TSDB: Reintroduce 'quiet zeros' for otel start time handling

model/value/value.go

@@ -26,6 +26,9 @@ const (
 	// complicated values in the future. It is 2 rather than 1 to make
 	// it easier to distinguish from the NormalNaN by a human when debugging.
 	StaleNaN uint64 = 0x7ff0000000000002
+
+	// QuietZeroNaN signals TSDB to add a zero, but do nothing if there is already a value at that timestamp.
+	QuietZeroNaN uint64 = 0x7ff0000000000003
 )
 
 // IsStaleNaN returns true when the provided NaN value is a stale marker.

storage/remote/otlptranslator/prometheusremotewrite/helper.go

@@ -595,9 +595,10 @@ const defaultIntervalForStartTimestamps = int64(300_000)
 // handleStartTime adds a zero sample at startTs only if startTs is within validIntervalForStartTimestamps of the sample timestamp.
 // The reason for doing this is that PRW v1 doesn't support Created Timestamps. After switching to PRW v2's direct CT support,
 // make use of its direct support fort Created Timestamps instead.
+// See https://github.com/prometheus/prometheus/issues/14600 for context.
 // See https://opentelemetry.io/docs/specs/otel/metrics/data-model/#resets-and-gaps to know more about how OTel handles
 // resets for cumulative metrics.
-func (c *PrometheusConverter) handleStartTime(startTs, ts int64, labels []prompb.Label, settings Settings, typ string, value float64, logger *slog.Logger) {
+func (c *PrometheusConverter) handleStartTime(startTs, ts int64, labels []prompb.Label, settings Settings, typ string, val float64, logger *slog.Logger) {
 	if !settings.EnableCreatedTimestampZeroIngestion {
 		return
 	}
@@ -619,10 +620,13 @@ func (c *PrometheusConverter) handleStartTime(startTs, ts int64, labels []prompb
 		return
 	}
 
-	logger.Debug("adding zero value at start_ts", "type", typ, "labels", labelsStringer(labels), "start_ts", startTs, "sample_ts", ts, "sample_value", value)
+	logger.Debug("adding zero value at start_ts", "type", typ, "labels", labelsStringer(labels), "start_ts", startTs, "sample_ts", ts, "sample_value", val)
 
-	// See https://github.com/prometheus/prometheus/issues/14600 for context.
-	c.addSample(&prompb.Sample{Timestamp: startTs}, labels)
+	var createdTimeValue float64
+	if settings.EnableStartTimeQuietZero {
+		createdTimeValue = math.Float64frombits(value.QuietZeroNaN)
+	}
+	c.addSample(&prompb.Sample{Timestamp: startTs, Value: createdTimeValue}, labels)
 }
 
 // handleHistogramStartTime similar to the method above but for native histograms..

storage/remote/otlptranslator/prometheusremotewrite/helper_test.go

@@ -18,9 +18,11 @@ package prometheusremotewrite
 
 import (
 	"context"
+	"math"
 	"testing"
 	"time"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/pdata/pcommon"
@@ -29,7 +31,9 @@ import (
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/common/promslog"
 
+	"github.com/prometheus/prometheus/model/value"
 	"github.com/prometheus/prometheus/prompb"
+	"github.com/prometheus/prometheus/util/testutil"
 )
 
 func TestCreateAttributes(t *testing.T) {
@@ -313,14 +317,14 @@ func TestPrometheusConverter_AddSummaryDataPoints(t *testing.T) {
 					timeSeriesSignature(labels): {
 						Labels: labels,
 						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(nowMinus2m30s)},
+							{Value: math.Float64frombits(value.QuietZeroNaN), Timestamp: convertTimeStamp(nowMinus2m30s)},
 							{Value: 0, Timestamp: convertTimeStamp(nowUnixNano)},
 						},
 					},
 					timeSeriesSignature(sumLabels): {
 						Labels: sumLabels,
 						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(nowMinus2m30s)},
+							{Value: math.Float64frombits(value.QuietZeroNaN), Timestamp: convertTimeStamp(nowMinus2m30s)},
 							{Value: 0, Timestamp: convertTimeStamp(nowUnixNano)},
 						},
 					},
@@ -361,14 +365,14 @@ func TestPrometheusConverter_AddSummaryDataPoints(t *testing.T) {
 					timeSeriesSignature(labels): {
 						Labels: labels,
 						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(nowMinus6m)},
+							{Value: math.Float64frombits(value.QuietZeroNaN), Timestamp: convertTimeStamp(nowMinus6m)},
 							{Value: 0, Timestamp: convertTimeStamp(nowUnixNano)},
 						},
 					},
 					timeSeriesSignature(sumLabels): {
 						Labels: sumLabels,
 						Samples: []prompb.Sample{
-							{Value: 0, Timestamp: convertTimeStamp(nowMinus6m)},
+							{Value: math.Float64frombits(value.QuietZeroNaN), Timestamp: convertTimeStamp(nowMinus6m)},
 							{Value: 0, Timestamp: convertTimeStamp(nowUnixNano)},
 						},
 					},
@@ -474,19 +478,25 @@ func TestPrometheusConverter_AddSummaryDataPoints(t *testing.T) {
 				Settings{
 					ExportCreatedMetric:                        true,
 					EnableCreatedTimestampZeroIngestion:        true,
+					EnableStartTimeQuietZero:                   true,
 					ValidIntervalCreatedTimestampZeroIngestion: tt.overrideValidInterval,
 				},
 				metric.Name(),
 				promslog.NewNopLogger(),
 			)
 			require.NoError(t, err)
 
-			assert.Equal(t, tt.want(), converter.unique)
+			testutil.RequireEqualWithOptions(t, tt.want(), converter.unique, []cmp.Option{cmp.Comparer(equalSamples)})
 			assert.Empty(t, converter.conflicts)
 		})
 	}
 }
 
+func equalSamples(a, b prompb.Sample) bool {
+	// Compare Float64bits so NaN values which are exactly the same will compare equal.
+	return a.Timestamp == b.Timestamp && math.Float64bits(a.Value) == math.Float64bits(b.Value)
+}
+
 func TestPrometheusConverter_AddHistogramDataPoints(t *testing.T) {
 	ts := pcommon.Timestamp(time.Now().UnixNano())
 	tests := []struct {

storage/remote/otlptranslator/prometheusremotewrite/metrics_to_prw.go

@@ -47,6 +47,7 @@ type Settings struct {
 
 	// Mimir specifics.
 	EnableCreatedTimestampZeroIngestion        bool
+	EnableStartTimeQuietZero                   bool
 	ValidIntervalCreatedTimestampZeroIngestion time.Duration
 }
 

tsdb/db_test.go

@@ -105,6 +105,15 @@ func openTestDB(t testing.TB, opts *Options, rngs []int64) (db *DB) {
 	return db
 }
 
+// queryHead is a helper to query the head for a given time range and labelset.
+func queryHead(t testing.TB, head *Head, mint, maxt int64, label labels.Label) (map[string][]chunks.Sample, error) {
+	q, err := NewBlockQuerier(head, mint, maxt)
+	if err != nil {
+		return nil, err
+	}
+	return query(t, q, labels.MustNewMatcher(labels.MatchEqual, label.Name, label.Value)), nil
+}
+
 // query runs a matcher query against the querier and fully expands its data.
 func query(t testing.TB, q storage.Querier, matchers ...*labels.Matcher) map[string][]chunks.Sample {
 	ss := q.Select(context.Background(), false, nil, matchers...)

tsdb/head_append.go

@@ -497,14 +497,18 @@ func (s *memSeries) appendable(t int64, v float64, headMaxt, minValidTime, oooTi
 			if s.lastHistogramValue != nil || s.lastFloatHistogramValue != nil {
 				return false, 0, storage.NewDuplicateHistogramToFloatErr(t, v)
 			}
-			if math.Float64bits(s.lastValue) != math.Float64bits(v) {
+			if math.Float64bits(s.lastValue) != math.Float64bits(v) && math.Float64bits(v) != value.QuietZeroNaN {
 				return false, 0, storage.NewDuplicateFloatErr(t, s.lastValue, v)
 			}
 			// Sample is identical (ts + value) with most current (highest ts) sample in sampleBuf.
 			return false, 0, nil
 		}
 	}
 
+	if math.Float64bits(v) == value.QuietZeroNaN { // Say it's allowed; it will be dropped later in commitSamples.
+		return true, 0, nil
+	}
+
 	// The sample cannot go in the in-order chunk. Check if it can go in the out-of-order chunk.
 	if oooTimeWindow > 0 && t >= headMaxt-oooTimeWindow {
 		return true, headMaxt - t, nil
@@ -1144,6 +1148,8 @@ func (a *headAppender) commitSamples(acc *appenderCommitContext) {
 		switch {
 		case err != nil:
 			// Do nothing here.
+		case oooSample && math.Float64bits(s.V) == value.QuietZeroNaN:
+			// No-op: we don't store quiet zeros out-of-order.
 		case oooSample:
 			// Sample is OOO and OOO handling is enabled
 			// and the delta is within the OOO tolerance.
@@ -1190,6 +1196,9 @@ func (a *headAppender) commitSamples(acc *appenderCommitContext) {
 				acc.floatsAppended--
 			}
 		default:
+			if math.Float64bits(s.V) == value.QuietZeroNaN {
+				s.V = 0 // Note that this is modifying the copy which is what will be appended but the WAL got the NaN already.
+			}
 			ok, chunkCreated = series.append(s.T, s.V, a.appendID, acc.appendChunkOpts)
 			if ok {
 				if s.T < acc.inOrderMint {

tsdb/head_test.go

@@ -547,15 +547,6 @@ func TestHead_HighConcurrencyReadAndWrite(t *testing.T) {
 		})
 	}
 
-	// queryHead is a helper to query the head for a given time range and labelset.
-	queryHead := func(mint, maxt uint64, label labels.Label) (map[string][]chunks.Sample, error) {
-		q, err := NewBlockQuerier(head, int64(mint), int64(maxt))
-		if err != nil {
-			return nil, err
-		}
-		return query(t, q, labels.MustNewMatcher(labels.MatchEqual, label.Name, label.Value)), nil
-	}
-
 	// readerTsCh will be used by the coordinator go routine to coordinate which timestamps the reader should read.
 	readerTsCh := make(chan uint64)
 
@@ -583,7 +574,7 @@ func TestHead_HighConcurrencyReadAndWrite(t *testing.T) {
 				lbls.Range(func(l labels.Label) {
 					lbl = l
 				})
-				samples, err := queryHead(ts-qryRange, ts, lbl)
+				samples, err := queryHead(t, head, int64(ts-qryRange), int64(ts), lbl)
 				if err != nil {
 					return false, err
 				}
@@ -6098,6 +6089,118 @@ func TestCuttingNewHeadChunks(t *testing.T) {
 	}
 }
 
+func TestAppendQuietZeroDuplicates(t *testing.T) {
+	ts := int64(1695209650)
+	lbls := labels.FromStrings("foo", "bar")
+	h, _ := newTestHead(t, DefaultBlockDuration, wlog.CompressionNone, false)
+	defer func() {
+		require.NoError(t, h.Close())
+	}()
+
+	a := h.Appender(context.Background())
+	_, err := a.Append(0, lbls, ts, 42.0)
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts, 42.0) // Exactly the same value.
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts, math.Float64frombits(value.QuietZeroNaN)) // Should be a no-op.
+	require.NoError(t, err)
+	require.NoError(t, a.Commit())
+
+	result, err := queryHead(t, h, math.MinInt64, math.MaxInt64, labels.Label{Name: "foo", Value: "bar"})
+	require.NoError(t, err)
+	expectedSamples := []chunks.Sample{sample{t: ts, f: 42.0}}
+	require.Equal(t, expectedSamples, result[`{foo="bar"}`])
+
+	a = h.Appender(context.Background())
+	_, err = a.Append(0, lbls, ts+10, math.Float64frombits(value.QuietZeroNaN)) // This is at a different timestamp so should append a real zero.
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts+15, 5.0) // We append a normal value to reflect what would happen in reality.
+	require.NoError(t, err)
+	require.NoError(t, a.Commit())
+
+	result, err = queryHead(t, h, math.MinInt64, math.MaxInt64, labels.Label{Name: "foo", Value: "bar"})
+	require.NoError(t, err)
+	expectedSamples = []chunks.Sample{
+		sample{t: ts, f: 42.0},
+		sample{t: ts + 10, f: 0},
+		sample{t: ts + 15, f: 5},
+	}
+	require.Equal(t, expectedSamples, result[`{foo="bar"}`])
+
+	a = h.Appender(context.Background())
+	_, err = a.Append(0, lbls, ts+5, math.Float64frombits(value.QuietZeroNaN)) // This is out-of-order, so should be dropped.
+	require.NoError(t, err)
+	require.NoError(t, a.Commit())
+
+	result, err = queryHead(t, h, math.MinInt64, math.MaxInt64, labels.Label{Name: "foo", Value: "bar"})
+	require.NoError(t, err)
+	require.Equal(t, expectedSamples, result[`{foo="bar"}`]) // Same expectedSamples as before.
+}
+
+func TestQuietZeroWALReplay(t *testing.T) {
+	ts := int64(1695209650)
+	lbls := labels.FromStrings("foo", "bar")
+	h, w := newTestHead(t, DefaultBlockDuration, wlog.CompressionNone, true)
+
+	a := h.Appender(context.Background())
+	_, err := a.Append(0, lbls, ts, 42.0)
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts, 42.0) // Exactly the same value.
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts, math.Float64frombits(value.QuietZeroNaN)) // Should be a no-op.
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts+10, math.Float64frombits(value.QuietZeroNaN)) // This is at a different timestamp so should append a real zero.
+	require.NoError(t, err)
+	_, err = a.Append(0, lbls, ts+5, math.Float64frombits(value.QuietZeroNaN)) // This is out-of-order, so should be dropped.
+	require.NoError(t, err)
+	require.NoError(t, a.Commit())
+
+	result, err := queryHead(t, h, math.MinInt64, math.MaxInt64, labels.Label{Name: "foo", Value: "bar"})
+	require.NoError(t, err)
+	expectedSamples := []chunks.Sample{
+		sample{t: ts, f: 42.0},
+		sample{t: ts + 10, f: 0},
+	}
+	require.Equal(t, expectedSamples, result[`{foo="bar"}`])
+
+	require.NoError(t, h.Close())
+
+	// Next we replay the WAL by creating a new head and then verify that previous samples are there as we expect them.
+	w, err = wlog.New(nil, nil, w.Dir(), wlog.CompressionNone)
+	require.NoError(t, err)
+	opts := DefaultHeadOptions()
+	opts.ChunkRange = 1000
+	opts.ChunkDirRoot = w.Dir()
+	h, err = NewHead(nil, nil, w, nil, opts, nil)
+	require.NoError(t, err)
+	require.NoError(t, h.Init(0))
+	defer func() {
+		require.NoError(t, h.Close())
+	}()
+
+	result, err = queryHead(t, h, math.MinInt64, math.MaxInt64, labels.Label{Name: "foo", Value: "bar"})
+	require.NoError(t, err)
+	require.Equal(t, expectedSamples, result[`{foo="bar"}`])
+
+	// For correctness, we also verify that the WAL contains the expected records.
+	recs := readTestWAL(t, h.wal.Dir())
+	require.NotEmpty(t, recs, "WAL should contain records")
+
+	if samples, ok := recs[1].([]record.RefSample); ok {
+		require.Len(t, samples, 5)
+		require.Equal(t, record.RefSample{Ref: 1, T: ts, V: 42.0}, samples[0])
+		require.Equal(t, record.RefSample{Ref: 1, T: ts, V: 42.0}, samples[1])
+		require.True(t, math.IsNaN(samples[2].V))
+		require.Equal(t, ts, samples[2].T)
+		require.True(t, math.IsNaN(samples[3].V))
+		require.Equal(t, ts+10, samples[3].T)
+		require.True(t, math.IsNaN(samples[4].V))
+		require.Equal(t, ts+5, samples[4].T)
+	} else {
+		t.Fatalf("unexpected record type: %T", recs[1])
+	}
+}
+
 // TestHeadDetectsDuplicateSampleAtSizeLimit tests a regression where a duplicate sample
 // is appended to the head, right when the head chunk is at the size limit.
 // The test adds all samples as duplicate, thus expecting that the result has

tsdb/head_wal.go

@@ -30,6 +30,7 @@ import (
 	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/metadata"
+	"github.com/prometheus/prometheus/model/value"
 	"github.com/prometheus/prometheus/storage"
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
 	"github.com/prometheus/prometheus/tsdb/chunks"
@@ -589,6 +590,9 @@ func (wp *walSubsetProcessor) processWALSamples(h *Head, mmappedChunks, oooMmapp
 			if s.T <= ms.mmMaxTime {
 				continue
 			}
+			if math.Float64bits(s.V) == value.QuietZeroNaN {
+				s.V = 0
+			}
 			if _, chunkCreated := ms.append(s.T, s.V, 0, appendChunkOpts); chunkCreated {
 				h.metrics.chunksCreated.Inc()
 				h.metrics.chunks.Inc()
@@ -989,6 +993,9 @@ func (wp *wblSubsetProcessor) processWBLSamples(h *Head) (unknownRefs, unknownHi
 				unknownRefs++
 				continue
 			}
+			if math.Float64bits(s.V) == value.QuietZeroNaN {
+				continue
+			}
 			ok, chunkCreated, _ := ms.insert(s.T, s.V, nil, nil, h.chunkDiskMapper, oooCapMax, h.logger)
 			if chunkCreated {
 				h.metrics.chunksCreated.Inc()