feat(cluster-api): implement watch-filter arg

<!-- If this is your first PR, welcome! Please make sure you read the [contributing guidelines](../CONTRIBUTING.md#contributing-a-patch). -->

**What type of PR is this?**

/kind feature           implement watch-filter cluster-api arg

**What this PR does / why we need it**:

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #330

**Special notes for your reviewer**:

_Please confirm that if this PR changes any image versions, then that's the sole change this PR makes._

**TODOs**:
<!-- Put an "X" character inside the brackets of each completed task. Some may be optional depending on the PR. -->

- [ ] squashed commits
- [ ] includes documentation
- [ ] adds unit tests

controllers/osccluster_controller.go

@@ -37,6 +37,7 @@ import (
 	"sigs.k8s.io/cluster-api/util"
 	"sigs.k8s.io/cluster-api/util/annotations"
 	"sigs.k8s.io/cluster-api/util/conditions"
+	"sigs.k8s.io/cluster-api/util/predicates"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
@@ -49,6 +50,7 @@ type OscClusterReconciler struct {
 	client.Client
 	Recorder         record.EventRecorder
 	ReconcileTimeout time.Duration
+	WatchFilterValue string
 }
 
 //+kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=oscclusters,verbs=get;list;watch;create;update;patch;delete
@@ -500,8 +502,9 @@ func (r *OscClusterReconciler) reconcileDelete(ctx context.Context, clusterScope
 }
 
 // SetupWithManager sets up the controller with the Manager.
-func (r *OscClusterReconciler) SetupWithManager(mgr ctrl.Manager) error {
+func (r *OscClusterReconciler) SetupWithManager(ctx context.Context, mgr ctrl.Manager) error {
 	return ctrl.NewControllerManagedBy(mgr).
 		For(&infrastructurev1beta1.OscCluster{}).
+		WithEventFilter(predicates.ResourceNotPausedAndHasFilterLabel(ctrl.LoggerFrom(ctx), r.WatchFilterValue)).
 		Complete(r)
 }

controllers/oscmachine_controller.go

@@ -55,6 +55,7 @@ type OscMachineReconciler struct {
 	client.Client
 	Recorder         record.EventRecorder
 	ReconcileTimeout time.Duration
+	WatchFilterValue string
 }
 
 //+kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=oscmachines,verbs=get;list;watch;create;update;patch;delete
@@ -393,6 +394,7 @@ func (r *OscMachineReconciler) SetupWithManager(ctx context.Context, mgr ctrl.Ma
 		return errors.Errorf("failed to create mapper for Cluster to OscMachines: %+v", err)
 	}
 	err = ctrl.NewControllerManagedBy(mgr).
+		WithEventFilter(predicates.ResourceNotPausedAndHasFilterLabel(ctrl.LoggerFrom(ctx), r.WatchFilterValue)).
 		For(&infrastructurev1beta1.OscMachine{}).
 		Watches(
 			&source.Kind{Type: &clusterv1.Machine{}},

controllers/oscmachinetemplate_capacity_controller.go

@@ -27,6 +27,7 @@ import (
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/client-go/tools/record"
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
+	"sigs.k8s.io/cluster-api/util/predicates"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/controller"
@@ -43,6 +44,7 @@ type OscMachineTemplateReconciler struct {
 	client.Client
 	Recorder         record.EventRecorder
 	ReconcileTimeout time.Duration
+	WatchFilterValue string
 }
 
 // +kubebuilder:rbac:groups=infrastructure.cluster.x-k8s.io,resources=oscmachinetemplates,verbs=get;list;watch;create;update;patch;delete
@@ -147,5 +149,6 @@ func (r *OscMachineTemplateReconciler) SetupWithManager(ctx context.Context, mgr
 	return ctrl.NewControllerManagedBy(mgr).
 		WithOptions(options).
 		For(&infrastructurev1beta1.OscMachineTemplate{}).
+		WithEventFilter(predicates.ResourceNotPausedAndHasFilterLabel(ctrl.LoggerFrom(ctx), r.WatchFilterValue)).
 		Complete(r)
 }

main.go

@@ -18,6 +18,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"os"
 	"time"
 
@@ -59,11 +60,14 @@ func main() {
 	var metricsAddr string
 	var enableLeaderElection bool
 	var probeAddr string
+	var watchFilterValue string
 	flag.StringVar(&metricsAddr, "metrics-bind-address", ":8080", "The address the metric endpoint binds to.")
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "leader-elect", true,
 		"Enable leader election for controller manager. "+
 			"Enabling this will ensure there is only one active controller manager.")
+	flag.StringVar(&watchFilterValue, "watch-filter", "", fmt.Sprintf("Label value that the controller watches to reconcile cluster-api objects. Label key is always %s. If unspecified, the controller watches for all cluster-api objects.", clusterv1.WatchLabel))
+
 	opts := zap.Options{}
 	opts.BindFlags(flag.CommandLine)
 	flag.Parse()
@@ -88,21 +92,23 @@ func main() {
 		os.Exit(1)
 	}
 
+	ctx := ctrl.SetupSignalHandler()
+
 	if err = (&controllers.OscClusterReconciler{
 		Client:           mgr.GetClient(),
 		Recorder:         mgr.GetEventRecorderFor("osccluster-controller"),
 		ReconcileTimeout: reconcileTimeout,
-	}).SetupWithManager(mgr); err != nil {
+		WatchFilterValue: watchFilterValue,
+	}).SetupWithManager(ctx, mgr); err != nil {
 		setupLog.Error(err, "unable to create controller", "controller", "OscCluster")
 		os.Exit(1)
 	}
 
-	ctx := ctrl.SetupSignalHandler()
-
 	if err = (&controllers.OscMachineReconciler{
 		Client:           mgr.GetClient(),
 		Recorder:         mgr.GetEventRecorderFor("oscmachine-controller"),
 		ReconcileTimeout: reconcileTimeout,
+		WatchFilterValue: watchFilterValue,
 	}).SetupWithManager(ctx, mgr, controller.Options{}); err != nil {
 		setupLog.Error(err, "unable to create controller", "controller", "OscMachine")
 		os.Exit(1)
@@ -112,6 +118,7 @@ func main() {
 		Client:           mgr.GetClient(),
 		Recorder:         mgr.GetEventRecorderFor("oscmachinetemplate-controller"),
 		ReconcileTimeout: reconcileTimeout,
+		WatchFilterValue: watchFilterValue,
 	}).SetupWithManager(ctx, mgr, controller.Options{}); err != nil {
 		setupLog.Error(err, "unable to create controller", "controller", "OscMachineTemplate")
 		os.Exit(1)