Check Docker version in Kubelet /healthz handler

pkg/kubelet/kubelet.go

@@ -1361,6 +1361,23 @@ func (kl *Kubelet) syncLoop(updates <-chan PodUpdate, handler SyncHandler) {
 	}
 }
 
+// Returns Docker version for this Kubelet.
+func (kl *Kubelet) GetDockerVersion() (string, error) {
+	if kl.dockerClient == nil {
+		return "", fmt.Errorf("No Docker client")
+	}
+	env, err := kl.dockerClient.Version()
+	if err != nil {
+		return "", err
+	}
+	for _, entry := range *env {
+		if strings.HasPrefix(entry, "Version=") {
+			return strings.Split(entry, "=")[1], nil
+		}
+	}
+	return "", fmt.Errorf("Docker version unknown")
+}
+
 // GetKubeletContainerLogs returns logs from the container
 // The second parameter of GetPodStatus and FindPodContainer methods represents pod UUID, which is allowed to be blank
 // TODO: this method is returning logs of random container attempts, when it should be returning the most recent attempt

pkg/kubelet/server.go

@@ -31,7 +31,6 @@ import (
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
-	"github.com/GoogleCloudPlatform/kubernetes/pkg/healthz"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/httplog"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/types"
@@ -64,6 +63,7 @@ func ListenAndServeKubeletServer(host HostInterface, address net.IP, port uint,
 type HostInterface interface {
 	GetContainerInfo(podFullName string, uid types.UID, containerName string, req *info.ContainerInfoRequest) (*info.ContainerInfo, error)
 	GetRootInfo(req *info.ContainerInfoRequest) (*info.ContainerInfo, error)
+	GetDockerVersion() (string, error)
 	GetMachineInfo() (*info.MachineInfo, error)
 	GetBoundPods() ([]api.BoundPod, error)
 	GetPodByName(namespace, name string) (*api.BoundPod, bool)
@@ -88,7 +88,7 @@ func NewServer(host HostInterface, enableDebuggingHandlers bool) Server {
 
 // InstallDefaultHandlers registers the default set of supported HTTP request patterns with the mux.
 func (s *Server) InstallDefaultHandlers() {
-	healthz.InstallHandler(s.mux)
+	s.mux.HandleFunc("/healthz", s.handleHealthz)
 	s.mux.HandleFunc("/podInfo", s.handlePodInfoOld)
 	s.mux.HandleFunc("/api/v1beta1/podInfo", s.handlePodInfoVersioned)
 	s.mux.HandleFunc("/boundPods", s.handleBoundPods)
@@ -109,6 +109,25 @@ func (s *Server) error(w http.ResponseWriter, err error) {
 	http.Error(w, fmt.Sprintf("Internal Error: %v", err), http.StatusInternalServerError)
 }
 
+// handleHealthz handles /healthz request and checks Docker version
+func (s *Server) handleHealthz(w http.ResponseWriter, req *http.Request) {
+	version, err := s.host.GetDockerVersion()
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("unknown Docker version"))
+		return
+	}
+	const minDockerVersion = "1.3.0"
+	if version < minDockerVersion {
+		w.WriteHeader(http.StatusInternalServerError)
+		msg := "Docker version is too old (" + version + ")"
+		w.Write([]byte(msg))
+		return;
+	}
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("ok"))
+}
+
 // handleContainerLogs handles containerLogs request against the Kubelet
 func (s *Server) handleContainerLogs(w http.ResponseWriter, req *http.Request) {
 	defer req.Body.Close()

pkg/kubelet/server_test.go

@@ -42,6 +42,7 @@ type fakeKubelet struct {
 	boundPodsFunc     func() ([]api.BoundPod, error)
 	logFunc           func(w http.ResponseWriter, req *http.Request)
 	runFunc           func(podFullName string, uid types.UID, containerName string, cmd []string) ([]byte, error)
+	dockerVersionFunc func() (string, error)
 	containerLogsFunc func(podFullName, containerName, tail string, follow bool, stdout, stderr io.Writer) error
 }
 
@@ -61,6 +62,10 @@ func (fk *fakeKubelet) GetRootInfo(req *info.ContainerInfoRequest) (*info.Contai
 	return fk.rootInfoFunc(req)
 }
 
+func (fk *fakeKubelet) GetDockerVersion() (string, error) {
+	return fk.dockerVersionFunc()
+}
+
 func (fk *fakeKubelet) GetMachineInfo() (*info.MachineInfo, error) {
 	return fk.machineInfoFunc()
 }