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Advanced managed cluster configuration with PolicyGenTemplate resources

Deploying additional changes to clusters

If you require cluster configuration changes outside of the base GitOps ZTP pipeline configuration, there are three options:

Apply the additional configuration after the ZTP pipeline is complete

When the GitOps ZTP pipeline deployment is complete, the deployed cluster is ready for application workloads. At this point, you can install additional Operators and apply configurations specific to your requirements. Ensure that additional configurations do not negatively affect the performance of the platform or allocated CPU budget.

Add content to the ZTP library

The base source custom resources (CRs) that you deploy with the GitOps ZTP pipeline can be augmented with custom content as required.

Create extra manifests for the cluster installation

Extra manifests are applied during installation and make the installation process more efficient.

Providing additional source CRs or modifying existing source CRs can significantly impact the performance or CPU profile of OpenShift Container Platform.
Additional resources

Using PolicyGenTemplate CRs to override source CRs content

PolicyGenTemplate custom resources (CRs) allow you to overlay additional configuration details on top of the base source CRs provided with the GitOps plugin in the ztp-site-generate container. You can think of PolicyGenTemplate CRs as a logical merge or patch to the base CR. Use PolicyGenTemplate CRs to update a single field of the base CR, or overlay the entire contents of the base CR. You can update values and insert fields that are not in the base CR.

The following example procedure describes how to update fields in the generated PerformanceProfile CR for the reference configuration based on the PolicyGenTemplate CR in the group-du-sno-ranGen.yaml file. Use the procedure as a basis for modifying other parts of the PolicyGenTemplate based on your requirements.

Prerequisites

  • Create a Git repository where you manage your custom site configuration data. The repository must be accessible from the hub cluster and be defined as a source repository for Argo CD.

Procedure

  1. Review the baseline source CR for existing content. You can review the source CRs listed in the reference PolicyGenTemplate CRs by extracting them from the zero touch provisioning (ZTP) container.

    1. Create an /out folder:

      $ mkdir -p ./out

    2. Extract the source CRs:

      $ podman run --log-driver=none --rm registry.redhat.io/openshift4/ztp-site-generate-rhel8:v4.11.1 extract /home/ztp --tar | tar x -C ./out

  2. Review the baseline PerformanceProfile CR in ./out/source-crs/PerformanceProfile.yaml:

    apiVersion: performance.openshift.io/v2
kind: PerformanceProfile
metadata:
  name: $name
  annotations:
    ran.openshift.io/ztp-deploy-wave: "10"
spec:
  additionalKernelArgs:
  - "idle=poll"
  - "rcupdate.rcu_normal_after_boot=0"
  cpu:
    isolated: $isolated
    reserved: $reserved
  hugepages:
    defaultHugepagesSize: $defaultHugepagesSize
    pages:
      - size: $size
        count: $count
        node: $node
  machineConfigPoolSelector:
    pools.operator.machineconfiguration.openshift.io/$mcp: ""
  net:
    userLevelNetworking: true
  nodeSelector:
    node-role.kubernetes.io/$mcp: ''
  numa:
    topologyPolicy: "restricted"
  realTimeKernel:
    enabled: true

    Any fields in the source CR which contain $…​ are removed from the generated CR if they are not provided in the PolicyGenTemplate CR.

  3. Update the PolicyGenTemplate entry for PerformanceProfile in the group-du-sno-ranGen.yaml reference file. The following example PolicyGenTemplate CR stanza supplies appropriate CPU specifications, sets the hugepages configuration, and adds a new field that sets globallyDisableIrqLoadBalancing to false.

    - fileName: PerformanceProfile.yaml
  policyName: "config-policy"
  metadata:
    name: openshift-node-performance-profile
  spec:
    cpu:
      # These must be tailored for the specific hardware platform
      isolated: "2-19,22-39"
      reserved: "0-1,20-21"
    hugepages:
      defaultHugepagesSize: 1G
      pages:
        - size: 1G
          count: 10
    globallyDisableIrqLoadBalancing: false

  4. Commit the PolicyGenTemplate change in Git, and then push to the Git repository being monitored by the GitOps ZTP argo CD application.

Example output

The ZTP application generates an RHACM policy that contains the generated PerformanceProfile CR. The contents of that CR are derived by merging the metadata and spec contents from the PerformanceProfile entry in the PolicyGenTemplate onto the source CR. The resulting CR has the following content:

---
apiVersion: performance.openshift.io/v2
kind: PerformanceProfile
metadata:
    name: openshift-node-performance-profile
spec:
    additionalKernelArgs:
        - idle=poll
        - rcupdate.rcu_normal_after_boot=0
    cpu:
        isolated: 2-19,22-39
        reserved: 0-1,20-21
    globallyDisableIrqLoadBalancing: false
    hugepages:
        defaultHugepagesSize: 1G
        pages:
            - count: 10
              size: 1G
    machineConfigPoolSelector:
        pools.operator.machineconfiguration.openshift.io/master: ""
    net:
        userLevelNetworking: true
    nodeSelector:
        node-role.kubernetes.io/master: ""
    numa:
        topologyPolicy: restricted
    realTimeKernel:
        enabled: true

In the /source-crs folder that you extract from the ztp-site-generate container, the $ syntax is not used for template substitution as implied by the syntax. Rather, if the policyGen tool sees the $ prefix for a string and you do not specify a value for that field in the related PolicyGenTemplate CR, the field is omitted from the output CR entirely.

An exception to this is the $mcp variable in /source-crs YAML files that is substituted with the specified value for mcp from the PolicyGenTemplate CR. For example, in example/policygentemplates/group-du-standard-ranGen.yaml, the value for mcp is worker:

spec:
  bindingRules:
    group-du-standard: ""
  mcp: "worker"

The policyGen tool replace instances of $mcp with worker in the output CRs.

Adding new content to the GitOps ZTP pipeline

The source CRs in the GitOps ZTP site generator container provide a set of critical features and node tuning settings for RAN Distributed Unit (DU) applications. These are applied to the clusters that you deploy with ZTP. To add or modify existing source CRs in the ztp-site-generate container, rebuild the ztp-site-generate container and make it available to the hub cluster, typically from the disconnected registry associated with the hub cluster. Any valid OpenShift Container Platform CR can be added.

Perform the following procedure to add new content to the ZTP pipeline.

Procedure

  1. Create a directory containing a Containerfile and the source CR YAML files that you want to include in the updated ztp-site-generate container, for example:

    ztp-update/
├── example-cr1.yaml
├── example-cr2.yaml
└── ztp-update.in

  2. Add the following content to the ztp-update.in Containerfile:

    FROM registry.redhat.io/openshift4/ztp-site-generate-rhel8:v4.11

ADD example-cr2.yaml /kustomize/plugin/ran.openshift.io/v1/policygentemplate/source-crs/
ADD example-cr1.yaml /kustomize/plugin/ran.openshift.io/v1/policygentemplate/source-crs/

  3. Open a terminal at the ztp-update/ folder and rebuild the container:

    $ podman build -t ztp-site-generate-rhel8-custom:v4.11-custom-1

  4. Push the built container image to your disconnected registry, for example:

    $ podman push localhost/ztp-site-generate-rhel8-custom:v4.11-custom-1 registry.example.com:5000/ztp-site-generate-rhel8-custom:v4.11-custom-1

  5. Patch the Argo CD instance on the hub cluster to point to the newly built container image:

    $ oc patch -n openshift-gitops argocd openshift-gitops --type=json -p '[{"op": "replace", "path":"/spec/repo/initContainers/0/image", "value": "registry.example.com:5000/ztp-site-generate-rhel8-custom:v4.11-custom-1"} ]'

    When the Argo CD instance is patched, the openshift-gitops-repo-server pod automatically restarts.

Verification

  1. Verify that the new openshift-gitops-repo-server pod has completed initialization and that the previous repo pod is terminated:

    $ oc get pods -n openshift-gitops | grep openshift-gitops-repo-server
    Example output
    openshift-gitops-server-7df86f9774-db682          1/1     Running   	     1          28s

    You must wait until the new openshift-gitops-repo-server pod has completed initialization and the previous pod is terminated before the newly added container image content is available.

Additional resources

  • Alternatively, you can patch the ArgoCD instance as described in Configuring the hub cluster with ArgoCD by modifying argocd-openshift-gitops-patch.json with an updated initContainer image before applying the patch file.

Configuring policy compliance evaluation timeouts for PolicyGenTemplate CRs

Use Red Hat Advanced Cluster Management (RHACM) installed on a hub cluster to monitor and report on whether your managed clusters are compliant with applied policies. RHACM uses policy templates to apply predefined policy controllers and policies. Policy controllers are Kubernetes custom resource definition (CRD) instances.

You can override the default policy evaluation intervals with PolicyGenTemplate custom resources (CRs). You configure duration settings that define how long a ConfigurationPolicy CR can be in a state of policy compliance or non-compliance before RHACM re-evaluates the applied cluster policies.

The zero touch provisioning (ZTP) policy generator generates ConfigurationPolicy CR policies with pre-defined policy evaluation intervals. The default value for the noncompliant state is 10 seconds. The default value for the compliant state is 10 minutes. To disable the evaluation interval, set the value to never.

Prerequisites

  • You have installed the OpenShift CLI (oc).

  • You have logged in to the hub cluster as a user with cluster-admin privileges.

  • You have created a Git repository where you manage your custom site configuration data.

Procedure

  1. To configure the evaluation interval for all policies in a PolicyGenTemplate CR, add evaluationInterval to the spec field, and then set the appropriate compliant and noncompliant values. For example:

    spec:
  evaluationInterval:
    compliant: 30m
    noncompliant: 20s

  2. To configure the evaluation interval for the spec.sourceFiles object in a PolicyGenTemplate CR, add evaluationInterval to the sourceFiles field, for example:

    spec:
  sourceFiles:
   - fileName: SriovSubscription.yaml
     policyName: "sriov-sub-policy"
     evaluationInterval:
       compliant: never
       noncompliant: 10s

  3. Commit the PolicyGenTemplate CRs files in the Git repository and push your changes.

Verification

Check that the managed spoke cluster policies are monitored at the expected intervals.

  1. Log in as a user with cluster-admin privileges on the managed cluster.

  2. Get the pods that are running in the open-cluster-management-agent-addon namespa