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Publisher is getting blocked after after consuming 1st message_reply. It is not sending any messages to subscriber.

I have already tried that if I don't use 'start_consuming()' method publisher sends data continuously but it does not print reply_message from subscriber. If I used 'start_consuming()' method it just blocks the publisher and waits.

#publisher.py
#!/usr/bin/env python
import pika
import sys
import uuid

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

channel.queue_declare(queue='task_queue', durable=True)
channel.queue_declare(queue='reply_queue', durable=True)

message = "Hello World!"
corr_id = str(uuid.uuid4())

def on_response(ch, method, properties, body):
    print("----- On_response -----")
    print("Received CORR_ID : ", properties.correlation_id)
    if(corr_id == properties.correlation_id):
        resp = body.decode('utf-8')
        print("RESPONSE : ", resp)
    ch.basic_ack(delivery_tag=method.delivery_tag)

def consume_response(channel):
    channel.basic_consume(queue='reply_queue', on_message_callback=on_response)
    channel.start_consuming()

while True:
    channel.basic_publish(
        exchange='',
        routing_key='task_queue',
        body=message,
        properties=pika.BasicProperties(
            reply_to='reply_queue',
            correlation_id=corr_id
        ))
    print(" [x] Sent %r" % message)
    consume_response(channel)

#subscriber.py
#!/usr/bin/env python
import pika
import time

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

channel.queue_declare(queue='task_queue', durable=True)
print(' [*] Waiting for messages. To exit press CTRL+C')


def callback(ch, method, properties, body):
    print(" [x] Received %r" % body.decode('utf-8'))
    #time.sleep(body.count(b'.'))
    print(" [x] Done")
    print("CORR_ID : ",str(properties.correlation_id))
    print("Reply : ", str(properties.reply_to))
    ch.basic_ack(delivery_tag=method.delivery_tag)
    res = "Received "+str(body.decode('utf-8'))
    ch.basic_publish(
        exchange='',
        routing_key='reply_queue',
        properties = pika.BasicProperties(
            correlation_id=\
                properties.correlation_id
        ),
        body=res
    )


channel.basic_qos(prefetch_count=1)
channel.basic_consume(queue='task_queue', on_message_callback=callback)

channel.start_consuming()

Actual result is-
publisher                                           subscriber
   (1)----------publish message 'Hello'-------------->  |
    | <---------reply_to_publisher_queue---------------(2)
   (3)prints_the message
   (4)publisher waits for consuming messages

I want to design this-

(expected)
publisher                                           subscriber
   (1)----------publish message 'Hello'-------------->  |
    | <---------reply_to_publisher_queue---------------(2)
   (3)prints_the message
   (4)----------publish message 'Hello'-------------->  |
    | <---------reply_to_publisher_queue---------------(5)
    .
    .
    .
   continues....

Kindly help.

Shital Jadhav
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    I see that you are trying to implement like RPC calls. Did you check https://www.rabbitmq.com/tutorials/tutorial-six-python.html? – bumblebee Jul 19 '19 at 13:35
  • yes, I have checked this code. After 'start_consuming()' call it prints the received message on console and starts consuming only. It does not publish any message further. If I comment the 'start_consuming()' then it just consumes silently. – Shital Jadhav Jul 22 '19 at 04:39

1 Answers1

0

I replaced the line channel.start_consuming() with channel.connection.process_data_events(time_limit=1) in publisher.py and it worked as I expected.

I have also followed https://github.com/pika/pika/issues/770.

Shital Jadhav
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