Add option to use pod name rather than IP address for Kubernetes (#1190)

Change to use a new 'endpoints' directive and use a constant

Add initial docs for 'endpoints' directive

Add tests to Kubernetes setup for endpoints

Changes based on PR feedback

endpoint_pod_names is a boolean config option. Chahanged docs to reflect this.

Add a test when endpoints_pod_names is not set

Update README.md

Remove endpointNameModeName as it is no longer used

plugin/kubernetes/setup_test.go

@@ -471,3 +471,66 @@ func TestKubernetesParse(t *testing.T) {
 		}
 	}
 }
+
+func TestKubernetesEndpointsParse(t *testing.T) {
+	tests := []struct {
+		input                string // Corefile data as string
+		shouldErr            bool   // true if test case is exected to produce an error.
+		expectedErrContent   string // substring from the expected error. Empty for positive cases.
+		expectedEndpointMode bool
+	}{
+		// valid endpoints mode
+		{
+			`kubernetes coredns.local {
+	endpoint_pod_names
+}`,
+			false,
+			"",
+			true,
+		},
+		// endpoints invalid
+		{
+			`kubernetes coredns.local {
+	endpoint_pod_names giant_seed
+}`,
+			true,
+			"rong argument count or unexpected",
+			false,
+		},
+		// endpoint not set
+		{
+			`kubernetes coredns.local {
+}`,
+			false,
+			"",
+			false,
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		k8sController, _, err := kubernetesParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error, but did not find error for input '%s'. Error was: '%v'", i, test.input, err)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+				continue
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+			continue
+		}
+
+		// Endpoints
+		foundEndpointNameMode := k8sController.endpointNameMode
+		if foundEndpointNameMode != test.expectedEndpointMode {
+			t.Errorf("Test %d: Expected kubernetes controller to be initialized with endpoints mode '%v'. Instead found endpoints mode '%v' for input '%s'", i, test.expectedEndpointMode, foundEndpointNameMode, test.input)
+		}
+	}
+}