Change scheduler to poll for minions

plugin/cmd/scheduler/scheduler.go

@@ -30,6 +30,8 @@ import (
 	verflag "github.com/GoogleCloudPlatform/kubernetes/pkg/version/flag"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
 	"github.com/GoogleCloudPlatform/kubernetes/plugin/pkg/scheduler"
+
+	"github.com/golang/glog"
 )
 
 var (
@@ -38,11 +40,11 @@ var (
 
 // storeToMinionLister turns a store into a minion lister. The store must contain (only) minions.
 type storeToMinionLister struct {
-	s cache.Store
+	cache.Store
 }
 
-func (s storeToMinionLister) List() (machines []string, err error) {
-	for _, m := range s.s.List() {
+func (s *storeToMinionLister) List() (machines []string, err error) {
+	for _, m := range s.Store.List() {
 		machines = append(machines, m.(*api.Minion).ID)
 	}
 	return machines, nil
@@ -50,11 +52,11 @@ func (s storeToMinionLister) List() (machines []string, err error) {
 
 // storeToPodLister turns a store into a pod lister. The store must contain (only) pods.
 type storeToPodLister struct {
-	s cache.Store
+	cache.Store
 }
 
-func (s storeToPodLister) ListPods(selector labels.Selector) (pods []api.Pod, err error) {
-	for _, m := range s.s.List() {
+func (s *storeToPodLister) ListPods(selector labels.Selector) (pods []api.Pod, err error) {
+	for _, m := range s.List() {
 		pod := m.(*api.Pod)
 		if selector.Matches(labels.Set(pod.Labels)) {
 			pods = append(pods, *pod)
@@ -63,13 +65,31 @@ func (s storeToPodLister) ListPods(selector labels.Selector) (pods []api.Pod, er
 	return pods, nil
 }
 
+// minionEnumerator allows a cache.Poller to enumerate items in an api.PodList
+type minionEnumerator struct {
+	*api.MinionList
+}
+
+// Returns the number of items in the pod list.
+func (me *minionEnumerator) Len() int {
+	if me.MinionList == nil {
+		return 0
+	}
+	return len(me.Items)
+}
+
+// Returns the item (and ID) with the particular index.
+func (me *minionEnumerator) Get(index int) (string, interface{}) {
+	return me.Items[index].ID, &me.Items[index]
+}
+
 type binder struct {
-	kubeClient *client.Client
+	*client.Client
 }
 
 // Bind just does a POST binding RPC.
-func (b binder) Bind(binding *api.Binding) error {
-	return b.kubeClient.Post().Path("bindings").Body(binding).Do().Error()
+func (b *binder) Bind(binding *api.Binding) error {
+	return b.Post().Path("bindings").Body(binding).Do().Error()
 }
 
 func main() {
@@ -90,8 +110,8 @@ func main() {
 		// This query will only find pods with no assigned host.
 		return kubeClient.
 			Get().
-			Path("pods").
 			Path("watch").
+			Path("pods").
 			SelectorParam("fields", labels.Set{"DesiredState.Host": ""}.AsSelector()).
 			UintParam("resourceVersion", resourceVersion).
 			Watch()
@@ -104,8 +124,8 @@ func main() {
 		// This query will only find pods that do have an assigned host.
 		return kubeClient.
 			Get().
-			Path("pods").
 			Path("watch").
+			Path("pods").
 			ParseSelectorParam("fields", "DesiredState.Host!=").
 			UintParam("resourceVersion", resourceVersion).
 			Watch()
@@ -114,25 +134,44 @@ func main() {
 	// Watch minions.
 	// Minions may be listed frequently, so provide a local up-to-date cache.
 	minionCache := cache.NewStore()
-	cache.NewReflector(func(resourceVersion uint64) (watch.Interface, error) {
-		// This query will only find pods that do have an assigned host.
-		return kubeClient.
-			Get().
-			Path("minions").
-			Path("watch").
-			UintParam("resourceVersion", resourceVersion).
-			Watch()
-	}, &api.Minion{}, minionCache).Run()
+	if false {
+		// Disable this code until minions support watches.
+		cache.NewReflector(func(resourceVersion uint64) (watch.Interface, error) {
+			// This query will only find pods that do have an assigned host.
+			return kubeClient.
+				Get().
+				Path("watch").
+				Path("minions").
+				UintParam("resourceVersion", resourceVersion).
+				Watch()
+		}, &api.Minion{}, minionCache).Run()
+	} else {
+		cache.NewPoller(func() (cache.Enumerator, error) {
+			// This query will only find pods that do have an assigned host.
+			list := &api.MinionList{}
+			err := kubeClient.Get().Path("minions").Do().Into(list)
+			if err != nil {
+				return nil, err
+			}
+			return &minionEnumerator{list}, nil
+		}, 10*time.Second, minionCache).Run()
+	}
 
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
 	algo := algorithm.NewRandomFitScheduler(
-		storeToPodLister{podCache}, r)
+		&storeToPodLister{podCache}, r)
 
 	s := scheduler.New(&scheduler.Config{
-		MinionLister: storeToMinionLister{minionCache},
+		MinionLister: &storeToMinionLister{minionCache},
 		Algorithm:    algo,
-		NextPod:      func() *api.Pod { return podQueue.Pop().(*api.Pod) },
-		Binder:       binder{kubeClient},
+		Binder:       &binder{kubeClient},
+		NextPod: func() *api.Pod {
+			return podQueue.Pop().(*api.Pod)
+		},
+		Error: func(pod *api.Pod, err error) {
+			glog.Errorf("Error scheduling %v: %v; retrying", pod.ID, err)
+			podQueue.Add(pod.ID, pod)
+		},
 	})
 
 	s.Run()

plugin/pkg/scheduler/scheduler.go

@@ -31,7 +31,7 @@ type Binder interface {
 // Scheduler watches for new unscheduled pods. It attempts to find
 // minions that they fit on and writes bindings back to the api server.
 type Scheduler struct {
-	c *Config
+	config *Config
 }
 
 type Config struct {
@@ -53,28 +53,28 @@ type Config struct {
 // New returns a new scheduler.
 func New(c *Config) *Scheduler {
 	s := &Scheduler{
-		c: c,
+		config: c,
 	}
 	return s
 }
 
-// Run begins watching and scheduling.
+// Run begins watching and scheduling. It starts a goroutine and returns immediately.
 func (s *Scheduler) Run() {
 	go util.Forever(s.scheduleOne, 0)
 }
 
 func (s *Scheduler) scheduleOne() {
-	pod := s.c.NextPod()
-	dest, err := s.c.Algorithm.Schedule(*pod, s.c.MinionLister)
+	pod := s.config.NextPod()
+	dest, err := s.config.Algorithm.Schedule(*pod, s.config.MinionLister)
 	if err != nil {
-		s.c.Error(pod, err)
+		s.config.Error(pod, err)
 		return
 	}
 	b := &api.Binding{
 		PodID: pod.ID,
 		Host:  dest,
 	}
-	if err := s.c.Binder.Bind(b); err != nil {
-		s.c.Error(pod, err)
+	if err := s.config.Binder.Bind(b); err != nil {
+		s.config.Error(pod, err)
 	}
 }