Blocking get aio_pika

[josephbiko]

I expected

await queue.get() to be blocking in aio_pika, but even when I don't set the timeout parameter I instantly get an error:

aio_pika.exceptions.QueueEmpty

Anyway to get a blocking get in aio_pika?

[mosquito]

When queue is empty an exception aio_pika.exceptions.QueueEmpty raising. That's because AMQP server respond instantly. But when you try to set prefetch_count=1 on the channel, and you will try to get the message when channel has unacked message this method will wait.

aio-pika is a wrapper around the pika, the pika is a wrapper around the AMQP protocol, this is not changing server-client interaction.

[josephbiko]

Is there also a way to just wait until a message is available? Or do I need to sleep&check until something is available?

[mosquito]

You should call consume for the queue. This example do it easer.

[mosquito]

This example demonstrated the asynchronous message processing

[josephbiko]

Yes, but this is a normal consumer, I just want to retrieve a single message from the queue

[mosquito]

The basic.get method marked as synchronous on the documentation (page 54)

Synchronous: Yes; expected response is from method(s) basic.get­ok, basic.get­empty

You should use this method on very specific cases.

[josephbiko]

Allow me to illustrate, What i do know is: ` while True:

        msg = await q.get(fail=False)

        if msg:
            break

        await asyncio.sleep(1)`

[nurettin]

If we use consume, it will just get messages regardless of whether the consume callback has finished it's work or not. This is undesirable when your consumer can not work concurrently. Ideally, this would do nicely:

consume(callback, wait_until_callback_finishes_before_receiving_any_more_messages=True)

Edit: Nevermind, I thought I tested with prefetch_count=1 but it was probably left as default. It's working fine because aio-pika doesn't receive any new messages until you ack or reject.

[mosquito]

@nurettin just set_qos(prefetch_count=1) and stop consuming before ack