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sogno-job-queue

Provides utility classes to be used in a frontend and backend in tandem with a rabbitmq-broker.

Publisher

The publisher provides everything needed to publish messages on an exchange. Routing logic is not included here bu in the Listenener

Example

from amqp import AmqpPublisher
import asyncio

publisher = AmqpPublisher(
    amqp_username="user", 
    amqp_password="testpw", 
    amqp_exchange_name="test_exchange",
    amqp_host="127.0.0.1",
    amqp_port=5672
)

async def send():
    for i in range(1000):
        await publisher.publish("job.test", i)
        await asyncio.sleep(1)

asyncio.run(send())

This sends 1000 integers to the exchange "test_exchange" under the topic "job.test"

Listener

This class provides both an active request for a message as well as an passive consumer usablitiy. It is assumed that the listener also establishes the routing logic if not already configured from a different place.

Example (passive)

from amqp import AmqpListener
import asyncio

listener = AmqpListener(
    amqp_username="user",
    amqp_password="testpw",
    amqp_queue_name="test_queue",
    amqp_host="127.0.0.1",
    amqp_port=5672,
)


async def listen():
    await listener.bind_to_exchange(exchange_name="test_exchange")
    listener.add_message_processor(print)
    await listener.process_messages()

asyncio.run(listen())

Again we create an AmqpListener object with everything needed for configuration of the broker. In the listen() coroutine the queue is bound to the already existing exchange. Then we add a callback function (in this case print()) that takes the message body as string as an argument. It will be called every time a message is recieved and can be either sync or async. .process_messages() starts an infinite loop of consuming messages, if the callback function returns without error the message will be ackknowledeged automatically.

Excample (aktive)

from amqp import AmqpListener
import asyncio

listener = AmqpListener(
    amqp_username="user",
    amqp_password="testpw",
    amqp_queue_name="test_queue",
    amqp_port=5672,
)


async def listen():
    await listener.bind_to_exchange(exchange_name="test_exchange")
    for i in range(1000):
        msg = await listener.get_message()
        async with msg.process():
            print(msg)
        await asyncio.sleep(1)


asyncio.run(listen())

Instead of passively listening we can actively request a message from a queue. If there is no message this is repeated until a message is available. Returned is an aio_pika.IncommingMessage object that can be processed. The message has to be acknowledged manually, done here using the .process() context manager.

Known Issues

None of these are considered pressing issue, if they hinder development for somebody feel free to open an issue or contact us.

  • Asynchronous but not threadsafe.
  • Exchange has to be declared (from elsewhere) before queue is bound.
  • Listener fails once and succeds in retry in testsetup (Error message suggests a problem with setup on windows)
  • Passive listening only gives access to the message body (this was chosen to avoid the need to dive into the implementation of the amqp client).