Expanded Postings Cache can cache results without the nearly created series under high load.

.github/workflows/test-build-deploy.yml

@@ -61,6 +61,24 @@ jobs:
           ln -s $GITHUB_WORKSPACE/* /go/src/github.com/cortexproject/cortex
       - name: Run Tests
         run: make BUILD_IN_CONTAINER=false test
+  test-no-race:
+    runs-on: ubuntu-20.04
+    container:
+      image: quay.io/cortexproject/build-image:master-0ddced051
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Setup Git safe.directory
+        run: |
+          echo "this step is needed because when running in container, actions/checkout does not set safe.directory effectively."
+          echo "See https://github.com/actions/runner/issues/2033. We should use --system instead of --global"
+          git config --system --add safe.directory $GITHUB_WORKSPACE
+      - name: Sym Link Expected Path to Workspace
+        run: |
+          mkdir -p /go/src/github.com/cortexproject/cortex
+          ln -s $GITHUB_WORKSPACE/* /go/src/github.com/cortexproject/cortex
+      - name: Run Tests
+        run: make BUILD_IN_CONTAINER=false test-no-race
 
   security:
     name: CodeQL

Makefile

@@ -218,6 +218,9 @@ lint:
 test:
 	go test -tags netgo -timeout 30m -race -count 1 ./...
 
+test-no-race:
+	go test -tags netgo -timeout 30m -count 1 ./...
+
 cover:
 	$(eval COVERDIR := $(shell mktemp -d coverage.XXXXXXXXXX))
 	$(eval COVERFILE := $(shell mktemp $(COVERDIR)/unit.XXXXXXXXXX))

pkg/ingester/ingester.go

@@ -1204,6 +1204,8 @@ func (i *Ingester) Push(ctx context.Context, req *cortexpb.WriteRequest) (*corte
 
 	// Walk the samples, appending them to the users database
 	app := db.Appender(ctx).(extendedAppender)
+	var newSeries []labels.Labels
+
 	for _, ts := range req.Timeseries {
 		// The labels must be sorted (in our case, it's guaranteed a write request
 		// has sorted labels once hit the ingester).
@@ -1233,6 +1235,10 @@ func (i *Ingester) Push(ctx context.Context, req *cortexpb.WriteRequest) (*corte
 				copiedLabels = cortexpb.FromLabelAdaptersToLabelsWithCopy(ts.Labels)
 				// Retain the reference in case there are multiple samples for the series.
 				if ref, err = app.Append(0, copiedLabels, s.TimestampMs, s.Value); err == nil {
+					// Keep track of what series needs to be expired on the postings cache
+					if db.postingCache != nil {
+						newSeries = append(newSeries, copiedLabels)
+					}
 					succeededSamplesCount++
 					continue
 				}
@@ -1274,6 +1280,10 @@ func (i *Ingester) Push(ctx context.Context, req *cortexpb.WriteRequest) (*corte
 					// Copy the label set because both TSDB and the active series tracker may retain it.
 					copiedLabels = cortexpb.FromLabelAdaptersToLabelsWithCopy(ts.Labels)
 					if ref, err = app.AppendHistogram(0, copiedLabels, hp.TimestampMs, h, fh); err == nil {
+						// Keep track of what series needs to be expired on the postings cache
+						if db.postingCache != nil {
+							newSeries = append(newSeries, copiedLabels)
+						}
 						succeededHistogramsCount++
 						continue
 					}
@@ -1342,6 +1352,17 @@ func (i *Ingester) Push(ctx context.Context, req *cortexpb.WriteRequest) (*corte
 	if err := app.Commit(); err != nil {
 		return nil, wrapWithUser(err, userID)
 	}
+
+	// This is a workaround of https://github.com/prometheus/prometheus/pull/15579
+	// Calling expire here may result in the series names being expired multiple times,
+	// as there may be multiple Push operations concurrently for the same new timeseries.
+	// TODO: alanprot remove this when/if the PR is merged
+	if db.postingCache != nil {
+		for _, s := range newSeries {
+			db.postingCache.ExpireSeries(s)
+		}
+	}
+
 	i.TSDBState.appenderCommitDuration.Observe(time.Since(startCommit).Seconds())
 
 	// If only invalid samples or histograms are pushed, don't change "last update", as TSDB was not modified.

pkg/ingester/ingester_no_race_test.go

@@ -0,0 +1,90 @@
+//go:build !race
+
+package ingester
+
+import (
+	"context"
+	"fmt"
+	"math"
+	"strconv"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/prometheus/model/labels"
+	"github.com/stretchr/testify/require"
+	"github.com/weaveworks/common/user"
+
+	"github.com/cortexproject/cortex/pkg/cortexpb"
+	"github.com/cortexproject/cortex/pkg/ingester/client"
+	"github.com/cortexproject/cortex/pkg/ring"
+	"github.com/cortexproject/cortex/pkg/util/services"
+	"github.com/cortexproject/cortex/pkg/util/test"
+)
+
+// Running this test without race check as there is a known prometheus race condition.
+// See https://github.com/prometheus/prometheus/pull/15141 and https://github.com/prometheus/prometheus/pull/15316
+func TestExpandedCachePostings_Race(t *testing.T) {
+	cfg := defaultIngesterTestConfig(t)
+	cfg.BlocksStorageConfig.TSDB.BlockRanges = []time.Duration{2 * time.Hour}
+	cfg.LifecyclerConfig.JoinAfter = 0
+	cfg.BlocksStorageConfig.TSDB.PostingsCache.Head.Enabled = true
+
+	r := prometheus.NewRegistry()
+	i, err := prepareIngesterWithBlocksStorage(t, cfg, r)
+	require.NoError(t, err)
+	require.NoError(t, services.StartAndAwaitRunning(context.Background(), i))
+	defer services.StopAndAwaitTerminated(context.Background(), i) //nolint:errcheck
+
+	// Wait until the ingester is ACTIVE
+	test.Poll(t, 100*time.Millisecond, ring.ACTIVE, func() interface{} {
+		return i.lifecycler.GetState()
+	})
+
+	ctx := user.InjectOrgID(context.Background(), "test")
+
+	wg := sync.WaitGroup{}
+	labelNames := 100
+	seriesPerLabelName := 200
+
+	for j := 0; j < labelNames; j++ {
+		metricName := fmt.Sprintf("test_metric_%d", j)
+		wg.Add(seriesPerLabelName * 2)
+		for k := 0; k < seriesPerLabelName; k++ {
+			go func() {
+				defer wg.Done()
+				_, err := i.Push(ctx, cortexpb.ToWriteRequest(
+					[]labels.Labels{labels.FromStrings(labels.MetricName, metricName, "k", strconv.Itoa(k))},
+					[]cortexpb.Sample{{Value: 1, TimestampMs: 9}}, nil, nil, cortexpb.API))
+				require.NoError(t, err)
+			}()
+
+			go func() {
+				defer wg.Done()
+				err := i.QueryStream(&client.QueryRequest{
+					StartTimestampMs: 0,
+					EndTimestampMs:   math.MaxInt64,
+					Matchers:         []*client.LabelMatcher{{Type: client.EQUAL, Name: labels.MetricName, Value: metricName}},
+				}, &mockQueryStreamServer{ctx: ctx})
+				require.NoError(t, err)
+			}()
+		}
+
+		wg.Wait()
+
+		s := &mockQueryStreamServer{ctx: ctx}
+		err = i.QueryStream(&client.QueryRequest{
+			StartTimestampMs: 0,
+			EndTimestampMs:   math.MaxInt64,
+			Matchers:         []*client.LabelMatcher{{Type: client.EQUAL, Name: labels.MetricName, Value: metricName}},
+		}, s)
+		require.NoError(t, err)
+
+		set, err := seriesSetFromResponseStream(s)
+		require.NoError(t, err)
+		res, err := client.MatrixFromSeriesSet(set)
+		require.NoError(t, err)
+		require.Equal(t, seriesPerLabelName, res.Len())
+	}
+}