So, the Content Distribution Network is in place and several tests indicate it is working well — page loads are much faster, the URLs of the CDN content are re-written properly — but the next question is whether new materials will be automatically added to the CDN. The picture at the left (and yes, this is an excuse to post a cute dog picture, too) should appear with a link to the high-resolution (1.8 Mb) image. On the blog itself, that link should be of the format http://blog.tedroche.com/wp-content/uploads/2003/12/NameOfPicture.jpg, while if the picture is picked up by the CDN synchronization software, it should upload to the CDN and the URL be rewritten to http://static.blog.tedroche.com/etcetera. Let’s try it out and see what happens…
Woah. Success first time. Pretty cool.
Some details on what I’ve got set up: I’m using the Rackspace Cloud Files service as the CDN. I had worked with Rackspace before on some hosting projects, and have a friend working there, so I thought I’d try them out first. It appears that their CDN services are in an early stage and don’t have all of the features of soe of the more mature products. In particular, it appears that the blog software is reponsible for pushing any new or updated content to the CDN. By contrast, the Amazon S3 offering has an ‘origin pull’ feature that will pull content from the original source when it is first requested, and subsequently cache it.
In order to get the contents of my local blog to sync with the CDN, I added the CDN-Sync-Tool plugin. A lot of web searching seemed to indicate I could find this in the WordPress Plugins directory online, but the tool has been pulled from the directory. Apparently, it is undergoing some redevelopment. The version I found was on GitHub under https://github.com/WDGDC/CDN-Sync-Tool and installation was not more complex that downloading the ZIP and unzipping it in the plugins folder. Bear in mind that you should be comfortable with using the command line and have the skills to review the files you are installing on your machine, as there has been no review by the WordPress folks, and the code is currently under development and you may need to deal with bugs, incompatibilities and support problems. So, this isn’t the path I’d recommend for less-technical WordPress developers, and likely isn’t the path I’d recommend for a client looking to put a CDN into production use.
Note that most cache programs and their CDN features are set up in such a way that logged-in users may see a slower site, but more up-to-date, site, and that in order to test caching you’ll need to log out of your WordPress session.