add option '--hostname-override' to deal with cases where kubelet is launched

with --hostname-override flag

Fixes #23

Author: Murali Reddy

README.md

@@ -48,6 +48,7 @@ Alternatively you can download the prebuilt binary from https://github.com/cloud
   --cluster-asn                     ASN number under which cluster nodes will run iBGP
   --peer-asn                        ASN number of the BGP peer to which cluster nodes will advertise cluster ip and node's pod cidr
   --peer-router                     The ip address of the external router to which all nodes will peer and advertise the cluster ip and pod cidr's
+  --hostname-override               If non-empty, this string will be used as identification of node name instead of the actual hostname.
 ```
 
 ### Try Kube-router with cluster installers

app/controllers/network_policy_controller.go

@@ -770,7 +770,7 @@ func NewNetworkPolicyController(clientset *kubernetes.Clientset, config *options
 
 	npc.syncPeriod = config.IPTablesSyncPeriod
 
-	node, err := utils.GetNodeObject(clientset)
+	node, err := utils.GetNodeObject(clientset, config.HostnameOverride)
 	if err != nil {
 		panic(err.Error())
 	}

app/controllers/network_routes_controller.go

@@ -35,6 +35,7 @@ type NetworkRoutingController struct {
 	asnNumber          uint32
 	peerAsnNumber      uint32
 	clusterCIDR        string
+	hostnameOverride   string
 }
 var(
 	activeNodes = make(map[string]bool)
@@ -49,7 +50,7 @@ func (nrc *NetworkRoutingController) Run(stopCh <-chan struct{}, wg *sync.WaitGr
 	cidrlen, _ := cidr.Mask.Size()
 	oldCidr := cidr.IP.String() + "/" + strconv.Itoa(cidrlen)
 
-	currentCidr, err := utils.GetPodCidrFromNodeSpec(nrc.clientset)
+	currentCidr, err := utils.GetPodCidrFromNodeSpec(nrc.clientset, nrc.hostnameOverride)
 	if err != nil {
 		glog.Errorf("Failed to get pod CIDR from node spec: %s", err.Error())
 	}
@@ -160,7 +161,7 @@ func (nrc *NetworkRoutingController) watchBgpUpdates() {
 
 func (nrc *NetworkRoutingController) advertiseRoute() error {
 
-	cidr, err := utils.GetPodCidrFromNodeSpec(nrc.clientset)
+	cidr, err := utils.GetPodCidrFromNodeSpec(nrc.clientset, nrc.hostnameOverride)
 	if err != nil {
 		return err
 	}
@@ -357,8 +358,8 @@ func NewNetworkRoutingController(clientset *kubernetes.Clientset, kubeRouterConf
 		nrc.peerAsnNumber = uint32(asn)
 	}
 
-
-	node, err := utils.GetNodeObject(clientset)
+	nrc.hostnameOverride = kubeRouterConfig.HostnameOverride
+	node, err := utils.GetNodeObject(clientset, nrc.hostnameOverride)
 	if err != nil {
 		panic(err.Error())
 	}

app/controllers/network_services_controller.go

@@ -528,14 +528,14 @@ func NewNetworkServicesController(clientset *kubernetes.Clientset, config *optio
 	}
 
 	if config.RunRouter {
-		cidr, err := utils.GetPodCidrFromNodeSpec(nsc.client)
+		cidr, err := utils.GetPodCidrFromNodeSpec(nsc.client, config.HostnameOverride)
 		if err != nil {
 			return nil, fmt.Errorf("Failed to get pod CIDR details from Node.spec: %s", err.Error())
 		}
 		nsc.podCidr = cidr
 	}
 
-	node, err := utils.GetNodeObject(clientset)
+	node, err := utils.GetNodeObject(clientset, config.HostnameOverride)
 	if err != nil {
 		panic(err.Error())
 	}

app/options/options.go

@@ -23,6 +23,7 @@ type KubeRouterConfig struct {
 	PeerRouter         string
 	ClusterAsn         string
 	PeerAsn            string
+	HostnameOverride   string
 }
 
 func NewKubeRouterConfig() *KubeRouterConfig {
@@ -54,4 +55,5 @@ func (s *KubeRouterConfig) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.PeerRouter, "peer-router", s.PeerRouter, "The ip address of the external router to which all nodes will peer and advertise the cluster ip and pod cidr's")
 	fs.StringVar(&s.ClusterAsn, "cluster-asn", s.ClusterAsn, "ASN number under which cluster nodes will run iBGP")
 	fs.StringVar(&s.PeerAsn, "peer-asn", s.PeerAsn, "ASN number of the BGP peer to which cluster nodes will advertise cluster ip and node's pod cidr")
+	fs.StringVar(&s.HostnameOverride, "hostname-override", s.HostnameOverride, "If non-empty, will use this string as identification instead of the actual hostname.")
 }

utils/fqdn.go

@@ -9,7 +9,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
-func GetNodeObject(clientset *kubernetes.Clientset) (*apiv1.Node, error) {
+func GetNodeObject(clientset *kubernetes.Clientset, hostnameOverride string) (*apiv1.Node, error) {
 
 	// assuming kube-router is running as pod, first check env NODE_NAME
 	nodeName := os.Getenv("NODE_NAME")
@@ -27,12 +27,13 @@ func GetNodeObject(clientset *kubernetes.Clientset) (*apiv1.Node, error) {
 		return node, nil
 	}
 
-	// if env NODE_NAME is not set then check if node is registerd by FQDN
-	fqdnHostName := GetFqdn()
-	node, err = clientset.Core().Nodes().Get(fqdnHostName, metav1.GetOptions{})
-	if err == nil {
-		return node, nil
+	// if env NODE_NAME is not set and node is not registered with hostname, then use host name override
+	if hostnameOverride != "" {
+		node, err = clientset.Core().Nodes().Get(hostnameOverride, metav1.GetOptions{})
+		if err == nil {
+			return node, nil
+		}
 	}
 
-	return nil, fmt.Errorf("Failed to identify the node by NODE_NAME, hostname or FQDN name of the host")
+	return nil, fmt.Errorf("Failed to identify the node by NODE_NAME, hostname or --hostname-override")
 }

utils/node.go

@@ -45,8 +45,8 @@ func InsertPodCidrInCniSpec(cniConfFilePath string, cidr string) error {
 	return nil
 }
 
-func GetPodCidrFromNodeSpec(clientset *kubernetes.Clientset) (string, error) {
-	node, err := GetNodeObject(clientset)
+func GetPodCidrFromNodeSpec(clientset *kubernetes.Clientset, hostnameOverride string) (string, error) {
+	node, err := GetNodeObject(clientset, hostnameOverride)
 	if err != nil {
 		return "", fmt.Errorf("Failed to get pod CIDR allocated for the node due to: " + err.Error())
 	}