diff --git a/pkg/client/cache/delta_fifo.go b/pkg/client/cache/delta_fifo.go
index 3603c5f0028..8ff9d7a36c9 100644
--- a/pkg/client/cache/delta_fifo.go
+++ b/pkg/client/cache/delta_fifo.go
@@ -363,10 +363,12 @@ func (f *DeltaFIFO) GetByKey(key string) (item interface{}, exists bool, err err
 // added/updated. The item is removed from the queue (and the store) before it
 // is returned, so if you don't successfully process it, you need to add it back
 // with AddIfNotPresent().
+// process function is called under lock, so it is safe update data structures
+// in it that need to be in sync with the queue (e.g. knownKeys).
 //
 // Pop returns a 'Deltas', which has a complete list of all the things
 // that happened to the object (deltas) while it was sitting in the queue.
-func (f *DeltaFIFO) Pop() interface{} {
+func (f *DeltaFIFO) Pop(process PopProcessFunc) (interface{}, error) {
 	f.lock.Lock()
 	defer f.lock.Unlock()
 	for {
@@ -386,7 +388,7 @@ func (f *DeltaFIFO) Pop() interface{} {
 		delete(f.items, id)
 		// Don't need to copyDeltas here, because we're transferring
 		// ownership to the caller.
-		return item
+		return item, process(item)
 	}
 }
 
diff --git a/pkg/client/cache/delta_fifo_test.go b/pkg/client/cache/delta_fifo_test.go
index 8efd982b5a4..2bead89a848 100644
--- a/pkg/client/cache/delta_fifo_test.go
+++ b/pkg/client/cache/delta_fifo_test.go
@@ -24,7 +24,7 @@ import (
 
 // helper function to reduce stuttering
 func testPop(f *DeltaFIFO) testFifoObject {
-	return f.Pop().(Deltas).Newest().Object.(testFifoObject)
+	return Pop(f).(Deltas).Newest().Object.(testFifoObject)
 }
 
 // keyLookupFunc adapts a raw function to be a KeyLookup.
@@ -104,7 +104,7 @@ func TestDeltaFIFO_compressorWorks(t *testing.T) {
 	if e, a := expect, oldestTypes; !reflect.DeepEqual(e, a) {
 		t.Errorf("Expected %#v, got %#v", e, a)
 	}
-	if e, a := (Deltas{{Added, mkFifoObj("foo", 25)}}), f.Pop().(Deltas); !reflect.DeepEqual(e, a) {
+	if e, a := (Deltas{{Added, mkFifoObj("foo", 25)}}), Pop(f).(Deltas); !reflect.DeepEqual(e, a) {
 		t.Fatalf("Expected %#v, got %#v", e, a)
 	}
 
@@ -126,7 +126,7 @@ func TestDeltaFIFO_addUpdate(t *testing.T) {
 	got := make(chan testFifoObject, 2)
 	go func() {
 		for {
-			obj := f.Pop().(Deltas).Newest().Object.(testFifoObject)
+			obj := testPop(f)
 			t.Logf("got a thing %#v", obj)
 			t.Logf("D len: %v", len(f.queue))
 			got <- obj
@@ -240,7 +240,7 @@ func TestDeltaFIFO_ReplaceMakesDeletions(t *testing.T) {
 	}
 
 	for _, expected := range expectedList {
-		cur := f.Pop().(Deltas)
+		cur := Pop(f).(Deltas)
 		if e, a := expected, cur; !reflect.DeepEqual(e, a) {
 			t.Errorf("Expected %#v, got %#v", e, a)
 		}
@@ -279,9 +279,9 @@ func TestDeltaFIFO_addIfNotPresent(t *testing.T) {
 	f := NewDeltaFIFO(testFifoObjectKeyFunc, nil, nil)
 
 	f.Add(mkFifoObj("b", 3))
-	b3 := f.Pop()
+	b3 := Pop(f)
 	f.Add(mkFifoObj("c", 4))
-	c4 := f.Pop()
+	c4 := Pop(f)
 	if e, a := 0, len(f.items); e != a {
 		t.Fatalf("Expected %v, got %v items in queue", e, a)
 	}
@@ -358,15 +358,15 @@ func TestDeltaFIFO_HasSynced(t *testing.T) {
 		{
 			actions: []func(f *DeltaFIFO){
 				func(f *DeltaFIFO) { f.Replace([]interface{}{mkFifoObj("a", 1), mkFifoObj("b", 2)}, "0") },
-				func(f *DeltaFIFO) { f.Pop() },
+				func(f *DeltaFIFO) { Pop(f) },
 			},
 			expectedSynced: false,
 		},
 		{
 			actions: []func(f *DeltaFIFO){
 				func(f *DeltaFIFO) { f.Replace([]interface{}{mkFifoObj("a", 1), mkFifoObj("b", 2)}, "0") },
-				func(f *DeltaFIFO) { f.Pop() },
-				func(f *DeltaFIFO) { f.Pop() },
+				func(f *DeltaFIFO) { Pop(f) },
+				func(f *DeltaFIFO) { Pop(f) },
 			},
 			expectedSynced: true,
 		},
diff --git a/pkg/client/cache/fifo.go b/pkg/client/cache/fifo.go
index f98bea6f445..17e52929775 100644
--- a/pkg/client/cache/fifo.go
+++ b/pkg/client/cache/fifo.go
@@ -22,12 +22,17 @@ import (
 	"k8s.io/kubernetes/pkg/util/sets"
 )
 
+// PopProcessFunc is passed to Pop() method of Queue interface.
+// It is supposed to process the element popped from the queue.
+type PopProcessFunc func(interface{}) error
+
 // Queue is exactly like a Store, but has a Pop() method too.
 type Queue interface {
 	Store
 
-	// Pop blocks until it has something to return.
-	Pop() interface{}
+	// Pop blocks until it has something to process.
+	// It returns the object that was process and the result of processing.
+	Pop(PopProcessFunc) (interface{}, error)
 
 	// AddIfNotPresent adds a value previously
 	// returned by Pop back into the queue as long
@@ -39,6 +44,16 @@ type Queue interface {
 	HasSynced() bool
 }
 
+// Helper function for popping from Queue.
+func Pop(queue Queue) interface{} {
+	var result interface{}
+	queue.Pop(func(obj interface{}) error {
+		result = obj
+		return nil
+	})
+	return result
+}
+
 // FIFO receives adds and updates from a Reflector, and puts them in a queue for
 // FIFO order processing. If multiple adds/updates of a single item happen while
 // an item is in the queue before it has been processed, it will only be
@@ -183,12 +198,13 @@ func (f *FIFO) GetByKey(key string) (item interface{}, exists bool, err error) {
 	return item, exists, nil
 }
 
-// Pop waits until an item is ready and returns it. If multiple items are
+// Pop waits until an item is ready and processes it. If multiple items are
 // ready, they are returned in the order in which they were added/updated.
-// The item is removed from the queue (and the store) before it is returned,
-// so if you don't successfully process it, you need to add it back with
-// AddIfNotPresent().
-func (f *FIFO) Pop() interface{} {
+// The item is removed from the queue (and the store) before it is processed,
+// so if you don't successfully process it, it should be added back with
+// AddIfNotPresent(). process function is called under lock, so it is safe
+// update data structures in it that need to be in sync with the queue.
+func (f *FIFO) Pop(process PopProcessFunc) (interface{}, error) {
 	f.lock.Lock()
 	defer f.lock.Unlock()
 	for {
@@ -206,7 +222,7 @@ func (f *FIFO) Pop() interface{} {
 			continue
 		}
 		delete(f.items, id)
-		return item
+		return item, process(item)
 	}
 }
 
diff --git a/pkg/client/cache/fifo_test.go b/pkg/client/cache/fifo_test.go
index 974fa6d3b73..0f2ceb8eaa1 100644
--- a/pkg/client/cache/fifo_test.go
+++ b/pkg/client/cache/fifo_test.go
@@ -52,7 +52,7 @@ func TestFIFO_basic(t *testing.T) {
 	lastInt := int(0)
 	lastUint := uint64(0)
 	for i := 0; i < amount*2; i++ {
-		switch obj := f.Pop().(testFifoObject).val.(type) {
+		switch obj := Pop(f).(testFifoObject).val.(type) {
 		case int:
 			if obj <= lastInt {
 				t.Errorf("got %v (int) out of order, last was %v", obj, lastInt)
@@ -85,7 +85,7 @@ func TestFIFO_addUpdate(t *testing.T) {
 	got := make(chan testFifoObject, 2)
 	go func() {
 		for {
-			got <- f.Pop().(testFifoObject)
+			got <- Pop(f).(testFifoObject)
 		}
 	}()
 
@@ -111,7 +111,7 @@ func TestFIFO_addReplace(t *testing.T) {
 	got := make(chan testFifoObject, 2)
 	go func() {
 		for {
-			got <- f.Pop().(testFifoObject)
+			got <- Pop(f).(testFifoObject)
 		}
 	}()
 
@@ -139,21 +139,21 @@ func TestFIFO_detectLineJumpers(t *testing.T) {
 	f.Add(mkFifoObj("foo", 13))
 	f.Add(mkFifoObj("zab", 30))
 
-	if e, a := 13, f.Pop().(testFifoObject).val; a != e {
+	if e, a := 13, Pop(f).(testFifoObject).val; a != e {
 		t.Fatalf("expected %d, got %d", e, a)
 	}
 
 	f.Add(mkFifoObj("foo", 14)) // ensure foo doesn't jump back in line
 
-	if e, a := 1, f.Pop().(testFifoObject).val; a != e {
+	if e, a := 1, Pop(f).(testFifoObject).val; a != e {
 		t.Fatalf("expected %d, got %d", e, a)
 	}
 
-	if e, a := 30, f.Pop().(testFifoObject).val; a != e {
+	if e, a := 30, Pop(f).(testFifoObject).val; a != e {
 		t.Fatalf("expected %d, got %d", e, a)
 	}
 
-	if e, a := 14, f.Pop().(testFifoObject).val; a != e {
+	if e, a := 14, Pop(f).(testFifoObject).val; a != e {
 		t.Fatalf("expected %d, got %d", e, a)
 	}
 }
@@ -172,7 +172,7 @@ func TestFIFO_addIfNotPresent(t *testing.T) {
 
 	expectedValues := []int{1, 2, 4}
 	for _, expected := range expectedValues {
-		if actual := f.Pop().(testFifoObject).val; actual != expected {
+		if actual := Pop(f).(testFifoObject).val; actual != expected {
 			t.Fatalf("expected value %d, got %d", expected, actual)
 		}
 	}
@@ -208,15 +208,15 @@ func TestFIFO_HasSynced(t *testing.T) {
 		{
 			actions: []func(f *FIFO){
 				func(f *FIFO) { f.Replace([]interface{}{mkFifoObj("a", 1), mkFifoObj("b", 2)}, "0") },
-				func(f *FIFO) { f.Pop() },
+				func(f *FIFO) { Pop(f) },
 			},
 			expectedSynced: false,
 		},
 		{
 			actions: []func(f *FIFO){
 				func(f *FIFO) { f.Replace([]interface{}{mkFifoObj("a", 1), mkFifoObj("b", 2)}, "0") },
-				func(f *FIFO) { f.Pop() },
-				func(f *FIFO) { f.Pop() },
+				func(f *FIFO) { Pop(f) },
+				func(f *FIFO) { Pop(f) },
 			},
 			expectedSynced: true,
 		},
diff --git a/pkg/client/cache/reflector_test.go b/pkg/client/cache/reflector_test.go
index d28bdb7b247..f560e449cae 100644
--- a/pkg/client/cache/reflector_test.go
+++ b/pkg/client/cache/reflector_test.go
@@ -252,7 +252,7 @@ func TestReflectorListAndWatch(t *testing.T) {
 
 	// Verify we received the right ids with the right resource versions.
 	for i, id := range ids {
-		pod := s.Pop().(*api.Pod)
+		pod := Pop(s).(*api.Pod)
 		if e, a := id, pod.Name; e != a {
 			t.Errorf("%v: Expected %v, got %v", i, e, a)
 		}
diff --git a/pkg/controller/framework/controller.go b/pkg/controller/framework/controller.go
index cfffabe8cd4..c6363952b0c 100644
--- a/pkg/controller/framework/controller.go
+++ b/pkg/controller/framework/controller.go
@@ -124,8 +124,7 @@ func (c *Controller) Requeue(obj interface{}) error {
 // concurrently.
 func (c *Controller) processLoop() {
 	for {
-		obj := c.config.Queue.Pop()
-		err := c.config.Process(obj)
+		obj, err := c.config.Queue.Pop(cache.PopProcessFunc(c.config.Process))
 		if err != nil {
 			if c.config.RetryOnError {
 				// This is the safe way to re-enqueue.
diff --git a/pkg/controller/service/servicecontroller.go b/pkg/controller/service/servicecontroller.go
index 0fb1820869e..30ebe095497 100644
--- a/pkg/controller/service/servicecontroller.go
+++ b/pkg/controller/service/servicecontroller.go
@@ -184,29 +184,32 @@ func (s *ServiceController) init() error {
 // Loop infinitely, processing all service updates provided by the queue.
 func (s *ServiceController) watchServices(serviceQueue *cache.DeltaFIFO) {
 	for {
-		newItem := serviceQueue.Pop()
-		deltas, ok := newItem.(cache.Deltas)
-		if !ok {
-			glog.Errorf("Received object from service watcher that wasn't Deltas: %+v", newItem)
-		}
-		delta := deltas.Newest()
-		if delta == nil {
-			glog.Errorf("Received nil delta from watcher queue.")
-			continue
-		}
-		err, retryDelay := s.processDelta(delta)
-		if retryDelay != 0 {
-			// Add the failed service back to the queue so we'll retry it.
-			glog.Errorf("Failed to process service delta. Retrying in %s: %v", retryDelay, err)
-			go func(deltas cache.Deltas, delay time.Duration) {
-				time.Sleep(delay)
-				if err := serviceQueue.AddIfNotPresent(deltas); err != nil {
-					glog.Errorf("Error requeuing service delta - will not retry: %v", err)
-				}
-			}(deltas, retryDelay)
-		} else if err != nil {
-			runtime.HandleError(fmt.Errorf("Failed to process service delta. Not retrying: %v", err))
-		}
+		serviceQueue.Pop(func(obj interface{}) error {
+			deltas, ok := obj.(cache.Deltas)
+			if !ok {
+				runtime.HandleError(fmt.Errorf("Received object from service watcher that wasn't Deltas: %+v", obj))
+				return nil
+			}
+			delta := deltas.Newest()
+			if delta == nil {
+				runtime.HandleError(fmt.Errorf("Received nil delta from watcher queue."))
+				return nil
+			}
+			err, retryDelay := s.processDelta(delta)
+			if retryDelay != 0 {
+				// Add the failed service back to the queue so we'll retry it.
+				runtime.HandleError(fmt.Errorf("Failed to process service delta. Retrying in %s: %v", retryDelay, err))
+				go func(deltas cache.Deltas, delay time.Duration) {
+					time.Sleep(delay)
+					if err := serviceQueue.AddIfNotPresent(deltas); err != nil {
+						runtime.HandleError(fmt.Errorf("Error requeuing service delta - will not retry: %v", err))
+					}
+				}(deltas, retryDelay)
+			} else if err != nil {
+				runtime.HandleError(fmt.Errorf("Failed to process service delta. Not retrying: %v", err))
+			}
+			return nil
+		})
 	}
 }
 
diff --git a/pkg/volume/util.go b/pkg/volume/util.go
index 0b20a4be734..696f9254b08 100644
--- a/pkg/volume/util.go
+++ b/pkg/volume/util.go
@@ -142,8 +142,7 @@ func (c *realRecyclerClient) WatchPod(name, namespace string, stopChannel chan s
 	cache.NewReflector(podLW, &api.Pod{}, queue, 1*time.Minute).RunUntil(stopChannel)
 
 	return func() *api.Pod {
-		obj := queue.Pop()
-		return obj.(*api.Pod)
+		return cache.Pop(queue).(*api.Pod)
 	}
 }
 
diff --git a/plugin/pkg/scheduler/factory/factory.go b/plugin/pkg/scheduler/factory/factory.go
index f02d7fa877b..0bbbcbf3329 100644
--- a/plugin/pkg/scheduler/factory/factory.go
+++ b/plugin/pkg/scheduler/factory/factory.go
@@ -415,7 +415,7 @@ func (f *ConfigFactory) Run() {
 
 func (f *ConfigFactory) getNextPod() *api.Pod {
 	for {
-		pod := f.PodQueue.Pop().(*api.Pod)
+		pod := cache.Pop(f.PodQueue).(*api.Pod)
 		if f.responsibleForPod(pod) {
 			glog.V(4).Infof("About to try and schedule pod %v", pod.Name)
 			return pod
diff --git a/plugin/pkg/scheduler/scheduler_test.go b/plugin/pkg/scheduler/scheduler_test.go
index 106815f89a0..cb326ec0e26 100644
--- a/plugin/pkg/scheduler/scheduler_test.go
+++ b/plugin/pkg/scheduler/scheduler_test.go
@@ -26,7 +26,7 @@ import (
 
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/testapi"
-	"k8s.io/kubernetes/pkg/client/cache"
+	clientcache "k8s.io/kubernetes/pkg/client/cache"
 	"k8s.io/kubernetes/pkg/client/record"
 	"k8s.io/kubernetes/pkg/labels"
 	"k8s.io/kubernetes/pkg/util/diff"
@@ -202,8 +202,8 @@ func TestSchedulerForgetAssumedPodAfterDelete(t *testing.T) {
 	// Setup stores to test pod's workflow:
 	// - queuedPodStore: pods queued before processing
 	// - scheduledPodStore: pods that has a scheduling decision
-	scheduledPodStore := cache.NewStore(cache.MetaNamespaceKeyFunc)
-	queuedPodStore := cache.NewFIFO(cache.MetaNamespaceKeyFunc)
+	scheduledPodStore := clientcache.NewStore(clientcache.MetaNamespaceKeyFunc)
+	queuedPodStore := clientcache.NewFIFO(clientcache.MetaNamespaceKeyFunc)
 
 	// Port is the easiest way to cause a fit predicate failure
 	podPort := 8080
@@ -232,7 +232,7 @@ func TestSchedulerForgetAssumedPodAfterDelete(t *testing.T) {
 			return nil
 		}},
 		NextPod: func() *api.Pod {
-			return queuedPodStore.Pop().(*api.Pod)
+			return clientcache.Pop(queuedPodStore).(*api.Pod)
 		},
 		Error: func(p *api.Pod, err error) {
 			t.Errorf("Unexpected error when scheduling pod %+v: %v", p, err)