README.md

Ordered Concurrently

A library for parallel processing with ordered output in Go. This module processes work concurrently / in parallel and returns output in a channel in the order of input. It is useful in concurrently / parallelly processing items in a queue, and get output in the order provided by the queue.

Usage

Get Module

go get github.com/tejzpr/ordered-concurrently/v3

Import Module in your source code

import concurrently "github.com/tejzpr/ordered-concurrently/v3" 

Create a work function by implementing WorkFunction interface

// Create a type based on your input to the work function
type loadWorker int

// The work that needs to be performed
// The input type should implement the WorkFunction interface
func (w loadWorker) Run(ctx context.Context) interface{} {
	time.Sleep(time.Millisecond * time.Duration(rand.Intn(100)))
	return w * 2
}

Demo

Go Playground

Run

Example - 1

func main() {
	max := 10
	inputChan := make(chan concurrently.WorkFunction)
	ctx := context.Background()
	output := concurrently.Process(ctx, inputChan, &concurrently.Options{PoolSize: 10, OutChannelBuffer: 10})
	go func() {
		for work := 0; work < max; work++ {
			inputChan <- loadWorker(work)
		}
		close(inputChan)
	}()
	for out := range output {
		log.Println(out.Value)
	}
}

Example - 2 - Process unknown number of inputs

func main() {
	inputChan := make(chan concurrently.WorkFunction, 10)
	ctx := context.Background()
	output := concurrently.Process(ctx, inputChan, &concurrently.Options{PoolSize: 10, OutChannelBuffer: 10})

	ticker := time.NewTicker(100 * time.Millisecond)
	done := make(chan bool)
	wg := &sync.WaitGroup{}
	go func() {
		input := 0
		for {
			select {
			case <-done:
				return
			case <-ticker.C:
				inputChan <- loadWorker(input)
				wg.Add(1)
				input++
			default:
			}
		}
	}()

	var res []loadWorker
	go func() {
		for out := range output {
			res = append(res, out.Value.(loadWorker))
			wg.Done()
		}
	}()

	time.Sleep(1600 * time.Millisecond)
	ticker.Stop()
	done <- true
	close(inputChan)
	wg.Wait()

	// Check if output is sorted
	isSorted := sort.SliceIsSorted(res, func(i, j int) bool {
		return res[i] < res[j]
	})
	if !isSorted {
		log.Println("output is not sorted")
	}
}

Credits

1. u/justinisrael for inputs on improving resource usage.
2. mh-cbon for identifying potential deadlocks.