Problems with files on separate domain not loading for random periods of time

Question

I have a separate domain name for static content such as images, js files, and css files. I load this static content on the main site from this other domain to double the amount of concurrent connections the browser makes to load the page faster. This seems to work and I haven't had any issues myself, but I've been getting e-mails from users (with screenshots) where none of the static content will load for random periods of about 30 minutes to an hour or so. It only happens for a select few, not everyone on the site.

The other domain is hosted on the same server as the main domain. Restarting the browser and clearing the cache does nothing, it just goes away and starts working again after a while. I can't think of anything that would cause this, any ideas?

Answer 1

WAG (Wild Ass Guess): Do you have different DNS settings for the domains, e.g. TTL, or one is an A record and the other a CNAME?

WAG: Do the people having the problem live behind a caching proxy server?

WAG: Are the server configs identical? I.e. does one have ETAGS enabled and the other one doesn't? Same file expiration times?

WAG: From what you describe I doubt this is the case, but do you have a CDN (Content Delivery Network) somewhere in the mix?

Try using an external machine to poll specific files under each domain every N minutes (or whatever) and try plotting the errors. If possible run this same test from machines in very different locations (LA, NY, London, WhereEver) and compare the results. There might be a pattern in there somewhere. Munin is a nice package for gathering/graphing this kind of info.

Good Luck.

Answer 2

It turned out to be an issue with the DNS setup. If you are having a similar issue, I suggest checking out http://tools.pingdom.com.