858/4/check/gate-neutron-dsvm-functional/3fb0ba3/:


The port briefly appears, disappears, then returns about 10 seconds later. ovs-vswitchd:


2016-08-30T23:14:21.077Z|00731|bridge|INFO|bridge test-brf4f80ab5: added interface portcfbbde on port 3
2016-08-30T23:14:21.231Z|00732|bridge|INFO|bridge test-br103b76e6: added interface porta0d188 on port 5
2016-08-30T23:14:21.233Z|00733|ofproto|WARN|test-brd2a45bde: cannot get STP status on nonexistent port 1
2016-08-30T23:14:21.233Z|00734|ofproto|WARN|test-brd2a45bde: cannot get RSTP status on nonexistent port 1
2016-08-30T23:14:21.243Z|00735|netdev_linux|INFO|ioctl(SIOCGIFHWADDR) on portcfbbde device failed: No such device
2016-08-30T23:14:21.279Z|00736|bridge|WARN|could not open network device test-veth1cc1f5 (No such device)
2016-08-30T23:14:21.281Z|00737|bridge|INFO|bridge test-br13e2a48f: added interface fg-d2460f21-26 on port 1
2016-08-30T23:14:21.330Z|00738|bridge|INFO|bridge test-brd2a45bde: added interface test8bc7fc8a on port 2
2016-08-30T23:14:21.345Z|00739|bridge|WARN|could not open network device test-veth1cc1f5 (No such device)
2016-08-30T23:14:21.350Z|00740|bridge|INFO|bridge test-br103b76e6: added interface porta0d188 on port 5



Corresponding timing on functional test:

2016-08-30 23:14:21.081 28059 DEBUG neutron.agent.linux.utils [req-9b1471ca-d98a-4ae2-a406-0617a68f0d78 - - - - -] Running command: ['ip', '-o', 'link', 'show', 'test-br103b76e6'] create_process neutron/agent/linux/utils.py:83
2016-08-30 23:14:21.104 28059 DEBUG neutron.agent.linux.utils [req-9b1471ca-d98a-4ae2-a406-0617a68f0d78 - - - - -] Exit code: 0 execute neutron/agent/linux/utils.py:140
2016-08-30 23:14:21.106 28059 DEBUG neutron.agent.ovsdb.impl_idl [-] Running txn command(idx=0): DelPortCommand(bridge=None, if_exists=True, port=porta0d188) do_commit neutron/agent/ovsdb/impl_idl.py:98
2016-08-30 23:14:21.106 28059 DEBUG neutron.agent.ovsdb.impl_idl [-] Transaction caused no change do_commit neutron/agent/ovsdb/impl_idl.py:125
2016-08-30 23:14:21.107 28059 DEBUG neutron.agent.ovsdb.impl_idl [-] Running txn command(idx=0): AddPortCommand(bridge=test-br103b76e6, port=porta0d188, may_exist=False) do_commit neutron/agent/ovsdb/impl_idl.py:98
2016-08-30 23:14:21.108 28059 DEBUG neutron.agent.ovsdb.impl_idl [-] Running txn command(idx=1): DbSetCommand(table=Interface, record=porta0d188, col_values=(('type', 'internal'), ('external_ids', {'iface-status': 'active', 'iface-id': '91ce28ed-5bda-4371-82f9-91ca73d2d4b0', 'attached-mac': 'fa:16:3e:53:78:2d'}))) do_commit neutron/agent/ovsdb/impl_idl.py:98
2016-08-30 23:14:21.247 28059 DEBUG neutron.agent.linux.utils [req-9b1471ca-d98a-4ae2-a406-0617a68f0d78 - - - - -] Running command (rootwrap daemon): ['ip', 'link', 'set', 'porta0d188', 'address', 'fa:16:3e:53:78:2d'] execute_rootwrap_daemon neutron/agent/linux/utils.py:99
2016-08-30 23:14:21.254 28059 ERROR neutron.agent.linux.utils [req-9b1471ca-d98a-4ae2-a406-0617a68f0d78 - - - - -] Exit code: 1; Stdin: ; Stdout: ; Stderr: Cannot find device "porta0d188"


So ovs-vswitchd claims it added it at 21.231, but then the link set command issued from the agent at 21.247 shows that it wasn't there. For some reason ovs-vswitchd then adds it again at 21.350. So OVS seems to drop the port immediately after adding it and then re-add it a little over 100 milliseconds later after we have already continued on...