From 16453a33346c4d8e407623e3e49daf476e91a353 Mon Sep 17 00:00:00 2001
From: Kenan Karamehmedovic <kenan435@gmail.com>
Date: Fri, 18 Nov 2016 13:37:26 +0100
Subject: [PATCH] Fail fast if there is already a node with same name as the
 one being joined.

---
 cmd/kubeadm/app/cmd/join.go       |  5 +++++
 cmd/kubeadm/app/node/BUILD        |  1 +
 cmd/kubeadm/app/node/bootstrap.go | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/cmd/kubeadm/app/cmd/join.go b/cmd/kubeadm/app/cmd/join.go
index c2bd76abc21..b6c7780e973 100644
--- a/cmd/kubeadm/app/cmd/join.go
+++ b/cmd/kubeadm/app/cmd/join.go
@@ -145,6 +145,11 @@ func (j *Join) Run(out io.Writer) error {
 		return err
 	}
 
+	err = kubenode.CheckForNodeNameDuplicates(connectionDetails)
+	if err != nil {
+		return err
+	}
+
 	kubeconfig, err := kubenode.PerformTLSBootstrap(connectionDetails)
 	if err != nil {
 		return err
diff --git a/cmd/kubeadm/app/node/BUILD b/cmd/kubeadm/app/node/BUILD
index 86970ec037b..d11e982f881 100644
--- a/cmd/kubeadm/app/node/BUILD
+++ b/cmd/kubeadm/app/node/BUILD
@@ -21,6 +21,7 @@ go_library(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
+        "//pkg/api/v1:go_default_library",
         "//pkg/apis/certificates:go_default_library",
         "//pkg/client/clientset_generated/release_1_5:go_default_library",
         "//pkg/client/clientset_generated/release_1_5/typed/certificates/v1alpha1:go_default_library",
diff --git a/cmd/kubeadm/app/node/bootstrap.go b/cmd/kubeadm/app/node/bootstrap.go
index 808b361ec09..c2a8815a349 100644
--- a/cmd/kubeadm/app/node/bootstrap.go
+++ b/cmd/kubeadm/app/node/bootstrap.go
@@ -24,6 +24,7 @@ import (
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
+	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/apis/certificates"
 	clientset "k8s.io/kubernetes/pkg/client/clientset_generated/release_1_5"
 	certclient "k8s.io/kubernetes/pkg/client/clientset_generated/release_1_5/typed/certificates/v1alpha1"
@@ -34,6 +35,7 @@ import (
 
 // ConnectionDetails represents a master API endpoint connection
 type ConnectionDetails struct {
+	ClientSet  *clientset.Clientset
 	CertClient *certclient.CertificatesV1alpha1Client
 	Endpoint   string
 	CACert     []byte
@@ -82,6 +84,7 @@ func EstablishMasterConnection(s *kubeadmapi.NodeConfiguration, clusterInfo *kub
 				// connection established, stop all wait threads
 				close(stopChan)
 				result <- &ConnectionDetails{
+					ClientSet:  clientSet,
 					CertClient: clientSet.CertificatesV1alpha1Client,
 					Endpoint:   apiEndpoint,
 					CACert:     caCert,
@@ -124,6 +127,24 @@ func createClients(caCert []byte, endpoint, token string, nodeName types.NodeNam
 	return clientSet, nil
 }
 
+// check to see if there are other nodes in the cluster with identical node names.
+func CheckForNodeNameDuplicates(connection *ConnectionDetails) error {
+	hostName, err := os.Hostname()
+	if err != nil {
+		return fmt.Errorf("Failed to get node hostname [%v]", err)
+	}
+	nodeList, err := connection.ClientSet.Nodes().List(v1.ListOptions{})
+	if err != nil {
+		return fmt.Errorf("Failed to list the nodes in the cluster: [%v]\n", err)
+	}
+	for _, node := range nodeList.Items {
+		if hostName == node.Name {
+			return fmt.Errorf("Node with name [%q] already exists.", node.Name)
+		}
+	}
+	return nil
+}
+
 // checks the connection requirements for a specific API endpoint
 func checkAPIEndpoint(clientSet *clientset.Clientset, endpoint string) error {
 	// check general connectivity