fix(v2): make segment upload hedging limiter respect context

Author: kolesnikovae

pkg/experiment/ingester/segment.go

@@ -22,6 +22,7 @@ import (
 	"github.com/opentracing/opentracing-go"
 	"github.com/thanos-io/objstore"
 	"golang.org/x/exp/maps"
+	"golang.org/x/time/rate"
 
 	profilev1 "github.com/grafana/pyroscope/api/gen/proto/go/google/v1"
 	metastorev1 "github.com/grafana/pyroscope/api/gen/proto/go/metastore/v1"
@@ -51,9 +52,9 @@ type segmentsWriter struct {
 	ctx    context.Context
 	cancel context.CancelFunc
 
-	metrics      *segmentMetrics
-	headMetrics  *memdb.HeadMetrics
-	retryLimiter *retry.RateLimiter
+	metrics             *segmentMetrics
+	headMetrics         *memdb.HeadMetrics
+	hedgedUploadLimiter *rate.Limiter
 }
 
 type shard struct {
@@ -137,7 +138,7 @@ func newSegmentWriter(l log.Logger, metrics *segmentMetrics, hm *memdb.HeadMetri
 		shards:      make(map[shardKey]*shard),
 		metastore:   metastoreClient,
 	}
-	sw.retryLimiter = retry.NewRateLimiter(sw.config.UploadHedgeRateMax, int(sw.config.UploadHedgeRateBurst))
+	sw.hedgedUploadLimiter = rate.NewLimiter(rate.Limit(sw.config.UploadHedgeRateMax), int(sw.config.UploadHedgeRateBurst))
 	sw.ctx, sw.cancel = context.WithCancel(context.Background())
 	flushWorkers := runtime.GOMAXPROCS(-1)
 	if config.FlushConcurrency > 0 {
@@ -605,39 +606,38 @@ func (sw *segmentsWriter) uploadBlock(ctx context.Context, blockData []byte, met
 	// if the request is not completed within a certain time, we trigger
 	// a second upload attempt. Upload errors are retried explicitly and
 	// are included into the call duration.
-	uploadWithRetry := func(ctx context.Context, hedge bool) (any, error) {
-		retryConfig := backoff.Config{
-			MinBackoff: sw.config.UploadMinBackoff,
-			MaxBackoff: sw.config.UploadMaxBackoff,
-			MaxRetries: sw.config.UploadMaxRetries,
-		}
-		var attemptErr error
-		if hedge {
-			// Hedged requests are not retried.
-			retryConfig.MaxRetries = 1
-			attemptStart := time.Now()
-			defer func() {
-				sw.metrics.segmentHedgedUploadDuration.
-					WithLabelValues(statusLabelValue(attemptErr)).
-					Observe(time.Since(attemptStart).Seconds())
-			}()
-		}
-		// Retry on all errors.
-		retries := backoff.New(ctx, retryConfig)
-		for retries.Ongoing() && ctx.Err() == nil {
-			if attemptErr = sw.bucket.Upload(ctx, path, bytes.NewReader(blockData)); attemptErr == nil {
-				break
-			}
-			retries.Wait()
-		}
-		return nil, attemptErr
-	}
-
 	hedgedUpload := retry.Hedged[any]{
-		Call:      uploadWithRetry,
-		Trigger:   time.After(sw.config.UploadHedgeAfter),
-		Throttler: sw.retryLimiter,
-		FailFast:  false,
+		Trigger: time.After(sw.config.UploadHedgeAfter),
+		Call: func(ctx context.Context, hedge bool) (any, error) {
+			retryConfig := backoff.Config{
+				MinBackoff: sw.config.UploadMinBackoff,
+				MaxBackoff: sw.config.UploadMaxBackoff,
+				MaxRetries: sw.config.UploadMaxRetries,
+			}
+			var attemptErr error
+			if hedge {
+				if limitErr := sw.hedgedUploadLimiter.Wait(ctx); limitErr != nil {
+					return nil, limitErr
+				}
+				// Hedged requests are not retried.
+				retryConfig.MaxRetries = 0
+				attemptStart := time.Now()
+				defer func() {
+					sw.metrics.segmentHedgedUploadDuration.
+						WithLabelValues(statusLabelValue(attemptErr)).
+						Observe(time.Since(attemptStart).Seconds())
+				}()
+			}
+			// Retry on all errors.
+			retries := backoff.New(ctx, retryConfig)
+			for retries.Ongoing() {
+				if attemptErr = sw.bucket.Upload(ctx, path, bytes.NewReader(blockData)); attemptErr == nil {
+					break
+				}
+				retries.Wait()
+			}
+			return nil, attemptErr
+		},
 	}
 
 	if _, err = hedgedUpload.Do(ctx); err != nil {

pkg/experiment/ingester/segment_test.go

@@ -3,6 +3,8 @@ package ingester
 import (
 	"bytes"
 	"context"
+	"errors"
+	"flag"
 	"fmt"
 	"io"
 	"math/rand"
@@ -14,21 +16,21 @@ import (
 	"testing"
 	"time"
 
-	"github.com/grafana/pyroscope/pkg/experiment/block/metadata"
-
 	gprofile "github.com/google/pprof/profile"
 	"github.com/grafana/dskit/flagext"
 	model2 "github.com/prometheus/common/model"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/time/rate"
 
 	profilev1 "github.com/grafana/pyroscope/api/gen/proto/go/google/v1"
 	ingesterv1 "github.com/grafana/pyroscope/api/gen/proto/go/ingester/v1"
 	"github.com/grafana/pyroscope/api/gen/proto/go/ingester/v1/ingesterv1connect"
 	metastorev1 "github.com/grafana/pyroscope/api/gen/proto/go/metastore/v1"
 	typesv1 "github.com/grafana/pyroscope/api/gen/proto/go/types/v1"
 	"github.com/grafana/pyroscope/pkg/experiment/block"
+	"github.com/grafana/pyroscope/pkg/experiment/block/metadata"
 	"github.com/grafana/pyroscope/pkg/experiment/ingester/memdb"
 	testutil2 "github.com/grafana/pyroscope/pkg/experiment/ingester/memdb/testutil"
 	"github.com/grafana/pyroscope/pkg/experiment/metastore"
@@ -1004,3 +1006,78 @@ func hasUnsymbolizedLabel(t *testing.T, block *metastorev1.BlockMeta) bool {
 	}
 	return false
 }
+
+type mockBucket struct {
+	*memory.InMemBucket
+	uploads atomic.Int64
+}
+
+func (m *mockBucket) Upload(ctx context.Context, _ string, _ io.Reader) error {
+	m.uploads.Add(1)
+	<-ctx.Done()
+	return ctx.Err()
+}
+
+func TestUploadBlock_HedgedUploadLimiter(t *testing.T) {
+	t.Run("available", func(t *testing.T) {
+		t.Parallel()
+
+		bucket := &mockBucket{InMemBucket: memory.NewInMemBucket()}
+		logger := test.NewTestingLogger(t)
+
+		var config Config
+		config.RegisterFlags(flag.NewFlagSet("test", flag.PanicOnError))
+		config.UploadTimeout = time.Millisecond * 250
+		config.UploadHedgeAfter = time.Millisecond
+		config.UploadHedgeRateMax = 10
+		config.UploadHedgeRateBurst = 10
+		config.UploadMaxRetries = 0
+
+		sw := &segmentsWriter{
+			config:              config,
+			logger:              logger,
+			bucket:              bucket,
+			hedgedUploadLimiter: rate.NewLimiter(rate.Limit(config.UploadHedgeRateMax), int(config.UploadHedgeRateBurst)),
+			metrics:             newSegmentMetrics(nil),
+		}
+
+		// To avoid flakiness: there are no guarantees that the
+		// hedged request is triggered before the upload timeout
+		// expiration.
+		hedgedRequestTriggered := func() bool {
+			bucket.uploads.Store(0)
+			err := sw.uploadBlock(context.Background(), nil, new(metastorev1.BlockMeta), new(segment))
+			return errors.Is(err, context.DeadlineExceeded) && int64(2) == bucket.uploads.Load()
+		}
+
+		require.Eventually(t, hedgedRequestTriggered, time.Second*10, time.Millisecond*50)
+	})
+
+	t.Run("exhausted", func(t *testing.T) {
+		t.Parallel()
+
+		bucket := &mockBucket{InMemBucket: memory.NewInMemBucket()}
+		logger := test.NewTestingLogger(t)
+
+		var config Config
+		config.RegisterFlags(flag.NewFlagSet("test", flag.PanicOnError))
+		config.UploadTimeout = time.Millisecond * 250
+		config.UploadHedgeAfter = time.Millisecond
+		config.UploadHedgeRateMax = 0.1
+		config.UploadHedgeRateBurst = 10
+		config.UploadMaxRetries = 0
+
+		sw := &segmentsWriter{
+			config:              config,
+			logger:              logger,
+			bucket:              bucket,
+			hedgedUploadLimiter: rate.NewLimiter(rate.Limit(config.UploadHedgeRateMax), int(config.UploadHedgeRateBurst)),
+			metrics:             newSegmentMetrics(nil),
+		}
+
+		require.True(t, sw.hedgedUploadLimiter.ReserveN(time.Now(), int(config.UploadHedgeRateBurst)).OK())
+		err := sw.uploadBlock(context.Background(), nil, new(metastorev1.BlockMeta), new(segment))
+		require.ErrorIs(t, err, context.DeadlineExceeded)
+		require.Equal(t, int64(1), bucket.uploads.Load())
+	})
+}

pkg/experiment/ingester/service.go

@@ -75,7 +75,7 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	f.DurationVar(&cfg.UploadMinBackoff, prefix+".upload-retry-min-period", 50*time.Millisecond, "Minimum delay when backing off.")
 	f.DurationVar(&cfg.UploadMaxBackoff, prefix+".upload-retry-max-period", defaultSegmentDuration, "Maximum delay when backing off.")
 	f.DurationVar(&cfg.UploadHedgeAfter, prefix+".upload-hedge-after", defaultSegmentDuration, "Time after which to hedge the upload request.")
-	f.Float64Var(&cfg.UploadHedgeRateMax, prefix+".upload-hedge-rate-max", defaultHedgedRequestMaxRate, "Maximum number of hedged requests per second.")
+	f.Float64Var(&cfg.UploadHedgeRateMax, prefix+".upload-hedge-rate-max", defaultHedgedRequestMaxRate, "Maximum number of hedged requests per second. 0 disables rate limiting.")
 	f.UintVar(&cfg.UploadHedgeRateBurst, prefix+".upload-hedge-rate-burst", defaultHedgedRequestBurst, "Maximum number of hedged requests in a burst.")
 	f.BoolVar(&cfg.MetadataDLQEnabled, prefix+".metadata-dlq-enabled", true, "Enables dead letter queue (DLQ) for metadata. If the metadata update fails, it will be stored and updated asynchronously.")
 	f.DurationVar(&cfg.MetadataUpdateTimeout, prefix+".metadata-update-timeout", 2*time.Second, "Timeout for metadata update requests.")

pkg/util/retry/hedged.go

@@ -26,13 +26,6 @@ type Hedged[T any] struct {
 	//  - the result received first is returned, regardless of anything.
 	//  - if Call fails before the trigger fires, it won't be retried.
 	FailFast bool
-
-	// Throttler executes call retries. Optional.
-	Throttler
-}
-
-type Throttler interface {
-	Run(func())
 }
 
 type Call[T any] func(ctx context.Context, isRetry bool) (T, error)
@@ -76,13 +69,7 @@ func (s Hedged[T]) Do(ctx context.Context) (T, error) {
 	case <-attemptCtx.Done():
 		// Call has returned, or caller cancelled the request.
 	case <-s.Trigger:
-		if s.Throttler != nil {
-			s.Throttler.Run(func() {
-				attempt(true)
-			})
-		} else {
-			attempt(true)
-		}
+		attempt(true)
 	}
 
 	wg.Wait()

pkg/util/retry/hedged_test.go

@@ -3,7 +3,6 @@ package retry
 import (
 	"context"
 	"errors"
-	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -155,50 +154,3 @@ func Test_Hedging(t *testing.T) {
 		})
 	}
 }
-
-func Test_Hedging_Limiter(t *testing.T) {
-	type testCase struct {
-		description string
-		runner      Throttler
-		maxAttempts int64
-	}
-
-	const attempts = 5
-	testCases := []testCase{
-		{
-			description: "zero limit disables retries",
-			runner:      NewLimiter(0),
-			maxAttempts: attempts,
-		},
-		{
-			description: "number of attempts does not exceed the limit",
-			runner:      NewLimiter(2),
-			maxAttempts: attempts + 2,
-		},
-	}
-
-	for _, c := range testCases {
-		c := c
-		t.Run(c.description, func(t *testing.T) {
-			t.Parallel()
-
-			var n int64
-			attempt := Hedged[int]{
-				Throttler: NewLimiter(0),
-				Call: func(context.Context, bool) (int, error) {
-					atomic.AddInt64(&n, 1)
-					<-time.After(time.Millisecond)
-					return 0, nil
-				},
-			}
-
-			for i := 0; i < 5; i++ {
-				_, _ = attempt.Do(context.Background())
-			}
-
-			if n > c.maxAttempts {
-				t.Fatal("number of attempts exceeded")
-			}
-		})
-	}
-}