Fast polling using C, memcached, nginx and libevent

It should be noted that this post was written over one year ago and we are not using polling any longer, but comet solution.<p>We wanted to do realtime notifications and polling isn't a way to do this. We tried different options and in the end wrote our own comet solution using JBoss Netty. Working with JBoss Netty was really great, but we hit perfomance limits on lots of open connections (100.000+).<p>At that time node.js was released and I did some experiments with it and found it it had great perfomance and very low memory footprint. I also had an university course on the V8 VM (by the actual Google team :)) so I was pretty interested in V8 and node.js at that time. I experimented more with this and eventually we rewrote our comet solution to node.js<p>Fast forward today we are still running node.js and processing many millions notifications each day. I would recommend digging into node if you are interested in building a scaleable notification system. Our comet implementation for node.js is under 1 KLOC.<p>Other posts you might be interested in:<p>* <a href="http://amix.dk/blog/post/19484#Comet-with-node-js-and-V8" rel="nofollow">http://amix.dk/blog/post/19484#Comet-with-node-js-and-V8</a><p>* <a href="http://amix.dk/blog/post/19456#Plurk-Comet-Handling-of-100-000-open-connections" rel="nofollow">http://amix.dk/blog/post/19456#Plurk-Comet-Handling-of-100-0...</a><p>* <a href="http://amix.dk/blog/post/19489#Comet-long-polling-for-all-browsers-using-ScriptCommunicator" rel="nofollow">http://amix.dk/blog/post/19489#Comet-long-polling-for-all-br...</a>

What is the bottleneck here? I am surprised that the CPU utilisation is just 2%, which means, either the disk or the network is the bottleneck. Both these aren't discussed. And of course, one shouldn't forget the fact that if CPU is the bottleneck, we need "true" concurrency and there should be threads on every single core. :-)

Check the second comment on that post. I'm glad someone else looked at that guy's C and thought "Whoooaaa, oh no."<p>How can we take posts like this seriously?

It was nice to see zedshaw reviewing C code in the comments there.

I'm interested to hear other peoples' thoughts on comet versus polling. I've done polling solutions before and am in the process of setting up a comet based solution.<p>In my opinion, having fewer requests to the server is better. But if someone can combat me on this, I'd really be interested in hearing another voice.