Question

I want to understand What is event driven io. I am hearing it is different than traditional blocking request/response model. Do we have any example to explain this? and how will it contribute to the increase in performance?

Examples will be highly appreciated.

Answer 1

I’m guessing since it’s been 4 months you’ve got your answers. Regardless here goes…

Netty
http://www.jboss.org/netty

Mina
http://mina.apache.org/

C10K
http://www.kegel.com/c10k.html

To understand part of the problem that evented io is trying to solve take a look at the C10K link above. Scability is one of the main benefits of evented io.

A traditional web server will handle a request and then return a response (synchronous/blocking). Each request would typically require it’s own thread.

An event driven web server will handle a request, then create an event (asynchronous/nonblocking io), and then return the response. Multiple requests are shared by a single thread/process.

Evented IO should be able to handle more requests per thread than a typical web server. You might not speed up your web application with evented IO, but it should handle large numbers of connections a lot easier than a traditional web server. This means requiring less machines for scaling.

Though I would argue that evented io architecture will force you to develop your web application to handle smaller chunks of data. Much like a google mail type application that uses a lot of ajax calls to poll for data on the server and then does small updates in the browser. This itself has many benefits that will help speed up AND improve scaling on your server.

Netty and Mina provide plenty of example code.