If you pass model.Earliest.Time() to prometheus/client_golang it sends -9223372036854776, which is 192 milliseconds less than the original. This value will cause an overflow when read by prometheus/web/api/v1, turning it into a very large positive time.
I am using github.com/prometheus/client_golang v1.11.0
and github.com/prometheus/client_model v0.2.0.
To illustrate:
https://go.dev/play/p/b_75bSN2Gyr
package main
import (
"fmt"
"strconv"
"time"
"github.com/prometheus/common/model"
)
// As found in github.com/prometheus/common/model
func formatTime(t time.Time) string {
return strconv.FormatFloat(float64(t.Unix())+float64(t.Nanosecond())/1e9, 'f', -1, 64)
}
// As found in github.com/prometheus/prometheus/model/timestamp
func FromTime(t time.Time) int64 {
return t.Unix()*1000 + int64(t.Nanosecond())/int64(time.Millisecond)
}
func main() {
t1 := model.Earliest.Time()
fmt.Println(formatTime(t1))
t2 := time.Unix(-9223372036854776, 0) // this is the number output by the previous line
fmt.Println(t1, FromTime(t1))
fmt.Println(t2, FromTime(t2))
}I believe the problem arises because strconv.FormatFloat() is asked to round the number as if it came from a float64, and model.Earliest is the largest negative int64 so it doesn't fit in a float64, and the milliseconds get dropped.
This arose while trying to work round #621
If you pass
model.Earliest.Time()to prometheus/client_golang it sends -9223372036854776, which is 192 milliseconds less than the original. This value will cause an overflow when read byprometheus/web/api/v1, turning it into a very large positive time.I am using github.com/prometheus/client_golang v1.11.0
and github.com/prometheus/client_model v0.2.0.
To illustrate:
https://go.dev/play/p/b_75bSN2Gyr
I believe the problem arises because
strconv.FormatFloat()is asked to round the number as if it came from afloat64, andmodel.Earliestis the largest negativeint64so it doesn't fit in afloat64, and the milliseconds get dropped.This arose while trying to work round #621