RabbitMQ

RabbitMQ is an open-source message broker that implements AMQP (Advanced Message Queue Protocol).

setup

We can pull the RabbitMQ image first and run a container then or we run this command to do both

docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3.9-management

About this docker commands:

-it: Run a container in interactive mode.This means you can execute commands inside the container while it is still running.
--rm: Automatically remove the container when it exits.
--name: Name of the container.
-p: Publish a container's port(s) to the host.

Now we can then open the RabbitMQ on our browser located on http://localhost:15672/. The default username and password is guest.

Using Python (send-my-name)

Install library

pip install pika

Producer

We have Producer to send the message by channel to Consumer, we need channel first. After import pika, we need to create a connection and a channel.

connection_parameters = pika.ConnectionParameters('localhost')
connection = pika.BlockingConnection(connection_parameters)
channel  = connection.channel()

We need queue to control the message send by Producer, We can create a queue using the following line by give name to it.

channel.queue_declare(queue='name-send')

The best and easiest way to publish a message on the queue is by using .basic_public method.

message = "hello I am mgh27"
channel.basic_publish(exchange='', routing_key='name-send', body=message)

Finally, we close the connection in Producer side.

connection.close()

Consumer

At the first its like the Producer we have make channel.

import pika
connection_parameters = pika.ConnectionParameters('localhost')
connection = pika.BlockingConnection(connection_parameters)
channel  = connection.channel()
channel.queue_declare(queue='name-send')

We can consume the message by use this code.

def on_message_received(ch, method, properties, body):
    print(f" [x] received {body}")
channel.basic_consume(queue='name-send', auto_ack=True, on_message_callback=on_message_received)
print("[*] Start listening")
channel.start_consuming()

In the preceding code,on_message_callback means that what to do when message is received, auto_ack=True means that it automatically acknowledges receipt of the message if it is false it come back to the queue if consumer did not process it.

Execution

At the first we running consume.py, we can see this line in command line.

[*] Start listening for message.

Then after executing producer.py, it sends "hello I am mgh27" to the name-send queue and consumer receives and prints that on the terminal.

What if we have multiple consumers? By having this kind of implementation, it executes Round-robin algorithm. But what if after receiving the third message, the first consumer is busy, and the second consumer is free? Since it uses Round-robin algorithm, it could be problematic.