Description of problem:

After rebooting compute node br-tun bridge is missing and the following error is seen in ovs-vsctl show:

Bridge br-int
        Controller "tcp:127.0.0.1:6633"
            is_connected: true
        fail_mode: secure
        datapath_type: system
        Port qr-a64ea052-e8
            tag: 1
            Interface qr-a64ea052-e8
                type: internal
        Port qg-de731566-5c
            tag: 2
            Interface qg-de731566-5c
                type: internal
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
                error: "No usable peer 'patch-int' exists in 'system' datapath."
        Port br-int
            Interface br-int
                type: internal
        Port int-br-ex
            Interface int-br-ex
                type: patch
                options: {peer=phy-br-ex}
        Port qr-94e0b649-6e
            tag: 1
            Interface qr-94e0b649-6e
                type: internal
        Port ha-59828361-e7
            tag: 3
            Interface ha-59828361-e7
                type: internal



Version-Release number of selected component (if applicable):

 ovs_version: "2.13.2"

Post restarting  neutron_ovs_agent container, br-tun and ovs flows are restored.


How reproducible:

Often - but important only occurs when there are number instances on the compute is high


Steps to Reproduce:
1- Reboot compute node with high number of instances
2- Post reboot br-tun will be found missing

Actual results:

br-tun is found missing

Expected results:

br-tun should be up as normal

Additional info:

Restarting neutron_ovs_agent container is working workaround for this.