PyRMQ 3.4.5

Python with RabbitMQ—simplified so you won't have to.

PyRMQ

Python with RabbitMQ—simplified so you won't have to.

Features

Stop worrying about boilerplating and implementing retry logic for your queues. PyRMQ already does it for you.

• Use out-of-the-box Consumer and Publisher classes created from pika for your projects and tests.
• Custom DLX-DLK-based retry logic for message consumption.
• Message priorities
• Works with Python 3.
• Production ready

Getting Started

Installation

PyRMQ is available at PyPi.

pip install pyrmq

Usage

Publishing

Just instantiate the feature you want with their respective settings. PyRMQ already works out of the box with RabbitMQ's default initialization settings.

from pyrmq import Publisher
publisher = Publisher(
    exchange_name="exchange_name",
    queue_name="queue_name",
    routing_key="routing_key",
)
publisher.publish({"pyrmq": "My first message"})

Publish message with priorities

To enable prioritization of messages, instantiate your queue with the queue argument x-max-priority. It takes an integer that sets the number of possible priority values with a higher number commanding more priority. Then, simply publish your message with the priority argument specified. Any number higher than the set max priority is floored or considered the same. Read more about message priorities here.

from pyrmq import Publisher
publisher = Publisher(
    exchange_name="exchange_name",
    queue_name="queue_name",
    routing_key="routing_key",
    queue_args={"x-max-priority": 3},
)
publisher.publish({"pyrmq": "My first message"}, priority=1)

:warning: Warning
Adding arguments on an existing queue is not possible. If you wish to add queue arguments, you will need to either
delete the existing queue then recreate the queue with arguments or simply make a new queue with the arguments.

Consuming

Instantiating a Consumer automatically starts it in its own thread making it non-blocking by default. When run after the code from before, you should be able to receive the published data.

from pyrmq import Consumer

def callback(data):
    print(f"Received {data}!")

consumer = Consumer(
    exchange_name="exchange_name",
    queue_name="queue_name",
    routing_key="routing_key",
    callback=callback
)
consumer.start()

DLX-DLK Retry Logic

What if you wanted to retry a failure on a consumed message? PyRMQ offers a custom solution that keeps your message in queues while retrying periodically for a set amount of times.

This approach uses dead letter exchanges and queues to republish a message to your original queue once it has expired. PyRMQ creates this "retry" queue for you with the default naming convention of appending your original queue with .retry.

from pyrmq import Consumer

def callback(data):
    print(f"Received {data}!")
    raise Exception

consumer = Consumer(
    exchange_name="exchange_name",
    queue_name="queue_name",
    routing_key="routing_key",
    callback=callback,
    is_dlk_retry_enabled=True,
)
consumer.start()

This will start a loop of passing your message between the original queue and the retry queue until it reaches the default number of max_retries.

DLX-DLK Retry backoff vs Periodic retries

Since RabbitMQ does not remove expired messages that aren't at the head of the queue, this leads to a congestion of the retry queue that is bottlenecked with an unexpired message at the head. As such, as of 3.3.0, PyRMQ will be using a simple periodic retry.

Using other exchange types

You can use another exchange type just by simply specifying it in the Publisher class. The default is direct.

from pyrmq import Publisher

queue_args = {"routing.sample": "sample", "x-match": "all"}

publisher = Publisher(
    exchange_name="exchange_name",
    exchange_type="headers",
    queue_args=queue_args
)

message_properties = {"headers": {"routing.sample": "sample"}}
publisher.publish({"pyrmq": "My first message"}, message_properties=message_properties)

This is an example of how to publish to a headers exchange that will get routed based on its headers.

Binding an exchange to another exchange

By default, the exchange_name you pass when initializing a Consumer is declared and bound to the passed queue_name. What if you want to bind and declare this exchange to another exchange as well?

This is done by using bound_exchange. This parameter accepts an object with two keys: name of your exchange and its type. Let's take a look at an example to see this in action.

from pyrmq import Consumer

def callback(data):
    print(f"Received {data}!")
    raise Exception

consumer = Consumer(
    exchange_name="direct_exchange",
    queue_name="direct_queue",
    routing_key="routing_key",
    bound_exchange={"name": "headers_exchange_name", "type": "headers"},
    callback=callback,
    is_dlk_retry_enabled=True,
)
consumer.start()

In the example above, we want to consume from an exchange called direct_exchange that is directly bound to queue direct_queue. We want direct_exchange to get its messages from another exchange called headers_exchange_name of type headers. By using bound_exchange, PyRMQ declares direct_exchange and direct_queue along with any queue or exchange arguments you may have first then declares the bound exchange next and binds them together. This is done to alleviate the need to declare your bound exchange manually.

:warning: Important
Since this method uses e2e bindings, if you're using a headers exchange to bind
your consumer to, they and your publisher must all have the same routing key to route the messages properly. This
is not needed for exchange to queue bindings as the routing key is optional for those.

Documentation

Visit https://pyrmq.readthedocs.io for the most up-to-date documentation.

Testing

For development, just run:

pytest

To test for all the supported Python versions:

pip install tox
tox

To test for a specific Python version:

tox -e py38