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POObject transfer between Node.js and Django using AMQP
 

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  1. POObject transfer between Node.js and Django using AMQP
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    <p>I'm beginning with websockets and I'm very confused with the number libraries and configuration options. I just want to setup a project where a node.js server calls a method in python/django and when the last has finished, it transfers the result back to the node.js server. This is what I have so far: </p> <p>Nodes.js AMQP from <a href="http://www.rabbitmq.com/blog/2011/08/16/using-the-rabbitmq-service-on-cloud-foundry-with-nodejs/" rel="nofollow">this tutorial</a>:</p> <pre><code>var conn = amqp.createConnection(); conn.on('ready', function(){ var exchange = conn.exchange('?1', {'type': 'fanout', durable: false}, function() { exchange.publish('?2', {add: [1,2]}); }); }); </code></pre> <p>Django Celery from <a href="http://ask.github.com/django-celery/getting-started/first-steps-with-django.html" rel="nofollow">this tutorial</a>:</p> <pre><code>from celery.decorators import task @task() def add(x, y): return x + y </code></pre> <p>I don't know if this is the way to go, and I would be glad if someone could shed a light on this issue.</p> <p>--- <strong>EDIT</strong></p> <p>I succeed in making a simple string transfer using AMQP:</p> <h2>test.py</h2> <pre><code> import pika 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, props, body): print " [x] Received %r" % (body,) response = body + " MODIFIED" #response = get_a_concept() print " [x] Done" ch.basic_publish(exchange='', routing_key=props.reply_to, properties=pika.BasicProperties(correlation_id = \ props.correlation_id), body=str(response)) ch.basic_ack(delivery_tag = method.delivery_tag) channel.basic_qos(prefetch_count=1) channel.basic_consume(callback, queue='task_queue') channel.start_consuming() </code></pre> <h2>app.js</h2> <pre><code> var connection = amqp.createConnection({ host: 'localhost' }); connection.addListener('ready', function() { var exchange = connection.exchange('', { 'type' : 'direct', durable : false }, function() { var queue = connection.queue('incoming', { durable : false, exclusive : true }, function() { queue.subscribe(function(msg) { console.log("received message: "); console.log(msg.data.toString()); }); }); exchange.publish('task_queue', "it works!", { 'replyTo' : 'incoming' }); }); </code></pre> <p>});</p> <hr> <p>Still, I'm not sure if this is the best implementation, I'm not even using queue.bind() method here. The problem arises when I try to pass a complex object (json or even a simple array). Changing this line </p> <pre><code> body= (["a","b","c"])#str(response)) </code></pre> <p>causes the following error:</p> <pre><code> Traceback (most recent call last): File "test.py", line 56, in &lt;module&gt; channel.start_consuming() File "/Library/Python/2.7/site-packages/pika/adapters/blocking_connection.py", line 293, in start_consuming (...) File "/Library/Python/2.7/site-packages/pika/simplebuffer.py", line 62, in write self.buf.write(data) TypeError: must be string or read-only character buffer, not list </code></pre> <p>Is there any solution for serializing complex objects? Am I missing something?</p>
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    1. COI am not familiar with node but it should have some sort of async http library. From your description of what you want it seems that celery might be unescessary. If you don't need what celery provides just make a django view that gets the data you need returned to node.js and call its url from node!
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    2. COThanks. It's possible to make http resquests as you suggested, I'll try that. But in my case, I have long run tasks for django (not this add), I'm afraid http request is not suitable when lots of clients makes lots of long-run task requests..
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    3. COWhat about using something like json to serialize the data? Look at simplejson for python (not sure about the node.js side though).
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      1. USCharles L.
 

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