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// Hook go-metrics into expvar
// on any /debug/metrics request, load all vars from the registry into expvar, and execute regular expvar handler
package exp
import (
"expvar"
"fmt"
"net/http"
"sync"
"github.com/rcrowley/go-metrics"
)
type exp struct {
expvarLock sync.Mutex // expvar panics if you try to register the same var twice, so we must probe it safely
registry metrics.Registry
}
func (exp *exp) expHandler(w http.ResponseWriter, r *http.Request) {
// load our variables into expvar
exp.syncToExpvar()
// now just run the official expvar handler code (which is not publicly callable, so pasted inline)
w.Header().Set("Content-Type", "application/json; charset=utf-8")
fmt.Fprintf(w, "{\n")
first := true
expvar.Do(func(kv expvar.KeyValue) {
if !first {
fmt.Fprintf(w, ",\n")
}
first = false
fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
})
fmt.Fprintf(w, "\n}\n")
}
// Exp will register an expvar powered metrics handler with http.DefaultServeMux on "/debug/vars"
func Exp(r metrics.Registry) {
h := ExpHandler(r)
// this would cause a panic:
// panic: http: multiple registrations for /debug/vars
// http.HandleFunc("/debug/vars", e.expHandler)
// haven't found an elegant way, so just use a different endpoint
http.Handle("/debug/metrics", h)
}
// ExpHandler will return an expvar powered metrics handler.
func ExpHandler(r metrics.Registry) http.Handler {
e := exp{sync.Mutex{}, r}
return http.HandlerFunc(e.expHandler)
}
func (exp *exp) getInt(name string) *expvar.Int {
var v *expvar.Int
exp.expvarLock.Lock()
p := expvar.Get(name)
if p != nil {
v = p.(*expvar.Int)
} else {
v = new(expvar.Int)
expvar.Publish(name, v)
}
exp.expvarLock.Unlock()
return v
}
func (exp *exp) getFloat(name string) *expvar.Float {
var v *expvar.Float
exp.expvarLock.Lock()
p := expvar.Get(name)
if p != nil {
v = p.(*expvar.Float)
} else {
v = new(expvar.Float)
expvar.Publish(name, v)
}
exp.expvarLock.Unlock()
return v
}
func (exp *exp) publishCounter(name string, metric metrics.Counter) {
v := exp.getInt(name)
v.Set(metric.Count())
}
func (exp *exp) publishGauge(name string, metric metrics.Gauge) {
v := exp.getInt(name)
v.Set(metric.Value())
}
func (exp *exp) publishGaugeFloat64(name string, metric metrics.GaugeFloat64) {
exp.getFloat(name).Set(metric.Value())
}
func (exp *exp) publishHistogram(name string, metric metrics.Histogram) {
h := metric.Snapshot()
ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
exp.getInt(name + ".count").Set(h.Count())
exp.getFloat(name + ".min").Set(float64(h.Min()))
exp.getFloat(name + ".max").Set(float64(h.Max()))
exp.getFloat(name + ".mean").Set(float64(h.Mean()))
exp.getFloat(name + ".std-dev").Set(float64(h.StdDev()))
exp.getFloat(name + ".50-percentile").Set(float64(ps[0]))
exp.getFloat(name + ".75-percentile").Set(float64(ps[1]))
exp.getFloat(name + ".95-percentile").Set(float64(ps[2]))
exp.getFloat(name + ".99-percentile").Set(float64(ps[3]))
exp.getFloat(name + ".999-percentile").Set(float64(ps[4]))
}
func (exp *exp) publishMeter(name string, metric metrics.Meter) {
m := metric.Snapshot()
exp.getInt(name + ".count").Set(m.Count())
exp.getFloat(name + ".one-minute").Set(float64(m.Rate1()))
exp.getFloat(name + ".five-minute").Set(float64(m.Rate5()))
exp.getFloat(name + ".fifteen-minute").Set(float64((m.Rate15())))
exp.getFloat(name + ".mean").Set(float64(m.RateMean()))
}
func (exp *exp) publishTimer(name string, metric metrics.Timer) {
t := metric.Snapshot()
ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
exp.getInt(name + ".count").Set(t.Count())
exp.getFloat(name + ".min").Set(float64(t.Min()))
exp.getFloat(name + ".max").Set(float64(t.Max()))
exp.getFloat(name + ".mean").Set(float64(t.Mean()))
exp.getFloat(name + ".std-dev").Set(float64(t.StdDev()))
exp.getFloat(name + ".50-percentile").Set(float64(ps[0]))
exp.getFloat(name + ".75-percentile").Set(float64(ps[1]))
exp.getFloat(name + ".95-percentile").Set(float64(ps[2]))
exp.getFloat(name + ".99-percentile").Set(float64(ps[3]))
exp.getFloat(name + ".999-percentile").Set(float64(ps[4]))
exp.getFloat(name + ".one-minute").Set(float64(t.Rate1()))
exp.getFloat(name + ".five-minute").Set(float64(t.Rate5()))
exp.getFloat(name + ".fifteen-minute").Set(float64((t.Rate15())))
exp.getFloat(name + ".mean-rate").Set(float64(t.RateMean()))
}
func (exp *exp) syncToExpvar() {
exp.registry.Each(func(name string, i interface{}) {
switch i.(type) {
case metrics.Counter:
exp.publishCounter(name, i.(metrics.Counter))
case metrics.Gauge:
exp.publishGauge(name, i.(metrics.Gauge))
case metrics.GaugeFloat64:
exp.publishGaugeFloat64(name, i.(metrics.GaugeFloat64))
case metrics.Histogram:
exp.publishHistogram(name, i.(metrics.Histogram))
case metrics.Meter:
exp.publishMeter(name, i.(metrics.Meter))
case metrics.Timer:
exp.publishTimer(name, i.(metrics.Timer))
default:
panic(fmt.Sprintf("unsupported type for '%s': %T", name, i))
}
})
}