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histogram.go
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histogram.go
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package memmetrics
import (
"fmt"
"time"
"github.com/codahale/hdrhistogram"
"github.com/mailgun/timetools"
)
// HDRHistogram is a tiny wrapper around github.com/codahale/hdrhistogram that provides convenience functions for measuring http latencies
type HDRHistogram struct {
// lowest trackable value
low int64
// highest trackable value
high int64
// significant figures
sigfigs int
h *hdrhistogram.Histogram
}
// NewHDRHistogram creates a new HDRHistogram
func NewHDRHistogram(low, high int64, sigfigs int) (h *HDRHistogram, err error) {
defer func() {
if msg := recover(); msg != nil {
err = fmt.Errorf("%s", msg)
}
}()
return &HDRHistogram{
low: low,
high: high,
sigfigs: sigfigs,
h: hdrhistogram.New(low, high, sigfigs),
}, nil
}
// Export export a HDRHistogram
func (h *HDRHistogram) Export() *HDRHistogram {
var hist *hdrhistogram.Histogram
if h.h != nil {
snapshot := h.h.Export()
hist = hdrhistogram.Import(snapshot)
}
return &HDRHistogram{low: h.low, high: h.high, sigfigs: h.sigfigs, h: hist}
}
// LatencyAtQuantile sets latency at quantile with microsecond precision
func (h *HDRHistogram) LatencyAtQuantile(q float64) time.Duration {
return time.Duration(h.ValueAtQuantile(q)) * time.Microsecond
}
// RecordLatencies Records latencies with microsecond precision
func (h *HDRHistogram) RecordLatencies(d time.Duration, n int64) error {
return h.RecordValues(int64(d/time.Microsecond), n)
}
// Reset reset a HDRHistogram
func (h *HDRHistogram) Reset() {
h.h.Reset()
}
// ValueAtQuantile sets value at quantile
func (h *HDRHistogram) ValueAtQuantile(q float64) int64 {
return h.h.ValueAtQuantile(q)
}
// RecordValues sets record values
func (h *HDRHistogram) RecordValues(v, n int64) error {
return h.h.RecordValues(v, n)
}
// Merge merge a HDRHistogram
func (h *HDRHistogram) Merge(other *HDRHistogram) error {
if other == nil {
return fmt.Errorf("other is nil")
}
h.h.Merge(other.h)
return nil
}
type rhOptSetter func(r *RollingHDRHistogram) error
// RollingClock sets a clock
func RollingClock(clock timetools.TimeProvider) rhOptSetter {
return func(r *RollingHDRHistogram) error {
r.clock = clock
return nil
}
}
// RollingHDRHistogram holds multiple histograms and rotates every period.
// It provides resulting histogram as a result of a call of 'Merged' function.
type RollingHDRHistogram struct {
idx int
lastRoll time.Time
period time.Duration
bucketCount int
low int64
high int64
sigfigs int
buckets []*HDRHistogram
clock timetools.TimeProvider
}
// NewRollingHDRHistogram created a new RollingHDRHistogram
func NewRollingHDRHistogram(low, high int64, sigfigs int, period time.Duration, bucketCount int, options ...rhOptSetter) (*RollingHDRHistogram, error) {
rh := &RollingHDRHistogram{
bucketCount: bucketCount,
period: period,
low: low,
high: high,
sigfigs: sigfigs,
}
for _, o := range options {
if err := o(rh); err != nil {
return nil, err
}
}
if rh.clock == nil {
rh.clock = &timetools.RealTime{}
}
buckets := make([]*HDRHistogram, rh.bucketCount)
for i := range buckets {
h, err := NewHDRHistogram(low, high, sigfigs)
if err != nil {
return nil, err
}
buckets[i] = h
}
rh.buckets = buckets
return rh, nil
}
// Export export a RollingHDRHistogram
func (r *RollingHDRHistogram) Export() *RollingHDRHistogram {
export := &RollingHDRHistogram{}
export.idx = r.idx
export.lastRoll = r.lastRoll
export.period = r.period
export.bucketCount = r.bucketCount
export.low = r.low
export.high = r.high
export.sigfigs = r.sigfigs
export.clock = r.clock
exportBuckets := make([]*HDRHistogram, len(r.buckets))
for i, hist := range r.buckets {
exportBuckets[i] = hist.Export()
}
export.buckets = exportBuckets
return export
}
// Append append a RollingHDRHistogram
func (r *RollingHDRHistogram) Append(o *RollingHDRHistogram) error {
if r.bucketCount != o.bucketCount || r.period != o.period || r.low != o.low || r.high != o.high || r.sigfigs != o.sigfigs {
return fmt.Errorf("can't merge")
}
for i := range r.buckets {
if err := r.buckets[i].Merge(o.buckets[i]); err != nil {
return err
}
}
return nil
}
// Reset reset a RollingHDRHistogram
func (r *RollingHDRHistogram) Reset() {
r.idx = 0
r.lastRoll = r.clock.UtcNow()
for _, b := range r.buckets {
b.Reset()
}
}
func (r *RollingHDRHistogram) rotate() {
r.idx = (r.idx + 1) % len(r.buckets)
r.buckets[r.idx].Reset()
}
// Merged gets merged histogram
func (r *RollingHDRHistogram) Merged() (*HDRHistogram, error) {
m, err := NewHDRHistogram(r.low, r.high, r.sigfigs)
if err != nil {
return m, err
}
for _, h := range r.buckets {
if errMerge := m.Merge(h); errMerge != nil {
return nil, errMerge
}
}
return m, nil
}
func (r *RollingHDRHistogram) getHist() *HDRHistogram {
if r.clock.UtcNow().Sub(r.lastRoll) >= r.period {
r.rotate()
r.lastRoll = r.clock.UtcNow()
}
return r.buckets[r.idx]
}
// RecordLatencies sets records latencies
func (r *RollingHDRHistogram) RecordLatencies(v time.Duration, n int64) error {
return r.getHist().RecordLatencies(v, n)
}
// RecordValues set record values
func (r *RollingHDRHistogram) RecordValues(v, n int64) error {
return r.getHist().RecordValues(v, n)
}