How to solve the consumer error in Rabbitmq using python - rabbitmq

Question

when I run Consumer.py for headersExchange in rabbitmq using python,it is getting error like below
I have mentioned consumer and publish program below
Traceback (most recent call last):
File "headersConsumer.py", line 32, in <module>
main()
File "headersConsumer.py", line 14, in main
channel.exchange_declare(exchange = 'headers_logs',exchange_type='headers',durable=True)
File "C:\Python38\lib\site-packages\pika\adapters\blocking_connection.py", line 2387, in
exchange_declare
self._flush_output(declare_ok_result.is_ready)
File "C:\Python38\lib\site-packages\pika\adapters\blocking_connection.py", line 1339, in
_flush_output
raise self._closing_reason # pylint: disable=E0702
pika.exceptions.ChannelClosedByBroker: (406, "PRECONDITION_FAILED
- inequivalent arg 'type' for exchange 'headers_logs' in vhost '/': received 'headers' but
current is 'fanout'")
I have written consumer code like this
#!/usr/bin/env python
import pika, sys, os
def main():
connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange = 'headers_logs',exchange_type='headers',durable=True)
channel.queue_declare(queue = "HeaderQueue1", durable=True)
channel.queue_bind(exchange = 'headers_logs', queue="HeadersQueue1", routing_key='',
arguments={'x-match': 'any', 'key1': 'one', 'key2': 'two'})
def callback(ch, method, properties, body):
print(" [x] %r" % body.decode())
print(' [*] Waiting for logs. To exit press CTRL+C')
channel.basic_consume(
queue="HeadersQueue1", on_message_callback=callback, auto_ack=True)
channel.start_consuming()
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
print('Interrupted')
try:
sys.exit(0)
except SystemExit:
os._exit(0)
I have written publish program likethis
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='headers_logs',exchange_type='headers')
message = ' '.join(sys.argv[1:]) or "Hello World!"
channel.basic_publish((exchange='headers_logs',routing_key="",body=message,properties=pika.BasicProperties(
delivery_mode = 2, # make message persistent
headers = {'key1':'one', 'key2': 'three'}
))
print(" [x] Sent %r" % message)
connection.close()
I am not understanding this error,Can anyone please suggest this error

Answer 1

PRECONDITION_FAILED means that you declared an exchange with set of parameters then you are trying to create the same queue name using different parameters.
in your case:
headers_logs' in vhost '/': received 'headers' but
current is 'fanout'")
so you are trying to change the exchange type from fanout to headers
Se here for more detail (this is for the queues but exchanges work in the same way).
Before a queue can be used it has to be declared. Declaring a queue
will cause it to be created if it does not already exist. The
declaration will have no effect if the queue does already exist and
its attributes are the same as those in the declaration. When the
existing queue attributes are not the same as those in the declaration
a channel-level exception with code 406 (PRECONDITION_FAILED) will be
raised.