Use --in-kube-cluster to indicate in-cluster mode

Author: itzg

Dockerfile

@@ -1,3 +1,5 @@
 FROM scratch
 COPY mc-router /
+# create a temp directory for k8s library logging
+COPY README.md /tmp/
 ENTRYPOINT ["/mc-router"]

cmd/mc-router/main.go

@@ -22,6 +22,7 @@ var (
 	versionFlag = kingpin.Flag("version", "Output version and exit").
 			Bool()
 	kubeConfigFile = kingpin.Flag("kube-config", "The path to a kubernetes configuration file").String()
+	inKubeCluster  = kingpin.Flag("in-kube-cluster", "Use in-cluster kubernetes config").Bool()
 )
 
 var (
@@ -55,11 +56,21 @@ func main() {
 		server.StartApiServer(*apiBinding)
 	}
 
-	err := server.K8sWatcher.Start(*kubeConfigFile)
-	if err != nil {
-		logrus.WithError(err).Warn("Skipping kubernetes integration")
-	} else {
-		defer server.K8sWatcher.Stop()
+	var err error
+	if *inKubeCluster {
+		err = server.K8sWatcher.StartInCluster()
+		if err != nil {
+			logrus.WithError(err).Warn("Unable to start k8s integration")
+		} else {
+			defer server.K8sWatcher.Stop()
+		}
+	} else if *kubeConfigFile != "" {
+		err := server.K8sWatcher.StartWithConfig(*kubeConfigFile)
+		if err != nil {
+			logrus.WithError(err).Warn("Unable to start k8s integration")
+		} else {
+			defer server.K8sWatcher.Stop()
+		}
 	}
 
 	<-c

server/k8s.go

@@ -6,13 +6,15 @@ import (
 	"k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/cache"
 	"k8s.io/client-go/tools/clientcmd"
 	"net"
 )
 
 type IK8sWatcher interface {
-	Start(kubeConfigFile string) error
+	StartWithConfig(kubeConfigFile string) error
+	StartInCluster() error
 	Stop()
 }
 
@@ -22,12 +24,25 @@ type k8sWatcherImpl struct {
 	stop chan struct{}
 }
 
-func (w *k8sWatcherImpl) Start(kubeConfigFile string) error {
+func (w *k8sWatcherImpl) StartInCluster() error {
+	config, err := rest.InClusterConfig()
+	if err != nil {
+		return errors.Wrap(err, "Unable to load in-cluster config")
+	}
+
+	return w.startWithLoadedConfig(config)
+}
+
+func (w *k8sWatcherImpl) StartWithConfig(kubeConfigFile string) error {
 	config, err := clientcmd.BuildConfigFromFlags("", kubeConfigFile)
 	if err != nil {
 		return errors.Wrap(err, "Could not load kube config file")
 	}
 
+	return w.startWithLoadedConfig(config)
+}
+
+func (w *k8sWatcherImpl) startWithLoadedConfig(config *rest.Config) error {
 	clientset, err := kubernetes.NewForConfig(config)
 	if err != nil {
 		return errors.Wrap(err, "Could not create kube clientset")