add autoscale option to enable support for Horizontal Pod Autoscaling

apis/v1alpha1/opentelemetrycollector_types.go

@@ -33,10 +33,22 @@ type OpenTelemetryCollectorSpec struct {
 	// +optional
 	Args map[string]string `json:"args,omitempty"`
 
+	// Autoscale turns on/off the autoscale feature. By default, it's enabled if the Replicas field is not set.
+	// +optional
+	Autoscale *bool `json:"autoscale,omitempty"`
+
 	// Replicas is the number of pod instances for the underlying OpenTelemetry Collector
 	// +optional
 	Replicas *int32 `json:"replicas,omitempty"`
 
+	// MinReplicas sets a lower bound to the autoscaling feature.
+	// +optional
+	MinReplicas *int32 `json:"minReplicas,omitempty"`
+
+	// MaxReplicas sets an upper bound to the autoscaling feature. When autoscaling is enabled and no value is provided, a default value is used.
+	// +optional
+	MaxReplicas *int32 `json:"maxReplicas,omitempty"`
+
 	// ImagePullPolicy indicates the pull policy to be used for retrieving the container image (Always, Never, IfNotPresent)
 	// +optional
 	ImagePullPolicy v1.PullPolicy `json:"imagePullPolicy,omitempty"`

apis/v1alpha1/opentelemetrycollector_webhook.go

@@ -109,5 +109,20 @@ func (r *OpenTelemetryCollector) validateCRDSpec() error {
 		}
 	}
 
+	// validate autoscale with horizontal pod autoscaler
+	if r.Spec.Autoscale != nil && *r.Spec.Autoscale {
+		if r.Spec.Replicas != nil {
+			return fmt.Errorf("the OpenTelemetry Spec autoscale configuration is incorrect, replicas should be nil")
+		}
+
+		if r.Spec.MaxReplicas == nil || *r.Spec.MaxReplicas < int32(1) {
+			return fmt.Errorf("the OpenTelemetry Spec autoscale configuration is incorrect, maaxReplicas should be defined and more than one")
+		}
+
+		if r.Spec.MinReplicas != nil && *r.Spec.MinReplicas > *r.Spec.MaxReplicas {
+			return fmt.Errorf("the OpenTelemetry Spec autoscale configuration is incorrect, minReplicas must not be greater than maxReplicas")
+		}
+	}
+
 	return nil
 }

bundle/manifests/opentelemetry-operator.clusterserviceversion.yaml

@@ -188,6 +188,18 @@ spec:
           - patch
           - update
           - watch
+        - apiGroups:
+          - autoscaling
+          resources:
+          - horizontalpodautoscalers
+          verbs:
+          - create
+          - delete
+          - get
+          - list
+          - patch
+          - update
+          - watch
         - apiGroups:
           - coordination.k8s.io
           resources:

bundle/manifests/opentelemetry.io_opentelemetrycollectors.yaml

@@ -59,6 +59,10 @@ spec:
                 description: Args is the set of arguments to pass to the OpenTelemetry
                   Collector binary
                 type: object
+              autoscale:
+                description: Autoscale turns on/off the autoscale feature. By default,
+                  it's enabled if the Replicas field is not set.
+                type: boolean
               config:
                 description: Config is the raw JSON to be used as the collector's
                   configuration. Refer to the OpenTelemetry Collector documentation
@@ -218,6 +222,16 @@ spec:
                 description: ImagePullPolicy indicates the pull policy to be used
                   for retrieving the container image (Always, Never, IfNotPresent)
                 type: string
+              maxReplicas:
+                description: MaxReplicas sets an upper bound to the autoscaling feature.
+                  When autoscaling is enabled and no value is provided, a default
+                  value is used.
+                format: int32
+                type: integer
+              minReplicas:
+                description: MinReplicas sets a lower bound to the autoscaling feature.
+                format: int32
+                type: integer
               mode:
                 description: Mode represents how the collector should be deployed
                   (deployment, daemonset, statefulset or sidecar)

config/crd/bases/opentelemetry.io_opentelemetrycollectors.yaml

@@ -57,6 +57,10 @@ spec:
                 description: Args is the set of arguments to pass to the OpenTelemetry
                   Collector binary
                 type: object
+              autoscale:
+                description: Autoscale turns on/off the autoscale feature. By default,
+                  it's enabled if the Replicas field is not set.
+                type: boolean
               config:
                 description: Config is the raw JSON to be used as the collector's
                   configuration. Refer to the OpenTelemetry Collector documentation
@@ -216,6 +220,16 @@ spec:
                 description: ImagePullPolicy indicates the pull policy to be used
                   for retrieving the container image (Always, Never, IfNotPresent)
                 type: string
+              maxReplicas:
+                description: MaxReplicas sets an upper bound to the autoscaling feature.
+                  When autoscaling is enabled and no value is provided, a default
+                  value is used.
+                format: int32
+                type: integer
+              minReplicas:
+                description: MinReplicas sets a lower bound to the autoscaling feature.
+                format: int32
+                type: integer
               mode:
                 description: Mode represents how the collector should be deployed
                   (deployment, daemonset, statefulset or sidecar)

config/rbac/role.yaml

@@ -99,6 +99,18 @@ rules:
   - patch
   - update
   - watch
+- apiGroups:
+  - autoscaling
+  resources:
+  - horizontalpodautoscalers
+  verbs:
+  - create
+  - delete
+  - get
+  - list
+  - patch
+  - update
+  - watch
 - apiGroups:
   - coordination.k8s.io
   resources:

controllers/opentelemetrycollector_controller.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/go-logr/logr"
 	appsv1 "k8s.io/api/apps/v1"
+	autoscalingv1 "k8s.io/api/autoscaling/v1"
 	corev1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -84,6 +85,11 @@ func NewReconciler(p Params) *OpenTelemetryCollectorReconciler {
 				reconcile.Deployments,
 				true,
 			},
+			{
+				"horizontal pod autoscalers",
+				reconcile.HorizontalPodAutoscalers,
+				true,
+			},
 			{
 				"daemon sets",
 				reconcile.DaemonSets,
@@ -173,6 +179,7 @@ func (r *OpenTelemetryCollectorReconciler) SetupWithManager(mgr ctrl.Manager) er
 		Owns(&corev1.ServiceAccount{}).
 		Owns(&corev1.Service{}).
 		Owns(&appsv1.Deployment{}).
+		Owns(&autoscalingv1.HorizontalPodAutoscaler{}).
 		Owns(&appsv1.DaemonSet{}).
 		Owns(&appsv1.StatefulSet{}).
 		Complete(r)

docs/api.md

@@ -1404,6 +1404,13 @@ OpenTelemetryCollectorSpec defines the desired state of OpenTelemetryCollector.
           Args is the set of arguments to pass to the OpenTelemetry Collector binary<br/>
         </td>
         <td>false</td>
+      </tr><tr>
+        <td><b>autoscale</b></td>
+        <td>boolean</td>
+        <td>
+          Autoscale turns on/off the autoscale feature. By default, it's enabled if the Replicas field is not set.<br/>
+        </td>
+        <td>false</td>
       </tr><tr>
         <td><b>config</b></td>
         <td>string</td>
@@ -1446,6 +1453,24 @@ OpenTelemetryCollectorSpec defines the desired state of OpenTelemetryCollector.
           ImagePullPolicy indicates the pull policy to be used for retrieving the container image (Always, Never, IfNotPresent)<br/>
         </td>
         <td>false</td>
+      </tr><tr>
+        <td><b>maxReplicas</b></td>
+        <td>integer</td>
+        <td>
+          MaxReplicas sets an upper bound to the autoscaling feature. When autoscaling is enabled and no value is provided, a default value is used.<br/>
+          <br/>
+            <i>Format</i>: int32<br/>
+        </td>
+        <td>false</td>
+      </tr><tr>
+        <td><b>minReplicas</b></td>
+        <td>integer</td>
+        <td>
+          MinReplicas sets a lower bound to the autoscaling feature.<br/>
+          <br/>
+            <i>Format</i>: int32<br/>
+        </td>
+        <td>false</td>
       </tr><tr>
         <td><b>mode</b></td>
         <td>enum</td>

pkg/collector/deployment.go

@@ -33,6 +33,12 @@ func Deployment(cfg config.Config, logger logr.Logger, otelcol v1alpha1.OpenTele
 	annotations := Annotations(otelcol)
 	podAnnotations := PodAnnotations(otelcol)
 
+	// if autoscale is enabled, set replicas to minReplicas
+	replicas := otelcol.Spec.Replicas
+	if otelcol.Spec.Autoscale != nil && *otelcol.Spec.Autoscale {
+		replicas = otelcol.Spec.MinReplicas
+	}
+
 	return appsv1.Deployment{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:        naming.Collector(otelcol),
@@ -41,7 +47,7 @@ func Deployment(cfg config.Config, logger logr.Logger, otelcol v1alpha1.OpenTele
 			Annotations: annotations,
 		},
 		Spec: appsv1.DeploymentSpec{
-			Replicas: otelcol.Spec.Replicas,
+			Replicas: replicas,
 			Selector: &metav1.LabelSelector{
 				MatchLabels: labels,
 			},

pkg/collector/horizontalpodautoscaler.go

@@ -0,0 +1,52 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+	"github.com/go-logr/logr"
+	autoscalingv1 "k8s.io/api/autoscaling/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	"github.com/open-telemetry/opentelemetry-operator/apis/v1alpha1"
+	"github.com/open-telemetry/opentelemetry-operator/internal/config"
+	"github.com/open-telemetry/opentelemetry-operator/pkg/naming"
+)
+
+func HorizontalPodAutoscaler(cfg config.Config, logger logr.Logger, otelcol v1alpha1.OpenTelemetryCollector) autoscalingv1.HorizontalPodAutoscaler {
+	labels := Labels(otelcol)
+	labels["app.kubernetes.io/name"] = naming.Collector(otelcol)
+
+	annotations := Annotations(otelcol)
+	var cpuTarget int32 = 90
+
+	return autoscalingv1.HorizontalPodAutoscaler{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:        naming.Collector(otelcol),
+			Namespace:   otelcol.Namespace,
+			Labels:      labels,
+			Annotations: annotations,
+		},
+		Spec: autoscalingv1.HorizontalPodAutoscalerSpec{
+			ScaleTargetRef: autoscalingv1.CrossVersionObjectReference{
+				APIVersion: "apps/v1",
+				Kind:       "Deployment",
+				Name:       naming.Collector(otelcol),
+			},
+			MinReplicas:                    otelcol.Spec.MinReplicas,
+			MaxReplicas:                    *otelcol.Spec.MaxReplicas,
+			TargetCPUUtilizationPercentage: &cpuTarget,
+		},
+	}
+}

pkg/collector/horizontalpodautoscaler_test.go

@@ -0,0 +1,54 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	"github.com/open-telemetry/opentelemetry-operator/apis/v1alpha1"
+	"github.com/open-telemetry/opentelemetry-operator/internal/config"
+	. "github.com/open-telemetry/opentelemetry-operator/pkg/collector"
+)
+
+func TestHPA(t *testing.T) {
+	// prepare
+	enable := true
+	var minReplicas int32 = 3
+	var maxReplicas int32 = 5
+
+	otelcol := v1alpha1.OpenTelemetryCollector{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "my-instance",
+		},
+		Spec: v1alpha1.OpenTelemetryCollectorSpec{
+			MinReplicas: &minReplicas,
+			MaxReplicas: &maxReplicas,
+			Autoscale:   &enable,
+		},
+	}
+
+	cfg := config.New()
+	hpa := HorizontalPodAutoscaler(cfg, logger, otelcol)
+
+	// verify
+	assert.Equal(t, "my-instance-collector", hpa.Name)
+	assert.Equal(t, "my-instance-collector", hpa.Labels["app.kubernetes.io/name"])
+	assert.Equal(t, int32(3), *hpa.Spec.MinReplicas)
+	assert.Equal(t, int32(5), hpa.Spec.MaxReplicas)
+	assert.Equal(t, int32(90), *hpa.Spec.TargetCPUUtilizationPercentage)
+}

pkg/collector/reconcile/deployment.go

@@ -98,6 +98,11 @@ func expectedDeployments(ctx context.Context, params Params, expected []appsv1.D
 			updated.ObjectMeta.Labels[k] = v
 		}
 
+		// if autoscale is enabled, use replicas from current Status
+		if params.Instance.Spec.Autoscale != nil && *params.Instance.Spec.Autoscale {
+			updated.Spec.Replicas = &existing.Status.Replicas
+		}
+
 		patch := client.MergeFrom(existing)
 
 		if err := params.Client.Patch(ctx, updated, patch); err != nil {