github.com/psiphon-inc/goarista@v0.0.0-20160825065156-d002785f4c67/monitor/histogram.go (about)

     1  // Copyright (C) 2015  Arista Networks, Inc.
     2  // Use of this source code is governed by the Apache License 2.0
     3  // that can be found in the COPYING file.
     4  
     5  package monitor
     6  
     7  import (
     8  	"expvar"
     9  	"strings"
    10  	"time"
    11  
    12  	"github.com/aristanetworks/goarista/monitor/stats"
    13  )
    14  
    15  // Histogram contains the data needed to properly export itself to expvar
    16  // and provide a pretty printed version
    17  type Histogram struct {
    18  	name      string
    19  	histogram *stats.Histogram
    20  }
    21  
    22  // NewHistogram creates a new histogram and registers an HTTP handler for it.
    23  // "name" must end with "Histogram", so that the "/debug/latency" handler can
    24  // pretty print it.
    25  func NewHistogram(name string, numBuckets int, growth float64, smallest float64,
    26  	minValue int64) *Histogram {
    27  
    28  	histogramOptions := stats.HistogramOptions{
    29  		NumBuckets:         numBuckets,
    30  		GrowthFactor:       growth,
    31  		SmallestBucketSize: smallest,
    32  		MinValue:           minValue,
    33  	}
    34  
    35  	hist := stats.NewHistogram(histogramOptions)
    36  	histogram := &Histogram{
    37  		name:      name,
    38  		histogram: hist,
    39  	}
    40  	expvar.Publish(name, histogram)
    41  	return histogram
    42  
    43  }
    44  
    45  func (h *Histogram) String() string {
    46  	return h.addUnits(h.histogram.Delta1m().String()) +
    47  		h.addUnits(h.histogram.Delta10m().String()) +
    48  		h.addUnits(h.histogram.Delta1h().String()) +
    49  		h.addUnits(h.histogram.Value().String())
    50  }
    51  
    52  // UpdateLatencyValues updates the stats.Histogram's buckets with the new
    53  // datapoint and updates the string associated with the expvar.String
    54  func (h *Histogram) UpdateLatencyValues(t0, t1 time.Time) {
    55  	h.histogram.Add(int64(t1.Sub(t0) / time.Microsecond))
    56  }
    57  
    58  func (h *Histogram) addUnits(hist string) string {
    59  	i := strings.Index(hist, "\n")
    60  	return hist[:i] + "µs" + hist[i:]
    61  }