When a OCB is enabled, and a new MC is created, nodes are drained twice when the resulting osImage build is applied.

    

4.16
    

Always
    

    1. Enable OCB in the worker pool

oc create -f - << EOF
apiVersion: machineconfiguration.openshift.io/v1alpha1
kind: MachineOSConfig
metadata:
  name: worker
spec:
  machineConfigPool:
    name: worker
  buildInputs:
    imageBuilder:
      imageBuilderType: PodImageBuilder
    baseImagePullSecret:
      name: $(oc get secret -n openshift-config pull-secret -o json | jq "del(.metadata.namespace, .metadata.creationTimestamp, .metadata.resourceVersion, .metadata.uid, .metadata.name)" | jq '.metadata.name="pull-copy"' | oc -n openshift-machine-config-operator create -f - &> /dev/null; echo -n "pull-copy")
    renderedImagePushSecret:
      name: $(oc get -n openshift-machine-config-operator sa builder -ojsonpath='{.secrets[0].name}')
    renderedImagePushspec: "image-registry.openshift-image-registry.svc:5000/openshift-machine-config-operator/ocb-image:latest"
EOF



    2. Wait for the image to be built

    3. When the opt-in image has been finished and applied create a new MC

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: test-machine-config-1
spec:
  config:
    ignition:
      version: 3.1.0
    storage:
      files:
      - contents:
          source: data:text/plain;charset=utf-8;base64,dGVzdA==
        filesystem: root
        mode: 420
        path: /etc/test-file-1.test

    4. Wait for the image to be built
    

Once the image is built it is applied to the worker nodes.

If we have a look at the drain operation, we can see that every worker node was drained twice instead of once:

oc -n openshift-machine-config-operator logs $(oc -n openshift-machine-config-operator get pods -l k8s-app=machine-config-controller -o jsonpath='{.items[0].metadata.name}') -c machine-config-controller | grep "initiating drain"
I0430 13:28:48.740300       1 drain_controller.go:182] node ip-10-0-70-208.us-east-2.compute.internal: initiating drain
I0430 13:30:08.330051       1 drain_controller.go:182] node ip-10-0-70-208.us-east-2.compute.internal: initiating drain
I0430 13:32:32.431789       1 drain_controller.go:182] node ip-10-0-69-154.us-east-2.compute.internal: initiating drain
I0430 13:33:50.643544       1 drain_controller.go:182] node ip-10-0-69-154.us-east-2.compute.internal: initiating drain
I0430 13:48:08.183488       1 drain_controller.go:182] node ip-10-0-70-208.us-east-2.compute.internal: initiating drain
I0430 13:49:01.379416       1 drain_controller.go:182] node ip-10-0-70-208.us-east-2.compute.internal: initiating drain
I0430 13:50:52.933337       1 drain_controller.go:182] node ip-10-0-69-154.us-east-2.compute.internal: initiating drain
I0430 13:52:12.191203       1 drain_controller.go:182] node ip-10-0-69-154.us-east-2.compute.internal: initiating drain


    

Nodes should drained only once when applying a new MC