Encode sparse histograms in protobuf

Signed-off-by: beorn7 <[email protected]>

Author: beorn7

go.mod

@@ -7,7 +7,7 @@ require (
 	github.com/google/go-cmp v0.4.0 // indirect
 	github.com/json-iterator/go v1.1.9
 	github.com/kr/pretty v0.1.0 // indirect
-	github.com/prometheus/client_model v0.2.0
+	github.com/prometheus/client_model v0.2.1-0.20200406191659-4b803f3550a4
 	github.com/prometheus/common v0.9.1
 	github.com/prometheus/procfs v0.0.8
 	github.com/stretchr/testify v1.4.0 // indirect

go.sum

@@ -73,6 +73,8 @@ github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90 h1:S/YWwWx
 github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/prometheus/client_model v0.2.0 h1:uq5h0d+GuxiXLJLNABMgp2qUWDPiLvgCzz2dUR+/W/M=
 github.com/prometheus/client_model v0.2.0/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
+github.com/prometheus/client_model v0.2.1-0.20200406191659-4b803f3550a4 h1:7Ws+6l4/5eJPHAxe0Axwo4XJwSAA4i0ipEjuoLXWFyo=
+github.com/prometheus/client_model v0.2.1-0.20200406191659-4b803f3550a4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/prometheus/common v0.4.1 h1:K0MGApIoQvMw27RTdJkPbr3JZ7DNbtxQNyi5STVM6Kw=
 github.com/prometheus/common v0.4.1/go.mod h1:TNfzLD0ON7rHzMJeJkieUDPYmFC7Snx/y86RQel1bk4=
 github.com/prometheus/common v0.9.1 h1:KOMtN28tlbam3/7ZKEYKHhKoJZYYj3gMH4uc62x7X7U=

prometheus/histogram.go

@@ -14,9 +14,7 @@
 package prometheus
 
 import (
-	"bytes"
 	"fmt"
-	"io"
 	"math"
 	"runtime"
 	"sort"
@@ -215,7 +213,7 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 	h := &histogram{
 		desc:             desc,
 		upperBounds:      opts.Buckets,
-		sparseResolution: opts.SparseBucketsResolution,
+		sparseResolution: uint32(opts.SparseBucketsResolution),
 		sparseThreshold:  opts.SparseBucketsZeroThreshold,
 		labelPairs:       makeLabelPairs(desc, labelValues),
 		counts:           [2]*histogramCounts{{}, {}},
@@ -355,7 +353,7 @@ type histogram struct {
 	upperBounds      []float64
 	labelPairs       []*dto.LabelPair
 	exemplars        []atomic.Value // One more than buckets (to include +Inf), each a *dto.Exemplar.
-	sparseResolution uint8
+	sparseResolution uint32         // Instead of uint8 to be ready for protobuf encoding.
 	sparseThreshold  float64
 
 	now func() time.Time // To mock out time.Now() for testing.
@@ -400,9 +398,11 @@ func (h *histogram) Write(out *dto.Metric) error {
 	}
 
 	his := &dto.Histogram{
-		Bucket:      make([]*dto.Bucket, len(h.upperBounds)),
-		SampleCount: proto.Uint64(count),
-		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		Bucket:          make([]*dto.Bucket, len(h.upperBounds)),
+		SampleCount:     proto.Uint64(count),
+		SampleSum:       proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		SbResolution:    &h.sparseResolution,
+		SbZeroThreshold: &h.sparseThreshold,
 	}
 	out.Histogram = his
 	out.Label = h.labelPairs
@@ -452,38 +452,43 @@ func (h *histogram) Write(out *dto.Metric) error {
 			coldCounts.sparseBucketsNegative.Range(addAndReset(&hotCounts.sparseBucketsNegative))
 		}()
 
-		var buf bytes.Buffer
-		// TODO(beorn7): encode zero bucket threshold and count.
-		fmt.Println("Zero bucket:", zeroBucket) // DEBUG
-		fmt.Println("Positive buckets:")        // DEBUG
-		if _, err := encodeSparseBuckets(&buf, &coldCounts.sparseBucketsPositive, zeroBucket); err != nil {
-			return err
-		}
-		fmt.Println("Negative buckets:") // DEBUG
-		if _, err := encodeSparseBuckets(&buf, &coldCounts.sparseBucketsNegative, zeroBucket); err != nil {
-			return err
-		}
+		his.SbZeroCount = proto.Uint64(zeroBucket)
+		his.SbNegative = makeSparseBuckets(&coldCounts.sparseBucketsNegative)
+		his.SbPositive = makeSparseBuckets(&coldCounts.sparseBucketsPositive)
 	}
 	return nil
 }
 
-func encodeSparseBuckets(w io.Writer, buckets *sync.Map, zeroBucket uint64) (n int, err error) {
-	// TODO(beorn7): Add actual encoding of spare buckets.
+func makeSparseBuckets(buckets *sync.Map) *dto.SparseBuckets {
 	var ii []int
 	buckets.Range(func(k, v interface{}) bool {
 		ii = append(ii, k.(int))
 		return true
 	})
 	sort.Ints(ii)
-	fmt.Println(len(ii), "buckets")
-	var prev uint64
-	for _, i := range ii {
+
+	if len(ii) == 0 {
+		return nil
+	}
+
+	sbs := dto.SparseBuckets{}
+	var prevCount uint64
+	var prevI int
+	for n, i := range ii {
 		v, _ := buckets.Load(i)
-		current := atomic.LoadUint64(v.(*uint64))
-		fmt.Printf("- %d: %d Δ=%d\n", i, current, int(current)-int(prev))
-		prev = current
+		count := atomic.LoadUint64(v.(*uint64))
+		if n == 0 || i-prevI != 1 {
+			sbs.Span = append(sbs.Span, &dto.SparseBuckets_Span{
+				Offset: proto.Int(i - prevI),
+				Length: proto.Uint32(1),
+			})
+		} else {
+			*sbs.Span[len(sbs.Span)-1].Length++
+		}
+		sbs.Delta = append(sbs.Delta, int64(count)-int64(prevCount)) // TODO(beorn7): Do proper overflow handling.
+		prevI, prevCount = i, count
 	}
-	return 0, nil
+	return &sbs
 }
 
 // addAndReset returns a function to be used with sync.Map.Range of spare