The need for speed

September 30, 2005

Mark Fletcher (the bloglines guru) explains the effect of speed on a web site / application:

The speed of your service directly affects its usage. We quickly discovered this with ONElist. When the web site was slow, people used it less, resulting in fewer page views. When it was fast, we saw an increase in usage … we thought that web site usage was very task oriented. Once they finished their task, they’d leave. The speed of the service wouldn’t affect the number of pages they viewed, just the time it took to complete their task. But we were wrong.

A slow site leads to an exponential increase in load on the service. … This is because people are impatient. If Joe Surfer has to wait more than a few seconds for a web page to load, he generally hits the Stop button in his browser and tries to load the page again.

This definitely reflects our general experiences with Sytadel, but I have seen another more powerful way to create exponential load. During the boom I was the technical lead for a very high volume dot com. 4am one morning (Australian time) I get a dreaded “server down” call (9am their time). Restarting Apache and watching the httpd process list grow to

100 in the first few seconds is very disconcerting. The server had been performing well for weeks and investigations later that day revealed the problem. The home page was constructed by using a number of include() statements to pull in various PHP code pieces. A technician for the site had added some new PHP code pieces but was getting the content piece via an fopen() on the full URL rather than using an include(). So, every home page view spawned 4 extra page views on the same server to construct the home page HTML itself.

The fact that I now use Google for all mathematical operations is also testament to this. While drilling down for the Windows calculator a couple of months ago I saw that Google toolbar input field sitting there just waiting for an equation. I had the answer faster than it would normally take to find the calcuator from the Windows Start menu.

Note: Originally posted to my Synop blog on 24 March, 2004.