Manage runner with label (#355)

* Update RunnerDeploymentSpec to have Selector field

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Update RunnerReplicaSetSpec to have Selector field

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Add CloneSelectorAndAddLabel to add Selector field

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Fix tests

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Use label to find RunnerReplicaSet/Runner

Signed-off-by: binoue <banji-inoue@cybozu.co.jp>

* Update controller-gen versions in CRD

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Update autoscaler to list Pods with labels

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Add debug log

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Modify RunnerDeployment tests

Signed-off-by: binoue <banji-inoue@cybozu.co.jp>

* Modify RunnerReplicaset test

Signed-off-by: binoue <banji-inoue@cybozu.co.jp>

* Modify integration test

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Use RunnerDeployment Template Labels as the default selector for backward compatibility

* Fix labeling

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Update func in Eventually to return (int, error)

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Update RunnerDeployment controller not to use label selector

Signed-off-by: Hiroshi Muraoka <h.muraoka714@gmail.com>

* Fix potential replicaset controller breakage on replicaset created before v0.17.0

* Fix errors on existing runner replica sets

* Ensure RunnerReplicaSet Spec Selector addition does not break controller

* Ensure RunnerDeployment Template.Spec.Labels change does result in template hash change

* Fix comment

Co-authored-by: binoue <banji-inoue@cybozu.co.jp>
Co-authored-by: Yusuke Kuoka <ykuoka@gmail.com>

api/v1alpha1/runnerdeployment_types.go

@@ -25,12 +25,15 @@ const (
 	AutoscalingMetricTypePercentageRunnersBusy                        = "PercentageRunnersBusy"
 )
 
-// RunnerReplicaSetSpec defines the desired state of RunnerDeployment
+// RunnerDeploymentSpec defines the desired state of RunnerDeployment
 type RunnerDeploymentSpec struct {
 	// +optional
 	// +nullable
 	Replicas *int `json:"replicas,omitempty"`
 
+	// +optional
+	// +nullable
+	Selector *metav1.LabelSelector `json:"selector"`
 	Template RunnerTemplate        `json:"template"`
 }
 

api/v1alpha1/runnerreplicaset_types.go

@@ -26,6 +26,9 @@ type RunnerReplicaSetSpec struct {
 	// +nullable
 	Replicas *int `json:"replicas,omitempty"`
 
+	// +optional
+	// +nullable
+	Selector *metav1.LabelSelector `json:"selector"`
 	Template RunnerTemplate        `json:"template"`
 }
 

api/v1alpha1/zz_generated.deepcopy.go

@@ -22,6 +22,7 @@ package v1alpha1
 
 import (
 	"k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 )
 
@@ -403,6 +404,11 @@ func (in *RunnerDeploymentSpec) DeepCopyInto(out *RunnerDeploymentSpec) {
 		*out = new(int)
 		**out = **in
 	}
+	if in.Selector != nil {
+		in, out := &in.Selector, &out.Selector
+		*out = new(metav1.LabelSelector)
+		(*in).DeepCopyInto(*out)
+	}
 	in.Template.DeepCopyInto(&out.Template)
 }
 
@@ -535,6 +541,11 @@ func (in *RunnerReplicaSetSpec) DeepCopyInto(out *RunnerReplicaSetSpec) {
 		*out = new(int)
 		**out = **in
 	}
+	if in.Selector != nil {
+		in, out := &in.Selector, &out.Selector
+		*out = new(metav1.LabelSelector)
+		(*in).DeepCopyInto(*out)
+	}
 	in.Template.DeepCopyInto(&out.Template)
 }
 

charts/actions-runner-controller/crds/actions.summerwind.dev_runnerdeployments.yaml

@@ -38,11 +38,42 @@ spec:
         metadata:
           type: object
         spec:
-          description: RunnerReplicaSetSpec defines the desired state of RunnerDeployment
+          description: RunnerDeploymentSpec defines the desired state of RunnerDeployment
           properties:
             replicas:
               nullable: true
               type: integer
+            selector:
+              description: A label selector is a label query over a set of resources. The result of matchLabels and matchExpressions are ANDed. An empty label selector matches all objects. A null label selector matches no objects.
+              nullable: true
+              properties:
+                matchExpressions:
+                  description: matchExpressions is a list of label selector requirements. The requirements are ANDed.
+                  items:
+                    description: A label selector requirement is a selector that contains values, a key, and an operator that relates the key and values.
+                    properties:
+                      key:
+                        description: key is the label key that the selector applies to.
+                        type: string
+                      operator:
+                        description: operator represents a key's relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.
+                        type: string
+                      values:
+                        description: values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.
+                        items:
+                          type: string
+                        type: array
+                    required:
+                      - key
+                      - operator
+                    type: object
+                  type: array
+                matchLabels:
+                  additionalProperties:
+                    type: string
+                  description: matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". The requirements are ANDed.
+                  type: object
+              type: object
             template:
               properties:
                 metadata:

charts/actions-runner-controller/crds/actions.summerwind.dev_runnerreplicasets.yaml

@@ -43,6 +43,37 @@ spec:
             replicas:
               nullable: true
               type: integer
+            selector:
+              description: A label selector is a label query over a set of resources. The result of matchLabels and matchExpressions are ANDed. An empty label selector matches all objects. A null label selector matches no objects.
+              nullable: true
+              properties:
+                matchExpressions:
+                  description: matchExpressions is a list of label selector requirements. The requirements are ANDed.
+                  items:
+                    description: A label selector requirement is a selector that contains values, a key, and an operator that relates the key and values.
+                    properties:
+                      key:
+                        description: key is the label key that the selector applies to.
+                        type: string
+                      operator:
+                        description: operator represents a key's relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.
+                        type: string
+                      values:
+                        description: values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.
+                        items:
+                          type: string
+                        type: array
+                    required:
+                      - key
+                      - operator
+                    type: object
+                  type: array
+                matchLabels:
+                  additionalProperties:
+                    type: string
+                  description: matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". The requirements are ANDed.
+                  type: object
+              type: object
             template:
               properties:
                 metadata:

config/crd/bases/actions.summerwind.dev_runnerdeployments.yaml

@@ -38,11 +38,42 @@ spec:
         metadata:
           type: object
         spec:
-          description: RunnerReplicaSetSpec defines the desired state of RunnerDeployment
+          description: RunnerDeploymentSpec defines the desired state of RunnerDeployment
           properties:
             replicas:
               nullable: true
               type: integer
+            selector:
+              description: A label selector is a label query over a set of resources. The result of matchLabels and matchExpressions are ANDed. An empty label selector matches all objects. A null label selector matches no objects.
+              nullable: true
+              properties:
+                matchExpressions:
+                  description: matchExpressions is a list of label selector requirements. The requirements are ANDed.
+                  items:
+                    description: A label selector requirement is a selector that contains values, a key, and an operator that relates the key and values.
+                    properties:
+                      key:
+                        description: key is the label key that the selector applies to.
+                        type: string
+                      operator:
+                        description: operator represents a key's relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.
+                        type: string
+                      values:
+                        description: values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.
+                        items:
+                          type: string
+                        type: array
+                    required:
+                      - key
+                      - operator
+                    type: object
+                  type: array
+                matchLabels:
+                  additionalProperties:
+                    type: string
+                  description: matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". The requirements are ANDed.
+                  type: object
+              type: object
             template:
               properties:
                 metadata:

config/crd/bases/actions.summerwind.dev_runnerreplicasets.yaml

@@ -43,6 +43,37 @@ spec:
             replicas:
               nullable: true
               type: integer
+            selector:
+              description: A label selector is a label query over a set of resources. The result of matchLabels and matchExpressions are ANDed. An empty label selector matches all objects. A null label selector matches no objects.
+              nullable: true
+              properties:
+                matchExpressions:
+                  description: matchExpressions is a list of label selector requirements. The requirements are ANDed.
+                  items:
+                    description: A label selector requirement is a selector that contains values, a key, and an operator that relates the key and values.
+                    properties:
+                      key:
+                        description: key is the label key that the selector applies to.
+                        type: string
+                      operator:
+                        description: operator represents a key's relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.
+                        type: string
+                      values:
+                        description: values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.
+                        items:
+                          type: string
+                        type: array
+                    required:
+                      - key
+                      - operator
+                    type: object
+                  type: array
+                matchLabels:
+                  additionalProperties:
+                    type: string
+                  description: matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". The requirements are ANDed.
+                  type: object
+              type: object
             template:
               properties:
                 metadata:

controllers/autoscaling.go

@@ -10,6 +10,8 @@ import (
 	"time"
 
 	"github.com/summerwind/actions-runner-controller/api/v1alpha1"
+	kerrors "k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
 
@@ -257,11 +259,23 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunn
 		scaleDownFactor = sdf
 	}
 
-	// return the list of runners in namespace. Horizontal Runner Autoscaler should only be responsible for scaling resources in its own ns.
+	selector, err := metav1.LabelSelectorAsSelector(rd.Spec.Selector)
-	var runnerList v1alpha1.RunnerList
+	if err != nil {
-	if err := r.List(ctx, &runnerList, client.InNamespace(rd.Namespace)); err != nil {
 		return nil, err
 	}
+	// return the list of runners in namespace. Horizontal Runner Autoscaler should only be responsible for scaling resources in its own ns.
+	var runnerList v1alpha1.RunnerList
+	if err := r.List(
+		ctx,
+		&runnerList,
+		client.InNamespace(rd.Namespace),
+		client.MatchingLabelsSelector{Selector: selector},
+	); err != nil {
+		if !kerrors.IsNotFound(err) {
+			return nil, err
+		}
+	}
+
 	runnerMap := make(map[string]struct{})
 	for _, items := range runnerList.Items {
 		runnerMap[items.Name] = struct{}{}

controllers/autoscaling_test.go

@@ -443,7 +443,17 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
 					Name: "testrd",
 				},
 				Spec: v1alpha1.RunnerDeploymentSpec{
+					Selector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{
+							"foo": "bar",
+						},
+					},
 					Template: v1alpha1.RunnerTemplate{
+						ObjectMeta: metav1.ObjectMeta{
+							Labels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Spec: v1alpha1.RunnerSpec{
 							Organization: tc.org,
 						},

controllers/integration_test.go

@@ -3,13 +3,14 @@ package controllers
 import (
 	"context"
 	"fmt"
-	"github.com/google/go-github/v33/github"
-	github2 "github.com/summerwind/actions-runner-controller/github"
-	"k8s.io/apimachinery/pkg/runtime"
 	"net/http"
 	"net/http/httptest"
 	"time"
 
+	"github.com/google/go-github/v33/github"
+	github2 "github.com/summerwind/actions-runner-controller/github"
+	"k8s.io/apimachinery/pkg/runtime"
+
 	"github.com/summerwind/actions-runner-controller/github/fake"
 
 	corev1 "k8s.io/api/core/v1"
@@ -184,7 +185,17 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 					},
 					Spec: actionsv1alpha1.RunnerDeploymentSpec{
 						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
 							Spec: actionsv1alpha1.RunnerSpec{
 								Repository: "test/valid",
 								Image:      "bar",
@@ -301,7 +312,17 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 					},
 					Spec: actionsv1alpha1.RunnerDeploymentSpec{
 						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
 							Spec: actionsv1alpha1.RunnerSpec{
 								Repository: "test/valid",
 								Image:      "bar",
@@ -396,7 +417,17 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 					},
 					Spec: actionsv1alpha1.RunnerDeploymentSpec{
 						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
 							Spec: actionsv1alpha1.RunnerSpec{
 								Repository: "test/valid",
 								Image:      "bar",
@@ -515,7 +546,17 @@ var _ = Context("INTEGRATION: Inside of a new namespace", func() {
 					},
 					Spec: actionsv1alpha1.RunnerDeploymentSpec{
 						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
 							Spec: actionsv1alpha1.RunnerSpec{
 								Repository: "test/valid",
 								Image:      "bar",

controllers/runnerdeployment_controller.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"fmt"
 	"hash/fnv"
+	"reflect"
 	"sort"
 	"time"
 
@@ -143,6 +144,28 @@ func (r *RunnerDeploymentReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 		return ctrl.Result{RequeueAfter: 5 * time.Second}, nil
 	}
 
+	if !reflect.DeepEqual(newestSet.Spec.Selector, desiredRS.Spec.Selector) {
+		updateSet := newestSet.DeepCopy()
+		updateSet.Spec = *desiredRS.Spec.DeepCopy()
+
+		// A selector update change doesn't trigger replicaset replacement,
+		// but we still need to update the existing replicaset with it.
+		// Otherwise selector-based runner query will never work on replicasets created before the controller v0.17.0
+		// See https://github.com/summerwind/actions-runner-controller/pull/355#discussion_r585379259
+		if err := r.Client.Update(ctx, updateSet); err != nil {
+			log.Error(err, "Failed to update runnerreplicaset resource")
+
+			return ctrl.Result{}, err
+		}
+
+		// At this point, we are already sure that there's no need to create a new replicaset
+		// as the runner template hash is not changed.
+		//
+		// But we still need to requeue for the (possibly rare) cases that there are still old replicasets that needs
+		// to be cleaned up.
+		return ctrl.Result{RequeueAfter: 5 * time.Second}, nil
+	}
+
 	const defaultReplicas = 1
 
 	currentDesiredReplicas := getIntOrDefault(newestSet.Spec.Replicas, defaultReplicas)
@@ -258,18 +281,70 @@ func CloneAndAddLabel(labels map[string]string, labelKey, labelValue string) map
 	return newLabels
 }
 
+// Clones the given selector and returns a new selector with the given key and value added.
+// Returns the given selector, if labelKey is empty.
+//
+// Proudly copied from k8s.io/kubernetes/pkg/util/labels.CloneSelectorAndAddLabel
+func CloneSelectorAndAddLabel(selector *metav1.LabelSelector, labelKey, labelValue string) *metav1.LabelSelector {
+	if labelKey == "" {
+		// Don't need to add a label.
+		return selector
+	}
+
+	// Clone.
+	newSelector := new(metav1.LabelSelector)
+
+	newSelector.MatchLabels = make(map[string]string)
+	if selector.MatchLabels != nil {
+		for key, val := range selector.MatchLabels {
+			newSelector.MatchLabels[key] = val
+		}
+	}
+	newSelector.MatchLabels[labelKey] = labelValue
+
+	if selector.MatchExpressions != nil {
+		newMExps := make([]metav1.LabelSelectorRequirement, len(selector.MatchExpressions))
+		for i, me := range selector.MatchExpressions {
+			newMExps[i].Key = me.Key
+			newMExps[i].Operator = me.Operator
+			if me.Values != nil {
+				newMExps[i].Values = make([]string, len(me.Values))
+				copy(newMExps[i].Values, me.Values)
+			} else {
+				newMExps[i].Values = nil
+			}
+		}
+		newSelector.MatchExpressions = newMExps
+	} else {
+		newSelector.MatchExpressions = nil
+	}
+
+	return newSelector
+}
+
 func (r *RunnerDeploymentReconciler) newRunnerReplicaSet(rd v1alpha1.RunnerDeployment) (*v1alpha1.RunnerReplicaSet, error) {
+	return newRunnerReplicaSet(&rd, r.CommonRunnerLabels, r.Scheme)
+}
+
+func newRunnerReplicaSet(rd *v1alpha1.RunnerDeployment, commonRunnerLabels []string, scheme *runtime.Scheme) (*v1alpha1.RunnerReplicaSet, error) {
 	newRSTemplate := *rd.Spec.Template.DeepCopy()
+
 	templateHash := ComputeHash(&newRSTemplate)
 	// Add template hash label to selector.
 	labels := CloneAndAddLabel(rd.Spec.Template.Labels, LabelKeyRunnerTemplateHash, templateHash)
 
-	for _, l := range r.CommonRunnerLabels {
+	for _, l := range commonRunnerLabels {
 		newRSTemplate.Spec.Labels = append(newRSTemplate.Spec.Labels, l)
 	}
 
 	newRSTemplate.Labels = labels
 
+	selector := rd.Spec.Selector
+	if selector == nil {
+		selector = &metav1.LabelSelector{MatchLabels: labels}
+	}
+	newRSSelector := CloneSelectorAndAddLabel(selector, LabelKeyRunnerTemplateHash, templateHash)
+
 	rs := v1alpha1.RunnerReplicaSet{
 		TypeMeta: metav1.TypeMeta{},
 		ObjectMeta: metav1.ObjectMeta{
@@ -279,11 +354,12 @@ func (r *RunnerDeploymentReconciler) newRunnerReplicaSet(rd v1alpha1.RunnerDeplo
 		},
 		Spec: v1alpha1.RunnerReplicaSetSpec{
 			Replicas: rd.Spec.Replicas,
+			Selector: newRSSelector,
 			Template: newRSTemplate,
 		},
 	}
 
-	if err := ctrl.SetControllerReference(&rd, &rs, r.Scheme); err != nil {
+	if err := ctrl.SetControllerReference(rd, &rs, scheme); err != nil {
 		return &rs, err
 	}
 

controllers/runnerdeployment_controller_test.go

@@ -2,11 +2,13 @@ package controllers
 
 import (
 	"context"
-	"github.com/google/go-cmp/cmp"
+	"fmt"
-	"k8s.io/apimachinery/pkg/runtime"
 	"testing"
 	"time"
 
+	"github.com/google/go-cmp/cmp"
+	"k8s.io/apimachinery/pkg/runtime"
+
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/kubernetes/scheme"
@@ -36,7 +38,17 @@ func TestNewRunnerReplicaSet(t *testing.T) {
 			Name: "example",
 		},
 		Spec: actionsv1alpha1.RunnerDeploymentSpec{
+			Selector: &metav1.LabelSelector{
+				MatchLabels: map[string]string{
+					"foo": "bar",
+				},
+			},
 			Template: actionsv1alpha1.RunnerTemplate{
+				ObjectMeta: metav1.ObjectMeta{
+					Labels: map[string]string{
+						"foo": "bar",
+					},
+				},
 				Spec: actionsv1alpha1.RunnerSpec{
 					Labels: []string{"project1"},
 				},
@@ -49,10 +61,63 @@ func TestNewRunnerReplicaSet(t *testing.T) {
 		t.Fatalf("%v", err)
 	}
 
-	want := []string{"project1", "dev"}
+	if val, ok := rs.Labels["foo"]; ok {
-	if d := cmp.Diff(want, rs.Spec.Template.Spec.Labels); d != "" {
+		if val != "bar" {
+			t.Errorf("foo label does not have bar but %v", val)
+		}
+	} else {
+		t.Errorf("foo label does not exist")
+	}
+
+	hash1, ok := rs.Labels[LabelKeyRunnerTemplateHash]
+	if !ok {
+		t.Errorf("missing runner-template-hash label")
+	}
+
+	runnerLabel := []string{"project1", "dev"}
+	if d := cmp.Diff(runnerLabel, rs.Spec.Template.Spec.Labels); d != "" {
 		t.Errorf("%s", d)
 	}
+
+	rd2 := rd.DeepCopy()
+	rd2.Spec.Template.Spec.Labels = []string{"project2"}
+
+	rs2, err := r.newRunnerReplicaSet(*rd2)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	hash2, ok := rs2.Labels[LabelKeyRunnerTemplateHash]
+	if !ok {
+		t.Errorf("missing runner-template-hash label")
+	}
+
+	if hash1 == hash2 {
+		t.Errorf(
+			"runner replica sets from runner deployments with varying labels must have different template hash, but got %s and %s",
+			hash1, hash2,
+		)
+	}
+
+	rd3 := rd.DeepCopy()
+	rd3.Spec.Template.Labels["foo"] = "baz"
+
+	rs3, err := r.newRunnerReplicaSet(*rd3)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	hash3, ok := rs3.Labels[LabelKeyRunnerTemplateHash]
+	if !ok {
+		t.Errorf("missing runner-template-hash label")
+	}
+
+	if hash1 == hash3 {
+		t.Errorf(
+			"runner replica sets from runner deployments with varying meta labels must have different template hash, but got %s and %s",
+			hash1, hash3,
+		)
+	}
 }
 
 // SetupDeploymentTest will set up a testing environment.
@@ -112,7 +177,113 @@ var _ = Context("Inside of a new namespace", func() {
 	Describe("when no existing resources exist", func() {
 
 		It("should create a new RunnerReplicaSet resource from the specified template, add a another RunnerReplicaSet on template modification, and eventually removes old runnerreplicasets", func() {
-			name := "example-runnerdeploy"
+			name := "example-runnerdeploy-1"
+
+			{
+				rs := &actionsv1alpha1.RunnerDeployment{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      name,
+						Namespace: ns.Name,
+					},
+					Spec: actionsv1alpha1.RunnerDeploymentSpec{
+						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
+						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
+							Spec: actionsv1alpha1.RunnerSpec{
+								Repository: "foo/bar",
+								Image:      "bar",
+								Env: []corev1.EnvVar{
+									{Name: "FOO", Value: "FOOVALUE"},
+								},
+							},
+						},
+					},
+				}
+
+				err := k8sClient.Create(ctx, rs)
+
+				Expect(err).NotTo(HaveOccurred(), "failed to create test RunnerReplicaSet resource")
+
+				runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
+
+				Eventually(
+					func() (int, error) {
+						selector, err := metav1.LabelSelectorAsSelector(rs.Spec.Selector)
+						if err != nil {
+							return 0, err
+						}
+						err = k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+							client.MatchingLabelsSelector{Selector: selector},
+						)
+						if err != nil {
+							return 0, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return 0, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
+						}
+
+						return *runnerSets.Items[0].Spec.Replicas, nil
+					},
+					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(1))
+			}
+
+			{
+				// We wrap the update in the Eventually block to avoid the below error that occurs due to concurrent modification
+				// made by the controller to update .Status.AvailableReplicas and .Status.ReadyReplicas
+				//   Operation cannot be fulfilled on runnersets.actions.summerwind.dev "example-runnerset": the object has been modified; please apply your changes to the latest version and try again
+				var rd actionsv1alpha1.RunnerDeployment
+				Eventually(func() error {
+					err := k8sClient.Get(ctx, types.NamespacedName{Namespace: ns.Name, Name: name}, &rd)
+					if err != nil {
+						return fmt.Errorf("failed to get test RunnerReplicaSet resource: %v\n", err)
+					}
+					rd.Spec.Replicas = intPtr(2)
+
+					return k8sClient.Update(ctx, &rd)
+				},
+					time.Second*1, time.Millisecond*500).Should(BeNil())
+
+				runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
+
+				Eventually(
+					func() (int, error) {
+						selector, err := metav1.LabelSelectorAsSelector(rd.Spec.Selector)
+						if err != nil {
+							return 0, err
+						}
+						err = k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+							client.MatchingLabelsSelector{Selector: selector},
+						)
+						if err != nil {
+							return 0, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return 0, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
+						}
+
+						return *runnerSets.Items[0].Spec.Replicas, nil
+					},
+					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(2))
+			}
+		})
+
+		It("should create a new RunnerReplicaSet resource from the specified template without labels and selector, add a another RunnerReplicaSet on template modification, and eventually removes old runnerreplicasets", func() {
+			name := "example-runnerdeploy-2"
 
 			{
 				rs := &actionsv1alpha1.RunnerDeployment{
@@ -141,29 +312,25 @@ var _ = Context("Inside of a new namespace", func() {
 				runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
 
 				Eventually(
-					func() int {
+					func() (int, error) {
-						err := k8sClient.List(ctx, &runnerSets, client.InNamespace(ns.Name))
+						selector, err := metav1.LabelSelectorAsSelector(rs.Spec.Selector)
 						if err != nil {
-							logf.Log.Error(err, "list runner sets")
+							return 0, err
 						}
-
+						err = k8sClient.List(
-						return len(runnerSets.Items)
+							ctx,
-					},
+							&runnerSets,
-					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(1))
+							client.InNamespace(ns.Name),
-
+							client.MatchingLabelsSelector{Selector: selector},
-				Eventually(
+						)
-					func() int {
-						err := k8sClient.List(ctx, &runnerSets, client.InNamespace(ns.Name))
 						if err != nil {
-							logf.Log.Error(err, "list runner sets")
+							return 0, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return 0, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
 						}
 
-						if len(runnerSets.Items) == 0 {
+						return *runnerSets.Items[0].Spec.Replicas, nil
-							logf.Log.Info("No runnerreplicasets exist yet")
-							return -1
-						}
-
-						return *runnerSets.Items[0].Spec.Replicas
 					},
 					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(1))
 			}
@@ -172,13 +339,12 @@ var _ = Context("Inside of a new namespace", func() {
 				// We wrap the update in the Eventually block to avoid the below error that occurs due to concurrent modification
 				// made by the controller to update .Status.AvailableReplicas and .Status.ReadyReplicas
 				//   Operation cannot be fulfilled on runnersets.actions.summerwind.dev "example-runnerset": the object has been modified; please apply your changes to the latest version and try again
-				Eventually(func() error {
 				var rd actionsv1alpha1.RunnerDeployment
-
+				Eventually(func() error {
 					err := k8sClient.Get(ctx, types.NamespacedName{Namespace: ns.Name, Name: name}, &rd)
-
+					if err != nil {
-					Expect(err).NotTo(HaveOccurred(), "failed to get test RunnerReplicaSet resource")
+						return fmt.Errorf("failed to get test RunnerReplicaSet resource: %v\n", err)
-
+					}
 					rd.Spec.Replicas = intPtr(2)
 
 					return k8sClient.Update(ctx, &rd)
@@ -188,27 +354,126 @@ var _ = Context("Inside of a new namespace", func() {
 				runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
 
 				Eventually(
-					func() int {
+					func() (int, error) {
-						err := k8sClient.List(ctx, &runnerSets, client.InNamespace(ns.Name))
+						selector, err := metav1.LabelSelectorAsSelector(rd.Spec.Selector)
 						if err != nil {
-							logf.Log.Error(err, "list runner sets")
+							return 0, err
+						}
+						err = k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+							client.MatchingLabelsSelector{Selector: selector},
+						)
+						if err != nil {
+							return 0, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return 0, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
 						}
 
-						return len(runnerSets.Items)
+						return *runnerSets.Items[0].Spec.Replicas, nil
-					},
-					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(1))
-
-				Eventually(
-					func() int {
-						err := k8sClient.List(ctx, &runnerSets, client.InNamespace(ns.Name))
-						if err != nil {
-							logf.Log.Error(err, "list runner sets")
-						}
-
-						return *runnerSets.Items[0].Spec.Replicas
 					},
 					time.Second*5, time.Millisecond*500).Should(BeEquivalentTo(2))
 			}
 		})
+
+		It("should adopt RunnerReplicaSet created before 0.18.0 to have Spec.Selector", func() {
+			name := "example-runnerdeploy-2"
+
+			{
+				rd := &actionsv1alpha1.RunnerDeployment{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      name,
+						Namespace: ns.Name,
+					},
+					Spec: actionsv1alpha1.RunnerDeploymentSpec{
+						Replicas: intPtr(1),
+						Template: actionsv1alpha1.RunnerTemplate{
+							Spec: actionsv1alpha1.RunnerSpec{
+								Repository: "foo/bar",
+								Image:      "bar",
+								Env: []corev1.EnvVar{
+									{Name: "FOO", Value: "FOOVALUE"},
+								},
+							},
+						},
+					},
+				}
+
+				createRDErr := k8sClient.Create(ctx, rd)
+				Expect(createRDErr).NotTo(HaveOccurred(), "failed to create test RunnerReplicaSet resource")
+
+				Eventually(
+					func() (int, error) {
+						runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
+
+						err := k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+						)
+						if err != nil {
+							return 0, err
+						}
+
+						return len(runnerSets.Items), nil
+					},
+					time.Second*1, time.Millisecond*500).Should(BeEquivalentTo(1))
+
+				var rs17 *actionsv1alpha1.RunnerReplicaSet
+
+				Consistently(
+					func() (*metav1.LabelSelector, error) {
+						runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
+
+						err := k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+						)
+						if err != nil {
+							return nil, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return nil, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
+						}
+
+						rs17 = &runnerSets.Items[0]
+
+						return runnerSets.Items[0].Spec.Selector, nil
+					},
+					time.Second*1, time.Millisecond*500).Should(Not(BeNil()))
+
+				// We simulate the old, pre 0.18.0 RunnerReplicaSet by updating it.
+				// I've tried to use controllerutil.Set{Owner,Controller}Reference and k8sClient.Create(rs17)
+				// but it didn't work due to missing RD UID, where UID is generated on K8s API server on k8sCLient.Create(rd)
+				rs17.Spec.Selector = nil
+
+				updateRSErr := k8sClient.Update(ctx, rs17)
+				Expect(updateRSErr).NotTo(HaveOccurred())
+
+				Eventually(
+					func() (*metav1.LabelSelector, error) {
+						runnerSets := actionsv1alpha1.RunnerReplicaSetList{Items: []actionsv1alpha1.RunnerReplicaSet{}}
+
+						err := k8sClient.List(
+							ctx,
+							&runnerSets,
+							client.InNamespace(ns.Name),
+						)
+						if err != nil {
+							return nil, err
+						}
+						if len(runnerSets.Items) != 1 {
+							return nil, fmt.Errorf("runnerreplicasets is not 1 but %d", len(runnerSets.Items))
+						}
+
+						return runnerSets.Items[0].Spec.Selector, nil
+					},
+					time.Second*1, time.Millisecond*500).Should(Not(BeNil()))
+			}
+		})
+
 	})
 })

controllers/runnerreplicaset_controller.go

@@ -68,8 +68,18 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 		return ctrl.Result{}, nil
 	}
 
+	selector, err := metav1.LabelSelectorAsSelector(rs.Spec.Selector)
+	if err != nil {
+		return ctrl.Result{}, err
+	}
+	// Get the Runners managed by the target RunnerReplicaSet
 	var allRunners v1alpha1.RunnerList
-	if err := r.List(ctx, &allRunners, client.InNamespace(req.Namespace)); err != nil {
+	if err := r.List(
+		ctx,
+		&allRunners,
+		client.InNamespace(req.Namespace),
+		client.MatchingLabelsSelector{Selector: selector},
+	); err != nil {
 		if !kerrors.IsNotFound(err) {
 			return ctrl.Result{}, err
 		}
@@ -77,9 +87,14 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 
 	var myRunners []v1alpha1.Runner
 
-	var available, ready int
+	var (
+		available int
+		ready     int
+	)
 
 	for _, r := range allRunners.Items {
+		// This guard is required to avoid the RunnerReplicaSet created by the controller v0.17.0 or before
+		// to not treat all the runners in the namespace as its children.
 		if metav1.IsControlledBy(&r, &rs) {
 			myRunners = append(myRunners, r)
 
@@ -106,7 +121,7 @@ func (r *RunnerReplicaSetReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 
 		// get runners that are currently not busy
 		var notBusy []v1alpha1.Runner
-		for _, runner := range myRunners {
+		for _, runner := range allRunners.Items {
 			busy, err := r.GitHubClient.IsRunnerBusy(ctx, runner.Spec.Enterprise, runner.Spec.Organization, runner.Spec.Repository, runner.Name)
 			if err != nil {
 				notRegistered := false

controllers/runnerreplicaset_controller_test.go

@@ -115,7 +115,17 @@ var _ = Context("Inside of a new namespace", func() {
 					},
 					Spec: actionsv1alpha1.RunnerReplicaSetSpec{
 						Replicas: intPtr(1),
+						Selector: &metav1.LabelSelector{
+							MatchLabels: map[string]string{
+								"foo": "bar",
+							},
+						},
 						Template: actionsv1alpha1.RunnerTemplate{
+							ObjectMeta: metav1.ObjectMeta{
+								Labels: map[string]string{
+									"foo": "bar",
+								},
+							},
 							Spec: actionsv1alpha1.RunnerSpec{
 								Repository: "foo/bar",
 								Image:      "bar",
@@ -135,9 +145,26 @@ var _ = Context("Inside of a new namespace", func() {
 
 				Eventually(
 					func() int {
-						err := k8sClient.List(ctx, &runners, client.InNamespace(ns.Name))
+						selector, err := metav1.LabelSelectorAsSelector(
+							&metav1.LabelSelector{
+								MatchLabels: map[string]string{
+									"foo": "bar",
+								},
+							},
+						)
+						if err != nil {
+							logf.Log.Error(err, "failed to create labelselector")
+							return -1
+						}
+						err = k8sClient.List(
+							ctx,
+							&runners,
+							client.InNamespace(ns.Name),
+							client.MatchingLabelsSelector{Selector: selector},
+						)
 						if err != nil {
 							logf.Log.Error(err, "list runners")
+							return -1
 						}
 
 						for i, runner := range runners.Items {
@@ -176,7 +203,23 @@ var _ = Context("Inside of a new namespace", func() {
 
 				Eventually(
 					func() int {
-						err := k8sClient.List(ctx, &runners, client.InNamespace(ns.Name))
+						selector, err := metav1.LabelSelectorAsSelector(
+							&metav1.LabelSelector{
+								MatchLabels: map[string]string{
+									"foo": "bar",
+								},
+							},
+						)
+						if err != nil {
+							logf.Log.Error(err, "failed to create labelselector")
+							return -1
+						}
+						err = k8sClient.List(
+							ctx,
+							&runners,
+							client.InNamespace(ns.Name),
+							client.MatchingLabelsSelector{Selector: selector},
+						)
 						if err != nil {
 							logf.Log.Error(err, "list runners")
 						}
@@ -220,6 +263,7 @@ var _ = Context("Inside of a new namespace", func() {
 						err := k8sClient.List(ctx, &runners, client.InNamespace(ns.Name))
 						if err != nil {
 							logf.Log.Error(err, "list runners")
+							return -1
 						}
 
 						for i, runner := range runners.Items {