Go example regarding channels and backpressure

backpressure-detection.go

// https://play.golang.org/p/z2eYKhyoIk
package main

import "fmt"
import "time"
import "sync"

// Blocking detection for when pushing on filled buffered channel by using default.
func main() {
	ch1 := make(chan int, 2)
	ch1 <- 1
	ch1 <- 2
	
	var wg sync.WaitGroup
	wg.Add(1)
	
	// Simple goroutine to drain the channel after a second.
	go func() {
		time.Sleep(time.Second)
		
		fmt.Println("Draining channel!")

		for range ch1 {}
		wg.Done()
		
	}()
	
	for {
		select {
		// Imagine that we want to send ch1 some work, and at the
		// same time know about the channels backpressure.
		case ch1 <- 3:
			close(ch1)
			wg.Wait()
			fmt.Println("Done!")
			return
		default:
			fmt.Println("No more room on channel, wait a little.")
			time.Sleep(time.Duration(100) * time.Millisecond)
		}	
	}
}

backpressure.go

// https://play.golang.org/p/BaNEsD1hSu
package main

import "fmt"
import "time"

// Multiple workers draining work from the same channel. This could be used to
// handle fast -> slow process.
func main() {
	work := make(chan int)
	
	// Spawn 10 workers
	for i := 0; i < 10; i++ {
		go doWork(i, work)
	}
	
	// Generate some work.
	for i := 0; i < 100; i++ {
		work <- i
	}
	close(work)
	
	// Sleep little to allow the last bit of work to finish in the goroutine.
	time.Sleep(time.Second)
}

func doWork(id int, work <-chan int) {
	fmt.Printf("Worker %d started.\n", id)
	for i := range work {
		fmt.Printf("Work on %d by %d\n", i, id)
		time.Sleep(time.Duration(100) * time.Millisecond)
	}
	fmt.Printf("Worker %d finsihed.\n", id)
}