Reject series/write requests when max pending request limit is hit

cmd/thanos/receive.go

@@ -268,7 +268,19 @@ func runReceive(
 			return errors.Wrap(err, "parse limit configuration")
 		}
 	}
-	limiter, err := receive.NewLimiter(conf.writeLimitsConfig, reg, receiveMode, log.With(logger, "component", "receive-limiter"), conf.limitsConfigReloadTimer)
+	if conf.maxPendingGrpcWriteRequests > 0 {
+		level.Info(logger).Log("msg", "set max pending gRPC write request in limiter", "max_pending_requests", conf.maxPendingGrpcWriteRequests)
+	}
+	limiter, err := receive.NewLimiterWithOptions(
+		conf.writeLimitsConfig,
+		reg,
+		receiveMode,
+		log.With(logger, "component", "receive-limiter"),
+		conf.limitsConfigReloadTimer,
+		receive.LimiterOptions{
+			MaxPendingRequests: int32(conf.maxPendingGrpcWriteRequests),
+		},
+	)
 	if err != nil {
 		return errors.Wrap(err, "creating limiter")
 	}
@@ -408,6 +420,7 @@ func runReceive(
 			store.LazyRetrieval,
 			options...,
 		)
+
 		mts := store.NewLimitedStoreServer(store.NewInstrumentedStoreServer(reg, proxy), reg, conf.storeRateLimits)
 		rw := store.ReadWriteTSDBStore{
 			StoreServer:          mts,
@@ -974,6 +987,7 @@ type receiveConfig struct {
 	topMetricsMinimumCardinality  uint64
 	topMetricsUpdateInterval      time.Duration
 	matcherConverterCacheCapacity int
+	maxPendingGrpcWriteRequests   int
 
 	featureList *[]string
 }
@@ -1138,6 +1152,8 @@ func (rc *receiveConfig) registerFlag(cmd extkingpin.FlagClause) {
 		Default("5m").DurationVar(&rc.topMetricsUpdateInterval)
 	cmd.Flag("receive.store-matcher-converter-cache-capacity", "The number of label matchers to cache in the matcher converter for the Store API. Set to 0 to disable to cache. Default is 0.").
 		Default("0").IntVar(&rc.matcherConverterCacheCapacity)
+	cmd.Flag("receive.max-pending-grcp-write-requests", "Reject right away gRPC write requests when this number of requests are pending. Value 0 disables this feature.").
+		Default("0").IntVar(&rc.maxPendingGrpcWriteRequests)
 	rc.featureList = cmd.Flag("enable-feature", "Comma separated experimental feature names to enable. The current list of features is "+metricNamesFilter+".").Default("").Strings()
 }
 

pkg/receive/handler.go

@@ -36,7 +36,6 @@ import (
 	"github.com/prometheus/prometheus/tsdb"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
-	"go.uber.org/atomic"
 	"golang.org/x/exp/slices"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
@@ -142,9 +141,6 @@ type Handler struct {
 	writeTimeseriesTotal *prometheus.HistogramVec
 	writeE2eLatency      *prometheus.HistogramVec
 
-	pendingWriteRequests        prometheus.Gauge
-	pendingWriteRequestsCounter atomic.Int32
-
 	Limiter *Limiter
 }
 
@@ -235,12 +231,6 @@ func NewHandler(logger log.Logger, o *Options) *Handler {
 				Buckets:   []float64{1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 300, 600, 900, 1200, 1800, 3600},
 			}, []string{"code", "tenant", "rollup"},
 		),
-		pendingWriteRequests: promauto.With(registerer).NewGauge(
-			prometheus.GaugeOpts{
-				Name: "thanos_receive_pending_write_requests",
-				Help: "The number of pending write requests.",
-			},
-		),
 	}
 
 	h.forwardRequests.WithLabelValues(labelSuccess)
@@ -1083,12 +1073,15 @@ func quorumReached(successes []int, successThreshold int) bool {
 
 // RemoteWrite implements the gRPC remote write handler for storepb.WriteableStore.
 func (h *Handler) RemoteWrite(ctx context.Context, r *storepb.WriteRequest) (*storepb.WriteResponse, error) {
+	if h.Limiter.ShouldRejectNewRequest() {
+		return nil, status.Error(codes.ResourceExhausted, "too many pending write requests")
+	}
+	// NB: ShouldRejectNewRequest() increments the number of pending requests only when it returns false.
+	defer h.Limiter.DecrementPendingRequests()
+
 	span, ctx := tracing.StartSpan(ctx, "receive_grpc")
 	defer span.Finish()
 
-	h.pendingWriteRequests.Set(float64(h.pendingWriteRequestsCounter.Add(1)))
-	defer h.pendingWriteRequestsCounter.Add(-1)
-
 	_, err := h.handleRequest(ctx, uint64(r.Replica), r.Tenant, &prompb.WriteRequest{Timeseries: r.Timeseries})
 	if err != nil {
 		level.Debug(h.logger).Log("msg", "failed to handle request", "err", err)

pkg/receive/limiter.go

@@ -18,6 +18,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/thanos-io/thanos/pkg/extprom"
 	"github.com/thanos-io/thanos/pkg/gate"
+
+	"go.uber.org/atomic"
 )
 
 // Limiter is responsible for managing the configuration and initialization of
@@ -35,6 +37,19 @@ type Limiter struct {
 	configReloadFailedCounter prometheus.Counter
 	receiverMode              ReceiverMode
 	configReloadTimer         time.Duration
+
+	// Reject a request if this limit is reached.
+	// This filed is set at the instance creation and never changes afterwards.
+	// So it's safe to read it without a lock.
+	maxPendingRequests        int32
+	maxPendingRequestLimitHit prometheus.Counter
+	pendingRequests           atomic.Int32
+	pendingRequestsGauge      prometheus.Gauge
+}
+
+type LimiterOptions struct {
+	// Value 0 disables the max pending request limiting hehavior.
+	MaxPendingRequests int32
 }
 
 // headSeriesLimiter encompasses active/head series limiting logic.
@@ -62,16 +77,50 @@ func (l *Limiter) HeadSeriesLimiter() headSeriesLimiter {
 	return l.headSeriesLimiter
 }
 
+func (l *Limiter) ShouldRejectNewRequest() bool {
+	// maxPendingRequests doesn't change once set when a limiter instance is created.
+	// So, it's safe to read it without a lock.
+	if l.maxPendingRequests > 0 && l.pendingRequests.Load() >= l.maxPendingRequests {
+		if l.maxPendingRequestLimitHit != nil {
+			l.maxPendingRequestLimitHit.Inc()
+		}
+		return true
+	}
+	newValue := l.pendingRequests.Add(1)
+	if l.pendingRequestsGauge != nil {
+		l.pendingRequestsGauge.Set(float64(newValue))
+	}
+	return false
+}
+
+func (l *Limiter) DecrementPendingRequests() {
+	newValue := l.pendingRequests.Add(-1)
+	if l.pendingRequestsGauge != nil {
+		l.pendingRequestsGauge.Set(float64(newValue))
+	}
+}
+
 // NewLimiter creates a new *Limiter given a configuration and prometheus
 // registerer.
 func NewLimiter(configFile fileContent, reg prometheus.Registerer, r ReceiverMode, logger log.Logger, configReloadTimer time.Duration) (*Limiter, error) {
+	return NewLimiterWithOptions(configFile, reg, r, logger, configReloadTimer, LimiterOptions{})
+}
+
+func NewLimiterWithOptions(
+	configFile fileContent,
+	reg prometheus.Registerer,
+	r ReceiverMode,
+	logger log.Logger,
+	configReloadTimer time.Duration,
+	opts LimiterOptions) (*Limiter, error) {
 	limiter := &Limiter{
-		writeGate:         gate.NewNoop(),
-		requestLimiter:    &noopRequestLimiter{},
-		headSeriesLimiter: NewNopSeriesLimit(),
-		logger:            logger,
-		receiverMode:      r,
-		configReloadTimer: configReloadTimer,
+		writeGate:          gate.NewNoop(),
+		requestLimiter:     &noopRequestLimiter{},
+		headSeriesLimiter:  NewNopSeriesLimit(),
+		logger:             logger,
+		receiverMode:       r,
+		configReloadTimer:  configReloadTimer,
+		maxPendingRequests: opts.MaxPendingRequests,
 	}
 
 	if reg != nil {
@@ -92,6 +141,26 @@ func NewLimiter(configFile fileContent, reg prometheus.Registerer, r ReceiverMod
 				Help:      "How many times the limit configuration failed to reload.",
 			},
 		)
+		limiter.configReloadFailedCounter = promauto.With(limiter.registerer).NewCounter(
+			prometheus.CounterOpts{
+				Namespace: "thanos",
+				Subsystem: "receive",
+				Name:      "limits_config_reload_err_total",
+				Help:      "How many times the limit configuration failed to reload.",
+			},
+		)
+		limiter.maxPendingRequestLimitHit = promauto.With(limiter.registerer).NewCounter(
+			prometheus.CounterOpts{
+				Name: "thanos_receive_max_pending_write_request_limit_hit_total",
+				Help: "Number of times the max pending write request limit was hit",
+			},
+		)
+		limiter.pendingRequestsGauge = promauto.With(limiter.registerer).NewGauge(
+			prometheus.GaugeOpts{
+				Name: "thanos_receive_pending_write_requests",
+				Help: "Number of pending write requests",
+			},
+		)
 	}
 
 	if configFile == nil {

pkg/store/limiter.go

@@ -11,6 +11,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"go.uber.org/atomic"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 
 	"github.com/thanos-io/thanos/pkg/extkingpin"
 	"github.com/thanos-io/thanos/pkg/store/storepb"
@@ -108,11 +110,14 @@ func NewBytesLimiterFactory(limit units.Base2Bytes) BytesLimiterFactory {
 type SeriesSelectLimits struct {
 	SeriesPerRequest  uint64
 	SamplesPerRequest uint64
+	PendingRequests   int32
 }
 
 func (l *SeriesSelectLimits) RegisterFlags(cmd extkingpin.FlagClause) {
 	cmd.Flag("store.limits.request-series", "The maximum series allowed for a single Series request. The Series call fails if this limit is exceeded. 0 means no limit.").Default("0").Uint64Var(&l.SeriesPerRequest)
 	cmd.Flag("store.limits.request-samples", "The maximum samples allowed for a single Series request, The Series call fails if this limit is exceeded. 0 means no limit. NOTE: For efficiency the limit is internally implemented as 'chunks limit' considering each chunk contains a maximum of 120 samples.").Default("0").Uint64Var(&l.SamplesPerRequest)
+	cmd.Flag("store.limits.pending-requests", "Reject gRPC series requests right away when this number of requests are pending. Value 0 disables this feature.").
+		Default("0").Int32Var(&l.PendingRequests)
 }
 
 var _ storepb.StoreServer = &limitedStoreServer{}
@@ -123,6 +128,13 @@ type limitedStoreServer struct {
 	newSeriesLimiter      SeriesLimiterFactory
 	newSamplesLimiter     ChunksLimiterFactory
 	failedRequestsCounter *prometheus.CounterVec
+
+	// This is a read-only field once it's set.
+	// Value 0 disables the feature.
+	maxPendingRequests        int32
+	pendingRequests           atomic.Int32
+	maxPendingRequestLimitHit prometheus.Counter
+	pendingRequestsGauge      prometheus.Gauge
 }
 
 // NewLimitedStoreServer creates a new limitedStoreServer.
@@ -135,10 +147,25 @@ func NewLimitedStoreServer(store storepb.StoreServer, reg prometheus.Registerer,
 			Name: "thanos_store_selects_dropped_total",
 			Help: "Number of select queries that were dropped due to configured limits.",
 		}, []string{"reason"}),
+		pendingRequestsGauge: promauto.With(reg).NewGauge(prometheus.GaugeOpts{
+			Name: "thanos_store_server_pending_series_requests",
+			Help: "Number of pending series requests",
+		}),
+		maxPendingRequestLimitHit: promauto.With(reg).NewCounter(prometheus.CounterOpts{
+			Name: "thanos_store_server_hit_max_pending_series_requests_total",
+			Help: "Number of pending series requests that hit the max pending request limit",
+		}),
+		maxPendingRequests: selectLimits.PendingRequests,
 	}
 }
 
 func (s *limitedStoreServer) Series(req *storepb.SeriesRequest, srv storepb.Store_SeriesServer) error {
+	if s.maxPendingRequests > 0 && s.pendingRequests.Load() >= s.maxPendingRequests {
+		return status.Error(codes.ResourceExhausted, "too many pending series requests")
+	}
+	s.pendingRequestsGauge.Set(float64(s.pendingRequests.Add(1)))
+	defer s.pendingRequests.Add(-1)
+
 	seriesLimiter := s.newSeriesLimiter(s.failedRequestsCounter.WithLabelValues("series"))
 	chunksLimiter := s.newSamplesLimiter(s.failedRequestsCounter.WithLabelValues("chunks"))
 	limitedSrv := newLimitedServer(srv, seriesLimiter, chunksLimiter)

pkg/store/telemetry.go

@@ -11,8 +11,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 
 	"github.com/thanos-io/thanos/pkg/store/storepb"
-
-	"go.uber.org/atomic"
 )
 
 // seriesStatsAggregator aggregates results from fanned-out queries into a histogram given their
@@ -157,12 +155,8 @@ type instrumentedStoreServer struct {
 	storepb.StoreServer
 	seriesRequested prometheus.Histogram
 	chunksRequested prometheus.Histogram
-
-	pendingRequests        prometheus.Gauge
-	pendingRequestsCounter atomic.Int32
 }
 
-// NewInstrumentedStoreServer creates a new instrumentedStoreServer.
 func NewInstrumentedStoreServer(reg prometheus.Registerer, store storepb.StoreServer) storepb.StoreServer {
 	return &instrumentedStoreServer{
 		StoreServer: store,
@@ -176,17 +170,11 @@ func NewInstrumentedStoreServer(reg prometheus.Registerer, store storepb.StoreSe
 			Help:    "Number of requested chunks for Series calls",
 			Buckets: []float64{1, 100, 1000, 10000, 100000, 10000000, 100000000, 1000000000},
 		}),
-		pendingRequests: promauto.With(reg).NewGauge(prometheus.GaugeOpts{
-			Name: "thanos_store_server_pending_series_requests",
-			Help: "Number of pending series requests",
-		}),
 	}
 }
 
 func (s *instrumentedStoreServer) Series(req *storepb.SeriesRequest, srv storepb.Store_SeriesServer) error {
 	instrumented := newInstrumentedServer(srv)
-	s.pendingRequests.Set(float64(s.pendingRequestsCounter.Add(1)))
-	defer s.pendingRequestsCounter.Add(-1)
 
 	if err := s.StoreServer.Series(req, instrumented); err != nil {
 		return err