Hacking of the wordpress

Some weeks ago one of the web servers started to fail. The website showed gateway timeout errors. Restarting all three services (nginx, mysql and php-fpm) did the trick for some days and then it started again. So I was wondering, what the .. ? After some research I found out that each php-fpm process takes 100 or more MB of memory and there were, well some 5 or 6 processes. At some point web server started to use a swap space and of course became unavailable. Disabling of all the extensions, I had added to php, made no changes, so it should be website it self. Disabling of some wordpress plugins made it a bit better and made me wonder.

Recently I discovered a really nice tool from Facebook - XHProf. It is something similar to webgrind, just more cooler. It shows information about called functions, memory consumptions, cpu execution times, etc.

So I thought lets take a wordpress and put it under XHProf. It just blow my mind away. It made somewhere around 70 000 function calls. Oh yeah baby.. Today I put a fresh copy of wordpress onto another host and gave it another shot. Without Latvian language pack it makes around of 8 000 function calls. Seems ok. But when I add those language packs it varies somewhere between 50 000 and 60 000 function calls.

This is because of wordpress implementation of .mo files. I have always thought it is not the best way for storing language strings. It can't be translated online, it is slow and it takes a lot of memory to load those mo files.

Recently I have developed a translation tool for some websites and I thought to give it a try. It actually requires a bit of hacking of the wordpress core files, what I know is not the best practice, but still a tryout would be nice. This tool stores translated strings into the database and then there is a php class file on production side that takes those strings out of database and caches in php files as arrays. Cache is refreshed: 1. if apc is enabled, the hash key of site and language is not found there, or 2. the hash key is not found in table cache.

Now running this setup XHProf show, that only 17 386 function calls are made, it runs faster and takes less memory and the main thing - you can translate your wordpress interface online. Still lot of function calls, although.

To make this work, I had to rewrite parts of l10n.php file in wp-includes. Wordpress also would be better, if it would use more arrays as parameters and avoid call_user_func_array at all. I also decreased process count to two, one for each user and with nginx fastcgi caching turned on, it can handle approximately 6000 requests per second. Nice.

If you are more interested how I made this, please ask in the comments or by e-mail (gm (at) gm (dot) lv).