Concurrency Patterns: Worker Pools

Worker Pool Pattern

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

A common pattern for processing many jobs with a limited number of goroutines.

func worker(id int, jobs <-chan int, results chan<- int) {
    for j := range jobs {
        fmt.Printf("worker %d processing %d\n", id, j)
        results <- j * 2
    }
}

func main() {
    const numWorkers = 3
    jobs := make(chan int, 100)
    results := make(chan int, 100)

    for w := 1; w <= numWorkers; w++ {
        go worker(w, jobs, results)
    }

    for j := 1; j <= 5; j++ { jobs <- j }
    close(jobs)

    for a := 1; a <= 5; a++ { fmt.Println(<-results) }
}

Cancellation with context

ctx, cancel := context.WithCancel(context.Background())
go func() { time.Sleep(2 * time.Second); cancel() }()
select {
case <-ctx.Done(): fmt.Println("canceled")
case v := <-results: fmt.Println(v)
}