Add the /runningpods/ api endpoint (#611)

* Add the /runningpods/ api endpoint

This adds an API endpoint from the kubelet (/runningpods/). It is
an endpoint on kubelet which is considered a "debug" endpoint, so
it might be worth exposing through the options, but by default
it is exposed in most k8s configs AFAICT.

Gopkg.lock

@@ -1372,6 +1372,7 @@
     "k8s.io/apimachinery/pkg/fields",
     "k8s.io/apimachinery/pkg/labels",
     "k8s.io/apimachinery/pkg/runtime",
+    "k8s.io/apimachinery/pkg/runtime/serializer",
     "k8s.io/apimachinery/pkg/types",
     "k8s.io/apimachinery/pkg/util/intstr",
     "k8s.io/apimachinery/pkg/util/net",

cmd/virtual-kubelet/commands/root/http.go

@@ -86,7 +86,7 @@ func setupHTTPServer(ctx context.Context, p providers.Provider, cfg *apiServerCo
 		}
 
 		mux := http.NewServeMux()
-		vkubelet.AttachPodRoutes(p, mux)
+		vkubelet.AttachPodRoutes(p, mux, true)
 
 		s := &http.Server{
 			Handler:   mux,

vkubelet/api/pods.go

@@ -0,0 +1,53 @@
+package api
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/cpuguy83/strongerrors"
+	"github.com/virtual-kubelet/virtual-kubelet/log"
+	"k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
+)
+
+// ContainerLogsBackend is used in place of backend implementations for the provider's pods
+type RunningPodsBackend interface {
+	// GetPods retrieves a list of all pods running on the provider (can be cached).
+	GetPods(context.Context) ([]*v1.Pod, error)
+}
+
+func RunningPodsHandlerFunc(p RunningPodsBackend) http.HandlerFunc {
+	scheme := runtime.NewScheme()
+	v1.SchemeBuilder.AddToScheme(scheme)
+	codecs := serializer.NewCodecFactory(scheme)
+
+	return handleError(func(w http.ResponseWriter, req *http.Request) error {
+		ctx := req.Context()
+		ctx = log.WithLogger(ctx, log.L)
+		pods, err := p.GetPods(ctx)
+		if err != nil {
+			return err
+		}
+
+		// Borrowed from github.com/kubernetes/kubernetes/pkg/kubelet/server/server.go
+		// encodePods creates an v1.PodList object from pods and returns the encoded
+		// PodList.
+		podList := new(v1.PodList)
+		for _, pod := range pods {
+			podList.Items = append(podList.Items, *pod)
+		}
+		codec := codecs.LegacyCodec(v1.SchemeGroupVersion)
+		data, err := runtime.Encode(codec, podList)
+		if err != nil {
+			return strongerrors.System(err)
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		_, err = w.Write(data)
+		if err != nil {
+			return strongerrors.System(err)
+		}
+		return nil
+	})
+}

vkubelet/apiserver.go

@@ -21,9 +21,14 @@ type ServeMux interface {
 }
 
 // PodHandler creates an http handler for interacting with pods/containers.
-func PodHandler(p providers.Provider) http.Handler {
+func PodHandler(p providers.Provider, debug bool) http.Handler {
 	r := mux.NewRouter()
 
+	// This matches the behaviour in the reference kubelet
+	r.StrictSlash(true)
+	if debug {
+		r.HandleFunc("/runningpods/", api.RunningPodsHandlerFunc(p)).Methods("GET")
+	}
 	r.HandleFunc("/containerLogs/{namespace}/{pod}/{container}", api.PodLogsHandlerFunc(p)).Methods("GET")
 	r.HandleFunc("/exec/{namespace}/{pod}/{container}", api.PodExecHandlerFunc(p)).Methods("POST")
 	r.NotFoundHandler = http.HandlerFunc(NotFound)
@@ -58,8 +63,8 @@ func MetricsSummaryHandler(p providers.Provider) http.Handler {
 //
 // Callers should take care to namespace the serve mux as they see fit, however
 // these routes get called by the Kubernetes API server.
-func AttachPodRoutes(p providers.Provider, mux ServeMux) {
+func AttachPodRoutes(p providers.Provider, mux ServeMux, debug bool) {
-	mux.Handle("/", InstrumentHandler(PodHandler(p)))
+	mux.Handle("/", InstrumentHandler(PodHandler(p, debug)))
 }
 
 // AttachMetricsRoutes adds the http routes for pod/node metrics to the passed in serve mux.