add checkpoint to include Kubernetes cluster information

Fixes #3324

prog/weaver/checkpoint.go

@@ -1,12 +1,17 @@
 package main
 
 import (
+	"os"
+	"strconv"
 	"sync/atomic"
 	"syscall"
 	"time"
 
-	"github.com/weaveworks/go-checkpoint"
+	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
@@ -14,10 +19,12 @@ var newVersion atomic.Value
 var success atomic.Value
 
 const (
-	updateCheckPeriod = 6 * time.Hour
+	updateCheckPeriod  = 6 * time.Hour
+	configMapName      = "weave-net"
+	configMapNamespace = "kube-system"
 )
 
-func checkForUpdates(dockerVersion string, router *weave.NetworkRouter) {
+func checkForUpdates(dockerVersion string, router *weave.NetworkRouter, peers []string) {
 	newVersion.Store("")
 	success.Store(true)
 
@@ -48,10 +55,11 @@ func checkForUpdates(dockerVersion string, router *weave.NetworkRouter) {
 	}
 	kernelVersion := string(releaseBytes[:i])
 
-	flags := map[string]string{
-		"docker-version": dockerVersion,
-		"kernel-version": kernelVersion,
-	}
+	flags := make(map[string]string)
+	flags["docker-version"] = dockerVersion
+	flags["kernel-version"] = kernelVersion
+
+	checkpointKubernetes(flags, peers)
 
 	// Start background version checking
 	params := checkpoint.CheckParams{
@@ -77,3 +85,37 @@ func checkpointFlags(router *weave.NetworkRouter) []checkpoint.Flag {
 	}
 	return flags
 }
+
+// checkpoint Kubernetes specific details
+func checkpointKubernetes(flags map[string]string, peers []string) {
+	// checks if weaver is running in Kubernetes
+	host := os.Getenv("KUBERNETES_SERVICE_HOST")
+	if len(host) == 0 {
+		return
+	}
+	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(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-cluster-size"] = strconv.Itoa(len(peers))
+}

prog/weaver/main.go

@@ -385,7 +385,7 @@ func main() {
 		dockerVersion = dockerCli.DockerVersion()
 	}
 
-	checkForUpdates(dockerVersion, router)
+	checkForUpdates(dockerVersion, router, peers)
 
 	observeContainers := func(o docker.ContainerObserver) {
 		if dockerCli != nil {