Do not target services with port that does not exist

CHANGELOG.md

@@ -9,6 +9,9 @@ Unreleased section should follow [Release Toolkit](https://github.com/newrelic/r
 
 ## Unreleased
 
+### Enhancement
+- Skip prometheus services with non-existing port
+
 ## v2.19.0 - 2023-11-02
 
 ### 🚀 Enhancements

internal/pkg/endpoints/kubernetes.go

@@ -344,7 +344,16 @@ func serviceTargets(s *corev1.Service) []Target {
 		return nil
 	}
 
+	availablePorts := make(map[string]bool)
+	for _, port := range s.Spec.Ports {
+		availablePorts[fmt.Sprintf("%d", port.Port)] = true
+	}
+
 	if port != "" {
+		if !availablePorts[port] {
+			klog.WithError(err).Warnf("Port %s is not exposed on service  %s/%s", port, s.Namespace, s.Name)
+			return nil
+		}
 		u := url.URL{
 			Scheme:   scheme,
 			Host:     net.JoinHostPort(fmt.Sprintf("%s.%s.svc", s.Name, s.Namespace), port),
@@ -356,10 +365,10 @@ func serviceTargets(s *corev1.Service) []Target {
 
 	// No port specified so return a target for each Port defined for the Service.
 	var targets []Target
-	for _, port := range s.Spec.Ports {
+	for port := range availablePorts {
 		u := url.URL{
 			Scheme:   scheme,
-			Host:     net.JoinHostPort(fmt.Sprintf("%s.%s.svc", s.Name, s.Namespace), fmt.Sprintf("%d", port.Port)),
+			Host:     net.JoinHostPort(fmt.Sprintf("%s.%s.svc", s.Name, s.Namespace), port),
 			Path:     path,
 			RawQuery: query,
 		}

internal/pkg/endpoints/kubernetes_test.go

@@ -356,6 +356,13 @@ func populateFakeEndpointsDataSinglePort(clientset *fake.Clientset) error {
 				"prometheus.io/port":   "1",
 			},
 		},
+		Spec: corev1.ServiceSpec{
+			Ports: []corev1.ServicePort{
+				{
+					Port: 1,
+				},
+			},
+		},
 	}
 
 	_, err := clientset.CoreV1().Services("test-ns").Create(context.TODO(), s, metav1.CreateOptions{})
@@ -1640,6 +1647,36 @@ func TestServiceTargetsInvalidPortAnnotaion(t *testing.T) {
 	)
 }
 
+func TestServiceTargetsNonExistingPort(t *testing.T) {
+	t.Parallel()
+
+	assert.ElementsMatch(
+		t,
+		serviceTargets(&corev1.Service{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "my-service",
+				Namespace: "test-ns",
+				Annotations: map[string]string{
+					"prometheus.io/port": "5000",
+				},
+			},
+			Spec: corev1.ServiceSpec{
+				Ports: []corev1.ServicePort{
+					{
+						Name: "http-app",
+						Port: 80,
+					},
+					{
+						Name: "http-app2",
+						Port: 8080,
+					},
+				},
+			},
+		}),
+		[]Target{},
+	)
+}
+
 func TestServiceTargetsNoPort(t *testing.T) {
 	t.Parallel()