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Migrating reconcile code

Migrate your project’s reconcile code to the update Operator SDK v0.1.0 usage.

Prerequisites

  • Operator SDK v0.1.0 CLI installed on the development workstation

  • memcached-operator project previously deployed using an earlier version of Operator SDK

  • Custom types migrated from pkg/apis/

Procedure

  1. Add a controller to watch your CR.

    In v0.0.x projects, resources to be watched were previously defined in cmd/<operator-name>/main.go:

    sdk.Watch("cache.example.com/v1alpha1", "Memcached", "default", time.Duration(5)*time.Second)

    For v0.1.0 projects, you must define a Controller to watch resources:

    1. Add a controller to watch your CR type with operator-sdk add controller --api-version=<apiversion> --kind=<kind>.

      $ operator-sdk add controller --api-version=cache.example.com/v1alpha1 --kind=Memcached

$ tree pkg/controller
pkg/controller/
├── add_memcached.go
├── controller.go
└── memcached
    └── memcached_controller.go

    2. Inspect the add() function in your pkg/controller/<kind>/<kind>_controller.go file:

      import (
    cachev1alpha1 "github.com/example-inc/memcached-operator/pkg/apis/cache/v1alpha1"
    ...
)

func add(mgr manager.Manager, r reconcile.Reconciler) error {
    c, err := controller.New("memcached-controller", mgr, controller.Options{Reconciler: r})

    // Watch for changes to the primary resource Memcached
    err = c.Watch(&source.Kind{Type: &cachev1alpha1.Memcached{}}, &handler.EnqueueRequestForObject{})

    // Watch for changes to the secondary resource Pods and enqueue reconcile requests for the owner Memcached
    err = c.Watch(&source.Kind{Type: &corev1.Pod{}}, &handler.EnqueueRequestForOwner{
		IsController: true,
		OwnerType:    &cachev1alpha1.Memcached{},
	})
}

      Remove the second Watch() or modify it to watch a secondary resource type that is owned by your CR.

      Watching multiple resources lets you trigger the reconcile loop for multiple resources relevant to your application. See the watching and eventhandling documentation and the Kubernetes controller conventions documentation for more details.

      If your operator is watching more than one CR type, you can do one of the following depending on your application:

      • If the CR is owned by your primary CR, watch it as a secondary resource in the same controller to trigger the reconcile loop for the primary resource.

        // Watch for changes to the primary resource Memcached
    err = c.Watch(&source.Kind{Type: &cachev1alpha1.Memcached{}}, &handler.EnqueueRequestForObject{})

    // Watch for changes to the secondary resource AppService and enqueue reconcile requests for the owner Memcached
    err = c.Watch(&source.Kind{Type: &appv1alpha1.AppService{}}, &handler.EnqueueRequestForOwner{
		IsController: true,
		OwnerType:    &cachev1alpha1.Memcached{},
	})

      • Add a new controller to watch and reconcile the CR independently of the other CR.

        $ operator-sdk add controller --api-version=app.example.com/v1alpha1 --kind=AppService
          // Watch for changes to the primary resource AppService
    err = c.Watch(&source.Kind{Type: &appv1alpha1.AppService{}}, &handler.EnqueueRequestForObject{})

  2. Copy and modify reconcile code from pkg/stub/handler.go.

    In a v0.1.0 project, the reconcile code is defined in the Reconcile() method of a controller’s Reconciler. This is similar to the Handle() function in the older project. Note the difference in the arguments and return values:

    • Reconcile:

          func (r *ReconcileMemcached) Reconcile(request reconcile.Request) (reconcile.Result, error)

    • Handle:

          func (h *Handler) Handle(ctx context.Context, event sdk.Event) error

    Instead of receiving an sdk.Event (with the object), the Reconcile() function receives a Request (Name/Namespace key) to lookup the object.

    If the Reconcile() function returns an error, the controller will requeue and retry the Request. If no error is returned, then depending on the Result, the controller will either not retry the Request, immediately retry, or retry after a specified duration.

    1. Copy the code from the old project’s Handle() function over the existing code in your controller’s Reconcile() function. Be sure to keep the initial section in the Reconcile() code that looks up the object for the Request and checks to see if it is deleted.

      import (
    apierrors "k8s.io/apimachinery/pkg/api/errors"
    cachev1alpha1 "github.com/example-inc/memcached-operator/pkg/apis/cache/v1alpha1"
    ...
)
func (r *ReconcileMemcached) Reconcile(request reconcile.Request) (reconcile.Result, error) {
    // Fetch the Memcached instance
	instance := &cachev1alpha1.Memcached{}
    err := r.client.Get(context.TODO()
    request.NamespacedName, instance)
    if err != nil {
        if apierrors.IsNotFound(err) {
            // Request object not found, could have been deleted after reconcile request.
            // Owned objects are automatically garbage collected.
            // Return and don't requeue
            return reconcile.Result{}, nil
        }
        // Error reading the object - requeue the request.
        return reconcile.Result{}, err
    }

    // Rest of your reconcile code goes here.
    ...
}

    2. Change the return values in your reconcile code:

      1. Replace return err with return reconcile.Result{}, err.

      2. Replace return nil with return reconcile.Result{}, nil.

    3. In order to periodically reconcile a CR in your controller, you can set the RequeueAfter field for reconcile.Result. This will cause the controller to requeue the Request and trigger the reconcile after the desired duration. Note that the default value of 0 means no requeue.

      reconcilePeriod := 30 * time.Second
reconcileResult := reconcile.Result{RequeueAfter: reconcilePeriod}
...

// Update the status
err := r.client.Update(context.TODO(), memcached)
if err != nil {
    log.Printf("failed to update memcached status: %v", err)
    return reconcileResult, err
}
return reconcileResult, nil

    4. Replace the calls to the SDK client (Create, Update, Delete, Get, List) with the reconciler’s client.

      See the examples below and the controller-runtime client API documentation in the operator-sdk project for more details:

      // Create
dep := &appsv1.Deployment{...}
err := sdk.Create(dep)
// v0.0.1
err := r.client.Create(context.TODO(), dep)

// Update
err := sdk.Update(dep)
// v0.0.1
err := r.client.Update(context.TODO(), dep)

// Delete
err := sdk.Delete(dep)
// v0.0.1
err := r.client.Delete(context.TODO(), dep)

// List
podList := &corev1.PodList{}
labelSelector := labels.SelectorFromSet(labelsForMemcached(memcached.Name))
listOps := &metav1.ListOptions{LabelSelector: labelSelector}
err := sdk.List(memcached.Namespace, podList, sdk.WithListOptions(listOps))
// v0.1.0
listOps := &client.ListOptions{Namespace: memcached.Namespace, LabelSelector: labelSelector}
err := r.client.List(context.TODO(), listOps, podList)

// Get
dep := &appsv1.Deployment{APIVersion: "apps/v1", Kind: "Deployment", Name: name, Namespace: namespace}
err := sdk.Get(dep)
// v0.1.0
dep := &appsv1.Deployment{}
err = r.client.Get(context.TODO(), types.NamespacedName{Name: name, Namespace: namespace}, dep)

    5. Copy and initialize any other fields that you may have had in your Handler struct into the Reconcile<Kind> struct:

      // newReconciler returns a new reconcile.Reconciler
func newReconciler(mgr manager.Manager) reconcile.Reconciler {
	return &ReconcileMemcached{client: mgr.GetClient(), scheme: mgr.GetScheme(), foo: "bar"}
}

// ReconcileMemcached reconciles a Memcached object
type ReconcileMemcached struct {
    client client.Client
    scheme *runtime.Scheme
    // Other fields
    foo string
}

  3. Copy changes from main.go.

    The main function for a v0.1.0 operator in cmd/manager/main.go sets up the Manager, which registers the custom resources and starts all the controllers.

    There is no requirement to migrate the SDK functions sdk.Watch(),sdk.Handle(), and sdk.Run() from the old main.go since that logic is now defined in a controller.

    However, if there are any Operator-specific flags or settings defined in the old main.go file, copy those over.

    If you have any third party resource types registered with the SDK’s scheme, see Advanced Topics in the operator-sdk project for how to register those with the Manager’s scheme in the new project.

  4. Copy user defined files.

    If there are any user defined pkgs, scripts, or documentation in the older project, copy these files into the new project.

  5. Copy changes to deployment manifests.

    For any updates made to the following manifests in the old project, copy over the changes to their corresponding files in the new project. Be careful not to directly overwrite the files, but inspect and make any changes necessary:

    • tmp/build/Dockerfile to build/Dockerfile

      • There is no tmp directory in the new project layout

    • RBAC rules updates from deploy/rbac.yaml to deploy/role.yaml and deploy/role_binding.yaml

    • deploy/cr.yaml to deploy/crds/<group>_<version>_<kind>_cr.yaml

    • deploy/crd.yaml to deploy/crds/<group>_<version>_<kind>_crd.yaml

  6. Copy user defined dependencies.

    For any user defined dependencies added to the old project’s Gopkg.toml, copy and append them to the new project’s Gopkg.toml. Run dep ensure to update the vendor in the new project.

  7. Confirm your changes.

    At this point, you should be able to build and run your Operator to verify that it works.