223 lines
6.3 KiB
Go
223 lines
6.3 KiB
Go
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/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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package stats
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import (
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"bytes"
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"fmt"
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"io"
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"log"
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"math"
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"strconv"
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"strings"
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)
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// Histogram accumulates values in the form of a histogram with
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// exponentially increased bucket sizes.
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type Histogram struct {
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// Count is the total number of values added to the histogram.
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Count int64
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// Sum is the sum of all the values added to the histogram.
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Sum int64
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// SumOfSquares is the sum of squares of all values.
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SumOfSquares int64
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// Min is the minimum of all the values added to the histogram.
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Min int64
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// Max is the maximum of all the values added to the histogram.
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Max int64
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// Buckets contains all the buckets of the histogram.
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Buckets []HistogramBucket
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opts HistogramOptions
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logBaseBucketSize float64
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oneOverLogOnePlusGrowthFactor float64
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}
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// HistogramOptions contains the parameters that define the histogram's buckets.
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// The first bucket of the created histogram (with index 0) contains [min, min+n)
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// where n = BaseBucketSize, min = MinValue.
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// Bucket i (i>=1) contains [min + n * m^(i-1), min + n * m^i), where m = 1+GrowthFactor.
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// The type of the values is int64.
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type HistogramOptions struct {
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// NumBuckets is the number of buckets.
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NumBuckets int
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// GrowthFactor is the growth factor of the buckets. A value of 0.1
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// indicates that bucket N+1 will be 10% larger than bucket N.
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GrowthFactor float64
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// BaseBucketSize is the size of the first bucket.
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BaseBucketSize float64
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// MinValue is the lower bound of the first bucket.
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MinValue int64
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}
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// HistogramBucket represents one histogram bucket.
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type HistogramBucket struct {
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// LowBound is the lower bound of the bucket.
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LowBound float64
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// Count is the number of values in the bucket.
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Count int64
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}
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// NewHistogram returns a pointer to a new Histogram object that was created
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// with the provided options.
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func NewHistogram(opts HistogramOptions) *Histogram {
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if opts.NumBuckets == 0 {
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opts.NumBuckets = 32
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}
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if opts.BaseBucketSize == 0.0 {
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opts.BaseBucketSize = 1.0
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}
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h := Histogram{
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Buckets: make([]HistogramBucket, opts.NumBuckets),
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Min: math.MaxInt64,
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Max: math.MinInt64,
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opts: opts,
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logBaseBucketSize: math.Log(opts.BaseBucketSize),
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oneOverLogOnePlusGrowthFactor: 1 / math.Log(1+opts.GrowthFactor),
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}
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m := 1.0 + opts.GrowthFactor
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delta := opts.BaseBucketSize
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h.Buckets[0].LowBound = float64(opts.MinValue)
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for i := 1; i < opts.NumBuckets; i++ {
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h.Buckets[i].LowBound = float64(opts.MinValue) + delta
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delta = delta * m
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}
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return &h
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}
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// Print writes textual output of the histogram values.
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func (h *Histogram) Print(w io.Writer) {
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h.PrintWithUnit(w, 1)
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}
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// PrintWithUnit writes textual output of the histogram values .
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// Data in histogram is divided by a Unit before print.
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func (h *Histogram) PrintWithUnit(w io.Writer, unit float64) {
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avg := float64(h.Sum) / float64(h.Count)
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fmt.Fprintf(w, "Count: %d Min: %5.1f Max: %5.1f Avg: %.2f\n", h.Count, float64(h.Min)/unit, float64(h.Max)/unit, avg/unit)
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fmt.Fprintf(w, "%s\n", strings.Repeat("-", 60))
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if h.Count <= 0 {
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return
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}
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maxBucketDigitLen := len(strconv.FormatFloat(h.Buckets[len(h.Buckets)-1].LowBound, 'f', 6, 64))
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if maxBucketDigitLen < 3 {
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// For "inf".
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maxBucketDigitLen = 3
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}
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maxCountDigitLen := len(strconv.FormatInt(h.Count, 10))
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percentMulti := 100 / float64(h.Count)
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accCount := int64(0)
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for i, b := range h.Buckets {
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fmt.Fprintf(w, "[%*f, ", maxBucketDigitLen, b.LowBound/unit)
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if i+1 < len(h.Buckets) {
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fmt.Fprintf(w, "%*f)", maxBucketDigitLen, h.Buckets[i+1].LowBound/unit)
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} else {
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fmt.Fprintf(w, "%*s)", maxBucketDigitLen, "inf")
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}
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accCount += b.Count
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fmt.Fprintf(w, " %*d %5.1f%% %5.1f%%", maxCountDigitLen, b.Count, float64(b.Count)*percentMulti, float64(accCount)*percentMulti)
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const barScale = 0.1
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barLength := int(float64(b.Count)*percentMulti*barScale + 0.5)
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fmt.Fprintf(w, " %s\n", strings.Repeat("#", barLength))
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}
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}
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// String returns the textual output of the histogram values as string.
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func (h *Histogram) String() string {
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var b bytes.Buffer
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h.Print(&b)
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return b.String()
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}
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// Clear resets all the content of histogram.
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func (h *Histogram) Clear() {
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h.Count = 0
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h.Sum = 0
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h.SumOfSquares = 0
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h.Min = math.MaxInt64
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h.Max = math.MinInt64
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for i := range h.Buckets {
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h.Buckets[i].Count = 0
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}
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}
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// Opts returns a copy of the options used to create the Histogram.
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func (h *Histogram) Opts() HistogramOptions {
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return h.opts
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}
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// Add adds a value to the histogram.
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func (h *Histogram) Add(value int64) error {
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bucket, err := h.findBucket(value)
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if err != nil {
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return err
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}
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h.Buckets[bucket].Count++
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h.Count++
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h.Sum += value
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h.SumOfSquares += value * value
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if value < h.Min {
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h.Min = value
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}
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if value > h.Max {
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h.Max = value
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}
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return nil
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}
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func (h *Histogram) findBucket(value int64) (int, error) {
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delta := float64(value - h.opts.MinValue)
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var b int
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if delta >= h.opts.BaseBucketSize {
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// b = log_{1+growthFactor} (delta / baseBucketSize) + 1
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// = log(delta / baseBucketSize) / log(1+growthFactor) + 1
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// = (log(delta) - log(baseBucketSize)) * (1 / log(1+growthFactor)) + 1
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b = int((math.Log(delta)-h.logBaseBucketSize)*h.oneOverLogOnePlusGrowthFactor + 1)
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}
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if b >= len(h.Buckets) {
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return 0, fmt.Errorf("no bucket for value: %d", value)
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}
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return b, nil
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}
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// Merge takes another histogram h2, and merges its content into h.
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// The two histograms must be created by equivalent HistogramOptions.
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func (h *Histogram) Merge(h2 *Histogram) {
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if h.opts != h2.opts {
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log.Fatalf("failed to merge histograms, created by inequivalent options")
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}
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h.Count += h2.Count
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h.Sum += h2.Sum
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h.SumOfSquares += h2.SumOfSquares
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if h2.Min < h.Min {
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h.Min = h2.Min
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}
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if h2.Max > h.Max {
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h.Max = h2.Max
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}
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for i, b := range h2.Buckets {
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h.Buckets[i].Count += b.Count
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}
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}
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