I am following tutorial 4 (Routing). Following is the code for send.py
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
type='direct')
severity = sys.argv[1] if len(sys.argv) > 1 else 'info'
message = ' '.join(sys.argv[2:]) or 'Hello World!'
channel.basic_publish(exchange='direct_logs',
routing_key=severity,
body=message)
print(" [x] Sent %r:%r" % (severity, message))
connection.close()
and below is the code for receive.py
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
type='direct')
result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue
severities = sys.argv[1:]
if not severities:
sys.stderr.write("Usage: %s [info] [warning] [error]\n" % sys.argv[0])
sys.exit(1)
for severity in severities:
channel.queue_bind(exchange='direct_logs',
queue=queue_name,
routing_key=severity)
print(' [*] Waiting for logs. To exit press CTRL+C')
def callback(ch, method, properties, body):
print "Hello"
print(" [x] %r:%r" % (method.routing_key, body))
channel.basic_consume(callback,queue=queue_name,no_ack=True)
channel.start_consuming()
But when I am running the scripts I'm unable to fetch any message from the temporary queue. I guess my callback function is not being called. The codes are taken as it is from the site.
I am running the codes as:
python send.py
for which I'm getting:
[x] Sent 'info':'Hello World!'
And when I run
python rec.py info
I get:
[*] Waiting for logs. To exit press CTRL+C
And else nothing is printed.
I have even restarted RabbitMQ using
rabbitmqctl stop_app
rabbitmqctl start_app
Please let me know where am I going wrong and how can I get message
run the receive.py first
the problem is, rabbitmq will not hold messages that are not routed to queues.
your send.py does not declare a queue or a binding to the exchange, so when you send a message through the exchange, there is no queue to which the message can be delivered
if you run your receive.py first, you'll create the needed exchange, queue and binding
then your send.py will be able to send the messages and it will be routed to the queue for the receive.py to pick up
If the code is exactly like in the tutorial, you need to run rec.py first and then send.py
Related
I am practicing RabbitMQ through Official documents tutorial 4 on my MacBook
This is the final section code:
emit_log_direct.py
#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(
pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs', exchange_type='direct')
severity = sys.argv[1] if len(sys.argv) > 1 else 'info'
message = ' '.join(sys.argv[2:]) or 'Hello World!'
channel.basic_publish(
exchange='direct_logs', routing_key=severity, body=message)
print(" [x] Sent %r:%r" % (severity, message))
connection.close()
and receive_logs_direct.py
#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(
pika.ConnectionParameters(host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs', exchange_type='direct')
result = channel.queue_declare(queue='', exclusive=True)
queue_name = result.method.queue
severities = sys.argv[1:]
if not severities:
sys.stderr.write("Usage: %s [info] [warning] [error]\n" % sys.argv[0])
sys.exit(1)
for severity in severities:
channel.queue_bind(
exchange='direct_logs', queue=queue_name, routing_key=severity)
print(' [*] Waiting for logs. To exit press CTRL+C')
def callback(ch, method, properties, body):
print(" [x] %r:%r" % (method.routing_key, body))
channel.basic_consume(
queue=queue_name, on_message_callback=callback, auto_ack=True)
channel.start_consuming()
If I run :
python receive_logs_direct.py info warning error
it works fine, messages will show on screen
but if I add redirection like tutorial
python receive_logs_direct.py warning error > logs_from_rabbit.log
there is nothing write on logs_from_rabbit.log file
and I trying tee, the result is same, nothing to show
python receive_logs_direct.py warning error | tee logs_from_rabbit.log
but if I annotation receive_logs_direct.py last line channel.start_consuming(), print will working
maybe where I made mistake?
What does the channel.basic_consume' function return?
how i can access to message using variable i want consumed message and show it in browser?
i build django application send message to rabbitmq and consume messsage from it to show message
in browser like chat
import pika, sys
global message
def consume(room,username):
credentials = pika.PlainCredentials('admin', 'admin')
parameters = pika.ConnectionParameters('192.168.1.14',5672,'/', credentials)
connection = pika.BlockingConnection(parameters)
channel = connection.channel()
channel.exchange_declare(exchange='topic_exchange', exchange_type='topic')
result = channel.queue_declare('', exclusive=True)
queue_name = result.method.queue
arr= [room,username]
binding_key ='.'.join([str(i) for i in arr])
channel.queue_bind(exchange='topic_exchange', queue=queue_name, routing_key=binding_key)
print(' [*] Waiting for logs. To exit press CTRL+C')
def callback(ch, method, properties, body):
print(" [x] %r:%r" % (method.routing_key, body))
channel.basic_consume(queue=queue_name, on_message_callback=callback, auto_ack=True)
global message
#message =
channel.start_consuming()
return message
This isn't going to work. You are running a process that is consuming the messages and printing them. Some other process (django) is listening for requests from your browser.
Not sure how you hope it will work, but consider these alternatives-
your consumer writes the messages to a file, and django reads that file when it gets a request
django connects to the message bus and reads all waiting messages when it gets a request
your consumer writes the messages to a database
You build a websocket application that can push messages to currently connected browsers when it receives a message
New to python.
I am trying to create multiple consumer for a RabbitMQ client.
I am using PIKA and trying to do with multiprocessing.
It seems connecting but not being able to sustain the loop.
Can you please help.
The part of the code should also take care the writer option through the call back.
it should start the loop and should consume always
import multiprocessing
import time
import pika
# this is the writer part
def callback(ch, method, properties, body):
print (" [x] %r received %r" % (multiprocessing.current_process(), body,))
time.sleep(body.count('.'))
# print " [x] Done"
ch.basic_ack(delivery_tag=method.delivery_tag)
def consume():
credentials = pika.PlainCredentials(userid, password)
parameters = pika.ConnectionParameters(url, port, '/', credentials)
connection = pika.BlockingConnection(
parameters=parameters)
channel = connection.channel()
channel.queue_declare(queue='queuename', durable=True)
channel.basic_consume('queuename',callback)
print (' [*] Waiting for messages. To exit press CTRL+C')
channel.start_consuming()
userid = "user"
password = "pwd"
url = "localhost"
port = 5672
if __name__ == "__main__":
workers = 5
pool = multiprocessing.Pool(processes=workers)
for i in range(0, workers):
pool.apply_async(consume)
#Stay alive
try:
while True:
You aren't doing any exception handling in your sub-processes, so my guess is that exceptions are being thrown that you don't expect. This code works fine in my environment, using Pika 1.1.0 and Python 3.7.3.
Before I checked for exceptions in body.count() a TypeError would be thrown because body was not a str in that case.
Please note that I'm using the correct method to wait for sub-processes, according to these docs.
NOTE: the RabbitMQ team monitors the rabbitmq-users mailing list and only sometimes answers questions on StackOverflow.
I'm trying to receive multiple queues, I tried the code: https://stackoverflow.com/a/42351395/3303330
But it's necessary declare the "queue_declare". Hope you can help me guys, it's my code:
import pika
import time
from zeep import Client
parameters = pika.URLParameters('amqp://user:pass#theurl:5672/%2F')
connection = pika.BlockingConnection(parameters)
channel = connection.channel()
channel.queue_declare(queue='queue1', passive=True, durable=True, exclusive=False, auto_delete=False)
print(' [*] Waiting for messages. To exit press CTRL+C')
def callback(ch, method, header, body):
print(" [x] Received %r" % body)
time.sleep(body.count(b'.'))
ch.basic_ack(delivery_tag = method.delivery_tag)
channel.basic_consume(callback, queue='queue1')
channel.start_consuming()
It is not necessary to declare a queue more than once as long as you delcare it to be durable. You can declare more than one queue in your client code or using the RabbitMQ admin interface.
You can use your channel to consume messages from more than one queue. Just execute channel.basic_consume more than once using different queue parameter values.
I would like to send a message (directly) from a script and than process it, and send back the results.
So it's like a double publish-subscribe.
I have 2 scripts:
Processer
Client
The Client sends a message directly (simple string) to the Processer, and than the Processer script counts the characters in the string and sends back the results to the client.
This is how I tried to do:
The Processer waits for a message, calculates something and than answers back to the original sender.
#Processer.py:
import pika
import sys
#Sends back the score
#addr: Connection address
#exchName: Exchange name (where to send)
#rKey: Name of the queue for direct messages
#score: The detected score
def SendActualScore(addr, exchName, rKey, score):
#Send the image thru the created channel with the given routing key (queue name)
channel.basic_publish(exchange=exchName, routing_key=rKey, body=score)
print "(*) Sent: " + score
#When we receive something this is called
def CallbackImg(ch, method, properties, body):
print "(*) Received: " + str(body)
score = str(len(body))
#Send back the score
SendActualScore('localhost', 'valami', rKey, score)
#Subscribe connection
#Receive messages thru this
connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
#RECEIVE MESSAGES - Subscribe
channel.exchange_declare(exchange='valami', type='direct')
#Define a queue, where we don't need the name
#After we disconnected delete the queue (exclusive flag)
result = channel.queue_declare(exclusive=True)
#We need the name of our temporary queue
queue_name = result.method.queue
rKeys = sys.argv[1:]
for rKey in rKeys:
channel.queue_bind(exchange='valami', queue=queue_name, routing_key = rKey)
channel.basic_consume(CallbackImg, queue=queue_name, no_ack=True)
print(' [*] Waiting for messages. To exit press CTRL+C')
channel.start_consuming()
The Client just sends the message and than waits for the answer.
#Client.py:
import pika
import sys
connAddr = 'localhost'
#Establish connection
connection = pika.BlockingConnection(pika.ConnectionParameters(connAddr))
channel = connection.channel()
#Define an exchange channel, we don't need a queue
channel.exchange_declare(exchange='valami', type='direct')
#Send the image thru the created channel
channel.basic_publish(exchange='valami', routing_key='msg', body='Message in the body')
print "[*] Sent"
def Callback(ch, method, properties, body):
print "(*) Received: " + str(body)
result = channel.queue_declare(exclusive=True)
#We need the name of our temporary queue
queue_name = result.method.queue
channel.queue_bind(exchange='valami', queue=queue_name)
channel.basic_consume(Callback, queue=queue_name, no_ack=True)
print(' [*] Waiting for messages. To exit press CTRL+C')
channel.start_consuming()
There could be multiple Clients and I don't know how to send back the messages directly to them.
Have you checked the tutorials for RPC in RabbitMQ w/ python and pika? http://www.rabbitmq.com/tutorials/tutorial-six-python.html
The gist of what you need to do in your client, is found in the RPC tutorial, but with a few modifications.
In your client, you will need to create an exclusive queue - the same way you did in your server.
When you send your message from the client, you need to set the reply_to to the name of the client's exclusive queue
from the tutorial:
channel.basic_publish(exchange='',
routing_key='rpc_queue',
properties=pika.BasicProperties(
reply_to = callback_queue,
),
body=request)
On the server, when you receive a message, you need to read the reply_to header from the message and then basic_publish the reply to that queue.
Rather than thinking about "client" and "server", it may be helpful to frame this in terms of "message producer" and "message consumer".
In your scenario, you need both of your processes to be both a publisher and consumer. The "client" will publish the original message and consume the response. The "server" will consume the original message and publish a response.
The only real difference in your code will be the use of the reply_to header on the original message. This is the name of the queue to which you should publish the response.
Hope that helps!
P.S. I cover the core outline of this in my RabbitMQ Patterns eBook - both RPC and request / reply like you are needing. The book talks in principles and patterns, not in specific programming language (though I mostly write node.js and don't really know python).