DVO-114: Add watcher prototype to handle configuration changes

pkg/controller/configmap_watcher.go

@@ -0,0 +1,79 @@
+package controller
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	apicorev1 "k8s.io/api/core/v1"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/cache"
+)
+
+type ConfigMapWatcher struct {
+	clientset kubernetes.Interface
+	ch        chan struct{} // TODO - TBD configmap struct
+}
+
+var configMapName = "deployment-validation-operator-config"
+var configMapNamespace = "deployment-validation-operator"
+
+// NewConfigMapWatcher returns a watcher that can be used both:
+// basic: with GetStaticDisabledChecks method, it returns an existent ConfigMap data's disabled check
+// dynamic: with StartInformer it sets an Informer that will be triggered on ConfigMap update
+func NewConfigMapWatcher(cfg *rest.Config) (ConfigMapWatcher, error) {
+	clientset, err := kubernetes.NewForConfig(cfg)
+	if err != nil {
+		return ConfigMapWatcher{}, fmt.Errorf("initializing clientset: %w", err)
+	}
+
+	return ConfigMapWatcher{
+		clientset: clientset,
+	}, nil
+}
+
+// GetStaticDisabledChecks returns an existent ConfigMap data's disabled checks, if they exist
+func (cmw *ConfigMapWatcher) GetStaticDisabledChecks(ctx context.Context) ([]string, error) {
+	cm, err := cmw.clientset.CoreV1().
+		ConfigMaps(configMapNamespace).Get(ctx, configMapName, v1.GetOptions{})
+	if err != nil {
+		return []string{}, fmt.Errorf("gathering starting configmap: %w", err)
+	}
+
+	// TODO - Fix dummy return based on data being check1,check2,check3...
+	return strings.Split(cm.Data["disabled-checks"], ","), nil
+}
+
+// StartInformer will update the channel structure with new configuration data from ConfigMap update event
+func (cmw *ConfigMapWatcher) StartInformer(ctx context.Context) error {
+	factory := informers.NewSharedInformerFactoryWithOptions(
+		cmw.clientset, time.Second*30, informers.WithNamespace(configMapNamespace),
+	)
+	informer := factory.Core().V1().ConfigMaps().Informer()
+
+	informer.AddEventHandler(cache.ResourceEventHandlerFuncs{ // nolint:errcheck
+		UpdateFunc: func(oldObj, newObj interface{}) {
+			oldCm := oldObj.(*apicorev1.ConfigMap)
+			newCm := newObj.(*apicorev1.ConfigMap)
+
+			fmt.Printf("oldCm: %v\n", oldCm)
+			fmt.Printf("ConfigMap updated: %s/%s\n", newCm.Namespace, newCm.Name)
+
+			// TODO - Validate new configmap
+			cmw.ch <- struct{}{}
+		},
+	})
+
+	factory.Start(ctx.Done())
+
+	return nil
+}
+
+// ConfigChanged receives push notifications when the configuration is updated
+func (cmw *ConfigMapWatcher) ConfigChanged() <-chan struct{} {
+	return cmw.ch
+}

pkg/controller/configmap_watcher_test.go

@@ -0,0 +1,31 @@
+package controller
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	kubefake "k8s.io/client-go/kubernetes/fake"
+)
+
+func TestStaticConfigMapWatcher(t *testing.T) {
+	// Given
+	cm := &corev1.ConfigMap{
+		ObjectMeta: metav1.ObjectMeta{Namespace: configMapNamespace, Name: configMapName},
+		Data:       map[string]string{"disabled-checks": "check,check2"},
+	}
+	client := kubefake.NewSimpleClientset([]runtime.Object{cm}...)
+	mock := ConfigMapWatcher{
+		clientset: client,
+	}
+
+	// When
+	test, err := mock.GetStaticDisabledChecks(context.Background())
+
+	// Assert
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"check", "check2"}, test)
+}