goLang Learning Blocks ~ Concurrency design pattern using Channels

Hello!

Today I demonstrating concurrency design pattern FANin.

In this sample concurrency design pattern FANin is being demonstrated using GoRoutine, Channels, Range, Select

Imp points

• Range will keep iterating and fetching the value until channel will be closed

• Select is useful which we are dealing with multiple channels together and we need to fetch from the channel whichever is ready with value.

In this design pattern a single channel accepts inputs from multiple output channels.

Test the code

package main

import "fmt"

func main() {
	even := make(chan int)
	odd := make(chan int)
	fanin := make(chan int)

	// Send, this will alunch a go routine, which will execute saparatly from mai routine
	go sendChannel(even, odd)
	go receiveChannel(even, odd, fanin)
    
       // range on channel will iterate until channel will be closed
	for v := range fanin {
		fmt.Printf("FanIn Channel value %v \n", v)
	}
	fmt.Printf("About to Exit")
}

func sendChannel(e, o chan<- int) {
	defer close(e)
	defer close(o)
	for index := 0; index < 10; index++ {
		if index%2 == 0 {
			e <- index
		} else {
			o <- index
		}
	}
}

func receiveChannel(e, o <-chan int, f int) {
	var okay int
	for {
		select {
		case v, ok := <-e:     // v will capture the channel value and ok will capture the state of channel
			if !ok {                                // If channel is closed then increase okay
				fmt.Printf("Even channel closed: %v  \n", ok)
				okay++
			} else {
				fmt.Printf("Even channel Value received: %v  \n", v)
				f <- v                         // Assign the value to fanin channel 
			}
		case v, ok := <-o:
			if !ok {
				fmt.Printf("Odd channel closed: %v \n", ok)
				okay++
			} else {
				fmt.Printf("Odd channel Value received: %v  \n", v)
				f <- v
			}
		}

              // Loop exit condition 
		if okay == 2 {
			fmt.Printf("Loop ends: %v \n", okay)
                        close(f)
			return
		}
	}
}

Cheers
Dev

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