apiserver: add flow control metric current_inqueue_seats

Signed-off-by: Andrew Sy Kim <andrewsy@google.com>

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/queueset.go

@@ -448,6 +448,7 @@ func (req *request) wait() (bool, bool) {
 		qs.totRequestsCancelled++
 		metrics.AddReject(req.ctx, qs.qCfg.Name, req.fsName, "cancelled")
 		metrics.AddRequestsInQueues(req.ctx, qs.qCfg.Name, req.fsName, -1)
+		metrics.AddSeatsInQueues(req.ctx, qs.qCfg.Name, req.fsName, -req.MaxSeats())
 		req.NoteQueued(false)
 		qs.reqsGaugePair.RequestsWaiting.Add(-1)
 		qs.seatDemandIntegrator.Set(float64(qs.totSeatsInUse + qs.totSeatsWaiting))
@@ -652,6 +653,7 @@ func (qs *queueSet) removeTimedOutRequestsFromQueueToBoundLocked(queue *queue, f
 				disqueueSeats += req.MaxSeats()
 				req.NoteQueued(false)
 				metrics.AddRequestsInQueues(req.ctx, qs.qCfg.Name, req.fsName, -1)
+				metrics.AddSeatsInQueues(req.ctx, qs.qCfg.Name, req.fsName, -req.MaxSeats())
 			}
 			// we need to check if the next request has timed out.
 			return true
@@ -702,6 +704,7 @@ func (qs *queueSet) enqueueToBoundLocked(request *request) {
 	qs.totRequestsWaiting++
 	qs.totSeatsWaiting += request.MaxSeats()
 	metrics.AddRequestsInQueues(request.ctx, qs.qCfg.Name, request.fsName, 1)
+	metrics.AddSeatsInQueues(request.ctx, qs.qCfg.Name, request.fsName, request.MaxSeats())
 	request.NoteQueued(true)
 	qs.reqsGaugePair.RequestsWaiting.Add(1)
 	qs.seatDemandIntegrator.Set(float64(qs.totSeatsInUse + qs.totSeatsWaiting))
@@ -760,6 +763,7 @@ func (qs *queueSet) dispatchLocked() bool {
 	qs.totRequestsWaiting--
 	qs.totSeatsWaiting -= request.MaxSeats()
 	metrics.AddRequestsInQueues(request.ctx, qs.qCfg.Name, request.fsName, -1)
+	metrics.AddSeatsInQueues(request.ctx, qs.qCfg.Name, request.fsName, -request.MaxSeats())
 	request.NoteQueued(false)
 	qs.reqsGaugePair.RequestsWaiting.Add(-1)
 	defer qs.boundNextDispatchLocked(queue)

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/queueset_test.go

@@ -214,7 +214,7 @@ type uniformScenarioState struct {
 	execSeatsIntegrators                                                                   []fq.Integrator
 	seatDemandIntegratorCheck                                                              fq.Integrator
 	failedCount                                                                            uint64
-	expectedInqueue, expectedExecuting, expectedConcurrencyInUse string
+	expectedInqueueReqs, expectedInqueueSeats, expectedExecuting, expectedConcurrencyInUse string
 	executions, rejects                                                                    []int32
 }
 
@@ -226,7 +226,8 @@ func (uss *uniformScenarioState) exercise() {
 	for i, uc := range uss.clients {
 		uss.execSeatsIntegrators[i] = fq.NewNamedIntegrator(uss.clk, fmt.Sprintf("%s client %d execSeats", uss.name, i))
 		fsName := fmt.Sprintf("client%d", i)
-		uss.expectedInqueue = uss.expectedInqueue + fmt.Sprintf(`				apiserver_flowcontrol_current_inqueue_requests{flow_schema=%q,priority_level=%q} 0%s`, fsName, uss.name, "\n")
+		uss.expectedInqueueReqs = uss.expectedInqueueReqs + fmt.Sprintf(`				apiserver_flowcontrol_current_inqueue_requests{flow_schema=%q,priority_level=%q} 0%s`, fsName, uss.name, "\n")
+		uss.expectedInqueueSeats = uss.expectedInqueueSeats + fmt.Sprintf(`				apiserver_flowcontrol_current_inqueue_seats{flow_schema=%q,priority_level=%q} 0%s`, fsName, uss.name, "\n")
 		for j := 0; j < uc.nThreads; j++ {
 			ust := uniformScenarioThread{
 				uss:                 uss,
@@ -412,13 +413,24 @@ func (uss *uniformScenarioState) finalReview() {
 		e := `
 				# HELP apiserver_flowcontrol_current_inqueue_requests [BETA] Number of requests currently pending in queues of the API Priority and Fairness subsystem
 				# TYPE apiserver_flowcontrol_current_inqueue_requests gauge
-` + uss.expectedInqueue
+` + uss.expectedInqueueReqs
 		err := metrics.GatherAndCompare(e, "apiserver_flowcontrol_current_inqueue_requests")
 		if err != nil {
 			uss.t.Error(err)
 		} else {
 			uss.t.Log("Success with" + e)
 		}
+
+		e = `
+				# HELP apiserver_flowcontrol_current_inqueue_seats [ALPHA] Number of seats currently pending in queues of the API Priority and Fairness subsystem
+				# TYPE apiserver_flowcontrol_current_inqueue_seats gauge
+` + uss.expectedInqueueSeats
+		err = metrics.GatherAndCompare(e, "apiserver_flowcontrol_current_inqueue_seats")
+		if err != nil {
+			uss.t.Error(err)
+		} else {
+			uss.t.Log("Success with" + e)
+		}
 	}
 	expectedRejects := ""
 	for i := range uss.clients {

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/metrics/metrics.go

@@ -210,6 +210,16 @@ var (
 		},
 		[]string{priorityLevel, flowSchema},
 	)
+	apiserverCurrentInqueueSeats = compbasemetrics.NewGaugeVec(
+		&compbasemetrics.GaugeOpts{
+			Namespace:      namespace,
+			Subsystem:      subsystem,
+			Name:           "current_inqueue_seats",
+			Help:           "Number of seats currently pending in queues of the API Priority and Fairness subsystem",
+			StabilityLevel: compbasemetrics.ALPHA,
+		},
+		[]string{priorityLevel, flowSchema},
+	)
 	apiserverRequestQueueLength = compbasemetrics.NewHistogramVec(
 		&compbasemetrics.HistogramOpts{
 			Namespace:      namespace,
@@ -455,6 +465,7 @@ var (
 		apiserverNextSBounds,
 		apiserverNextDiscountedSBounds,
 		apiserverCurrentInqueueRequests,
+		apiserverCurrentInqueueSeats,
 		apiserverRequestQueueLength,
 		apiserverRequestConcurrencyLimit,
 		apiserverRequestConcurrencyInUse,
@@ -518,6 +529,11 @@ func AddRequestsInQueues(ctx context.Context, priorityLevel, flowSchema string,
 	apiserverCurrentInqueueRequests.WithLabelValues(priorityLevel, flowSchema).Add(float64(delta))
 }
 
+// AddSeatsInQueues adds the given delta to the gauge of the # of seats in the queues of the specified flowSchema and priorityLevel
+func AddSeatsInQueues(ctx context.Context, priorityLevel, flowSchema string, delta int) {
+	apiserverCurrentInqueueSeats.WithLabelValues(priorityLevel, flowSchema).Add(float64(delta))
+}
+
 // AddRequestsExecuting adds the given delta to the gauge of executing requests of the given flowSchema and priorityLevel
 func AddRequestsExecuting(ctx context.Context, priorityLevel, flowSchema string, delta int) {
 	apiserverCurrentExecutingRequests.WithLabelValues(priorityLevel, flowSchema).Add(float64(delta))