storage: ensure timestamp monotonicity within series.

Fixes https://github.com/prometheus/prometheus/issues/481

While doing so, clean up and fix a few other things:

- Fix `go vet` warnings (@fabxc to blame ;).

- Fix a racey problem with unarchiving: Whenever we unarchive a
  series, we essentially want to do something with it. However, until
  we have done something with it, it appears like a series that is
  ready to be archived or even purged. So e.g. it would be ignored
  during checkpointing. With this fix, we always load the chunkDescs
  upon unarchiving. This is wasteful if we only want to add a new
  sample to an archived time series, but the (presumably more common)
  case where we access an archived time series in a query doesn't
  become more expensive.

- The change above streamlined the getOrCreateSeries ond
  newMemorySeries flow. Also, the modTime is now always set correctly.

- Fix the leveldb-backed implementation of KeyValueStore.Delete. It
  had the wrong behavior of still returning true, nil if a
  non-existing key has been passed in.

storage/local/crashrecovery.go

@@ -250,17 +250,28 @@ func (p *persistence) sanitizeSeries(
 		// consistent with the checkpoint, so we have to take a closer
 		// look.
 		if s.headChunkClosed {
-			// This is the easy case as we don't have any chunks in
-			// heads.db. Treat this series as a freshly unarchived
-			// one. No chunks or chunkDescs in memory, no current
-			// head chunk.
+			// This is the easy case as we have all chunks on
+			// disk. Treat this series as a freshly unarchived one
+			// by loading the chunkDescs and setting all parameters
+			// based on the loaded chunkDescs.
+			cds, err := p.loadChunkDescs(fp, clientmodel.Latest)
+			if err != nil {
+				log.Errorf(
+					"Failed to load chunk descriptors for metric %v, fingerprint %v: %s",
+					s.metric, fp, err,
+				)
+				purge()
+				return fp, false
+			}
 			log.Warnf(
 				"Treating recovered metric %v, fingerprint %v, as freshly unarchived, with %d chunks in series file.",
-				s.metric, fp, chunksInFile,
+				s.metric, fp, len(cds),
 			)
-			s.chunkDescs = nil
-			s.chunkDescsOffset = chunksInFile
-			s.persistWatermark = 0
+			s.chunkDescs = cds
+			s.chunkDescsOffset = 0
+			s.savedFirstTime = cds[0].firstTime()
+			s.lastTime = cds[len(cds)-1].lastTime()
+			s.persistWatermark = len(cds)
 			s.modTime = modTime
 			return fp, true
 		}
@@ -275,8 +286,8 @@ func (p *persistence) sanitizeSeries(
 		// First, throw away the chunkDescs without chunks.
 		s.chunkDescs = s.chunkDescs[s.persistWatermark:]
 		numMemChunkDescs.Sub(float64(s.persistWatermark))
-		// Load all the chunk descs (which assumes we have none from the future).
-		cds, err := p.loadChunkDescs(fp, clientmodel.Now())
+		// Load all the chunk descs.
+		cds, err := p.loadChunkDescs(fp, clientmodel.Latest)
 		if err != nil {
 			log.Errorf(
 				"Failed to load chunk descriptors for metric %v, fingerprint %v: %s",
@@ -287,6 +298,7 @@ func (p *persistence) sanitizeSeries(
 		}
 		s.persistWatermark = len(cds)
 		s.chunkDescsOffset = 0
+		s.savedFirstTime = cds[0].firstTime()
 		s.modTime = modTime
 
 		lastTime := cds[len(cds)-1].lastTime()
@@ -395,14 +407,11 @@ func (p *persistence) cleanUpArchiveIndexes(
 		if _, err := p.archivedFingerprintToMetrics.Delete(fp); err != nil {
 			return err
 		}
-		series := newMemorySeries(clientmodel.Metric(m), false, clientmodel.Earliest)
-		cds, err := p.loadChunkDescs(clientmodel.Fingerprint(fp), clientmodel.Now())
+		cds, err := p.loadChunkDescs(clientmodel.Fingerprint(fp), clientmodel.Latest)
 		if err != nil {
 			return err
 		}
-		series.chunkDescs = cds
-		series.chunkDescsOffset = 0
-		series.persistWatermark = len(cds)
+		series := newMemorySeries(clientmodel.Metric(m), cds, p.seriesFileModTime(clientmodel.Fingerprint(fp)))
 		fpToSeries[clientmodel.Fingerprint(fp)] = series
 		return nil
 	}); err != nil {

storage/local/delta.go

@@ -94,9 +94,11 @@ func (c deltaEncodedChunk) add(s *metric.SamplePair) []chunk {
 	}
 
 	baseValue := c.baseValue()
-	// TODO(beorn7): Once https://github.com/prometheus/prometheus/issues/481 is
-	// fixed, we should panic here if dt is negative.
 	dt := s.Timestamp - c.baseTime()
+	if dt < 0 {
+		panic("time delta is less than zero")
+	}
+
 	dv := s.Value - baseValue
 	tb := c.timeBytes()
 	vb := c.valueBytes()
@@ -382,7 +384,7 @@ func (it *deltaEncodedChunkIterator) timestampAtIndex(idx int) clientmodel.Times
 		// Take absolute value for d8.
 		return clientmodel.Timestamp(binary.LittleEndian.Uint64(it.c[offset:]))
 	default:
-		panic("Invalid number of bytes for time delta")
+		panic("invalid number of bytes for time delta")
 	}
 }
 
@@ -407,7 +409,7 @@ func (it *deltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmodel.Sam
 			return it.baseV + clientmodel.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
 		// No d8 for ints.
 		default:
-			panic("Invalid number of bytes for integer delta")
+			panic("invalid number of bytes for integer delta")
 		}
 	} else {
 		switch it.vBytes {
@@ -417,7 +419,7 @@ func (it *deltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmodel.Sam
 			// Take absolute value for d8.
 			return clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
 		default:
-			panic("Invalid number of bytes for floating point delta")
+			panic("invalid number of bytes for floating point delta")
 		}
 	}
 }

storage/local/doubledelta.go

@@ -339,10 +339,7 @@ func (c doubleDeltaEncodedChunk) addFirstSample(s *metric.SamplePair) []chunk {
 func (c doubleDeltaEncodedChunk) addSecondSample(s *metric.SamplePair, tb, vb deltaBytes) []chunk {
 	baseTimeDelta := s.Timestamp - c.baseTime()
 	if baseTimeDelta < 0 {
-		// TODO(beorn7): We ignore this irregular case for now. Once
-		// https://github.com/prometheus/prometheus/issues/481 is
-		// fixed, we should panic here instead.
-		return []chunk{&c}
+		panic("base time delta is less than zero")
 	}
 	c = c[:doubleDeltaHeaderBytes]
 	if tb >= d8 || bytesNeededForUnsignedTimestampDelta(baseTimeDelta) >= d8 {
@@ -511,7 +508,7 @@ func (it *doubleDeltaEncodedChunkIterator) timestampAtIndex(idx int) clientmodel
 		// Take absolute value for d8.
 		return clientmodel.Timestamp(binary.LittleEndian.Uint64(it.c[offset:]))
 	default:
-		panic("Invalid number of bytes for time delta")
+		panic("invalid number of bytes for time delta")
 	}
 }
 
@@ -555,7 +552,7 @@ func (it *doubleDeltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmod
 				clientmodel.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
 		// No d8 for ints.
 		default:
-			panic("Invalid number of bytes for integer delta")
+			panic("invalid number of bytes for integer delta")
 		}
 	} else {
 		switch it.vBytes {
@@ -567,7 +564,7 @@ func (it *doubleDeltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmod
 			// Take absolute value for d8.
 			return clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
 		default:
-			panic("Invalid number of bytes for floating point delta")
+			panic("invalid number of bytes for floating point delta")
 		}
 	}
 }

storage/local/index/leveldb.go

@@ -109,13 +109,18 @@ func (l *LevelDB) Delete(key encoding.BinaryMarshaler) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	err = l.storage.Delete(k, l.writeOpts)
+	// Note that Delete returns nil if k does not exist. So we have to test
+	// for existence with Get first.
+	_, err = l.storage.Get(k, l.readOpts)
 	if err == leveldb.ErrNotFound {
 		return false, nil
 	}
 	if err != nil {
 		return false, err
 	}
+	if err = l.storage.Delete(k, l.writeOpts); err != nil {
+		return false, err
+	}
 	return true, nil
 }
 

storage/local/persistence.go

@@ -643,7 +643,7 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 						return
 					}
 				} else {
-					// This is the non-persisted head chunk. Fully marshal it.
+					// This is a non-persisted chunk. Fully marshal it.
 					if err = w.WriteByte(byte(chunkDesc.c.encoding())); err != nil {
 						return
 					}
@@ -853,6 +853,7 @@ func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, chunksToPersist in
 			modTime:          modTime,
 			chunkDescsOffset: int(chunkDescsOffset),
 			savedFirstTime:   clientmodel.Timestamp(savedFirstTime),
+			lastTime:         chunkDescs[len(chunkDescs)-1].lastTime(),
 			headChunkClosed:  persistWatermark >= numChunkDescs,
 		}
 	}
@@ -1173,38 +1174,27 @@ func (p *persistence) purgeArchivedMetric(fp clientmodel.Fingerprint) (err error
 
 // unarchiveMetric deletes an archived fingerprint and its metric, but (in
 // contrast to purgeArchivedMetric) does not un-index the metric.  If a metric
-// was actually deleted, the method returns true and the first time of the
-// deleted metric. The caller must have locked the fingerprint.
-func (p *persistence) unarchiveMetric(fp clientmodel.Fingerprint) (
-	deletedAnything bool,
-	firstDeletedTime clientmodel.Timestamp,
-	err error,
-) {
+// was actually deleted, the method returns true and the first time and last
+// time of the deleted metric. The caller must have locked the fingerprint.
+func (p *persistence) unarchiveMetric(fp clientmodel.Fingerprint) (deletedAnything bool, err error) {
 	defer func() {
 		if err != nil {
 			p.setDirty(true)
 		}
 	}()
 
-	firstTime, _, has, err := p.archivedFingerprintToTimeRange.Lookup(fp)
-	if err != nil || !has {
-		return false, firstTime, err
-	}
 	deleted, err := p.archivedFingerprintToMetrics.Delete(codable.Fingerprint(fp))
-	if err != nil {
-		return false, firstTime, err
-	}
-	if !deleted {
-		log.Errorf("Tried to delete non-archived fingerprint %s from archivedFingerprintToMetrics index. This should never happen.", fp)
+	if err != nil || !deleted {
+		return false, err
 	}
 	deleted, err = p.archivedFingerprintToTimeRange.Delete(codable.Fingerprint(fp))
 	if err != nil {
-		return false, firstTime, err
+		return false, err
 	}
 	if !deleted {
 		log.Errorf("Tried to delete non-archived fingerprint %s from archivedFingerprintToTimeRange index. This should never happen.", fp)
 	}
-	return true, firstTime, nil
+	return true, nil
 }
 
 // close flushes the indexing queue and other buffered data and releases any

storage/local/persistence_test.go

@@ -17,6 +17,7 @@ import (
 	"reflect"
 	"sync"
 	"testing"
+	"time"
 
 	clientmodel "github.com/prometheus/client_golang/model"
 
@@ -354,11 +355,11 @@ func testCheckpointAndLoadSeriesMapAndHeads(t *testing.T, encoding chunkEncoding
 
 	fpLocker := newFingerprintLocker(10)
 	sm := newSeriesMap()
-	s1 := newMemorySeries(m1, true, 0)
-	s2 := newMemorySeries(m2, false, 0)
-	s3 := newMemorySeries(m3, false, 0)
-	s4 := newMemorySeries(m4, true, 0)
-	s5 := newMemorySeries(m5, true, 0)
+	s1 := newMemorySeries(m1, nil, time.Time{})
+	s2 := newMemorySeries(m2, nil, time.Time{})
+	s3 := newMemorySeries(m3, nil, time.Time{})
+	s4 := newMemorySeries(m4, nil, time.Time{})
+	s5 := newMemorySeries(m5, nil, time.Time{})
 	s1.add(&metric.SamplePair{Timestamp: 1, Value: 3.14})
 	s3.add(&metric.SamplePair{Timestamp: 2, Value: 2.7})
 	s3.headChunkClosed = true
@@ -416,8 +417,8 @@ func testCheckpointAndLoadSeriesMapAndHeads(t *testing.T, encoding chunkEncoding
 		if loadedS3.head().c != nil {
 			t.Error("head chunk not evicted")
 		}
-		if loadedS3.chunkDescsOffset != -1 {
-			t.Errorf("want chunkDescsOffset -1, got %d", loadedS3.chunkDescsOffset)
+		if loadedS3.chunkDescsOffset != 0 {
+			t.Errorf("want chunkDescsOffset 0, got %d", loadedS3.chunkDescsOffset)
 		}
 		if !loadedS3.headChunkClosed {
 			t.Error("headChunkClosed is false")
@@ -546,22 +547,19 @@ func testFingerprintsModifiedBefore(t *testing.T, encoding chunkEncoding) {
 		}
 	}
 
-	unarchived, firstTime, err := p.unarchiveMetric(1)
+	unarchived, err := p.unarchiveMetric(1)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if !unarchived {
-		t.Fatal("expected actual unarchival")
+		t.Error("expected actual unarchival")
 	}
-	if firstTime != 2 {
-		t.Errorf("expected first time 2, got %v", firstTime)
-	}
-	unarchived, firstTime, err = p.unarchiveMetric(1)
+	unarchived, err = p.unarchiveMetric(1)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if unarchived {
-		t.Fatal("expected no unarchival")
+		t.Error("expected no unarchival")
 	}
 
 	expectedFPs = map[clientmodel.Timestamp][]clientmodel.Fingerprint{
@@ -831,16 +829,13 @@ func testIndexing(t *testing.T, encoding chunkEncoding) {
 		verifyIndexedState(i, t, batches[i], indexedFpsToMetrics, p)
 		for fp, m := range b.fpToMetric {
 			p.unindexMetric(fp, m)
-			unarchived, firstTime, err := p.unarchiveMetric(fp)
+			unarchived, err := p.unarchiveMetric(fp)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if !unarchived {
 				t.Errorf("%d. metric not unarchived", i)
 			}
-			if firstTime != 1 {
-				t.Errorf("%d. expected firstTime=1, got %v", i, firstTime)
-			}
 			delete(indexedFpsToMetrics, fp)
 		}
 	}

storage/local/series.go

@@ -162,6 +162,9 @@ type memorySeries struct {
 	// first chunk before its chunk desc is evicted. In doubt, this field is
 	// just set to the oldest possible timestamp.
 	savedFirstTime clientmodel.Timestamp
+	// The timestamp of the last sample in this series. Needed for fast access to
+	// ensure timestamp monotonicity during ingestion.
+	lastTime clientmodel.Timestamp
 	// Whether the current head chunk has already been finished.  If true,
 	// the current head chunk must not be modified anymore.
 	headChunkClosed bool
@@ -175,28 +178,29 @@ type memorySeries struct {
 }
 
 // newMemorySeries returns a pointer to a newly allocated memorySeries for the
-// given metric. reallyNew defines if the memorySeries is a genuinely new series
-// or (if false) a series for a metric being unarchived, i.e. a series that
-// existed before but has been evicted from memory. If reallyNew is false,
-// firstTime is ignored (and set to the lowest possible timestamp instead - it
-// will be set properly upon the first eviction of chunkDescs).
-func newMemorySeries(
-	m clientmodel.Metric,
-	reallyNew bool,
-	firstTime clientmodel.Timestamp,
-) *memorySeries {
-	if !reallyNew {
-		firstTime = clientmodel.Earliest
-	}
-	s := memorySeries{
-		metric:          m,
-		headChunkClosed: !reallyNew,
-		savedFirstTime:  firstTime,
-	}
-	if !reallyNew {
-		s.chunkDescsOffset = -1
-	}
-	return &s
+// given metric. chunkDescs and modTime in the new series are set according to
+// the provided parameters. chunkDescs can be nil or empty if this is a
+// genuinely new time series (i.e. not one that is being unarchived). In that
+// case, headChunkClosed is set to false, and firstTime and lastTime are both
+// set to clientmodel.Earliest. The zero value for modTime can be used if the
+// modification time of the series file is unknown (e.g. if this is a genuinely
+// new series).
+func newMemorySeries(m clientmodel.Metric, chunkDescs []*chunkDesc, modTime time.Time) *memorySeries {
+	firstTime := clientmodel.Earliest
+	lastTime := clientmodel.Earliest
+	if len(chunkDescs) > 0 {
+		firstTime = chunkDescs[0].firstTime()
+		lastTime = chunkDescs[len(chunkDescs)-1].lastTime()
+	}
+	return &memorySeries{
+		metric:           m,
+		chunkDescs:       chunkDescs,
+		headChunkClosed:  len(chunkDescs) > 0,
+		savedFirstTime:   firstTime,
+		lastTime:         lastTime,
+		persistWatermark: len(chunkDescs),
+		modTime:          modTime,
+	}
 }
 
 // add adds a sample pair to the series. It returns the number of newly
@@ -231,6 +235,8 @@ func (s *memorySeries) add(v *metric.SamplePair) int {
 	for _, c := range chunks[1:] {
 		s.chunkDescs = append(s.chunkDescs, newChunkDesc(c))
 	}
+
+	s.lastTime = v.Timestamp
 	return len(chunks) - 1
 }
 
@@ -243,7 +249,7 @@ func (s *memorySeries) maybeCloseHeadChunk() bool {
 	if s.headChunkClosed {
 		return false
 	}
-	if time.Now().Sub(s.head().lastTime().Time()) > headChunkTimeout {
+	if time.Now().Sub(s.lastTime.Time()) > headChunkTimeout {
 		s.headChunkClosed = true
 		// Since we cannot modify the head chunk from now on, we
 		// don't need to bother with cloning anymore.

storage/local/storage.go

@@ -135,6 +135,7 @@ type memorySeriesStorage struct {
 	numSeries                   prometheus.Gauge
 	seriesOps                   *prometheus.CounterVec
 	ingestedSamplesCount        prometheus.Counter
+	outOfOrderSamplesCount      prometheus.Counter
 	invalidPreloadRequestsCount prometheus.Counter
 	maintainSeriesDuration      *prometheus.SummaryVec
 }
@@ -203,6 +204,12 @@ func NewMemorySeriesStorage(o *MemorySeriesStorageOptions) Storage {
 			Name:      "ingested_samples_total",
 			Help:      "The total number of samples ingested.",
 		}),
+		outOfOrderSamplesCount: prometheus.NewCounter(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "out_of_order_samples_total",
+			Help:      "The total number of samples that were discarded because their timestamps were at or before the last received sample for a series.",
+		}),
 		invalidPreloadRequestsCount: prometheus.NewCounter(prometheus.CounterOpts{
 			Namespace: namespace,
 			Subsystem: subsystem,
@@ -550,6 +557,13 @@ func (s *memorySeriesStorage) Append(sample *clientmodel.Sample) {
 		s.fpLocker.Lock(fp)
 	}
 	series := s.getOrCreateSeries(fp, sample.Metric)
+
+	if sample.Timestamp <= series.lastTime {
+		s.fpLocker.Unlock(fp)
+		log.Warnf("Ignoring sample with out-of-order timestamp for fingerprint %v (%v): %v is not after %v", fp, series.metric, sample.Timestamp, series.lastTime)
+		s.outOfOrderSamplesCount.Inc()
+		return
+	}
 	completedChunksCount := series.add(&metric.SamplePair{
 		Value:     sample.Value,
 		Timestamp: sample.Timestamp,
@@ -562,18 +576,30 @@ func (s *memorySeriesStorage) Append(sample *clientmodel.Sample) {
 func (s *memorySeriesStorage) getOrCreateSeries(fp clientmodel.Fingerprint, m clientmodel.Metric) *memorySeries {
 	series, ok := s.fpToSeries.get(fp)
 	if !ok {
-		unarchived, firstTime, err := s.persistence.unarchiveMetric(fp)
+		var cds []*chunkDesc
+		var modTime time.Time
+		unarchived, err := s.persistence.unarchiveMetric(fp)
 		if err != nil {
-			log.Errorf("Error unarchiving fingerprint %v: %v", fp, err)
+			log.Errorf("Error unarchiving fingerprint %v (metric %v): %v", fp, m, err)
 		}
 		if unarchived {
 			s.seriesOps.WithLabelValues(unarchive).Inc()
+			// We have to load chunkDescs anyway to do anything with
+			// the series, so let's do it right now so that we don't
+			// end up with a series without any chunkDescs for a
+			// while (which is confusing as it makes the series
+			// appear as archived or purged).
+			cds, err = s.loadChunkDescs(fp, clientmodel.Latest)
+			if err != nil {
+				log.Errorf("Error loading chunk descs for fingerprint %v (metric %v): %v", fp, m, err)
+			}
+			modTime = s.persistence.seriesFileModTime(fp)
 		} else {
 			// This was a genuinely new series, so index the metric.
 			s.persistence.indexMetric(fp, m)
 			s.seriesOps.WithLabelValues(create).Inc()
 		}
-		series = newMemorySeries(m, !unarchived, firstTime)
+		series = newMemorySeries(m, cds, modTime)
 		s.fpToSeries.put(fp, series)
 		s.numSeries.Inc()
 	}
@@ -943,21 +969,8 @@ func (s *memorySeriesStorage) maintainMemorySeries(
 	if iOldestNotEvicted == -1 {
 		s.fpToSeries.del(fp)
 		s.numSeries.Dec()
-		// Make sure we have a head chunk descriptor (a freshly
-		// unarchived series has none).
-		if len(series.chunkDescs) == 0 {
-			cds, err := s.loadChunkDescs(fp, clientmodel.Latest)
-			if err != nil {
-				log.Errorf(
-					"Could not load chunk descriptors prior to archiving metric %v, metric will not be archived: %v",
-					series.metric, err,
-				)
-				return
-			}
-			series.chunkDescs = cds
-		}
 		if err := s.persistence.archiveMetric(
-			fp, series.metric, series.firstTime(), series.head().lastTime(),
+			fp, series.metric, series.firstTime(), series.lastTime,
 		); err != nil {
 			log.Errorf("Error archiving metric %v: %v", series.metric, err)
 			return
@@ -1154,6 +1167,7 @@ func (s *memorySeriesStorage) Describe(ch chan<- *prometheus.Desc) {
 	ch <- s.numSeries.Desc()
 	s.seriesOps.Describe(ch)
 	ch <- s.ingestedSamplesCount.Desc()
+	ch <- s.outOfOrderSamplesCount.Desc()
 	ch <- s.invalidPreloadRequestsCount.Desc()
 	ch <- numMemChunksDesc
 	s.maintainSeriesDuration.Describe(ch)
@@ -1178,6 +1192,7 @@ func (s *memorySeriesStorage) Collect(ch chan<- prometheus.Metric) {
 	ch <- s.numSeries
 	s.seriesOps.Collect(ch)
 	ch <- s.ingestedSamplesCount
+	ch <- s.outOfOrderSamplesCount
 	ch <- s.invalidPreloadRequestsCount
 	ch <- prometheus.MustNewConstMetric(
 		numMemChunksDesc,

storage/local/storage_test.go

@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"hash/fnv"
 	"math/rand"
+	"reflect"
 	"testing"
 	"testing/quick"
 	"time"
@@ -377,7 +378,7 @@ func TestRetentionCutoff(t *testing.T) {
 	s.WaitForIndexing()
 
 	var fp clientmodel.Fingerprint
-	for f := range s.fingerprintsForLabelPairs(metric.LabelPair{"job", "test"}) {
+	for f := range s.fingerprintsForLabelPairs(metric.LabelPair{Name: "job", Value: "test"}) {
 		fp = f
 		break
 	}
@@ -398,7 +399,7 @@ func TestRetentionCutoff(t *testing.T) {
 		t.Errorf("unexpected result for timestamp before retention period")
 	}
 
-	vals = it.RangeValues(metric.Interval{insertStart, now})
+	vals = it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now})
 	// We get 59 values here because the clientmodel.Now() is slightly later
 	// than our now.
 	if len(vals) != 59 {
@@ -408,7 +409,7 @@ func TestRetentionCutoff(t *testing.T) {
 		t.Errorf("unexpected timestamp for first sample: %v, expected %v", vals[0].Timestamp.Time(), expt.Time())
 	}
 
-	vals = it.BoundaryValues(metric.Interval{insertStart, now})
+	vals = it.BoundaryValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now})
 	if len(vals) != 2 {
 		t.Errorf("expected 2 values but got %d", len(vals))
 	}
@@ -441,7 +442,7 @@ func TestDropMetrics(t *testing.T) {
 	}
 	s.WaitForIndexing()
 
-	fps := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps := s.fingerprintsForLabelPairs(metric.LabelPair{Name: clientmodel.MetricNameLabel, Value: "test"})
 	if len(fps) != 2 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps))
 	}
@@ -449,7 +450,7 @@ func TestDropMetrics(t *testing.T) {
 	var fpList clientmodel.Fingerprints
 	for fp := range fps {
 		it := s.NewIterator(fp)
-		if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != N {
+		if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != N {
 			t.Fatalf("unexpected number of samples: %d", len(vals))
 		}
 		fpList = append(fpList, fp)
@@ -458,34 +459,38 @@ func TestDropMetrics(t *testing.T) {
 	s.DropMetricsForFingerprints(fpList[0])
 	s.WaitForIndexing()
 
-	fps2 := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps2 := s.fingerprintsForLabelPairs(metric.LabelPair{
+		Name: clientmodel.MetricNameLabel, Value: "test",
+	})
 	if len(fps2) != 1 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps2))
 	}
 
 	it := s.NewIterator(fpList[0])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 	it = s.NewIterator(fpList[1])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != N {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != N {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 
 	s.DropMetricsForFingerprints(fpList...)
 	s.WaitForIndexing()
 
-	fps3 := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps3 := s.fingerprintsForLabelPairs(metric.LabelPair{
+		Name: clientmodel.MetricNameLabel, Value: "test",
+	})
 	if len(fps3) != 0 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps3))
 	}
 
 	it = s.NewIterator(fpList[0])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 	it = s.NewIterator(fpList[1])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 }
@@ -1405,3 +1410,50 @@ func verifyStorage(t testing.TB, s *memorySeriesStorage, samples clientmodel.Sam
 	}
 	return result
 }
+
+func TestAppendOutOfOrder(t *testing.T) {
+	s, closer := NewTestStorage(t, 1)
+	defer closer.Close()
+
+	m := clientmodel.Metric{
+		clientmodel.MetricNameLabel: "out_of_order",
+	}
+
+	for _, t := range []int{0, 2, 2, 1} {
+		s.Append(&clientmodel.Sample{
+			Metric:    m,
+			Timestamp: clientmodel.Timestamp(t),
+			Value:     clientmodel.SampleValue(t),
+		})
+	}
+
+	fp, err := s.mapper.mapFP(m.FastFingerprint(), m)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pl := s.NewPreloader()
+	defer pl.Close()
+
+	err = pl.PreloadRange(fp, 0, 2, 5*time.Minute)
+	if err != nil {
+		t.Fatalf("error preloading chunks: %s", err)
+	}
+
+	it := s.NewIterator(fp)
+
+	want := metric.Values{
+		{
+			Timestamp: 0,
+			Value:     0,
+		},
+		{
+			Timestamp: 2,
+			Value:     2,
+		},
+	}
+	got := it.RangeValues(metric.Interval{OldestInclusive: 0, NewestInclusive: 2})
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("want %v, got %v", want, got)
+	}
+}