- Metric was originally added to mig-controller in fusor/mig-controller#379, got feedback from Clayton
- Metric name was adjusted after consulting with @lilic and @smarterclayton in fusor/mig-controller#385
- Metric was added to mig-operator in fusor/mig-operator#193
- Metric is intended to help us understand at a high level how customers are using app workload migration tooling (CAM) to move apps and PV data between OpenShift clusters, especially when moving from OpenShift 3->4.

Have finished the test of this feature against ocp4.4 + CAM 1.1.2 stage. It seems the feature has worked. 

Below are the key test steps:

$oc edit ns  openshift-migration
apiVersion: v1                                                                     
kind: Namespace                                                                    
metadata:                                                                          
  annotations:                                                                     
    openshift.io/node-selector: ""                                                 
  labels:                                                                          
    control-plane: controller-manager                                              
    controller-tools.k8s.io: "1.0"                                                 
    openshift.io/cluster-monitoring: "true"         // add this line                                 
  name: "openshift-migration"

$ oc exec -it migration-controller-6d59b8c4c6-bqmqm  /bin/bash
Defaulting container name to cam.
Use 'oc describe pod/migration-controller-6d59b8c4c6-bqmqm -n openshift-migration' to see all of the containers in this pod.

bash-4.4$ curl  http://mig-controller-metrics.openshift-migration.svc.cluster.local:2112/metrics
# HELP cam_app_workload_migrations Count of MigMigrations sorted by status and type
# TYPE cam_app_workload_migrations gauge
cam_app_workload_migrations{status="completed",type="final"} 1
cam_app_workload_migrations{status="completed",type="stage"} 0
cam_app_workload_migrations{status="failed",type="final"} 0
cam_app_workload_migrations{status="failed",type="stage"} 0
cam_app_workload_migrations{status="idle",type="final"} 0
cam_app_workload_migrations{status="idle",type="stage"} 0
cam_app_workload_migrations{status="running",type="final"} 0
cam_app_workload_migrations{status="running",type="stage"} 0

open "monitoring/metrics" page in OCP UI,  query the metric "cam_app_workload_migrations" from the prometheus UI inside of OpenShift, can get the migration information from UI.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2020:2326