Kuryr: Add information about amphora to ovn-octavia upgrades

modules/installation-osp-kuryr-octavia-configuration.adoc

@@ -199,7 +199,7 @@ controller-0$ sudo docker restart octavia_worker
 [NOTE]
 ====
 Depending on your {rh-openstack} environment, Octavia might not support UDP
-listeners. If you use Kuryr SDN on OpenStack version 15 or earlier, UDP services are not supported. 
+listeners. If you use Kuryr SDN on OpenStack version 15 or earlier, UDP services are not supported.
 {rh-openstack} version 16 or later support UDP.
 ====
 
@@ -240,3 +240,79 @@ If Kuryr uses `ovn` instead of Amphora, it offers the following benefits:
 * Reduced network latency.
 * Increased service creation speed by using OpenFlow rules instead of a VM for each Service.
 * Distributed load balancing actions across all nodes instead of centralized on Amphora VMs.
+
+
+[id="installation-osp-kuryr-octavia-driver_upgrade_{context}"]
+== Upgrading to Octavia OVN Driver on existing deployments
+
+It is possible to upgrade {product-title} that has been deployed before OVN Octavia driver was made available on the {rh-openstack} side.
+The steps to perform the upgrade from amphora to ovn-octavia are the next:
+
+[NOTE]
+====
+Upgrading from amphora to ovn-octavia loadbalancer requires recreation of the
+loadbalancers, which means there will be some downtime when accessing the pods
+through their associated services -- time needed to delete the amphora load
+balancer plus the time needed to create the ovn load balancer.
+====
+
+.Procedure
+
+. Check ovn-octavia driver is available
++
+----
+$ openstack loadbalancer provider list
++---------+-------------------------------------------------+
+| name    | description                                     |
++---------+-------------------------------------------------+
+| amphora | The Octavia Amphora driver.                     |
+| octavia | Deprecated alias of the Octavia Amphora driver. |
+| ovn     | Octavia OVN driver.                             |
++---------+-------------------------------------------------+
+----
+
+. Edit the `kuryr-config` ConfigMap to trigger the recreation. You simply need
+to delete the annotation that states the `default` kuryr-octavia-provider is
+being used:
++
+----
+$ oc -n openshift-kuryr edit cm kuryr-config
+...
+kind: ConfigMap
+metadata:
+  annotations:
+    networkoperator.openshift.io/kuryr-octavia-provider: default <-- Remove this line
+...
+----
+
+. Wait until Cluster Network Operator reconcile loop is executed and detects the
+modification, triggering the recreation of the kuryr-controller and kuryr-cni
+pods
+
+. Check `kuryr-config` ConfigMap annotation has been readded but indicating the
+`ovn` driver is being used
++
+----
+$ oc -n openshift-kuryr edit cm kuryr-config
+...
+kind: ConfigMap
+metadata:
+  annotations:
+    networkoperator.openshift.io/kuryr-octavia-provider: ovn
+...
+----
+
+. Wait until all the loadbalancers have been recreated. Only one amphora
+loadbalancer must remain (the one created by Cluster Network Operator) and the
+rest should be of ovn type:
++
+----
+$ openstack loadbalancer list | grep amphora
+a4db683b-2b7b-4988-a582-c39daaad7981 | ostest-7mbj6-kuryr-api-loadbalancer  | 84c99c906edd475ba19478a9a6690efd | 172.30.0.1     | ACTIVE              | amphora
+$ openstack loadbalancer list | grep ovn
+2dffe783-98ae-4048-98d0-32aa684664cc | openshift-apiserver-operator/metrics | 84c99c906edd475ba19478a9a6690efd | 172.30.167.119 | ACTIVE              | ovn
+0b1b2193-251f-4243-af39-2f99b29d18c5 | openshift-etcd/etcd                  | 84c99c906edd475ba19478a9a6690efd | 172.30.143.226 | ACTIVE              | ovn
+f05b07fc-01b7-4673-bd4d-adaa4391458e | openshift-dns-operator/metrics       | 84c99c906edd475ba19478a9a6690efd | 172.30.152.27  | ACTIVE              | ovn
+....
+----
+