ResourceTransformation


Metro and asynchronous disaster recovery (DR) involves migrating Kubernetes resources from a source cluster to a destination cluster. To ensure applications can come up correctly on the destination clusters, you may need to modify resources such as Service, ServiceAccount or ConfigMap to work as intended on your destination cluster. The ResourceTransformation feature allows you to define a set of rules that modify the Kubernetes resources before they are migrated to the destination cluster.

ResourceTransformation is a custom resource (CR) that accepts change rules that stork follows to modify resources from a source cluster before applying them onto a destination cluster.

ResourceTransformation schema

  • Path: the YAML path for a given Kubernetes resource you want to perform an operation on. Provide this in dot notation, e.g. metadata.labels.
  • Value: what value you want to update the selected resource to. For example, if path is spec.replicas, you can specify a value of 4.
  • Type: the currently supported data type you want to update values to. Type can be one of the following:

    Type Value Example
    KeyPair Comma separated key value pair for patching map type in resource specs a:b,c:d,e:f,g:h
    <key1:value1>, <key2:value2>, … <keyN:valueN>
    List Comma separated array element list for patching resource specs [a,b,c,d]
    Int Integer type value for updating resources 0
    String String type values “new-val”
    Bool Boolean values for setting path value True, False
    NOTE: Complex types such as Array of KeyPairs is not supported.
  • Operations What operation you want to perform on the given path in an unstructured Kubernetes object:

    • Add: sets a new nested path in an unstructured object specification with value. If path already exists, this will replace the existing value.
    • Modify: updates a nested path in an unstructured resource object with value. If the value is a KeyPair or List type, this will append value to the existing path.
    • Delete: removes the specified nested spec path from an unstructured object.
NOTE: You can specify multiple paths for the same resource and multiple resources in single ResourceTransformation CR.

ResourceTransformation spec

apiVersion: stork.libopenstorage.org/v1alpha1
kind : ResourceTransformation
metadata:
  name: name-of-transform-rules
specs:
 transformSpecs:
 - paths:
     - path: <spec-path-of-k8s-resources-to-modify>
       value: <value-to-be-updated-at-above-path>
       type: <type-of-value->
       operation: <operation-to-perform>
     - path: <spec-path-of-k8s-resources-to-modify>
       value: <value-to-be-updated-at-above-path>
       type: <type-of-value->
       operation: <operation-to-perform>
   resource: <k8s-resource-version/kind-format>

Supported Resources

Portworx can currently perform transformations on the following resources:

  • ConfigMap
  • Service
  • Secret
  • ServiceAccount
  • Role
  • RoleBinding
  • ClusterRole
  • ClusterRoleBinding
  • Ingress
  • NetworkPolicy
  • Endpoint

Example

The example in this topic modifies all Kubernetes services in the mysql namespace on the destination cluster during the migration based on the migration schedule.

Define the source service object

This Service spec defines the source service object. Note the following:

  • There’s currently no metadata.annotations defined in the following service object. Secondly the type of service being used is ClusterIP.
  • metadata.labels contains only the app: mysql key value pair.

    apiVersion: v1
    kind: Service
    metadata:
    name: mysql-service
    labels:
    app: mysql
    spec:
    type: ClusterIP
    selector:
    app: mysql
    ports:
    - name: transport
     port: 3306

Create a ResourceTransformation spec

This ResourceTransformation spec does two things when it’s called:

  • Changes the type from service to LoadBalancer.
  • Updates metadata.labels, adding the handler: project key value pair to it and replacing app: mysql with app:mysql-2.
  • Adds new metadata.annotations to the service object.

    apiVersion: stork.libopenstorage.org/v1alpha1
    kind : ResourceTransformation
    metadata:
    name: mysql-service-transform
    namespace: mysql
    specs:
    transformSpecs:
    - paths:
     - path: "spec.type"
       value: "LoadBalancer"
       type: "string"
       operation: "modify"
     - path: "metadata.labels"
       value: "handler:project,app:mysql-2"
       type: "keypair"
       operation: "modify"
     - path: "metadata.annotations"
       value: "handler:project,app:mysql-2"
       type: "keypair"
       operation: "add"
    resource: "/v1/Service"

When migrated, Portworx will use the rules defined in this ResourceTransformation spec to modify the object it creates on the destination cluster.

Use the ResourceTransformation Spec

A MigrationSchedule references the ResourceTransformation defined above in the spec.template.spec.transformSpecs field. When it triggers, the MigrationSchedule uses the ResourceTransformation defined above to change the object it deploys on the destination cluster:

apiVersion: stork.libopenstorage.org/v1alpha1
kind: MigrationSchedule
metadata:
 name: mysql-migration-transform-interval
 Namespace: mysql
spec:
 schedulePolicyName: migrate-every-5m
 template:
   spec:
     # This should be the name of the cluster pair
     clusterPair: remoteclusterpair
     # If set to false this will migrate only the volumes. No PVCs, apps, etc will be migrated
     includeResources: true
     # If set to false, the deployments and stateful set replicas will be set to
     # 0 on the destination. There will be an annotation with
     # "stork.openstorage.org/migrationReplicas" to store the replica count from the source
     startApplications: false
     # Update service resource as per transformation specs
     transformSpecs:
     - mysql-service-transform
     namespaces:
     - mysql-1-pvc-mysql-migration-transform-interval


Last edited: Friday, Oct 28, 2022