derpLb/main.go

package main

import (
	"fmt"
	"math/rand"
	"net/http"
	"sync"
	"time"
)

var mu sync.Mutex

type queue struct {
	size int
	load []int
}

func remove(s []int, i int) []int {
	copy(s[i:], s[i+1:])
	return s[:len(s)-1]
}

func work(q *queue) <-chan string {
	ch := make(chan string)
	go func() {
		for {
			mu.Lock()
			curLoad := len(q.load)
			mu.Unlock()
			if curLoad > 0 {
				mu.Lock()
				curValue := q.load[0]
				mu.Unlock()
				time.Sleep(time.Millisecond * time.Duration(curValue))
				mu.Lock()
				q.load = remove(q.load, 0)
				mu.Unlock()
				ch <- "finished"
			}
		}
	}()
	return ch
}

func load(q *queue) {
	go func() {
		for {
			time.Sleep(time.Millisecond * time.Duration(rand.Intn(1000)))
			mu.Lock()
			q.load = append(q.load, rand.Intn(1000))
			mu.Unlock()
		}
	}()
}

func printer(q *queue) {
	go func() {
		for {
			mu.Lock()
			fmt.Println(q)
			mu.Unlock()
			time.Sleep(time.Millisecond * 1000)
		}
	}()
}

func init() {
	rand.Seed(time.Now().UnixNano())
}

var q = queue{
	size: 10,
}

func main() {
	http.HandleFunc("/", handler)
	go http.ListenAndServe(":8080", nil)
	fmt.Println("here")
	load(&q)
	printer(&q)
	ch := work(&q)
	for {
		select {
		case <-ch:
			fmt.Println("finished something")
		}
	}
}

func handler(w http.ResponseWriter, req *http.Request) {
	mu.Lock()
	fmt.Fprintf(w, fmt.Sprintf("%v", q))
	mu.Unlock()
}