path: root/metrics/debug.go

package metrics

import (
    "runtime/debug"
    "time"
)

var (
    debugMetrics struct {
        GCStats struct {
            LastGC Gauge
            NumGC  Gauge
            Pause  Histogram
            //PauseQuantiles Histogram
            PauseTotal Gauge
        }
        ReadGCStats Timer
    }
    gcStats debug.GCStats
)

// Capture new values for the Go garbage collector statistics exported in
// debug.GCStats.  This is designed to be called as a goroutine.
func CaptureDebugGCStats(r Registry, d time.Duration) {
    for range time.Tick(d) {
        CaptureDebugGCStatsOnce(r)
    }
}

// Capture new values for the Go garbage collector statistics exported in
// debug.GCStats.  This is designed to be called in a background goroutine.
// Giving a registry which has not been given to RegisterDebugGCStats will
// panic.
//
// Be careful (but much less so) with this because debug.ReadGCStats calls
// the C function runtime·lock(runtime·mheap) which, while not a stop-the-world
// operation, isn't something you want to be doing all the time.
func CaptureDebugGCStatsOnce(r Registry) {
    lastGC := gcStats.LastGC
    t := time.Now()
    debug.ReadGCStats(&gcStats)
    debugMetrics.ReadGCStats.UpdateSince(t)

    debugMetrics.GCStats.LastGC.Update(gcStats.LastGC.UnixNano())
    debugMetrics.GCStats.NumGC.Update(gcStats.NumGC)
    if lastGC != gcStats.LastGC && 0 < len(gcStats.Pause) {
        debugMetrics.GCStats.Pause.Update(int64(gcStats.Pause[0]))
    }
    //debugMetrics.GCStats.PauseQuantiles.Update(gcStats.PauseQuantiles)
    debugMetrics.GCStats.PauseTotal.Update(int64(gcStats.PauseTotal))
}

// Register metrics for the Go garbage collector statistics exported in
// debug.GCStats.  The metrics are named by their fully-qualified Go symbols,
// i.e. debug.GCStats.PauseTotal.
func RegisterDebugGCStats(r Registry) {
    debugMetrics.GCStats.LastGC = NewGauge()
    debugMetrics.GCStats.NumGC = NewGauge()
    debugMetrics.GCStats.Pause = NewHistogram(NewExpDecaySample(1028, 0.015))
    //debugMetrics.GCStats.PauseQuantiles = NewHistogram(NewExpDecaySample(1028, 0.015))
    debugMetrics.GCStats.PauseTotal = NewGauge()
    debugMetrics.ReadGCStats = NewTimer()

    r.Register("debug.GCStats.LastGC", debugMetrics.GCStats.LastGC)
    r.Register("debug.GCStats.NumGC", debugMetrics.GCStats.NumGC)
    r.Register("debug.GCStats.Pause", debugMetrics.GCStats.Pause)
    //r.Register("debug.GCStats.PauseQuantiles", debugMetrics.GCStats.PauseQuantiles)
    r.Register("debug.GCStats.PauseTotal", debugMetrics.GCStats.PauseTotal)
    r.Register("debug.ReadGCStats", debugMetrics.ReadGCStats)
}

// Allocate an initial slice for gcStats.Pause to avoid allocations during
// normal operation.
func init() {
    gcStats.Pause = make([]time.Duration, 11)
}