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 } 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 } // Returns latency at quantile with microsecond precision func (h *HDRHistogram) LatencyAtQuantile(q float64) time.Duration { return time.Duration(h.ValueAtQuantile(q)) * time.Microsecond } // Records latencies with microsecond precision func (h *HDRHistogram) RecordLatencies(d time.Duration, n int64) error { return h.RecordValues(int64(d/time.Microsecond), n) } func (h *HDRHistogram) Reset() { h.h.Reset() } func (h *HDRHistogram) ValueAtQuantile(q float64) int64 { return h.h.ValueAtQuantile(q) } func (h *HDRHistogram) RecordValues(v, n int64) error { return h.h.RecordValues(v, n) } 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 func RollingClock(clock timetools.TimeProvider) rhOptSetter { return func(r *RollingHDRHistogram) error { r.clock = clock return nil } } // RollingHistogram 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 } 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 } 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 } 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() } 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 m.Merge(h); err != nil { return nil, err } } 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] } func (r *RollingHDRHistogram) RecordLatencies(v time.Duration, n int64) error { return r.getHist().RecordLatencies(v, n) } func (r *RollingHDRHistogram) RecordValues(v, n int64) error { return r.getHist().RecordValues(v, n) }