NETOBSERV-1568: reintroduce finalizer check to remove any remaining f…

…inalizer

Since removing ipfix, we don't use finalizers anymore. However users
upgrading from a 1.5 will still have one set in their CR. So we need,
for a release, to continue checking for the finalizer, and remove it if
found.

controllers/flowcollector_controller.go

@@ -11,6 +11,7 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
 	"sigs.k8s.io/controller-runtime/pkg/log"
 
 	flowslatest "github.com/netobserv/network-observability-operator/apis/flowcollector/v1beta2"
@@ -24,6 +25,10 @@ import (
 	"github.com/netobserv/network-observability-operator/pkg/watchers"
 )
 
+const (
+	flowsFinalizer = "flows.netobserv.io/finalizer"
+)
+
 // FlowCollectorReconciler reconciles a FlowCollector object
 type FlowCollectorReconciler struct {
 	client.Client
@@ -118,6 +123,10 @@ func (r *FlowCollectorReconciler) reconcile(ctx context.Context, clh *helper.Cli
 	loki := helper.NewLokiConfig(&desired.Spec.Loki, ns)
 	reconcilersInfo := r.newCommonInfo(clh, ns, previousNamespace, &loki)
 
+	if err := r.checkFinalizer(ctx, desired); err != nil {
+		return err
+	}
+
 	if err := cleanup.CleanPastReferences(ctx, r.Client, ns); err != nil {
 		return err
 	}
@@ -161,6 +170,18 @@ func (r *FlowCollectorReconciler) reconcile(ctx context.Context, clh *helper.Cli
 	return nil
 }
 
+// checkFinalizer returns true (and/or error) if the calling function needs to return
+func (r *FlowCollectorReconciler) checkFinalizer(ctx context.Context, desired *flowslatest.FlowCollector) error {
+	// Previous version of the operator had a finalizer, this isn't the case anymore.
+	// Remove any finalizer that could remain after an upgrade.
+	if controllerutil.ContainsFinalizer(desired, flowsFinalizer) {
+		controllerutil.RemoveFinalizer(desired, flowsFinalizer)
+		return r.Update(ctx, desired)
+	}
+
+	return nil
+}
+
 func (r *FlowCollectorReconciler) newCommonInfo(clh *helper.Client, ns, prevNs string, loki *helper.LokiConfig) reconcilers.Common {
 	return reconcilers.Common{
 		Client:            *clh,