Move Kubernetes API calls into kube-utils program

This reduces the size of the 'weaver' binary.

prog/kube-utils/main.go

@@ -314,6 +314,8 @@ func main() {
 		justReclaim       bool
 		justCheck         bool
 		justSetNodeStatus bool
+		justVersion       bool
+		justUID           bool
 		peerName          string
 		nodeName          string
 		logLevel          string
@@ -323,6 +325,8 @@ func main() {
 	flag.BoolVar(&runReclaimDaemon, "run-reclaim-daemon", false, "run background process that reclaim IP space from dead peers ")
 	flag.BoolVar(&justCheck, "check-peer-new", false, "return success if peer name is not stored in annotation")
 	flag.BoolVar(&justSetNodeStatus, "set-node-status", false, "set NodeNetworkUnavailable to false")
+	flag.BoolVar(&justVersion, "print-k8s-version", false, "print the Kubernetes version and exit")
+	flag.BoolVar(&justUID, "print-uid", false, "print a UID for this installation and exit")
 	flag.StringVar(&peerName, "peer-name", "unknown", "name of this Weave Net peer")
 	flag.StringVar(&nodeName, "node-name", "unknown", "name of this Kubernetes node")
 	flag.StringVar(&logLevel, "log-level", "info", "logging level (debug, info, warning, error)")
@@ -371,6 +375,21 @@ func main() {
 		}
 		return
 	}
+	if justVersion {
+		k8sVersion, err := c.Discovery().ServerVersion()
+		if err != nil {
+			common.Log.Fatalf("[kube-peers] Could not get Kubernetes version: %v", err)
+		}
+		fmt.Println(k8sVersion.String())
+	}
+	if justUID {
+		// use UID of `weave-net` configmap as unique ID of the Kubernetes cluster
+		cm, err := c.CoreV1().ConfigMaps(configMapNamespace).Get(context.Background(), configMapName, api.GetOptions{})
+		if err != nil {
+			common.Log.Fatalf("Unable to fetch ConfigMap %s/%s to infer unique cluster ID", configMapNamespace, configMapName)
+		}
+		fmt.Println(cm.ObjectMeta.UID)
+	}
 	if runReclaimDaemon {
 		// Handle SIGINT and SIGTERM
 		ch := make(chan os.Signal, 1)

prog/weave-kube/launch.sh

@@ -118,6 +118,10 @@ fi
 # weaver is running as the DB can only be opened by one process at a time
 /usr/bin/weaveutil set-db-flag "$DB_PREFIX" peer-reclaim ok
 
+# couple more variables
+WEAVE_KUBERNETES_VERSION=$(/home/weave/kube-utils -print-k8s-version)
+WEAVE_KUBERNETES_UID=$(/home/weave/kube-utils -print-uid)
+
 post_start_actions() {
     # Wait for weave process to become responsive
     while true ; do

prog/weaver/checkpoint.go

@@ -10,9 +10,6 @@ import (
 
 	checkpoint "github.com/weaveworks/go-checkpoint"
 	weave "github.com/weaveworks/weave/router"
-	api "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/rest"
 )
 
 var checker *checkpoint.Checker
@@ -20,9 +17,7 @@ var newVersion atomic.Value
 var success atomic.Value
 
 const (
-	updateCheckPeriod  = 6 * time.Hour
-	configMapName      = "weave-net"
-	configMapNamespace = "kube-system"
+	updateCheckPeriod = 6 * time.Hour
 )
 
 func checkForUpdates(dockerVersion string, router *weave.NetworkRouter, clusterSize uint) {
@@ -88,36 +83,13 @@ func checkpointFlags(router *weave.NetworkRouter) []checkpoint.Flag {
 	return flags
 }
 
-// checkpoint Kubernetes specific details
+// checkpoint Kubernetes specific details, passed in from launch script
 func checkpointKubernetes(ctx context.Context, flags map[string]string, clusterSize uint) {
-	// checks if weaver is running in Kubernetes
-	host := os.Getenv("KUBERNETES_SERVICE_HOST")
-	if len(host) == 0 {
-		return
+	version := os.Getenv("WEAVE_KUBERNETES_VERSION")
+	if len(version) == 0 {
+		return // not running under Kubernetes
 	}
-	config, err := rest.InClusterConfig()
-	if err != nil {
-		Log.Printf("Could not get Kubernetes in-cluster config: %v", err)
-		return
-	}
-	c, err := kubernetes.NewForConfig(config)
-	if err != nil {
-		Log.Printf("Could not make Kubernetes client: %v", err)
-		return
-	}
-	k8sVersion, err := c.Discovery().ServerVersion()
-	if err != nil {
-		Log.Printf("Could not get Kubernetes version: %v", err)
-		return
-	}
-	flags["kubernetes-version"] = k8sVersion.String()
-
-	// use UID of `weave-net` configmap as unique ID of the Kubenerets cluster
-	cm, err := c.CoreV1().ConfigMaps(configMapNamespace).Get(ctx, configMapName, api.GetOptions{})
-	if err != nil {
-		Log.Printf("Unable to fetch ConfigMap %s/%s to infer unique cluster ID", configMapNamespace, configMapName)
-		return
-	}
-	flags["kubernetes-cluster-uid"] = string(cm.ObjectMeta.UID)
+	flags["kubernetes-version"] = version
+	flags["kubernetes-cluster-uid"] = string(os.Getenv("WEAVE_KUBERNETES_UID"))
 	flags["kubernetes-cluster-size"] = fmt.Sprint(clusterSize)
 }