Fix octavia-interface timeout

Added Restart=on-failure policy to octavia-interface systemd unit
Added octavia_interface_wait_timeout variable to control
TimeoutStartSec in octavia-interface systemd unit

Change-Id: I9de6c27131ce78e85aac56ea5d91d9740fd58354
Closes-Bug: 2067036

ansible/roles/octavia/templates/octavia-interface.service.j2

@@ -7,6 +7,10 @@ After=docker.service
 Type=oneshot
 User=root
 Group=root
+Restart=on-failure
+{% if octavia_interface_wait_timeout is defined %}
+TimeoutStartSec={{ octavia_interface_wait_timeout }}
+{% endif %}
 RemainAfterExit=true
 ExecStartPre=/sbin/ip link set dev {{ octavia_network_interface }} address {{ port_info.port.mac_address }}
 ExecStart=/sbin/dhclient -v {{ octavia_network_interface }} -cf /etc/dhcp/octavia-dhclient.conf

doc/source/reference/networking/octavia.rst

@@ -437,6 +437,24 @@ Add ``octavia_network_type`` to ``globals.yml`` and set the value to ``tenant``
 
 Next，follow the deployment instructions as normal.
 
+Failure handling
+----------------
+
+On large deployments, where neutron-openvswitch-agent sync could takes
+more then 5 minutes, you can get an error on octavia-interface.service
+systemd unit, because it can't wait either o-hm0 interface is already
+attached to br-int, or octavia management VxLAN is already configured
+on that host. In this case you have to add ``octavia_interface_wait_timeout``
+to ``globals.yml`` and set the value to new timeout in seconds
+
+.. code-block:: yaml
+
+   octavia_interface_wait_timeout: 1800
+
+On deployments with up to 2500 network ports per network node sync process
+could take up to 30mins. But you have to consider this value according
+to your deployment size.
+
 OVN provider
 ============
 

releasenotes/notes/fix-octavia-interface-timeout-5e87ea2501d5ab3c.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixes 2067036.
+    Added ``octavia_interface_wait_timeout`` to control
+    octavia-interface.service timeout to be able wait
+    openvswitch agent sync has been finished and
+    octavia-lb-net is reachable from the host.
+    Also set restart policy for this unit to on-failure
+    `LP#2067036 <https://launchpad.net/bugs/2067036>`__