bugfix: validate maxReplica when minReplica is set for autoscaler (#4215)

* added check for maxReplica when minReplica is set for autoscaler

Signed-off-by: carsontham <carsontham@outlook.com>

* fix lint

---------

Signed-off-by: carsontham <carsontham@outlook.com>

Author: carsontham

.chloggen/autoscaler-maxreplica-check.yaml

@@ -0,0 +1,18 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. collector, target allocator, auto-instrumentation, opamp, github action)
+component: collector
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: added check for maxReplica when minReplica is set in autoscaler 
+
+# One or more tracking issues related to the change
+issues: [4160]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: When using the AutoScaler, maxReplica must be set when minReplica is set.
+
+

apis/v1beta1/collector_webhook.go

@@ -230,6 +230,11 @@ func (c CollectorWebhook) Validate(ctx context.Context, r *OpenTelemetryCollecto
 	if r.Spec.Autoscaler != nil && r.Spec.Autoscaler.MinReplicas != nil {
 		minReplicas = r.Spec.Autoscaler.MinReplicas
 	}
+
+	if r.Spec.Autoscaler != nil && r.Spec.Autoscaler.MinReplicas != nil && r.Spec.Autoscaler.MaxReplicas == nil {
+		return warnings, fmt.Errorf("spec.maxReplica must be set when spec.minReplica is set")
+	}
+
 	// check deprecated .Spec.MinReplicas if minReplicas is not set
 	if minReplicas == nil {
 		minReplicas = r.Spec.Replicas

apis/v1beta1/collector_webhook_test.go

@@ -919,6 +919,17 @@ func TestOTELColValidatingWebhook(t *testing.T) {
 			},
 			expectedErr: "maxReplicas should be defined and one or more",
 		},
+		{
+			name: "it should return error when minReplica is set but maxReplica is not set",
+			otelcol: v1beta1.OpenTelemetryCollector{
+				Spec: v1beta1.OpenTelemetryCollectorSpec{
+					Autoscaler: &v1beta1.AutoscalerSpec{
+						MinReplicas: &three,
+					},
+				},
+			},
+			expectedErr: "spec.maxReplica must be set when spec.minReplica is set",
+		},
 		{
 			name: "invalid replicas, greater than max",
 			otelcol: v1beta1.OpenTelemetryCollector{