Max concurrent requests limiter

max-concurrent-requests-limiter.go

package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {
	// Create request limiter
	// Only 10 requests are allowed to be in flight at a time
	maxConcurrentRequestsLimiterChannel := maxConcurrentRequestsLimiter(10)

	var waitGroup sync.WaitGroup

	for i := 0; i < 50; i++ {
		waitGroup.Add(1)

		go func(id int) {
			fmt.Printf("Waiting to request %d\n", id)
			// 1. No wait if concurrent requests is less than limit
			// 2. Waits once a concurrent request finishes
			maxConcurrentRequestsLimiterChannel <- true
			// Need to signal request was completed
			defer func() {
				<-maxConcurrentRequestsLimiterChannel
			}()

			fmt.Printf("Making request %d\n", id)
			<-time.After(3 * time.Second)
			fmt.Printf("Maked request %d\n", id)

			waitGroup.Done()
		}(i)
	}

	waitGroup.Wait()
}

func maxConcurrentRequestsLimiter(concurrentRequests uint) chan bool {
	return make(chan bool, concurrentRequests)
}