Make sampleAndWaterMarkHistograms not fall very far behind

Kubernetes-commit: 9e89b92a92c02cdd2c70c0f52a30936e9c3309c7

pkg/server/config.go

@@ -626,6 +626,7 @@ func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*G
 	if s.isPostStartHookRegistered(priorityAndFairnessConfigConsumerHookName) {
 	} else if c.FlowControl != nil {
 		err := s.AddPostStartHook(priorityAndFairnessConfigConsumerHookName, func(context PostStartHookContext) error {
+			go c.FlowControl.MaintainObservations(context.StopCh)
 			go c.FlowControl.Run(context.StopCh)
 			return nil
 		})

pkg/util/flowcontrol/apf_controller.go

@@ -227,6 +227,23 @@ func (cfgCtlr *configController) initializeConfigController(informerFactory kube
 		}})
 }
 
+// MaintainObservations keeps the observers from
+// metrics.PriorityLevelConcurrencyObserverPairGenerator from falling
+// too far behind
+func (cfgCtlr *configController) MaintainObservations(stopCh <-chan struct{}) {
+	wait.Until(cfgCtlr.updateObservations, 10*time.Second, stopCh)
+}
+
+func (cfgCtlr *configController) updateObservations() {
+	cfgCtlr.lock.Lock()
+	defer cfgCtlr.lock.Unlock()
+	for _, plc := range cfgCtlr.priorityLevelStates {
+		if plc.queues != nil {
+			plc.queues.UpdateObservations()
+		}
+	}
+}
+
 func (cfgCtlr *configController) Run(stopCh <-chan struct{}) error {
 	defer cfgCtlr.configQueue.ShutDown()
 	klog.Info("Starting API Priority and Fairness config controller")

pkg/util/flowcontrol/apf_filter.go

@@ -38,10 +38,13 @@ import (
 type Interface interface {
 	// Handle takes care of queuing and dispatching a request
 	// characterized by the given digest.  The given `noteFn` will be
-	// invoked with the results of request classification.  If Handle
+	// invoked with the results of request classification.  If the
-	// decides that the request should be executed then `execute()`
+	// request is queued then `queueNoteFn` will be called twice,
-	// will be invoked once to execute the request; otherwise
+	// first with `true` and then with `false`; otherwise
-	// `execute()` will not be invoked.
+	// `queueNoteFn` will not be called at all.  If Handle decides
+	// that the request should be executed then `execute()` will be
+	// invoked once to execute the request; otherwise `execute()` will
+	// not be invoked.
 	Handle(ctx context.Context,
 		requestDigest RequestDigest,
 		noteFn func(fs *fctypesv1a1.FlowSchema, pl *fctypesv1a1.PriorityLevelConfiguration),
@@ -49,6 +52,9 @@ type Interface interface {
 		execFn func(),
 	)
 
+	// MaintainObservations is a helper for maintaining statistics.
+	MaintainObservations(stopCh <-chan struct{})
+
 	// Run monitors config objects from the main apiservers and causes
 	// any needed changes to local behavior.  This method ceases
 	// activity and returns after the given channel is closed.

pkg/util/flowcontrol/controller_test.go

@@ -97,6 +97,9 @@ func (cqs *ctlrTestQueueSet) BeginConfigChange(qc fq.QueuingConfig) (fq.QueueSet
 	return ctlrTestQueueSetCompleter{cqs.cts, cqs, qc}, nil
 }
 
+func (cqs *ctlrTestQueueSet) UpdateObservations() {
+}
+
 func (cqs *ctlrTestQueueSet) Dump(bool) debug.QueueSetDump {
 	return debug.QueueSetDump{}
 }

pkg/util/flowcontrol/fairqueuing/interface.go

@@ -82,6 +82,10 @@ type QueueSet interface {
 	// exactly once.
 	StartRequest(ctx context.Context, hashValue uint64, flowDistinguisher, fsName string, descr1, descr2 interface{}, queueNoteFn QueueNoteFn) (req Request, idle bool)
 
+	// UpdateObservations makes sure any time-based statistics have
+	// caught up with the current clock reading
+	UpdateObservations()
+
 	// Dump saves and returns the instant internal state of the queue-set.
 	// Note that dumping process will stop the queue-set from proceeding
 	// any requests.

pkg/util/flowcontrol/fairqueuing/queueset/queueset.go

@@ -743,6 +743,11 @@ func (qs *queueSet) goroutineDoneOrBlocked() {
 	qs.counter.Add(-1)
 }
 
+func (qs *queueSet) UpdateObservations() {
+	qs.obsPair.RequestsWaiting.Add(0)
+	qs.obsPair.RequestsExecuting.Add(0)
+}
+
 func (qs *queueSet) Dump(includeRequestDetails bool) debug.QueueSetDump {
 	qs.lock.Lock()
 	defer qs.lock.Unlock()

pkg/util/flowcontrol/fairqueuing/testing/no-restraint.go

@@ -59,6 +59,9 @@ func (noRestraint) StartRequest(ctx context.Context, hashValue uint64, flowDisti
 	return noRestraintRequest{}, false
 }
 
+func (noRestraint) UpdateObservations() {
+}
+
 func (noRestraint) Dump(bool) debug.QueueSetDump {
 	return debug.QueueSetDump{}
 }