readme.md

goconcurrentqueue - Concurrent safe queues

The package goconcurrentqueue offers a public interface Queue with methods for a queue. It comes with multiple Queue's concurrent-safe implementations, meaning they could be used concurrently by multiple goroutines without adding race conditions.

Topics

• Installation
• Documentation
• Classes diagram
• Queues
  • FIFO
  • FixedFIFO
  • Benchmarks
• Get started
• History

Installation

Execute

go get github.com/enriquebris/goconcurrentqueue

This package is compatible with all golang versions >= 1.7.x

Documentation

Visit goconcurrentqueue at go.dev

Classes diagram

Queues

• First In First Out (FIFO)
  • FIFO
  • FixedFIFO
  • Benchmarks FixedFIFO vs FIFO

FIFO

FIFO: concurrent-safe auto expandable queue.

pros

• It is possible to enqueue as many items as needed.
• Extra methods to get and remove enqueued items:
  • Get: returns an element's value and keeps the element at the queue
  • Remove: removes an element (using a given position) from the queue

cons

• It is slightly slower than FixedFIFO.

FixedFIFO

FixedFIFO: concurrent-safe fixed capacity queue.

pros

• FixedFIFO is, at least, 2x faster than FIFO in concurrent scenarios (multiple GR accessing the queue simultaneously).

cons

• It has a fixed capacity meaning that no more items than this capacity could coexist at the same time.

Benchmarks FixedFIFO vs FIFO

The numbers for the following charts were obtained by running the benchmarks in a 2012 MacBook Pro (2.3 GHz Intel Core i7 - 16 GB 1600 MHz DDR3) with golang v1.12

Enqueue

Dequeue

Get started

FIFO queue simple usage

Live code - playground

package main

import (
	"fmt"

	"github.com/enriquebris/goconcurrentqueue"
)

type AnyStruct struct {
	Field1 string
	Field2 int
}

func main() {
	queue := goconcurrentqueue.NewFIFO()

	queue.Enqueue("any string value")
	queue.Enqueue(5)
	queue.Enqueue(AnyStruct{Field1: "hello world", Field2: 15})

	// will output: 3
	fmt.Printf("queue's length: %v\n", queue.GetLen())

	item, err := queue.Dequeue()
	if err != nil {
		fmt.Println(err)
		return
	}

	// will output "any string value"
	fmt.Printf("dequeued item: %v\n", item)

	// will output: 2
	fmt.Printf("queue's length: %v\n", queue.GetLen())

}

Wait until an element gets enqueued

Live code - playground

package main

import (
	"fmt"
	"time"

	"github.com/enriquebris/goconcurrentqueue"
)

func main() {
	var (
		fifo = goconcurrentqueue.NewFIFO()
		done = make(chan struct{})
	)

	go func() {
		fmt.Println("1 - Waiting for next enqueued element")
		value, _ := fifo.DequeueOrWaitForNextElement()
		fmt.Printf("2 - Dequeued element: %v\n", value)

		done <- struct{}{}
	}()

	fmt.Println("3 - Go to sleep for 3 seconds")
	time.Sleep(3 * time.Second)

	fmt.Println("4 - Enqueue element")
	fifo.Enqueue(100)

	<-done
}

Wait until an element gets enqueued with timeout

Live code - playground

package main

import (
	"context"
	"fmt"
	"time"

	"github.com/enriquebris/goconcurrentqueue"
)

func main() {
	var (
		fifo = goconcurrentqueue.NewFIFO()
		ctx, cancel = context.WithTimeout(context.Background(), 3*time.Second)
	)
	defer cancel()

	fmt.Println("1 - Waiting for next enqueued element")
	_, err := fifo.DequeueOrWaitForNextElementContext(ctx)
    
	if err != nil {
		fmt.Printf("2 - Failed waiting for new element: %v\n", err)
		return
	}
}

Dependency Inversion Principle using concurrent-safe queues

High level modules should not depend on low level modules. Both should depend on abstractions. Robert C. Martin

Live code - playground

package main

import (
	"fmt"

	"github.com/enriquebris/goconcurrentqueue"
)

func main() {
	var (
		queue          goconcurrentqueue.Queue
		dummyCondition = true
	)

	// decides which Queue's implementation is the best option for this scenario
	if dummyCondition {
		queue = goconcurrentqueue.NewFIFO()
	} else {
		queue = goconcurrentqueue.NewFixedFIFO(10)
	}

	fmt.Printf("queue's length: %v\n", queue.GetLen())
	workWithQueue(queue)
	fmt.Printf("queue's length: %v\n", queue.GetLen())
}

// workWithQueue uses a goconcurrentqueue.Queue to perform the work
func workWithQueue(queue goconcurrentqueue.Queue) error {
	// do some work

	// enqueue an item
	if err := queue.Enqueue("test value"); err != nil {
		return err
	}

	return nil
}

History

v0.7.0

• Prevents FIFO.DequeueOrWaitForNextElement to keep waiting for a waitChan while internal queues contain items

v0.6.3

• Prevents FIFO.DequeueOrWaitForNextElement to add useless wait channels

v0.6.2

• Prevents FIFO.DequeueOrWaitForNextElement to gets blocked when waiting for an enqueued element

v0.6.1

• FixedFifo.Enqueue prevents to get blocked trying to send the item over an invalid waitForNextElementChan channel

v0.6.0

• Added DequeueOrWaitForNextElementContext()

v0.5.1

• FIFO.DequeueOrWaitForNextElement() was modified to avoid deadlock when DequeueOrWaitForNextElement && Enqueue are invoked around the same time.
• Added multiple goroutine unit testings for FIFO.DequeueOrWaitForNextElement()

v0.5.0

• Added DequeueOrWaitForNextElement()

v0.4.0

• Added QueueError (custom error)

v0.3.0

• Added FixedFIFO queue's implementation (at least 2x faster than FIFO for multiple GRs)
• Added benchmarks for both FIFO / FixedFIFO
• Added GetCap() to Queue interface
• Removed Get() and Remove() methods from Queue interface

v0.2.0

• Added Lock/Unlock/IsLocked methods to control operations locking

v0.1.0

• First In First Out (FIFO) queue added