Caching is one of the things recommended whenever something is slow — "Your [database, website, server]? Well, duh! You need a cache!".
All things aside, it's not always easy to cache stuff. I find myself often in situations where I can't cache at all or where a caching solution is complex as hell to implement. All of the sudden you need to dissect your page and lazy load half of it with Ajax — bah. And that's just because those users never want to wait for a cache to expire or invalidate. They just expect the most recent ever! :-)
Sometimes however, caching can be so trivial, it even hurts.
Bypass the application server
There are lots of different techniques and strategies to employ when you start to think about caching. The fastest albeit not always available method is to bypass your app server stack completely. And here's how. :-)
My example is a pet project of mine where I display screenshots of different news outlets which are taken every 3 (three) hours — 0:00, 3:00 AM, 6:00 AM, 9:00 AM, 12:00 PM, 3:00 PM, 6:00 PM, 9:00 PM and so on. In between those fixed dates, the page basically never changes and why would I need PHP to render a page if it didn't change since the last request?
Correct, I don't! :)
And here's what I did to setup my cache:
- my homepage:
DirectoryIndex index.html home.php
- a cronjob:
*/10 * * * * fetch -q -o docroot/index.html http://example.org/home.php
In greater detail
home.php does all the PHP funkyness whenever I need a fresh rendered version of my website to track an error, or adjust something.
If I ever delete my cache (
index.html), my website will still be available. The
DirectoryIndex will use
home.php next and the request will be a little slower and also more expensive on my side, but the website will continue to work.
The cronjob will issue a
HTTP request (
fetch against my homepage and save the result to my
index.html. It's really so simple, it hurts. Currently, this cronjob is executed every 10 minutes so I can fiddle with the design and deploy a change more easily, but I could run that cronjob every hour or every few hours as well.
If you don't have
fetch, try the following
wget -q -O docroot/index.html http://example.org/home.php
That's all, a really simple cache which bypasses your application server. Enjoy!
If you're in for another nifty solution, I suggest you read Brandon Savage's article on caching with the Zend Framework and/or take a look at nginx+Memcached.
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