Simulate async and sync message posting

client.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	// "math/rand"
	"net/http"
	"time"
)

var jobs int
var async bool

func init() {
	flag.IntVar(&jobs, "n", 10, "No of jobs")
	flag.BoolVar(&async, "async", false, "Run async")
}

type MessagePosting struct {
	idx    int
	status string
}

func main() {
	t1 := time.Now()
	flag.Parse()
	c := make(chan string)
	FirePostings(jobs, c)
	if async {
		for i := jobs; i > 0; {
			select {
			case t := <-c:
				fmt.Print(t)
				i--
			}
		}
	}
	fmt.Printf("\nTime: %.2fs\n", time.Now().Sub(t1).Seconds())
}

func (mp *MessagePosting) process(c chan string) {
	var length int64
	t1 := time.Now()
	if mp.status == "queued" {
		res, err := http.Get("http://google.com")
		// time.Sleep(duration())
		res, err = http.Get("http://yahoo.com")
		mp.status = "done"
		by, err := ioutil.ReadAll(res.Body)
		if err != nil {
			panic(err)
		} else {
			length = int64(len(by))
		}
	}
	d := time.Now().Sub(t1).Seconds()
	data := []interface{}{mp.idx, mp.status, d, length}
	if async {
		c <- fmt.Sprintf("%d %s (%.2fs) %d\n", data...)
	} else {
		fmt.Printf("%d %s (%.2fs) %d\n", data...)
	}
}

func FirePostings(howmany int, c chan string) {
	fmt.Println("Queued:", howmany, "jobs\n")
	fmt.Println("Job#   Runtime Size")
	for i := 1; i < howmany+1; i++ {
		mp := &MessagePosting{
			idx:    i,
			status: "queued",
		}
		// if async run goroutine for each job
		if async {
			go mp.process(c)
		} else {
			mp.process(c)
		}

	}
}

// func duration() time.Duration {
// 	return time.Duration(rand.Int63n(int64(1 * time.Second)))
// }

output.txt

$ go run client.go -n 10 
Queued: 10 jobs

Job#   Runtime Size
1 done (0.67s) 231847
2 done (0.57s) 231887
3 done (0.56s) 231292
4 done (0.59s) 231175
5 done (0.56s) 231759
6 done (0.57s) 231871
7 done (0.56s) 231160
8 done (0.57s) 231812
9 done (0.59s) 231219
10 done (0.59s) 231116

Time: 5.82s

$ go run client.go -n 10 -async
Queued: 10 jobs

Job#   Runtime Size
5 done (0.70s) 154600
2 done (0.72s) 231881
9 done (0.73s) 231807
10 done (0.73s) 231808
3 done (0.74s) 231911
8 done (0.74s) 231149
6 done (0.74s) 231267
4 done (0.75s) 231854
7 done (0.75s) 232139
1 done (0.80s) 231137

Time: 0.80s