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package statsengine
const histogramBucketCount = 8
type histogram struct {
counts [histogramBucketCount]uint64
total uint64
}
type histogramSnapshotInput struct {
counts [histogramBucketCount]uint64
total uint64
}
var histogramBoundariesNs = [histogramBucketCount - 1]uint64{
1_000,
10_000,
100_000,
1_000_000,
10_000_000,
100_000_000,
1_000_000_000,
}
var histogramLabels = [histogramBucketCount]string{
"[0,1us)",
"[1us,10us)",
"[10us,100us)",
"[100us,1ms)",
"[1ms,10ms)",
"[10ms,100ms)",
"[100ms,1s)",
"[1s,+inf)",
}
func newHistogram() *histogram {
return &histogram{}
}
func (h *histogram) Increment(durationNs uint64) {
if h == nil {
return
}
idx := histogramBucketIndex(durationNs)
h.counts[idx]++
h.total++
}
func (h *histogram) Snapshot() HistogramSnapshot {
if h == nil {
return NewHistogramSnapshot(0, nil)
}
return buildHistogramSnapshot(h.snapshotInputs())
}
func (h *histogram) snapshotInputs() histogramSnapshotInput {
if h == nil {
return histogramSnapshotInput{}
}
return histogramSnapshotInput{
counts: h.counts,
total: h.total,
}
}
func buildHistogramSnapshot(in histogramSnapshotInput) HistogramSnapshot {
buckets := make([]HistogramBucketSnapshot, 0, histogramBucketCount)
for i := 0; i < histogramBucketCount; i++ {
lower, upper := histogramBucketRange(i)
buckets = append(buckets, HistogramBucketSnapshot{
Label: histogramLabels[i],
LowerNs: lower,
UpperNs: upper,
Count: in.counts[i],
})
}
return NewHistogramSnapshot(in.total, buckets)
}
func histogramBucketIndex(durationNs uint64) int {
for i, upper := range histogramBoundariesNs {
if durationNs < upper {
return i
}
}
return histogramBucketCount - 1
}
func histogramBucketRange(i int) (lower uint64, upper uint64) {
if i == 0 {
return 0, histogramBoundariesNs[0]
}
if i == histogramBucketCount-1 {
return histogramBoundariesNs[i-1], 0
}
return histogramBoundariesNs[i-1], histogramBoundariesNs[i]
}
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