6.6.2. Creating volume populators

Procedure

1. Create a namespace for the logical grouping and operation of the populator, and related resources, using the following example YAML file:

   Example namespace YAML file

   apiVersion: v1
   kind: Namespace
   metadata:
     name: hello

2. Create a CRD for your data source using the following example YAML file:

   Example CRD YAML file

   apiVersion: apiextensions.k8s.io/v1
   kind: CustomResourceDefinition
   metadata:
     name: hellos.hello.example.com
   spec:
     group: hello.example.com
     names:
       kind: Hello
       listKind: HelloList
       plural: hellos
       singular: hello
     scope: Namespaced
     versions:
     - name: v1alpha1
       schema:
         openAPIV3Schema:
           description: Hello is a specification for a Hello resource
           properties:
             apiVersion:
               description: 'APIVersion defines the versioned schema of this representation
                 of an object. Servers should convert recognized schemas to the latest
                 internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources'
               type: string
             kind:
               description: 'Kind is a string value representing the REST resource this
                 object represents. Servers may infer this from the endpoint the client
                 submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds'
               type: string
             spec:
               description: HelloSpec is the spec for a Hello resource
               properties:
                 fileContents:
                   type: string
                 fileName:
                   type: string
               required:
               - fileContents
               - fileName
               type: object
           required:
           - spec
           type: object
       served: true
       storage: true

3. Deploy the controller by creating a ServiceAccount, ClusterRole, ClusterRoleBindering, and Deployment to run the logic that implements the population:

   1. Create a service account for the populator using the following example YAML file:

      Example service account YAML file

      apiVersion: v1
      kind: ServiceAccount
      metadata:
        name: hello-account
        namespace: hello 

      1

      1

      Reference the namespace that you created earlier.

   2. Create a cluster role for the populator using the following example YAML file:

      Example cluster role YAML file

      kind: ClusterRole
      apiVersion: rbac.authorization.k8s.io/v1
      metadata:
        name: hello-role
      rules:
        - apiGroups: [hello.example.com]
          resources: [hellos]
          verbs: [get, list, watch]

   3. Create a cluster role binding using the following example YAML file:

      Example cluster role binding YAML file

      kind: ClusterRoleBinding
      apiVersion: rbac.authorization.k8s.io/v1
      metadata:
        name: hello-binding 

      1

      
      subjects:
        - kind: ServiceAccount
          name: hello-account 

      2

      
          namespace: hello 

      3

      
      roleRef:
        kind: ClusterRole
        name: hello-role 

      4

      
        apiGroup: rbac.authorization.k8s.io

      1

      Role binding name.

      2

      Reference the name of the service account that you created earlier.

      3

      Reference the name of the namespace for the service account that you created earlier.

      4

      Reference the cluster role you created earlier.

   4. Create a Deployment for the populator using the following example YAML file:

      Example deployment YAML file

      kind: Deployment
      apiVersion: apps/v1
      metadata:
        name: hello-populator
        namespace: hello 

      1

      
      spec:
        selector:
          matchLabels:
            app: hello
        template:
          metadata:
            labels:
              app: hello
          spec:
            serviceAccount: hello-account 

      2

      
            containers:
              - name: hello
                image: registry.k8s.io/sig-storage/hello-populator:v1.0.1
                imagePullPolicy: IfNotPresent
                args:
                  - --mode=controller
                  - --image-name=registry.k8s.io/sig-storage/hello-populator:v1.0.1
                  - --http-endpoint=:8080
                ports:
                  - containerPort: 8080
                    name: http-endpoint
                    protocol: TCP

      1

      Reference the namespace that you created earlier.

      2

      Reference the service account that you created earlier.

4. Create a volume populator to register the kind:Hello resource as a valid data source for the volume using the following example YAML file:

   Example volume populator YAML file

   kind: VolumePopulator
   apiVersion: populator.storage.k8s.io/v1beta1
   metadata:
     name: hello-populator 

   1

   
   sourceKind:
     group: hello.example.com
     kind: Hello

   1

   Volume populator name.

   PVCs that use an unregistered populator generate an event: "The datasource for this PVC does not match any registered VolumePopulator", indicating that the PVC might not be provisioned because you are using an unknown (unregistered) populator.