store/proxy: Deduplicate chunks on StoreAPI level. Recommend chunk sorting for StoreAPI.

CHANGELOG.md

@@ -31,6 +31,7 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 - [2513](https://github.com/thanos-io/thanos/pull/2513) Tools: Moved `thanos bucket` commands to `thanos tools bucket`, also
 moved `thanos check rules` to `thanos tools rules-check`. `thanos tools rules-check` also takes rules by `--rules` repeated flag not argument
 anymore.
+- [2603](https://github.com/thanos-io/thanos/pull/2603) Store/Querier: Significantly optimize cases where StoreAPIs or blocks returns exact overlapping chunks (e.g Store GW and sidecar or brute force Store Gateway HA).
 
 ## [v0.12.2](https://github.com/thanos-io/thanos/releases/tag/v0.12.2) - 2020.04.30
 

pkg/store/bucket.go

@@ -981,9 +981,8 @@ func (s *BucketStore) Series(req *storepb.SeriesRequest, srv storepb.Store_Serie
 	tracing.DoInSpan(ctx, "bucket_store_merge_all", func(ctx context.Context) {
 		begin := time.Now()
 
-		// Merge series set into an union of all block sets. This exposes all blocks are single seriesSet.
-		// Chunks of returned series might be out of order w.r.t to their time range.
-		// This must be accounted for later by clients.
+		// NOTE: We "carefully" assume series and chunks are sorted within each SeriesSet. This should be guaranteed by
+		// blockSeries method. In worst case deduplication logic won't deduplicate correctly, which will be accounted later.
 		set := storepb.MergeSeriesSets(res...)
 		for set.Next() {
 			var series storepb.Series

pkg/store/proxy.go

@@ -473,6 +473,7 @@ func (s *streamSeriesSet) At() ([]storepb.Label, []storepb.AggrChunk) {
 	}
 	return s.currSeries.Labels, s.currSeries.Chunks
 }
+
 func (s *streamSeriesSet) Err() error {
 	s.errMtx.Lock()
 	defer s.errMtx.Unlock()

pkg/store/proxy_test.go

@@ -294,15 +294,11 @@ func TestProxyStore_Series(t *testing.T) {
 			expectedSeries: []rawSeries{
 				{
 					lset:   []storepb.Label{{Name: "a", Value: "a"}},
-					chunks: [][]sample{{{0, 0}, {2, 1}, {3, 2}}, {{4, 3}}},
-				},
-				{
-					lset:   []storepb.Label{{Name: "a", Value: "a"}},
-					chunks: [][]sample{{{5, 4}}},
+					chunks: [][]sample{{{0, 0}, {2, 1}, {3, 2}}, {{4, 3}}, {{5, 4}}},
 				},
 				{
 					lset:   []storepb.Label{{Name: "a", Value: "b"}},
-					chunks: [][]sample{{{2, 2}, {3, 3}, {4, 4}}, {{1, 1}, {2, 2}, {3, 3}}}, // No sort merge.
+					chunks: [][]sample{{{1, 1}, {2, 2}, {3, 3}}, {{2, 2}, {3, 3}, {4, 4}}},
 				},
 				{
 					lset:   []storepb.Label{{Name: "a", Value: "c"}},
@@ -343,7 +339,7 @@ func TestProxyStore_Series(t *testing.T) {
 			expectedSeries: []rawSeries{
 				{
 					lset:   []storepb.Label{{Name: "a", Value: "b"}},
-					chunks: [][]sample{{{1, 1}, {2, 2}, {3, 3}}, {{1, 11}, {2, 22}, {3, 33}}},
+					chunks: [][]sample{{{1, 11}, {2, 22}, {3, 33}}, {{1, 1}, {2, 2}, {3, 3}}},
 				},
 			},
 		},
@@ -1220,7 +1216,7 @@ type rawSeries struct {
 }
 
 func seriesEquals(t *testing.T, expected []rawSeries, got []storepb.Series) {
-	testutil.Equals(t, len(expected), len(got), "got: %v", got)
+	testutil.Equals(t, len(expected), len(got), "got unexpected number of series: \n %v", got)
 
 	for i, series := range got {
 		testutil.Equals(t, expected[i].lset, series.Labels)

pkg/store/storepb/custom.go

@@ -4,6 +4,7 @@
 package storepb
 
 import (
+	"bytes"
 	"strings"
 	"unsafe"
 
@@ -45,6 +46,7 @@ func NewHintsSeriesResponse(hints *types.Any) *SeriesResponse {
 }
 
 // CompareLabels compares two sets of labels.
+// After lexicographical order, the set with fewer labels comes first.
 func CompareLabels(a, b []Label) int {
 	l := len(a)
 	if len(b) < l {
@@ -58,7 +60,7 @@ func CompareLabels(a, b []Label) int {
 			return d
 		}
 	}
-	// If all labels so far were in common, the set with fewer labels comes first.
+
 	return len(a) - len(b)
 }
 
@@ -73,13 +75,25 @@ func EmptySeriesSet() SeriesSet {
 	return emptySeriesSet{}
 }
 
-// MergeSeriesSets returns a new series set that is the union of the input sets.
+// MergeSeriesSets takes all series sets and returns as a union single series set.
+// It assumes series are sorted by labels within single SeriesSet, similar to remote read guarantees.
+// However, they can be partial: in such case, if the single SeriesSet returns the same series within many iterations,
+// MergeSeriesSets will merge those into one.
+//
+// It also assumes in a "best effort" way that chunks are sorted by min time. It's done as an optimization only, so if input
+// series' chunks are NOT sorted, the only consequence is that the duplicates might be not correctly removed. This is double checked
+// which on just-before PromQL level as well, so the only consequence is increased network bandwidth.
+// If all chunks were sorted, MergeSeriesSet ALSO returns sorted chunks by min time.
+//
+// Chunks within the same series can also overlap (within all SeriesSet
+// as well as single SeriesSet alone). If the chunk ranges overlap, the *exact* chunk duplicates will be removed
+// (except one), and any other overlaps will be appended into on chunks slice.
 func MergeSeriesSets(all ...SeriesSet) SeriesSet {
 	switch len(all) {
 	case 0:
 		return emptySeriesSet{}
 	case 1:
-		return all[0]
+		return newUniqueSeriesSet(all[0])
 	}
 	h := len(all) / 2
 
@@ -106,11 +120,6 @@ type mergedSeriesSet struct {
 	adone, bdone bool
 }
 
-// newMergedSeriesSet takes two series sets as a single series set.
-// Series that occur in both sets should have disjoint time ranges.
-// If the ranges overlap b samples are appended to a samples.
-// If the single SeriesSet returns same series within many iterations,
-// merge series set will not try to merge those.
 func newMergedSeriesSet(a, b SeriesSet) *mergedSeriesSet {
 	s := &mergedSeriesSet{a: a, b: b}
 	// Initialize first elements of both sets as Next() needs
@@ -150,33 +159,175 @@ func (s *mergedSeriesSet) Next() bool {
 	}
 
 	d := s.compare()
-
-	// Both sets contain the current series. Chain them into a single one.
 	if d > 0 {
 		s.lset, s.chunks = s.b.At()
 		s.bdone = !s.b.Next()
-	} else if d < 0 {
+		return true
+	}
+	if d < 0 {
 		s.lset, s.chunks = s.a.At()
 		s.adone = !s.a.Next()
-	} else {
-		// Concatenate chunks from both series sets. They may be expected of order
-		// w.r.t to their time range. This must be accounted for later.
-		lset, chksA := s.a.At()
-		_, chksB := s.b.At()
-
-		s.lset = lset
-		// Slice reuse is not generally safe with nested merge iterators.
-		// We err on the safe side an create a new slice.
-		s.chunks = make([]AggrChunk, 0, len(chksA)+len(chksB))
-		s.chunks = append(s.chunks, chksA...)
-		s.chunks = append(s.chunks, chksB...)
+		return true
+	}
 
-		s.adone = !s.a.Next()
-		s.bdone = !s.b.Next()
+	// Both a and b contains the same series. Go through all chunks, remove duplicates and concatenate chunks from both
+	// series sets. We best effortly assume chunks are sorted by min time. If not, we will not detect all deduplicate which will
+	// be account on select layer anyway. We do it still for early optimization.
+	lset, chksA := s.a.At()
+	_, chksB := s.b.At()
+	s.lset = lset
+
+	// Slice reuse is not generally safe with nested merge iterators.
+	// We err on the safe side an create a new slice.
+	s.chunks = make([]AggrChunk, 0, len(chksA)+len(chksB))
+
+	b := 0
+Outer:
+	for a := range chksA {
+		for {
+			if b >= len(chksB) {
+				// No more b chunks.
+				s.chunks = append(s.chunks, chksA[a:]...)
+				break Outer
+			}
+
+			cmp := chksA[a].Compare(chksB[b])
+			if cmp > 0 {
+				s.chunks = append(s.chunks, chksA[a])
+				break
+			}
+			if cmp < 0 {
+				s.chunks = append(s.chunks, chksB[b])
+				b++
+				continue
+			}
+
+			// Exact duplicated chunks, discard one from b.
+			b++
+		}
 	}
+
+	if b < len(chksB) {
+		s.chunks = append(s.chunks, chksB[b:]...)
+	}
+
+	s.adone = !s.a.Next()
+	s.bdone = !s.b.Next()
 	return true
 }
 
+// uniqueSeriesSet takes one series set and ensures each iteration contains single, full series.
+type uniqueSeriesSet struct {
+	SeriesSet
+	done bool
+
+	peek *Series
+
+	lset   []Label
+	chunks []AggrChunk
+}
+
+func newUniqueSeriesSet(wrapped SeriesSet) *uniqueSeriesSet {
+	return &uniqueSeriesSet{SeriesSet: wrapped}
+}
+
+func (s *uniqueSeriesSet) At() ([]Label, []AggrChunk) {
+	return s.lset, s.chunks
+}
+
+func (s *uniqueSeriesSet) Next() bool {
+	if s.Err() != nil {
+		return false
+	}
+
+	for !s.done {
+		if s.done = !s.SeriesSet.Next(); s.done {
+			break
+		}
+		lset, chks := s.SeriesSet.At()
+		if s.peek == nil {
+			s.peek = &Series{Labels: lset, Chunks: chks}
+			continue
+		}
+
+		if CompareLabels(lset, s.peek.Labels) != 0 {
+			s.lset, s.chunks = s.peek.Labels, s.peek.Chunks
+			s.peek = &Series{Labels: lset, Chunks: chks}
+			return true
+		}
+
+		// We assume non-overlapping, sorted chunks. This is best effort only, if it's otherwise it
+		// will just be duplicated, but well handled by StoreAPI consumers.
+		s.peek.Chunks = append(s.peek.Chunks, chks...)
+	}
+
+	if s.peek == nil {
+		return false
+	}
+
+	s.lset, s.chunks = s.peek.Labels, s.peek.Chunks
+	s.peek = nil
+	return true
+}
+
+// Compare returns positive 1 if chunk is smaller -1 if larger than b by min time, then max time.
+// It returns 0 if chunks are exactly the same.
+func (m AggrChunk) Compare(b AggrChunk) int {
+	if m.MinTime < b.MinTime {
+		return 1
+	}
+	if m.MinTime > b.MinTime {
+		return -1
+	}
+
+	// Same min time.
+	if m.MaxTime < b.MaxTime {
+		return 1
+	}
+	if m.MaxTime > b.MaxTime {
+		return -1
+	}
+
+	// We could use proto.Equal, but we need ordering as well.
+	for _, cmp := range []func() int{
+		func() int { return m.Raw.Compare(b.Raw) },
+		func() int { return m.Count.Compare(b.Count) },
+		func() int { return m.Sum.Compare(b.Sum) },
+		func() int { return m.Min.Compare(b.Min) },
+		func() int { return m.Max.Compare(b.Max) },
+		func() int { return m.Counter.Compare(b.Counter) },
+	} {
+		if c := cmp(); c == 0 {
+			continue
+		} else {
+			return c
+		}
+	}
+	return 0
+}
+
+// Compare returns positive 1 if chunk is smaller -1 if larger.
+// It returns 0 if chunks are exactly the same.
+func (m *Chunk) Compare(b *Chunk) int {
+	if m == nil && b == nil {
+		return 0
+	}
+	if b == nil {
+		return 1
+	}
+	if m == nil {
+		return -1
+	}
+
+	if m.Type < b.Type {
+		return 1
+	}
+	if m.Type > b.Type {
+		return -1
+	}
+	return bytes.Compare(m.Data, b.Data)
+}
+
 // LabelsToPromLabels converts Thanos proto labels to Prometheus labels in type safe manner.
 func LabelsToPromLabels(lset []Label) labels.Labels {
 	ret := make(labels.Labels, len(lset))