main.go

package main

import (
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"sync"
	"time"
)

type counter struct {
	success int
	failed  int
	rps     int
	mu      sync.Mutex
}

func newCounter() *counter {
	c := new(counter)
	go func() {
		for {
			c.mu.Lock()
			curr := c.success
			c.mu.Unlock()

			time.Sleep(time.Second)

			c.mu.Lock()
			c.rps = c.success - curr
			c.mu.Unlock()
		}
	}()
	return c
}

func (c *counter) Add() {
	c.mu.Lock()
	c.success++
	c.mu.Unlock()
}

func (c *counter) AddFail() {
	c.mu.Lock()
	c.failed++
	c.mu.Unlock()
}

func (c *counter) Report() (int, int, int) {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.success, c.failed, c.rps
}

func main() {
	var (
		maxR = flag.Int("r", 100, "max goroutines to launch")
	)
	flag.Parse()
	fmt.Printf("Launching %d goroutines \n", *maxR)

	http.DefaultTransport.(*http.Transport).MaxIdleConnsPerHost = *maxR

	client := &http.Client{Timeout: time.Millisecond * 200}
	c := newCounter()

	r, _ := http.NewRequest(http.MethodGet, "http://localhost:9090", nil)
	r.Header.Add("X-Email-Id", "someone@example.com")
	r.Header.Add("Connection", "keep-alive")
	for i := 0; i < *maxR; i++ {
		go func() {
			for {
				resp, err := client.Do(r)
				if err != nil {
					log.Printf("err sending req: %v", err)
					c.AddFail()
					continue
				}
				io.Copy(ioutil.Discard, resp.Body)
				resp.Body.Close()
				if resp.StatusCode == http.StatusOK {
					c.Add()
				} else {
					c.AddFail()
					log.Println("got resp code", resp.StatusCode)
				}
			}
		}()
	}
	var s, f, rps int
	for {
		time.Sleep(time.Second * 10)
		s, f, rps = c.Report()
		log.Printf("\ntotal successful requests: %v\ntotal failed requests: %v\nrps: %v", s, f, rps)
	}
}