fix: Fix missing series in monolithic mode (#17067)

In monolithic mode, unlike other API endpoints (query/labels/...), the series endpoint did not retrieve data from storage for the time window between end of `index_cache_validity` and `query_store_max_look_back_period`, and therefore missing series in the response.

pkg/ingester/flush_test.go

@@ -509,6 +509,10 @@ func (s *testStore) Volume(_ context.Context, _ string, _, _ model.Time, _ int32
 	return &logproto.VolumeResponse{}, nil
 }
 
+func (s *testStore) Series(_ context.Context, _ logql.SelectLogParams) ([]logproto.SeriesIdentifier, error) {
+	return nil, nil
+}
+
 func pushTestSamples(t *testing.T, ing logproto.PusherServer) map[string][]logproto.Stream {
 	userIDs := []string{"1", "2", "3"}
 

pkg/ingester/ingester.go

@@ -1356,7 +1356,48 @@ func (i *Ingester) series(ctx context.Context, req *logproto.SeriesRequest) (*lo
 	if err != nil {
 		return nil, err
 	}
-	return instance.Series(ctx, req)
+
+	resp, err := instance.Series(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	if start, end, ok := buildStoreRequest(i.cfg, req.Start, req.End, time.Now()); ok {
+		var storeSeries []logproto.SeriesIdentifier
+		var parsed syntax.Expr
+
+		groups := []string{""}
+		if len(req.Groups) != 0 {
+			groups = req.Groups
+		}
+
+		for _, group := range groups {
+			if group != "" {
+				parsed, err = syntax.ParseExpr(group)
+				if err != nil {
+					return nil, err
+				}
+			}
+			storeSeries, err = i.store.SelectSeries(ctx, logql.SelectLogParams{
+				QueryRequest: &logproto.QueryRequest{
+					Selector:  group,
+					Limit:     1,
+					Start:     start,
+					End:       end,
+					Direction: logproto.FORWARD,
+					Shards:    req.Shards,
+					Plan: &plan.QueryPlan{
+						AST: parsed,
+					},
+				},
+			})
+			if err != nil {
+				return nil, err
+			}
+			resp.Series = append(resp.Series, storeSeries...)
+		}
+	}
+	return resp, nil
 }
 
 func (i *Ingester) GetStats(ctx context.Context, req *logproto.IndexStatsRequest) (*logproto.IndexStatsResponse, error) {

pkg/ingester/ingester_test.go

@@ -51,6 +51,7 @@ import (
 	"github.com/grafana/loki/v3/pkg/storage/stores/index/stats"
 	"github.com/grafana/loki/v3/pkg/storage/stores/shipper/indexshipper/tsdb/sharding"
 	"github.com/grafana/loki/v3/pkg/util/constants"
+	"github.com/grafana/loki/v3/pkg/util/marshal"
 	"github.com/grafana/loki/v3/pkg/validation"
 )
 
@@ -458,7 +459,14 @@ func (s *mockStore) SelectSamples(_ context.Context, _ logql.SelectSampleParams)
 	return nil, nil
 }
 
-func (s *mockStore) SelectSeries(_ context.Context, _ logql.SelectLogParams) ([]logproto.SeriesIdentifier, error) {
+func (s *mockStore) SelectSeries(_ context.Context, req logql.SelectLogParams) ([]logproto.SeriesIdentifier, error) {
+	// NOTE: If the time range includes one hour before the current time, the return value is returned.
+	thresTime := time.Now().Add(-1 * time.Hour)
+	if !thresTime.Before(req.Start) && !thresTime.After(req.End) {
+		return []logproto.SeriesIdentifier{
+			{Labels: mustParseLabels(`{a="11",c="33"}`)},
+		}, nil
+	}
 	return nil, nil
 }
 
@@ -1390,6 +1398,141 @@ func TestVolume(t *testing.T) {
 	})
 }
 
+func Test_Series(t *testing.T) {
+	ingesterConfig := defaultIngesterTestConfig(t)
+	limits, err := validation.NewOverrides(defaultLimitsTestConfig(), nil)
+	require.NoError(t, err)
+
+	store := &mockStore{
+		chunks: map[string][]chunk.Chunk{},
+	}
+
+	mockRing := mockReadRingWithOneActiveIngester()
+
+	i, err := New(ingesterConfig, client.Config{}, store, limits, runtime.DefaultTenantConfigs(), nil, writefailures.Cfg{}, constants.Loki, log.NewNopLogger(), nil, mockRing, nil)
+	require.NoError(t, err)
+	defer services.StopAndAwaitTerminated(context.Background(), i) //nolint:errcheck
+
+	ctx := user.InjectOrgID(context.Background(), "test")
+	t.Run("only in-memory series", func(t *testing.T) {
+		i.cfg.QueryStore = false
+		req := logproto.PushRequest{
+			Streams: []logproto.Stream{
+				{
+					Labels: `{a="11",b="22"}`,
+				},
+				{
+					Labels: `{a="11",c="33"}`,
+				},
+			},
+		}
+		for i := 0; i < 10; i++ {
+			req.Streams[0].Entries = append(req.Streams[0].Entries, logproto.Entry{
+				Timestamp: time.Unix(0, 0),
+				Line:      fmt.Sprintf("line %d", i),
+			})
+			req.Streams[1].Entries = append(req.Streams[1].Entries, logproto.Entry{
+				Timestamp: time.Unix(0, 0),
+				Line:      fmt.Sprintf("line %d", i),
+			})
+		}
+		_, err = i.Push(ctx, &req)
+		require.NoError(t, err)
+
+		res, err := i.Series(ctx, &logproto.SeriesRequest{
+			Start:  time.Unix(0, 0),
+			End:    time.Unix(1, 0),
+			Groups: []string{`{a="11"}`},
+		})
+
+		expectedSeries := []logproto.SeriesIdentifier{
+			{Labels: mustParseLabels(`{a="11", b="22"}`)},
+			{Labels: mustParseLabels(`{a="11", c="33"}`)},
+		}
+		// ignore order
+		sortLabels(res.Series)
+		sortLabels(expectedSeries)
+
+		require.NoError(t, err)
+		require.ElementsMatch(t, expectedSeries, res.Series)
+	})
+
+	t.Run("in-memory and storage (If data exists in storage)", func(t *testing.T) {
+		i.cfg.QueryStore = true
+		req := logproto.PushRequest{
+			Streams: []logproto.Stream{
+				{
+					Labels: `{a="11",b="22"}`,
+				},
+			},
+		}
+		for i := 0; i < 10; i++ {
+			req.Streams[0].Entries = append(req.Streams[0].Entries, logproto.Entry{
+				Timestamp: time.Now(),
+				Line:      fmt.Sprintf("line %d", i),
+			},
+			)
+		}
+
+		_, err = i.Push(ctx, &req)
+		require.NoError(t, err)
+
+		res, err := i.Series(ctx, &logproto.SeriesRequest{
+			Start:  time.Now().Add(-20 * time.Hour),
+			End:    time.Now(),
+			Groups: []string{`{a="11"}`},
+		})
+
+		expectedSeries := []logproto.SeriesIdentifier{
+			{Labels: mustParseLabels(`{a="11", b="22"}`)},
+			{Labels: mustParseLabels(`{a="11", c="33"}`)},
+		}
+		// ignore order
+		sortLabels(res.Series)
+		sortLabels(expectedSeries)
+
+		require.NoError(t, err)
+		require.ElementsMatch(t, expectedSeries, res.Series)
+	})
+
+	t.Run("in-memory and storage (If no data exists in storage)", func(t *testing.T) {
+		i.cfg.QueryStore = true
+		req := logproto.PushRequest{
+			Streams: []logproto.Stream{
+				{
+					Labels: `{a="11",b="22"}`,
+				},
+			},
+		}
+		for i := 0; i < 10; i++ {
+			req.Streams[0].Entries = append(req.Streams[0].Entries, logproto.Entry{
+				Timestamp: time.Now(),
+				Line:      fmt.Sprintf("line %d", i),
+			},
+			)
+		}
+
+		_, err = i.Push(ctx, &req)
+		require.NoError(t, err)
+
+		res, err := i.Series(ctx, &logproto.SeriesRequest{
+			Start:  time.Now().Add(-30 * time.Minute),
+			End:    time.Now(),
+			Groups: []string{`{a="11"}`},
+		})
+
+		expectedSeries := []logproto.SeriesIdentifier{
+			{Labels: mustParseLabels(`{a="11", b="22"}`)},
+		}
+		// ignore order
+		sortLabels(res.Series)
+		sortLabels(expectedSeries)
+
+		require.NoError(t, err)
+		require.ElementsMatch(t, expectedSeries, res.Series)
+	})
+}
+
 type ingesterClient struct {
 	logproto.PusherClient
 	logproto.QuerierClient
@@ -1662,3 +1805,24 @@ func TestUpdateOwnedStreams(t *testing.T) {
 	ownedStreams := i.instances["test"].ownedStreamsSvc.getOwnedStreamCount()
 	require.Equal(t, 8, ownedStreams)
 }
+
+func mustParseLabels(s string) []logproto.SeriesIdentifier_LabelsEntry {
+	l, err := marshal.NewLabelSet(s)
+	if err != nil {
+		panic(fmt.Sprintf("Failed to parse %s", s))
+	}
+
+	result := make([]logproto.SeriesIdentifier_LabelsEntry, 0, len(l))
+	for k, v := range l {
+		result = append(result, logproto.SeriesIdentifier_LabelsEntry{Key: k, Value: v})
+	}
+	return result
+}
+
+func sortLabels(series []logproto.SeriesIdentifier) {
+	for i := range series {
+		sort.SliceStable(series[i].Labels, func(j, k int) bool {
+			return series[i].Labels[j].Key < series[i].Labels[k].Key
+		})
+	}
+}