<div>Hi Gavin, </div><div><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im"><blockquote type="cite" style="border-left-style:solid;border-width:1px;margin-left:0px;padding-left:10px">
<span><div><div>Hi everyone,<div><br></div><div>I'm interested in running pika's IOLoop in a thread and I came across this code sample : <a href="http://cms02.phys.ntu.edu.tw/tracs/env/browser/trunk/messaging/pika/mon.py" target="_blank">http://cms02.phys.ntu.edu.tw/tracs/env/browser/trunk/messaging/pika/mon.py</a></div>
<div><br></div><div>I was wondering why and what could be the advantages of wrapping the callbacks in methods (I can understand the on_exchange_declared() method that returns a different callback according to thread's name) ?</div>
</div></div></span></blockquote></div><div>As opposed to doing lambda's for callbacks? I'm not sure of the context of what you're comparing callback passing style to.</div></blockquote><div><br></div><div><br>
</div><div>For instance, for this callback: connection.callbacks.add(0, '_on_connection_open', self._on_connected() , one_shot=True )</div><div><br></div><div>The on_connected callback function in wrapped in the _on_connected() method</div>
<div><br><div> def _on_connected(self):<br> def on_connected(connection):<br> <a href="http://pika.log.info">pika.log.info</a>("%s: connected : %r " % ( self.tag , connection) )<br> connection.channel(self._on_channel_open() )<br>
self.connection = connection<br> return on_connected </div><div><br></div><div>Why not: connection.callbacks.add(0, '_on_connection_open', self.on_connected , one_shot=True )</div><div><br></div>
<div> def on_connected(self, connection):<br> <a href="http://pika.log.info">pika.log.info</a>("%s: connected : %r " % ( self.tag , connection) )<br> connection.channel(self._on_channel_open() )<br>
</div></div><div> self.connection = connection </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im"><blockquote type="cite" style="border-left-style:solid;border-width:1px;margin-left:0px;padding-left:10px">
<span><div><div><div>Another question is why considering multiprocessing over threading in this case ?</div></div></div></span></blockquote></div><div>The IOLoop is a singleton instance and you will run into contention issues and non-thread safe behaviors in use of the IOLoop and event processing. </div>
<div><br></div><div>I'm not sure what threading buys you in an asynchronous event based model of processing but needless complexity.</div><span class="HOEnZb"><font color="#888888"><div><br></div></font></span></blockquote>
<div> </div></div><div>My goal is to have an AMQP transport layer inside my application, running "in background", that handles incoming messages and put them into a python queue. I also want to be able to publish messages from other threads.</div>
<div>I've got it to work with threads and python queues in a thread-safe way. I was wondering what could be the benefits for me to use multiprocessing over threading.</div></div>