Error "unknown delivery tag" occurs when i try ack messages to RabbitMQ using pika (python)

Question

I want process messages in few threads but i'm getting error during execute this code:

from __future__ import with_statement import pika import sys from pika.adapters.blocking_connection import BlockingConnection from pika import connection, credentials import time import threading import random from pika.adapters.select_connection import SelectConnection from pika.connection import Connection import traceback   def doWork(body, args, channel):       r = random.random()     time.sleep(r * 10)     try:                 channel.basic_ack(delivery_tag=args.delivery_tag)      except :         traceback.print_exc()   auth = credentials.PlainCredentials(username="guest", password="guest") params = connection.ConnectionParameters(host="localhost", credentials=auth) conn = BlockingConnection(params) channel = conn.channel()   while True:      time.sleep(0.03)         try:          method_frame, header_frame, body = channel.basic_get(queue="test_queue")         if method_frame.NAME == 'Basic.GetEmpty':             continue                  t = threading.Thread(target=doWork, args=[body, method_frame, channel])         t.setDaemon(True)         t.start()      except Exception, e:         traceback.print_exc()         continue 

Error desctiption:

 Traceback (most recent call last):   File "C:\work\projects\mq\start.py", line 43, in      method_frame, header_frame, body = channel.basic_get(queue="test_queue")   File "C:\work\projects\mq\libs\pika\adapters\blocking_connection.py", line 318, in basic_get     self.basic_get_(self, self._on_basic_get, ticket, queue, no_ack)   File "C:\work\projects\mq\libs\pika\channel.py", line 469, in basic_get     no_ack=no_ack))   File "C:\work\projects\mq\libs\pika\adapters\blocking_connection.py", line 244, in send_method     self.connection.process_data_events()   File "C:\work\projects\mq\libs\pika\adapters\blocking_connection.py", line 94, in process_data_events     self._handle_read()   File "C:\work\projects\mq\libs\pika\adapters\base_connection.py", line 162, in _handle_read     self._on_data_available(data)   File "C:\work\projects\mq\libs\pika\connection.py", line 589, in _on_data_available     frame)                 # Args   File "C:\work\projects\mq\libs\pika\callback.py", line 124, in process     callback(*args, **keywords)   File "C:\work\projects\mq\libs\pika\adapters\blocking_connection.py", line 269, in _on_remote_close     frame.method.reply_text) AMQPChannelError: (406, 'PRECONDITION_FAILED - unknown delivery tag 204') 

Versions: pika 0.9.5, rabbitMQ 2.6.1

Answer 1

The problem probably is that you're setting no_ack=True like this:

consumer_tag = channel.basic_consume(     message_delivery_event,     no_ack=True,     queue=queue, ) 

And then acknowledging the messages:

channel.basic_ack(delivery_tag=args.delivery_tag) 

You have to chose if you want to acknowledge or not and set the correct consume parameter.