Python Language Introduction to RabbitMQ using AMQPStorm How to create a delayed queue in RabbitMQ

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Example

First we need to set up two basic channels, one for the main queue, and one for the delay queue. In my example at the end, I include a couple of additional flags that are not required, but makes the code more reliable; such as confirm delivery, delivery_mode and durable. You can find more information on these in the RabbitMQ manual.

After we have set up the channels we add a binding to the main channel that we can use to send messages from the delay channel to our main queue.

channel.queue.bind(exchange='amq.direct', routing_key='hello', queue='hello')

Next we need to configure our delay channel to forward messages to the main queue once they have expired.

delay_channel.queue.declare(queue='hello_delay', durable=True, arguments={
    'x-message-ttl': 5000,
    'x-dead-letter-exchange': 'amq.direct',
    'x-dead-letter-routing-key': 'hello'
})
  • x-message-ttl (Message - Time To Live)

    This is normally used to automatically remove old messages in the queue after a specific duration, but by adding two optional arguments we can change this behaviour, and instead have this parameter determine in milliseconds how long messages will stay in the delay queue.

  • x-dead-letter-routing-key

    This variable allows us to transfer the message to a different queue once they have expired, instead of the default behaviour of removing it completely.

  • x-dead-letter-exchange

    This variable determines which Exchange used to transfer the message from hello_delay to hello queue.

Publishing to the delay queue

When we are done setting up all the basic Pika parameters you simply send a message to the delay queue using basic publish.

delay_channel.basic.publish(exchange='',
                            routing_key='hello_delay',
                            body='test',
                            properties={'delivery_mod': 2})

Once you have executed the script you should see the following queues created in your RabbitMQ management module. enter image description here

Example.

from amqpstorm import Connection

connection = Connection('127.0.0.1', 'guest', 'guest')

# Create normal 'Hello World' type channel.
channel = connection.channel()
channel.confirm_deliveries()
channel.queue.declare(queue='hello', durable=True)

# We need to bind this channel to an exchange, that will be used to transfer
# messages from our delay queue.
channel.queue.bind(exchange='amq.direct', routing_key='hello', queue='hello')

# Create our delay channel.
delay_channel = connection.channel()
delay_channel.confirm_deliveries()

# This is where we declare the delay, and routing for our delay channel.
delay_channel.queue.declare(queue='hello_delay', durable=True, arguments={
    'x-message-ttl': 5000, # Delay until the message is transferred in milliseconds.
    'x-dead-letter-exchange': 'amq.direct', # Exchange used to transfer the message from A to B.
    'x-dead-letter-routing-key': 'hello' # Name of the queue we want the message transferred to.
})

delay_channel.basic.publish(exchange='',
                            routing_key='hello_delay',
                            body='test',
                            properties={'delivery_mode': 2})

print("[x] Sent")


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