Julian C. Dunn

Operating an Apache httpd-based origin in conjunction with a CDN presents some interesting challenges and opportunities. For example, one can actually eliminate a lot of sophisticated cache control directives by trusting that the CDN will Do The Right Thing ™ when communicating with client browsers. Furthermore, implementation of a few judicious Apache modules and mod_expires directives can go a long way towards reducing origin bandwidth and load on the webservers.

However, dynamically-generated web pages (including those generated via SSI) can result in unnecessary cache evictions due to the inability to determine last modification time. In this article I’ll explore exactly why SSIs are so irritating from a CDN-interaction perspective and why all I want for Christmas is a CDN-aware mod_include and/or mod_expires, as per the title of this post. Continue reading…

We at CBC.ca have made major improvements in our web platform over the last two years. When I first returned to CBC in September 2006, we were still running Apache 1.3.29 on SuSE Linux Enterprise Server. Since then, we’ve upgraded first to Apache 2.0.59 (still on SuSE) and, with the migration to Red Hat Enterprise Linux in July of this year, to Apache 2.2.8. (You can see the evolution of our web platform over at Netcraft.)

Two days after the Canadian Federal Election, we implemented the next major upgrade of that platform and that was to convert from the prefork MPM to the worker MPM. Since we monitor the performance of all our Apache servers using Cacti, I can share some detailed information about the performance improvement that has resulted from this change. Continue reading…