CODEWITHSUNDEEP
pythonmultithreadingrabbitmqpika
user2396041
user2396041

Reputation: 31

Rabbitmq - start_consuming may not be called from the scope of another BlockingConnection or BlockingChannel callback

I have two python processes, one consumer process and one producer process. Each process will start a rabbitmq connection and spawn multiple consumer/producer threads. Each thread will create a channel in the connection and perform the message sending and receiving logic.

This is my consumer thread 

def consumer_thread(connection, routing_key):
    channel = connection.channel()
    result = channel.queue_declare(exclusive=True)
    queue_name = result.method.queue
    channel.queue_bind(exchange="test", routing_key=routing_key, queue=queue_name)
    thread_name = current_thread().name

    def process(ch, method, properties, body):
        print(f"{thread_name} received {body}")

    channel.basic_consume(process, queue=queue_name, no_ack=True)
    channel.start_consuming()

This is my producer thread

def producer_thread(connection, routing_key, sleep_time):
    channel = connection.channel()
    thread_name = current_thread().name
    count = 0

    while True:
        count += 1
        channel.basic_publish("test", routing_key=routing_key,
                              body=f"msg {count} from {thread_name}")
        time.sleep(sleep_time)

And I start a rabbitmq connection using

connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))

However, when I run my code, for the first message received at consumer thread, I am getting this error message 

Traceback (most recent call last):
  File "D:\app\cortex-bin\Python36\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "D:\app\cortex-bin\Python36\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "D:\app\cortex\background\core\scratch\test.py", line 18, in consumer_thread
    channel.start_consuming()
  File "D:\app\cortex-bin\Python36\lib\site-packages\pika\adapters\blocking_connection.py", line 1817, in start_consuming
    'start_consuming may not be called from the scope of 'pika.exceptions.RecursionError: start_consuming may not be called from the scope of another BlockingConnection or BlockingChannel callback'

For all subsequent messages, they can be received by the consumer threads just fine.

May I know what's causing this exception? Thanks.

Upvotes: 0

Views: 1955

Answers (1)

Luke Bakken
Luke Bakken

Reputation: 9667

You can't access a Pika connection from multiple threads (comment). Your threads must start their own connection and channels.

Upvotes: 1

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