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/README.md

@@ -31,6 +31,7 @@ kubernetes [ZONES...] {
     namespaces NAMESPACE...
     labels EXPRESSION
     pods POD-MODE
+    endpoint_pod_names
     upstream ADDRESS...
     ttl TTL
     fallthrough
@@ -65,6 +66,16 @@ kubernetes [ZONES...] {
      option requires substantially more memory than in insecure mode, since it will maintain a watch
      on all pods.
 
+* `endpoint_pod_names` Use the pod name of the pod targeted by the endpoint as 
+   the endpoint name in A records, e.g.
+   `endpoint-name.my-service.namespace.svc.cluster.local. in A 1.2.3.4`
+   By default, the endpoint-name name selection is as follows: Use the hostname 
+   of the endpoint, or if hostname is not set, use the dashed form of the endpoint
+   ip address (e.g. `1-2-3-4.my-service.namespace.svc.cluster.local.`)
+   If this directive is included, then name selection for endpoints changes as
+   follows: Use the hostname of the endpoint, or if hostname is not set, use the
+   pod name of the pod targeted by the endpoint. If there is no pod targeted by 
+   the endpoint, use the dashed ip address form.
 * `upstream` **ADDRESS [ADDRESS...]** defines the upstream resolvers used for resolving services
   that point to external hosts (External Services).  **ADDRESS** can be an ip, an ip:port, or a path
   to a file structured like resolv.conf.

plugin/kubernetes/kubernetes.go

@@ -28,19 +28,20 @@ import (
 
 // Kubernetes implements a plugin that connects to a Kubernetes cluster.
 type Kubernetes struct {
-	Next          plugin.Handler
-	Zones         []string
-	Proxy         proxy.Proxy // Proxy for looking up names during the resolution process
-	APIServerList []string
-	APIProxy      *apiProxy
-	APICertAuth   string
-	APIClientCert string
-	APIClientKey  string
-	APIConn       dnsController
-	Namespaces    map[string]bool
-	podMode       string
-	Fallthrough   bool
-	ttl           uint32
+	Next             plugin.Handler
+	Zones            []string
+	Proxy            proxy.Proxy // Proxy for looking up names during the resolution process
+	APIServerList    []string
+	APIProxy         *apiProxy
+	APICertAuth      string
+	APIClientCert    string
+	APIClientKey     string
+	APIConn          dnsController
+	Namespaces       map[string]bool
+	podMode          string
+	endpointNameMode bool
+	Fallthrough      bool
+	ttl              uint32
 
 	primaryZoneIndex   int
 	interfaceAddrsFunc func() net.IP
@@ -276,10 +277,13 @@ func (k *Kubernetes) Records(state request.Request, exact bool) ([]msg.Service,
 	return services, err
 }
 
-func endpointHostname(addr api.EndpointAddress) string {
+func endpointHostname(addr api.EndpointAddress, endpointNameMode bool) string {
 	if addr.Hostname != "" {
 		return strings.ToLower(addr.Hostname)
 	}
+	if endpointNameMode && addr.TargetRef != nil && addr.TargetRef.Name != "" {
+		return addr.TargetRef.Name
+	}
 	if strings.Contains(addr.IP, ".") {
 		return strings.Replace(addr.IP, ".", "-", -1)
 	}
@@ -375,7 +379,7 @@ func (k *Kubernetes) findServices(r recordRequest, zone string) (services []msg.
 						// See comments in parse.go parseRequest about the endpoint handling.
 
 						if r.endpoint != "" {
-							if !match(r.endpoint, endpointHostname(addr)) {
+							if !match(r.endpoint, endpointHostname(addr, k.endpointNameMode)) {
 								continue
 							}
 						}
@@ -385,7 +389,7 @@ func (k *Kubernetes) findServices(r recordRequest, zone string) (services []msg.
 								continue
 							}
 							s := msg.Service{Host: addr.IP, Port: int(p.Port), TTL: k.ttl}
-							s.Key = strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name, endpointHostname(addr)}, "/")
+							s.Key = strings.Join([]string{zonePath, Svc, svc.Namespace, svc.Name, endpointHostname(addr, k.endpointNameMode)}, "/")
 
 							err = nil
 

plugin/kubernetes/kubernetes_test.go

@@ -34,15 +34,21 @@ func TestWildcard(t *testing.T) {
 
 func TestEndpointHostname(t *testing.T) {
 	var tests = []struct {
-		ip       string
-		hostname string
-		expected string
+		ip               string
+		hostname         string
+		expected         string
+		podName          string
+		endpointNameMode bool
 	}{
-		{"10.11.12.13", "", "10-11-12-13"},
-		{"10.11.12.13", "epname", "epname"},
+		{"10.11.12.13", "", "10-11-12-13", "", false},
+		{"10.11.12.13", "epname", "epname", "", false},
+		{"10.11.12.13", "", "10-11-12-13", "hello-abcde", false},
+		{"10.11.12.13", "epname", "epname", "hello-abcde", false},
+		{"10.11.12.13", "epname", "epname", "hello-abcde", true},
+		{"10.11.12.13", "", "hello-abcde", "hello-abcde", true},
 	}
 	for _, test := range tests {
-		result := endpointHostname(api.EndpointAddress{IP: test.ip, Hostname: test.hostname})
+		result := endpointHostname(api.EndpointAddress{IP: test.ip, Hostname: test.hostname, TargetRef: &api.ObjectReference{Name: test.podName}}, test.endpointNameMode)
 		if result != test.expected {
 			t.Errorf("Expected endpoint name for (ip:%v hostname:%v) to be '%v', but got '%v'", test.ip, test.hostname, test.expected, result)
 		}

plugin/kubernetes/reverse.go

@@ -42,7 +42,7 @@ func (k *Kubernetes) serviceRecordForIP(ip, name string) []msg.Service {
 		for _, eps := range ep.Subsets {
 			for _, addr := range eps.Addresses {
 				if addr.IP == ip {
-					domain := strings.Join([]string{endpointHostname(addr), ep.ObjectMeta.Name, ep.ObjectMeta.Namespace, Svc, k.primaryZone()}, ".")
+					domain := strings.Join([]string{endpointHostname(addr, k.endpointNameMode), ep.ObjectMeta.Name, ep.ObjectMeta.Namespace, Svc, k.primaryZone()}, ".")
 					return []msg.Service{{Host: domain}}
 				}
 			}

plugin/kubernetes/setup.go

@@ -104,6 +104,13 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, dnsControlOpts, error) {
 
 		for c.NextBlock() {
 			switch c.Val() {
+			case "endpoint_pod_names":
+				args := c.RemainingArgs()
+				if len(args) > 0 {
+					return nil, opts, c.ArgErr()
+				}
+				k8s.endpointNameMode = true
+				continue
 			case "pods":
 				args := c.RemainingArgs()
 				if len(args) == 1 {

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)
+		}
+	}
+}