Prometheus pushgateway helper script

main.go

package main

import (
	"flag"
	"io"
	"log"
	"net/http"
	"time"
)

var (
	source   = flag.String("s", "", "Source URL")
	dest     = flag.String("d", "", "Destination URL")
	interval = flag.Int("i", 10000, "Interval in milliseconds")
	repeat   = flag.Int("r", 6, "Number of times to repeat")
)

func must[T any](res T, err error) T {
	if err != nil {
		panic(err)
	}
	return res
}

func main() {
	flag.Parse()
	log.SetFlags(log.Lmicroseconds)

	if *source == "" {
		panic("source cannot be empty")
	}
	if *dest == "" {
		panic("destination cannot be empty")
	}
	if *interval <= 0 {
		panic("interval cannot be 0 or negative")
	}
	if *repeat <= 0 {
		panic("repeat cannot be 0 or negative")
	}

	start := time.Now()
	c := http.DefaultClient
	for i := 0; i < *repeat; i++ {
		source := must(c.Do(must(http.NewRequest("GET", *source, nil))))
		destReq := must(c.Do(must(http.NewRequest("POST", *dest, source.Body))))
		resp := must(io.ReadAll(destReq.Body))
		log.Println(string(resp))
		_ = source.Body.Close()
		_ = destReq.Body.Close()

		if i == *repeat-1 {
			break
		}
		next := start.Add(time.Duration(*interval) * time.Millisecond * time.Duration(i+1))
		time.Sleep(next.Sub(time.Now()))
	}
}