storage-operator: generate Volume controller

```
$ operator-sdk add controller --api-version storage.metalk8s.scality.com/v1alpha1 --kind Volume
$ go mod vendor
```

Author: NicolasT

storage-operator/go.mod

@@ -28,6 +28,7 @@ require (
 	go.uber.org/multierr v1.1.0 // indirect
 	go.uber.org/zap v1.9.1 // indirect
 	golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2 // indirect
+	k8s.io/api v0.0.0-20190222213804-5cb15d344471
 	k8s.io/apimachinery v0.0.0-20190221213512-86fb29eff628
 	k8s.io/client-go v2.0.0-alpha.0.0.20181126152608-d082d5923d3c+incompatible
 	k8s.io/code-generator v0.0.0-20180823001027-3dcf91f64f63

storage-operator/pkg/controller/add_volume.go

@@ -0,0 +1,10 @@
+package controller
+
+import (
+	"github.com/scality/metalk8s/storage-operator/pkg/controller/volume"
+)
+
+func init() {
+	// AddToManagerFuncs is a list of functions to create controllers and add them to a manager.
+	AddToManagerFuncs = append(AddToManagerFuncs, volume.Add)
+}

storage-operator/pkg/controller/volume/volume_controller.go

@@ -0,0 +1,153 @@
+package volume
+
+import (
+	"context"
+
+	storagev1alpha1 "github.com/scality/metalk8s/storage-operator/pkg/apis/storage/v1alpha1"
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/controller"
+	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
+	"sigs.k8s.io/controller-runtime/pkg/handler"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+	"sigs.k8s.io/controller-runtime/pkg/reconcile"
+	logf "sigs.k8s.io/controller-runtime/pkg/runtime/log"
+	"sigs.k8s.io/controller-runtime/pkg/source"
+)
+
+var log = logf.Log.WithName("controller_volume")
+
+/**
+* USER ACTION REQUIRED: This is a scaffold file intended for the user to modify with their own Controller
+* business logic.  Delete these comments after modifying this file.*
+ */
+
+// Add creates a new Volume Controller and adds it to the Manager. The Manager will set fields on the Controller
+// and Start it when the Manager is Started.
+func Add(mgr manager.Manager) error {
+	return add(mgr, newReconciler(mgr))
+}
+
+// newReconciler returns a new reconcile.Reconciler
+func newReconciler(mgr manager.Manager) reconcile.Reconciler {
+	return &ReconcileVolume{client: mgr.GetClient(), scheme: mgr.GetScheme()}
+}
+
+// add adds a new Controller to mgr with r as the reconcile.Reconciler
+func add(mgr manager.Manager, r reconcile.Reconciler) error {
+	// Create a new controller
+	c, err := controller.New("volume-controller", mgr, controller.Options{Reconciler: r})
+	if err != nil {
+		return err
+	}
+
+	// Watch for changes to primary resource Volume
+	err = c.Watch(&source.Kind{Type: &storagev1alpha1.Volume{}}, &handler.EnqueueRequestForObject{})
+	if err != nil {
+		return err
+	}
+
+	// TODO(user): Modify this to be the types you create that are owned by the primary resource
+	// Watch for changes to secondary resource Pods and requeue the owner Volume
+	err = c.Watch(&source.Kind{Type: &corev1.Pod{}}, &handler.EnqueueRequestForOwner{
+		IsController: true,
+		OwnerType:    &storagev1alpha1.Volume{},
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// blank assignment to verify that ReconcileVolume implements reconcile.Reconciler
+var _ reconcile.Reconciler = &ReconcileVolume{}
+
+// ReconcileVolume reconciles a Volume object
+type ReconcileVolume struct {
+	// This client, initialized using mgr.Client() above, is a split client
+	// that reads objects from the cache and writes to the apiserver
+	client client.Client
+	scheme *runtime.Scheme
+}
+
+// Reconcile reads that state of the cluster for a Volume object and makes changes based on the state read
+// and what is in the Volume.Spec
+// TODO(user): Modify this Reconcile function to implement your Controller logic.  This example creates
+// a Pod as an example
+// Note:
+// The Controller will requeue the Request to be processed again if the returned error is non-nil or
+// Result.Requeue is true, otherwise upon completion it will remove the work from the queue.
+func (r *ReconcileVolume) Reconcile(request reconcile.Request) (reconcile.Result, error) {
+	reqLogger := log.WithValues("Request.Namespace", request.Namespace, "Request.Name", request.Name)
+	reqLogger.Info("Reconciling Volume")
+
+	// Fetch the Volume instance
+	instance := &storagev1alpha1.Volume{}
+	err := r.client.Get(context.TODO(), request.NamespacedName, instance)
+	if err != nil {
+		if errors.IsNotFound(err) {
+			// Request object not found, could have been deleted after reconcile request.
+			// Owned objects are automatically garbage collected. For additional cleanup logic use finalizers.
+			// Return and don't requeue
+			return reconcile.Result{}, nil
+		}
+		// Error reading the object - requeue the request.
+		return reconcile.Result{}, err
+	}
+
+	// Define a new Pod object
+	pod := newPodForCR(instance)
+
+	// Set Volume instance as the owner and controller
+	if err := controllerutil.SetControllerReference(instance, pod, r.scheme); err != nil {
+		return reconcile.Result{}, err
+	}
+
+	// Check if this Pod already exists
+	found := &corev1.Pod{}
+	err = r.client.Get(context.TODO(), types.NamespacedName{Name: pod.Name, Namespace: pod.Namespace}, found)
+	if err != nil && errors.IsNotFound(err) {
+		reqLogger.Info("Creating a new Pod", "Pod.Namespace", pod.Namespace, "Pod.Name", pod.Name)
+		err = r.client.Create(context.TODO(), pod)
+		if err != nil {
+			return reconcile.Result{}, err
+		}
+
+		// Pod created successfully - don't requeue
+		return reconcile.Result{}, nil
+	} else if err != nil {
+		return reconcile.Result{}, err
+	}
+
+	// Pod already exists - don't requeue
+	reqLogger.Info("Skip reconcile: Pod already exists", "Pod.Namespace", found.Namespace, "Pod.Name", found.Name)
+	return reconcile.Result{}, nil
+}
+
+// newPodForCR returns a busybox pod with the same name/namespace as the cr
+func newPodForCR(cr *storagev1alpha1.Volume) *corev1.Pod {
+	labels := map[string]string{
+		"app": cr.Name,
+	}
+	return &corev1.Pod{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      cr.Name + "-pod",
+			Namespace: cr.Namespace,
+			Labels:    labels,
+		},
+		Spec: corev1.PodSpec{
+			Containers: []corev1.Container{
+				{
+					Name:    "busybox",
+					Image:   "busybox",
+					Command: []string{"sleep", "3600"},
+				},
+			},
+		},
+	}
+}