[Now that our main blogger is leaving, we’ve got to start picking up the slack and posting. I promise eventually to not just post about hardware and software bugs, but today that’s what I’ve got…]
Porter continues to be a rockstar hardware-wise, but I’ve been having some trouble with the proxy/caching webserver running on it. Sure, it’s caching, but every so often it would grab a version of page and decide to keep it for 3 days instead of the directed 1 hour. At first I thought it was a one-time deal from switching some cache settings on the server, but it kept happening… Walker staff would make a change to some content, wait, but it would never show up on the live page. Trouble.
The problem was caused by a line stored in the cached HTTP header: Cache-Control: max-age=259200. (that’s three days worth of seconds) (I’m including details so google can pick this up and hopefully save some poor guy a frustrating morning.) After some serious digging it appears the mod_cache module we’re using was taking whatever Cache-Control header was being sent by the browser and saving it in the cached header! In other words, I had configured the server to cache things for a maximum of 1 hour, but all it took to blow that up was a browser (or spider?) sending a request saying it didn’t want anything older than 3 days. Our caching server held on to that “3-days” part and decided the whole page should be valid for that long. Totally. Wrong.
I debated making changes to the mod_cache source and recompiling, but I finally found an easier answer: “CacheIgnoreHeaders Cache-Control". This tells the caching module to ignore the problem lines, and it seems to be golden. I’ll let it run for a while and see…
[In further bad news, the US got creamed 3-0 by the Czech Republic in their World Cup opener. Not unexpected, but it doesn’t bode well for getting past group play…]