Kubelet: wait up to 5m for Docker to come up.

The Kubelet assumes Docker is running during its execution and on
machine boot it is a race between Docker coming up and Kubelet calling
Docker. This PR waits for Docker to be up before the Kubelet begins
doing useful work. On timeout, Kubelet exits and expects to be
restarted.

pkg/kubelet/kubelet.go

@@ -52,14 +52,19 @@ import (
 	"github.com/golang/glog"
 )
 
-// taken from lmctfy https://github.com/google/lmctfy/blob/master/lmctfy/controllers/cpu_controller.cc
-const minShares = 2
-const sharesPerCPU = 1024
-const milliCPUToCPU = 1000
+const (
+	// taken from lmctfy https://github.com/google/lmctfy/blob/master/lmctfy/controllers/cpu_controller.cc
+	minShares     = 2
+	sharesPerCPU  = 1024
+	milliCPUToCPU = 1000
 
-// The oom_score_adj of the POD infrastructure container. The default is 0, so
-// any value below that makes it *less* likely to get OOM killed.
-const podOomScoreAdj = -100
+	// The oom_score_adj of the POD infrastructure container. The default is 0, so
+	// any value below that makes it *less* likely to get OOM killed.
+	podOomScoreAdj = -100
+
+	// Max amount of time to wait for the Docker daemon to come up.
+	maxWaitForDocker = 5 * time.Minute
+)
 
 // SyncHandler is an interface implemented by Kubelet, for testability
 type SyncHandler interface {
@@ -103,6 +108,22 @@ func NewMainKubelet(
 		return nil, fmt.Errorf("invalid minimum GC age %d", minimumGCAge)
 	}
 
+	// Wait for the Docker daemon to be up (with a timeout).
+	waitStart := time.Now()
+	dockerUp := false
+	for time.Since(waitStart) < maxWaitForDocker {
+		_, err := dockerClient.Version()
+		if err == nil {
+			dockerUp = true
+			break
+		}
+
+		time.Sleep(100 * time.Millisecond)
+	}
+	if !dockerUp {
+		return nil, fmt.Errorf("timed out waiting for Docker to come up")
+	}
+
 	serviceStore := cache.NewStore(cache.MetaNamespaceKeyFunc)
 	if kubeClient != nil {
 		// TODO: cache.NewListWatchFromClient is limited as it takes a client implementation rather