OpenStack Metadata API and OVN in Neutron

[Arkadi Poliakevitch]

- [x] This doc is inaccurate in this way: "Open and maintain a connection to the OVN Northbound database (using the ovsdbapp library). On first connection, and anytime a reconnect happens:

Do a full sync."

I can't see any connections from neutron_ovn_metadata_agent to OVN Northbound database and I can't find them in the python code either.

- [x] This is a doc addition request. The above means that something is missing from the documentation as when a network is created in openstack, the metadata port is not. Because the port is not created, the Port_Binding table in the OVN Southbound database is not updated and nothing happens on the chassis, i.e. the veth pair is not created, nor metadata proxy.

[Brian Haley (brian-haley)]

It does looks like the docs are out of date here, and I noticed they also still reference 'network:dhcp' instead of 'network:distributed' which is the device_owner for these OVN metadata ports. I'll mark as Confirmed but since the code is working will make Low priority.

[Arkadi Poliakevitch (arkadipol)]

The code only works if the metadata port is created manually (even if owned by network:dhcp) and host route 169.254.169.254/32 via <metadata_port_ip> is setup for the subnet of the network. It took me almost two days to figure it out by studying neutron_ovn_metadata_agent python code and comparing it to the documentation.

[Arkadi Poliakevitch (arkadipol)]

Bizarre. Yesterday the metadata port was not created automatically but today on a fresh openstack re-install, the neutron_ovn_metadata_agent did create the metadata port automatically owned by network:distributed with the correct host routing for 169.254.169.254. Hm... but how? It does not connect to the OVN Northbound database or did I miss it?

[Max Khon (fjoe)]

Do you have DHCP turned on or off in your subnet (when it did not work, and now, when it works).
See #1976366

Btw neutron-ovn-metadata-agent does not use Northbound database: it looks at Port_Binding table in Southbound database instead.