Properly handle nil cached services in the service controller's node reconciler.

pkg/cloudprovider/servicecontroller/servicecontroller.go

@@ -203,7 +203,10 @@ func (s *ServiceController) processDelta(delta *cache.Delta) (error, bool) {
 		if err != nil {
 			return err, retry
 		}
-		// Always update the cache upon success
+		// Always update the cache upon success.
+		// NOTE: Since we update the cached service if and only if we successully
+		// processed it, a cached service being nil implies that it hasn't yet
+		// been successfully processed.
 		cachedService.service = service
 		s.cache.set(namespacedName.String(), cachedService)
 	case cache.Deleted:
@@ -554,6 +557,13 @@ func (s *ServiceController) updateLoadBalancerHosts(services []*cachedService, h
 		func() {
 			service.mu.Lock()
 			defer service.mu.Unlock()
+			// If the service is nil, that means it hasn't yet been successfully dealt
+			// with by the load balancer reconciler. We can trust the load balancer
+			// reconciler to ensure the service's load balancer is created to target
+			// the correct nodes.
+			if service.service == nil {
+				return
+			}
 			if err := s.lockedUpdateLoadBalancerHosts(service.service, hosts); err != nil {
 				glog.Errorf("External error while updating TCP load balancer: %v.", err)
 				servicesToRetry = append(servicesToRetry, service)

pkg/cloudprovider/servicecontroller/servicecontroller_test.go

@@ -184,6 +184,16 @@ func TestUpdateNodesInExternalLoadBalancer(t *testing.T) {
 				{Name: "a999", Region: region, Hosts: []string{"node0", "node1", "node73"}},
 			},
 		},
+		{
+			// One service has an external load balancer and one is nil: one call.
+			services: []*api.Service{
+				newService("s0", "234", true),
+				nil,
+			},
+			expectedUpdateCalls: []fake_cloud.FakeUpdateBalancerCall{
+				{Name: "a234", Region: region, Hosts: []string{"node0", "node1", "node73"}},
+			},
+		},
 	}
 	for _, item := range table {
 		cloud := &fake_cloud.FakeCloud{}