Add supports for stats in ACI provider

This adds a new, optional, interface for providers that want to provide
stats.

vkubelet/apiserver.go

@@ -2,6 +2,7 @@ package vkubelet
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
@@ -12,6 +13,7 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/gorilla/mux"
+	"github.com/pkg/errors"
 	"github.com/virtual-kubelet/virtual-kubelet/log"
 	"k8s.io/kubernetes/pkg/kubelet/server/remotecommand"
 )
@@ -34,7 +36,7 @@ func NotFound(w http.ResponseWriter, r *http.Request) {
 	http.Error(w, "404 request not found", http.StatusNotFound)
 }
 
-func ApiserverStart(provider Provider) {
+func ApiserverStart(provider Provider, metricsAddr string) {
 	p = provider
 	certFilePath := os.Getenv("APISERVER_CERT_LOCATION")
 	keyFilePath := os.Getenv("APISERVER_KEY_LOCATION")
@@ -46,11 +48,62 @@ func ApiserverStart(provider Provider) {
 	r.HandleFunc("/exec/{namespace}/{pod}/{container}", ApiServerHandlerExec).Methods("POST")
 	r.NotFoundHandler = http.HandlerFunc(NotFound)
 
+	if metricsAddr != "" {
+		go MetricsServerStart(metricsAddr)
+	} else {
+		log.G(context.TODO()).Info("Skipping metrics server startup since no address was provided")
+	}
+
 	if err := http.ListenAndServeTLS(addr, certFilePath, keyFilePath, r); err != nil {
 		log.G(context.TODO()).WithError(err).Error("error setting up http server")
 	}
 }
 
+// MetricsServerStart starts an HTTP server on the provided addr for serving the kubelset summary stats API.
+// TLS is never enabled on this endpoint.
+func MetricsServerStart(addr string) {
+	r := mux.NewRouter()
+	r.HandleFunc("/stats/summary", MetricsSummaryHandler).Methods("GET")
+	r.HandleFunc("/stats/summary/", MetricsSummaryHandler).Methods("GET")
+	r.NotFoundHandler = http.HandlerFunc(NotFound)
+	if err := http.ListenAndServe(addr, r); err != nil {
+		log.G(context.TODO()).WithError(err).Error("Error starting http server")
+	}
+}
+
+// MetricsSummaryHandler is an HTTP handler for implementing the kubelet summary stats endpoint
+func MetricsSummaryHandler(w http.ResponseWriter, req *http.Request) {
+	ctx := loggingContext(req)
+
+	mp, ok := p.(MetricsProvider)
+	if !ok {
+		log.G(ctx).Debug("stats not implemented for provider")
+		http.Error(w, "not implememnted", http.StatusNotImplemented)
+		return
+	}
+
+	stats, err := mp.GetStatsSummary(req.Context())
+	if err != nil {
+		if errors.Cause(err) == context.Canceled {
+			return
+		}
+		log.G(ctx).Error("Error getting stats from provider:", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	b, err := json.Marshal(stats)
+	if err != nil {
+		log.G(ctx).WithError(err).Error("Could not marshal stats")
+		http.Error(w, "could not marshal stats: "+err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write(b); err != nil {
+		log.G(ctx).WithError(err).Debug("Could not write to client")
+	}
+}
+
 func ApiServerHandler(w http.ResponseWriter, req *http.Request) {
 	vars := mux.Vars(req)
 	if len(vars) != 3 {

vkubelet/provider.go

@@ -1,12 +1,14 @@
 package vkubelet
 
 import (
+	"context"
 	"io"
 	"time"
 
 	"k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/tools/remotecommand"
+	stats "k8s.io/kubernetes/pkg/kubelet/apis/stats/v1alpha1"
 )
 
 // Provider contains the methods required to implement a virtual-kubelet provider.
@@ -54,3 +56,8 @@ type Provider interface {
 	// OperatingSystem returns the operating system the provider is for.
 	OperatingSystem() string
 }
+
+// MetricsProvider is an optional interface that providers can implement to expose pod stats
+type MetricsProvider interface {
+	GetStatsSummary(context.Context) (*stats.Summary, error)
+}

vkubelet/vkubelet.go

@@ -48,7 +48,7 @@ func getEnv(key, defaultValue string) string {
 }
 
 // New creates a new virtual-kubelet server.
-func New(nodeName, operatingSystem, namespace, kubeConfig, provider, providerConfig, taintKey string, disableTaint bool) (*Server, error) {
+func New(nodeName, operatingSystem, namespace, kubeConfig, provider, providerConfig, taintKey string, disableTaint bool, metricsAddr string) (*Server, error) {
 	var config *rest.Config
 
 	// Check if the kubeConfig file exists.
@@ -137,7 +137,7 @@ func New(nodeName, operatingSystem, namespace, kubeConfig, provider, providerCon
 		return s, err
 	}
 
-	go ApiserverStart(p)
+	go ApiserverStart(p, metricsAddr)
 
 	tick := time.Tick(5 * time.Second)