When I work on a web application, I usually have the luxury of running everything that I need locally on my developer machine. My browser, Web-server and database all working together without ever having to put a single packet on a real network.

With today's web applications growing more complex and making use of asynchronous calls to the web server, this idealistic development environment makes it very difficult for the developer to assess the performance characteristics of the application. This can lead to surprises when the application is deployed to a real environment where users actually access it from remote locations.

A good way to bring reality back to this equation is to make use of a proxy server. I like to use Don's Proxy. It is simple Java-based application that takes 1 minute to setup and lets you inject latency, errors and throttle your connection bandwidth. All of this is made in a manner that is independent of your browser or your web server. Most importantly. it does not require any changes to your application's code or setup.

To use Don's Proxy, simply download the package, unzip and double-click the jar file. A simple GUI will open (screenshot) that will prompt you for a port for the proxy to listen to and a host/port for the destination of your test web server. In the example screenshot, the test web server is running locally at port 8080 and the proxy is setup to listen on port 9090.

Once the proxy is started, you just redirect your browser to the proxy's port and everything should work as before. The difference is that now, you can inject realistic network parameters like latency and bandwidth limitations. Don's Proxy also allows you to capture traffic as it goes through and perform other diagnostics without the use of a packet-sniffer.

Hopefully, a more common use of tools like this will help curb developer enthusiasm for flashy Ajax behavior. Your users will thank you.

Labels: testing, web development