method_frame always return None when using channel.basic_get

[amitli1]

I am trying to consume several messages from RabbitMQ queue without success.

I want to use basic_consume function and if there are more messages then pull them (instead of being called again to the callback function).

    import pika
    import time
    
    
    class RabbitMQPublisher:
        def __init__(self, queue_name):
            self.queue_name = queue_name
            self.connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
            self.channel    = self.connection.channel()
            self.channel.queue_declare(queue=self.queue_name)
    
        def publish_messages(self, num_messages):
            for i in range(num_messages):
                message = f'Message {i+1}'
                self.channel.basic_publish(exchange='', routing_key=self.queue_name, body=message)
                print(f'Sent: {message}')
    
        def close_connection(self):
            self.connection.close()
    
    class RabbitMQConsumer:
        def __init__(self, queue_name):
            self.queue_name = queue_name
            self.connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
            self.channel    = self.connection.channel()
            self.channel.queue_declare(queue=self.queue_name)
    
        def callback(self, ch, method, properties, body):
            print(f'Received: {body.decode()}')
            ch.basic_ack(delivery_tag=method.delivery_tag)
            self.pull_remaining_messages()
    
        def pull_remaining_messages(self):
            method_frame, header_frame, body = self.channel.basic_get(queue=self.queue_name, auto_ack=False)
            print(f"method_frame = {method_frame}")
            while method_frame:
                print(f'---> [pull_remaining_messages] Received: {body.decode()}')
                self.channel.basic_ack(delivery_tag=method_frame.delivery_tag)
                method_frame, header_frame, body = self.channel.basic_get(queue=self.queue_name, auto_ack=False)
    
        def start_consuming(self):
            self.channel.basic_consume(queue=self.queue_name, on_message_callback=self.callback, auto_ack=False)
            print('Waiting for messages. To exit press CTRL+C')
            self.channel.start_consuming()
    
    if __name__ == "__main__":
    
        publisher = RabbitMQPublisher('test_queue')
        publisher.publish_messages(100)
        publisher.close_connection()
    
        time.sleep(2)
    
        consumer = RabbitMQConsumer('test_queue')
        consumer.start_consuming()

Using the code above - I always get method_frame = None.

What am I missing ?

[michaelklishin]

basic_get is polling and it must not be used outside of basic integration tests. It will return None or its equivalent when there are no messages ready for delivery in the queue. See tutorial 2 and the doc guide on Publisher Confirms and Consumer Acknowledgements.

I repeat: DO NOT use basic.get in production, it defeats all benefits of messaging protocols.