# RabbitMQ for AUSF's Message Queueing

RabbitMQ is an open source message broker that supports multiple messaging protocols such as AMQP, MQTT, STOMP and HTTP. It can be deployed on-premises or in the cloud, and it offers features such as high availability, clustering, federation, security and management.

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I got this one from [Stackoverflow](https://stackoverflow.com/questions/39529747/advantages-disadvantages-of-brokered-vs-non-brokered-messaging-systems)
RabbitMQ type Broker system:

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## Advantages of using RabbitMQ on AUSF
One possible way to use RabbitMQ for 5G core’s AUSF is to implement a message queue solution that enables asynchronous communication between the AUSF and other network functions. This can provide some benefits such as:

* **Reliable message delivery**: Using a message queue can ensure that business-critical messages between network functions will not be lost and that they will be only be delivered to the recipient once. With this feature in place, additional de-duplication or loss-prevention logic is unnecessary.
* **Inter-function connectivity**: RabbitMQ can handle message encryption, transactionality and other communication aspects between network functions. This simplifies network function development and enables disparate architectures to work together.
* **Versatility**: RabbitMQ can support multiple languages, such as Java, Node.js, COBOL, C/C++, Go, .NET, Python, Ruby, and C#. It can also support numerous application programing interfaces (APIs) and protocols, including HTTP/2, which is used by the AUSF SBI.
* **Resilience**: Asynchronous messaging ensures network function-specific faults won’t impact the system. If one component in the system stalls, all others can continue interacting with the queue and processing messages. This decreases the chance that the entire system’s stability will be impacted by one part’s failure.
* **Improved security**: RabbitMQ can identify and authenticate all messages, and in some cases, it can set to encrypt messages at rest, in transit, or end-to-end. This can contribute to the overall security of the network functions and/or infrastructure.

To implement RabbitMQ for 5G core’s AUSF, one may need to use a message queue solution that supports the protocols and APIs that AUSF uses, such as HTTP/2. One may also need to configure the message queue settings to handle authentication, encryption, transactionality and other aspects of communication between AUSF and other network functions.

## Disadvantages of using RabbitMQ on AUSF

Some of the disadvantages of implementing RabbitMQ on AUSF are:

* **Performance overhead**: Using a message queue introduces an additional layer of complexity and latency in the communication between network functions. This may affect the performance and scalability of the system, especially for high-throughput or low-latency scenarios.
* **Deployment and maintenance costs**: Using RabbitMQ requires deploying and maintaining a broker or a cluster of brokers on machines or in the cloud. This may incur some costs in terms of hardware resources, cloud services fees, installation time and effort, monitoring and troubleshooting tools, etc.

## Brief Example of What Would the Code Look Like (not exactly)

package main

import (
	"fmt"
	"log"

	"github.com/rabbitmq/amqp091-go"
)

// AUSF is a struct that represents the Authentication Server Function
type AUSF struct {
	conn    *amqp.Connection // the connection to RabbitMQ broker
	channel *amqp.Channel    // the channel for sending and receiving messages
	queue   amqp.Queue       // the queue for AuthenticationResponse events
}

// NewAUSF creates a new instance of AUSF and connects to RabbitMQ broker
func NewAUSF() *AUSF {
	// Connect to RabbitMQ broker
	conn, err := amqp.Dial("amqp://guest:guest@localhost:5672/")
	if err != nil {
		log.Fatalf("Failed to connect to RabbitMQ: %v", err)
	}

	// Create a channel
	channel, err := conn.Channel()
	if err != nil {
		log.Fatalf("Failed to open a channel: %v", err)
	}

	// Declare a queue for AuthenticationResponse events
	queue, err := channel.QueueDeclare(
		"AuthenticationResponse", // name of the queue
		false,                    // durable
		false,                    // delete when unused
		false,                    // exclusive
		false,                    // no-wait
		nil,                      // arguments
	)
	if err != nil {
		log.Fatalf("Failed to declare a queue: %v", err)
	}

	return &AUSF{
		conn:    conn,
		channel: channel,
		queue:   queue,
	}
}

// Close closes the connection and the channel
func (a *AUSF) Close() {
	a.channel.Close()
	a.conn.Close()
}

// PublishAuthenticationResponse publishes an AuthenticationResponse event to the queue
func (a *AUSF) PublishAuthenticationResponse(body string) error {
	return a.channel.Publish(
		"",              // exchange
		a.queue.Name,    // routing key
		false,           // mandatory
		false,           // immediate
		amqp.Publishing{ // message to publish
			ContentType: "text/plain",
			Body:        []byte(body),
		},
	)
}

// ConsumeAuthenticationResponse consumes AuthenticationResponse events from the queue and calls a callback function
func (a *AUSF) ConsumeAuthenticationResponse(callback func(string)) error {
	msgs, err := a.channel.Consume(
		a.queue.Name, // queue name
		"",           // consumer tag
		true,         // auto-acknowledge
		false,        // exclusive
		false,        // no-local
		false,        // no-wait
		nil,          // arguments
	)
	if err != nil {
		return err
	}

	go func() {
		for msg := range msgs {
			callback(string(msg.Body))
		}
	}()

	return nil
}

func main() {
	fmt.Println("Starting AUSF...")

	ausf := NewAUSF()
	defer ausf.Close()

	err := ausf.ConsumeAuthenticationResponse(func(body string) {
		fmt.Printf("Received AuthenticationResponse: %s\n", body)
	})
	if err != nil {
		log.Fatalf("Failed to consume AuthenticationResponse: %v", err)
	}

	err = ausf.PublishAuthenticationResponse("User123 authenticated")
	if err != nil {
		log.Fatalf("Failed to publish AuthenticationResponse: %v", err)
	}

	fmt.Println("Press ENTER to exit")
	fmt.Scanln()
}

## Compared with ZeroMQ, brokerless message queuing
Due to the absence of a Go Language implementation, ZeroMQ, despite its faster performance, is not compatible with free5gc.
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