Prometheus Go客户端库的ExponentialBuckets API的最低粒度是多少？

Question

I am experimenting with Prometheus Go client library. Does ExponentialBuckets API accept parameter start of less than 1.0 (e.g., 0.001)?

Answer 1

package prometheus

import "github.com/prometheus/client_golang/prometheus"

func ExponentialBuckets

func ExponentialBuckets(start, factor float64, count int) []float64

ExponentialBuckets creates 'count' buckets, where the lowest bucket has an upper bound of 'start' and each following bucket's upper bound is 'factor' times the previous bucket's upper bound. The final +Inf bucket is not counted and not included in the returned slice. The returned slice is meant to be used for the Buckets field of HistogramOpts.

The function panics if 'count' is 0 or negative, if 'start' is 0 or negative, or if 'factor' is less than or equal 1.

---

Try start equal to the minimum normal positive float64.

package main

import (
    "fmt"
    "math"
)

func main() {
    // Minimum normal positive float64
    // 0 00000000001 0000000000000000000000000000000000000000000000000000
    // 2.2250738585072014e−308
    start := math.Float64frombits(uint64(1 << (63 - 11)))
    fmt.Println(start)
}

Output:

2.2250738585072014e-308