I thought we can use "Connection" TABLE from ovn-sbdb. But unfortunately it is not creating a separate row for each ovn-controller client. So when a ovn-controller is down, we are not sure which ovn-controller is down. May be we need to enhance ovsdb-server to update the particulars of the inactive ovn-controller in external_ids/other_config columns of "Connection" Table.

Another approach can be, ovn-controller has to periodically update their status in ovn-sbdb, like the way neutron agents periodically report their status to neutron server?

Once we have the mechanism to identify the status of ovn-controller, we should work on how we display this information to users.

1) neutron agent-list
+--------------------------------------+--------------------+-------------------+-------------------+-------+----------------+---------------------------+
| id                                   | agent_type         | host              | availability_zone | alive | admin_state_up | binary                    |
+--------------------------------------+--------------------+-------------------+-------------------+-------+----------------+---------------------------+
| 4cd5fcdd-4771-48be-9e72-63f2b99f3490 | L3 agent           | devstack.rdocloud | nova              | xxx   | True           | neutron-l3-agent          |
| 5e0fb37c-1167-4a44-a260-00dd4edc6fd1 | Metadata agent     | devstack.rdocloud |                   | xxx   | True           | neutron-metadata-agent    |
| 6aae495b-c967-4d20-b1bf-f2380ba054ea | DHCP agent         | devstack.rdocloud | nova              | xxx   | True           | neutron-dhcp-agent        |
| fc6fd801-65dc-43e2-b374-de8e1560b545 | Open vSwitch agent | devstack.rdocloud |                   | xxx   | True           | neutron-openvswitch-agent |

We have to decide which agent types OVN support. It doesn't support DHCP agent. It has Metadata agent(how to report its status?). We can use "L3 agent" type for ovn-controller which has "enable-chassis-as-gw" flag. Do we need to have a separate agent type for computes or shall we go ahead with "Open vSwitch agent"?

Alternatively we can define separate agent types for OVN, example
OVN-Gateway
OVN-compute

I think we can also support below commands in OVN.
(neutron) l3-agent-list-hosting-router router1
+--------------------------------------+-------------------+----------------+-------+----------+
| id                                   | host              | admin_state_up | alive | ha_state |
+--------------------------------------+-------------------+----------------+-------+----------+
| 4cd5fcdd-4771-48be-9e72-63f2b99f3490 | devstack.rdocloud | True           | xxx   |          |
+--------------------------------------+-------------------+----------------+-------+----------+
(neutron) router-list-on-l3-agent 4cd5fcdd-4771-48be-9e72-63f2b99f3490
+--------------------------------------+---------+----------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| id                                   | name    | tenant_id                        | external_gateway_info                                                                                                                                                                                                                                                      |
+--------------------------------------+---------+----------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 8eb1443d-8dcf-4363-a2c3-3972ca7c7af3 | router1 | ec89a2978ea24af0b38bffa96f479cf6 | {"network_id": "d9a982af-be3c-430e-b782-828be637ba1b", "enable_snat": true, "external_fixed_ips": [{"subnet_id": "ed4a67aa-fb97-4f71-9a60-6d3053f135b4", "ip_address": "172.24.4.5"}, {"subnet_id": "5aab5450-6d6b-48f8-9b30-0c3645964df2", "ip_address": "2001:db8::b"}]} |

Any thoughts?