Inconsitent behaviour of BlockingChannel.Consume generator

I run the following code with one message in ‘test’ queue:

import pika

connection = pika.BlockingConnection()
channel = connection.channel()
channel.basic_qos(prefetch_count=1)

for method_frame, properties, body in channel.consume('test', inactivity_timeout=0):
    # Display the message parts
    print method_frame
    # Acknowledge the message
    channel.basic_nack(method_frame.delivery_tag, requeue=True)

since i’m requeing, i exepct the generator to always return the same message, over and over. in reality, the loop returns a message every 6/7 iterations, and on other times, it returns (None, None, None). It seems like some kind of a race condition, because if i set inactivity_timeout to be a very small non-zero (like 0.01), it works as expected… is this a bug, or am i missing something? (note: this is the only consumer on the queue)

[lukebakken]

I didn’t keep digging, but my gut feeling was that when I pass 0 to process_data_events() It doesn’t actually process the frame of the message being available again

In the case when zero is used as inactivity_timeout, the entire frame is more likely to not be available immediately, and you are more likely to hit the (None, None, None) case.

inactivity_timeout exists so that users can do useful work during the consume loop. In any case, the (None, None, None) return value is normal and should be handled.

Thanks!

[Avivsalem]

As I wrote on the original issue, when passing non-zero to inactivity_timeout, no matter how small, it works as I expected… So I looked at the implementation of the generator, and looked for uses of inactivity_timeout. I saw it being passed to process_data_events() as a parameter. I didn’t keep digging, but my gut feeling was that when I pass 0 to process_data_events() It doesn’t actually process the frame of the message being available again, while when I pass a non-zero small number, I does process the frame… Again…i didn’t investigate deeply, just reporting on my results, and my hypothesis…