Chapter 8. Message migration when scaling down pods

Procedure

1. At the command line, log in to OpenShift as a cluster administrator (or as a user that has project administrator access to the global openshift project), for example:

   $ oc login -u system:admin

   Note

   Using the openshift project makes the image files that you install later in this procedure globally available to all projects in your OpenShift cluster.

   As an alternative to using the openshift project (e.g., if a cluster administrator is unavailable), you can log in to a specific OpenShift project to which you have administrator access and in which you want to configure a scaledown controller, for example:

   $ oc login -u <USERNAME>
   $ oc project <PROJECT_NAME>

   Logging into a specific project means that the image files that you install later in this procedure are available only in that project’s namespace.

2. Run the following commands to install the scaledown controller images files and template:

   $ oc replace --force -f \
   https://raw.githubusercontent.com/jboss-container-images/jboss-amq-7-broker-openshift-image/73-7.3.0.GA/amq-broker-7-scaledown-controller-image-streams.yaml
   $ oc replace --force -f \
   https://raw.githubusercontent.com/jboss-container-images/jboss-amq-7-broker-openshift-image/73-7.3.0.GA/templates/amq-broker-73-persistence-clustered-controller.yaml
   $ oc import-image amq-broker-72-scaledown-controller-openshift:1.0

Procedure

1. Configure the Broker on OCP StatefulSet controller template in your namespace.

2. Configure the scaledown controller template in your StatefulSet definition. The following code example represents the drainer pod definition:

   apiVersion: apps/v1
   kind: StatefulSet
   metadata:
     name: my-statefulset
     annotations:
       statefulsets.kubernetes.io/drainer-pod-template: |
         {
           "metadata": {
             "labels": {
               "app": "datastore-drainer"
             }
           },
           "spec": {
             "containers": [
               {
                 "name": "drainer",
                 "image": "my-drain-container",
                 "volumeMounts": [
                   {
                     "name": "data",
                     "mountPath": "/var/data"
                   }
                 ]
               }
             ]
           }
         }
   spec: