Chapter 3. Leader Worker Set Operator

Procedure

1. Log in to the OpenShift Container Platform web console.
2. Verify that the cert-manager Operator for Red Hat OpenShift is installed.

3. Install the Leader Worker Set Operator.

   1. Navigate to Operators OperatorHub.
   2. Enter Leader Worker Set Operator into the filter box.
   3. Select the Leader Worker Set Operator and click Install.

   4. On the Install Operator page:

      1. The Update channel is set to stable-v1.0, which installs the latest stable release of Leader Worker Set Operator 1.0.
      2. Under Installation mode, select A specific namespace on the cluster.
      3. Under Installed Namespace, select Operator recommended Namespace: openshift-lws-operator.

      4. Under Update approval, select one of the following update strategies:

         • The Automatic strategy allows Operator Lifecycle Manager (OLM) to automatically update the Operator when a new version is available.
         • The Manual strategy requires a user with appropriate credentials to approve the Operator update.
      5. Click Install.

4. Create the custom resource (CR) for the Leader Worker Set Operator:

   1. Navigate to Installed Operators Leader Worker Set Operator.
   2. Under Provided APIs, click Create instance in the LeaderWorkerSetOperator pane.
   3. Click Create.

Procedure

1. Create a new project by running the following command:

   $ oc new-project my-namespace

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2. Create a file named leader-worker-set.yaml

   apiVersion: leaderworkerset.x-k8s.io/v1
   kind: LeaderWorkerSet
   metadata:
     generation: 1
     name: my-lws
     namespace: my-namespace
   spec:
     leaderWorkerTemplate:
       leaderTemplate:
         metadata: {}
         spec:
           containers:
           - image: nginxinc/nginx-unprivileged:1.27
             name: leader
             resources: {}
       restartPolicy: RecreateGroupOnPodRestart
       size: 3
       workerTemplate:
         metadata: {}
         spec:
           containers:
           - image: nginxinc/nginx-unprivileged:1.27
             name: worker
             ports:
             - containerPort: 8080
               protocol: TCP
             resources: {}
     networkConfig:
       subdomainPolicy: Shared
     replicas: 2
     rolloutStrategy:
       rollingUpdateConfiguration:
         maxSurge: 1
         maxUnavailable: 1
       type: RollingUpdate
     startupPolicy: LeaderCreated

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   where:

   metadata.name

   Specifies the name of the leader worker set resource.

   metadata.namespace

   Specifies the namespace for the leader worker set to run in.

   spec.leaderWorkerTemplate.leaderTemplate

   Specifies the pod template for the leader pods.

   spec.leaderWorkerTemplate.restartPolicy

   Specifies the restart policy for when pod failures occur. Allowed values are RecreateGroupOnPodRestart to restart the whole group or None to not restart the group.

   spec.leaderWorkerTemplate.size

   Specifies the number of pods to create for each group, including the leader pod. For example, a value of 3 creates 1 leader pod and 2 worker pods. The default value is 1.

   spec.leaderWorkerTemplate.workerTemplate

   Specifies the pod template for the worker pods.

   spec.networkConfig.subdomainPolicy

   Specifies the policy to use when creating the headless service. Allowed values are UniquePerReplica or Shared. The default value is Shared.

   spec.replicas

   Specifies the number of replicas, or leader-worker groups. The default value is 1.

   spec.rolloutStrategy.rollingUpdateConfiguration.maxSurge

   Specifies the maximum number of replicas that can be scheduled above the replicas value during rolling updates. The value can be specified as an integer or a percentage.

   For more information on all available fields to configure, see LeaderWorkerSet API upstream documentation.

3. Apply the leader worker set configuration by running the following command:

   $ oc apply -f leader-worker-set.yaml

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Verification

1. Verify that pods were created by running the following command:

   $ oc get pods -n my-namespace

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   Example output

   NAME         READY   STATUS    RESTARTS   AGE
   my-lws-0     1/1     Running   0          4s
   my-lws-0-1   1/1     Running   0          3s
   my-lws-0-2   1/1     Running   0          3s
   my-lws-1     1/1     Running   0          7s
   my-lws-1-1   1/1     Running   0          6s
   my-lws-1-2   1/1     Running   0          6s

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   • my-lws-0 is the leader pod for the first group.
   • my-lws-1 is the leader pod for the second group.

2. Review the stateful sets by running the following command:

   $ oc get statefulsets

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   Example output

   NAME       READY   AGE
   my-lws     4/4     111s
   my-lws-0   2/2     57s
   my-lws-1   2/2     60s

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   • my-lws is the leader stateful set for all leader-worker groups.
   • my-lws-0 is the worker stateful set for the first group.
   • my-lws-1 is the worker stateful set for the second group.

Procedure

1. Log in to the OpenShift Container Platform web console.
2. Navigate to Operators Installed Operators.
3. Select openshift-lws-operator from the Project dropdown list.

4. Delete the LeaderWorkerSetOperator instance.

   1. Click Leader Worker Set Operator and select the LeaderWorkerSetOperator tab.
   2. Click the Options menu next to the cluster entry and select Delete LeaderWorkerSetOperator.
   3. In the confirmation dialog, click Delete.

5. Uninstall the Leader Worker Set Operator.

   1. Navigate to Operators Installed Operators.
   2. Click the Options menu next to the Leader Worker Set Operator entry and click Uninstall Operator.
   3. In the confirmation dialog, click Uninstall.

Procedure

1. Log in to the OpenShift Container Platform web console.

2. Remove CRDs that were created when the Leader Worker Set Operator was installed:

   1. Navigate to Administration CustomResourceDefinitions.
   2. Enter LeaderWorkerSetOperator in the Name field to filter the CRDs.
   3. Click the Options menu next to the LeaderWorkerSetOperator CRD and select Delete CustomResourceDefinition.
   4. In the confirmation dialog, click Delete.

3. Delete the openshift-lws-operator namespace.

   1. Navigate to Administration Namespaces.
   2. Enter openshift-lws-operator into the filter box.
   3. Click the Options menu next to the openshift-lws-operator entry and select Delete Namespace.
   4. In the confirmation dialog, enter openshift-lws-operator and click Delete.