When you deploy an application into the Service Mesh, there are several differences between the behavior of applications in the upstream community version of Istio and the behavior of applications within a Red Hat OpenShift Service Mesh installation.

Creating control plane templates

You can create reusable configurations with ServiceMeshControlPlane templates. Individual users can extend the templates you create with their own configurations. Templates can also inherit configuration information from other templates. For example, you can create an accounting control plane for the accounting team and a marketing control plane for the marketing team. If you create a development template and a production template, members of the marketing team and the accounting team can extend the development and production templates with team specific customization.

When you configure control plane templates, which follow the same syntax as the ServiceMeshControlPlane, users inherit settings in a hierarchical fashion. The Operator is delivered with a default template with default settings for Red Hat OpenShift Service Mesh. To add custom templates you must create a ConfigMap named smcp-templates in the openshift-operators project and mount the ConfigMap in the Operator container at /usr/local/share/istio-operator/templates.

Creating the ConfigMap

Follow this procedure to create the ConfigMap.

Prerequisites
  • An installed, verified Service Mesh Operator.

  • An account with cluster administrator access.

  • Location of the Operator deployment.

  • Access to the OpenShift Container Platform Command-line Interface (CLI) also known as oc.

Procedure
  1. Log in to the OpenShift Container Platform CLI as a cluster administrator.

  2. From the CLI, run this command to create the ConfigMap named smcp-templates in the openshift-operators project and replace <templates-directory> with the location of the ServiceMeshControlPlane files on your local disk:

    $ oc create configmap --from-file=<templates-directory> smcp-templates -n openshift-operators
  3. Locate the Operator ClusterServiceVersion name.

    $ oc get clusterserviceversion -n openshift-operators | grep 'Service Mesh'
    maistra.v1.0.0            Red Hat OpenShift Service Mesh   1.0.0                Succeeded
  4. Edit the Operator cluster service version to instruct the Operator to use the smcp-templates ConfigMap.

    $ oc edit clusterserviceversion -n openshift-operators maistra.v1.0.0
  5. Add a volume mount and volume to the Operator deployment.

    deployments:
      - name: istio-operator
        spec:
          template:
            spec:
              containers:
                volumeMounts:
                  - name: discovery-cache
                    mountPath: /home/istio-operator/.kube/cache/discovery
                  - name: smcp-templates
                    mountPath: /usr/local/share/istio-operator/templates/
              volumes:
                - name: discovery-cache
                  emptyDir:
                    medium: Memory
                - name: smcp-templates
                  configMap:
                    name: smcp-templates
    ...
  6. Save your changes and exit the editor.

  7. You can now use the template parameter in the ServiceMeshControlPlane to specify a template.

      apiVersion: maistra.io/v1
      kind: ServiceMeshControlPlane
      metadata:
        name: minimal-install
      spec:
        template: default

Red Hat OpenShift Service Mesh's sidecar injection

Red Hat OpenShift Service Mesh relies on a proxy sidecar within the application’s pod to provide Service Mesh capabilities to the application. You can enable automatic sidecar injection or manage it manually. Red Hat recommends automatic injection using the annotation with no need to label projects. This ensures that your application contains the appropriate configuration for the Service Mesh upon deployment. This method requires fewer privileges and does not conflict with other OpenShift capabilities such as builder pods.

The upstream version of Istio injects the sidecar by default if you have labeled the project. Red Hat OpenShift Service Mesh requires you to opt in to having the sidecar automatically injected to a deployment, so you are not required to label the project. This avoids injecting a sidecar if it is not wanted (for example, in build or deploy pods).

The webhook checks the configuration of pods deploying into all projects to see if they are opting in to injection with the appropriate annotation.

Enabling automatic sidecar injection

When deploying an application into the Red Hat OpenShift Service Mesh you must opt in to injection by specifying the sidecar.istio.io/inject annotation with a value of "true". Opting in ensures that the sidecar injection does not interfere with other OpenShift features such as builder pods used by numerous frameworks within the OpenShift ecosystem.

Prerequisites
  • Identify the deployments for which you want to enable automatic sidecar injection.

  • Locate the application’s YAML configuration file.

Procedure
  1. Open the application’s configuration YAML file in an editor.

  2. Add sidecar.istio.io/inject to the configuration YAML with a value of "true" as illustrated here:

    Sleep test application example
    apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
      name: sleep
    spec:
      replicas: 1
      template:
        metadata:
          annotations:
            sidecar.istio.io/inject: "true"
          labels:
            app: sleep
        spec:
          containers:
          - name: sleep
            image: tutum/curl
            command: ["/bin/sleep","infinity"]
            imagePullPolicy: IfNotPresent
  3. Save the configuration file.

Next steps