Implement message prioritization in task queue

Question

How to implement priority queue using RabbitMQ using Python client(Pika/Kombu) or any other Task Queue ?

P.S. -> To implement Task Queue in Message Prioritization.

Answer 1

You can declare a priority queue using pika.

channel.queue_declare('queue_name', {''x-max-priority': 10})

To send a message with priority

channel.basic_publish(exchange='exchange_name',
                      routing_key='routing_key',
                      body='Messsage',
                      properties=BasicProperties(priority=1))

You can set the priority value between 1 to 10, i.e. the maximum priority value that you have set. You can set a maximum priority value of 255, but RabbitMQ recommends the maximum value to be 10. Reference

To consume the message, you define a callback function and call the basic_consume method

def callback(ch, method, properties, body):

    # Getting the message
    message = body.decode()

    ## Do the logic
    print('Received message {}'.format(message))

    # Sending acknowledgment back
    ch.basic_ack(delivery_tag=method.delivery_tag)

channel.basic_consume(callback, queue='queue_name')

The consumer for a priority queue is the same as the consumer for a normal queue. When you set a priority the messages get reordered based on the priority at the broker side. So you consume the messages normally without getting bothered about the messages.

Note: You cannot redeclare a queue as a priority queue. You gotta delete the old queue and declare the new one as a priority queue.