fix(k8s): join host and port instead of concatenating

An IPv6 address concatenated with ":port" is ambiguous and unusable in a
URL. This matters more now that node resolution prefers the ExternalIP on
the node object, which is IPv6 on a dual-stack or IPv6 cluster.

net.JoinHostPort brackets IPv6 and leaves IPv4 and hostnames unchanged.

Author: james00012

modules/k8s/service.go

@@ -3,7 +3,9 @@ package k8s
 import (
 	"context"
 	"fmt"
+	"net"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -154,7 +156,7 @@ func GetServiceEndpointContextE(t testing.TestingT, ctx context.Context, options
 	switch service.Spec.Type {
 	case corev1.ServiceTypeClusterIP:
 
-		return fmt.Sprintf("%s:%d", service.Spec.ClusterIP, servicePort), nil
+		return net.JoinHostPort(service.Spec.ClusterIP, strconv.Itoa(servicePort)), nil
 	case corev1.ServiceTypeNodePort:
 		return findEndpointForNodePortServiceContext(t, ctx, options, service, int32(servicePort))
 	case corev1.ServiceTypeExternalName:
@@ -176,10 +178,10 @@ func GetServiceEndpointContextE(t testing.TestingT, ctx context.Context, options
 		}
 
 		if ingress[0].Hostname == "" {
-			return fmt.Sprintf("%s:%d", ingress[0].IP, servicePort), nil
+			return net.JoinHostPort(ingress[0].IP, strconv.Itoa(servicePort)), nil
 		}
 
-		return fmt.Sprintf("%s:%d", ingress[0].Hostname, servicePort), nil
+		return net.JoinHostPort(ingress[0].Hostname, strconv.Itoa(servicePort)), nil
 	default:
 		return "", NewUnknownServiceTypeError(service)
 	}
@@ -210,7 +212,7 @@ func findEndpointForNodePortServiceContext(
 		return "", err
 	}
 
-	return fmt.Sprintf("%s:%d", nodeHostname, nodePort), nil
+	return net.JoinHostPort(nodeHostname, strconv.FormatInt(int64(nodePort), 10)), nil
 }
 
 // FindNodePortContextE returns the allocated NodePort for the given servicePort from the service definition.

modules/k8s/service_endpoint_format_test.go

@@ -0,0 +1,40 @@
+package k8s_test
+
+import (
+	"testing"
+
+	"github.com/gruntwork-io/terratest/modules/k8s/v2"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+)
+
+// TestGetServiceEndpointBracketsIPv6 pins that endpoints are host/port joined rather than concatenated. An IPv6
+// address concatenated with ":port" is ambiguous and unusable in a URL, and this matters more now that node
+// resolution prefers the ExternalIP recorded on the node, which is IPv6 on a dual-stack or IPv6 cluster.
+func TestGetServiceEndpointBracketsIPv6(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name      string
+		clusterIP string
+		expected  string
+	}{
+		{"ipv4 is unchanged", "10.0.0.1", "10.0.0.1:80"},
+		{"ipv6 is bracketed", "2600:1f18:abcd::1", "[2600:1f18:abcd::1]:80"},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			service := &corev1.Service{
+				Spec: corev1.ServiceSpec{Type: corev1.ServiceTypeClusterIP, ClusterIP: testCase.clusterIP},
+			}
+
+			endpoint, err := k8s.GetServiceEndpointContextE(t, t.Context(), nil, service, 80)
+			require.NoError(t, err)
+			assert.Equal(t, testCase.expected, endpoint)
+		})
+	}
+}