Like Apache: .htaccess

You can’t do this. You shouldn’t. If you need .htaccess, you’re probably doing it wrong.

Why?

This is a great question. For starters, for .htaccess to work Apache needs to check EVERY directory in the requested path for the existence of a .htaccess file and if it exists it reads EVERY one of them and parses it. This happens for EVERY request. Remember that the second you change that file, it’s effective. This is because Apache reads it every time.

Numbers

http://example.com/site/files/images/layout/header.png

Let’s say we’re not doing any funky aliasing and the file system looks like the path. This covers most of the sites out there. There is the / directory, then site/, files/, images/, and layout/. This amounts to 5 directories that could have a .htaccess file. Let’s say you added a .htaccess in /, files/ and images/. That’s three .htaccess files. That’s pretty typical.

Now the numbers, that’s 6 file system stats and 4 file system reads. Including one for the requested file. This happens for every read. We’ll ignore parsing time because both NGINX and Apache need to do this and we’ll consider the difference in time for this negligible.

Requests / Hour NGINX FS Stats NGINX FS Reads Apache FD Stats Apache FS Reads Comment
1 1 1 6 4 Single Request [Pretty much no load]
10 10 10 60 40 Ten Requests [Pretty much no load]
3,600 3,600 3,600 21,600 14,400 1 req/sec [Very low load]
144,000 144,000 144,000 864,000 576,000 40 req/sec [Moderate traffic - nothing very large]
324,000 324,000 324,000 1,944,00 1,296,000 90 req/sec [Higher traffic site - not massive]
576,000 576,000 576,000 3,456,000 2,304,000 160 req/sec [Pretty high traffic - still not massive though]

More Numbers

The default for Apache is to use AllowOverride All. Let’s look at this for a Drupal website. One image for the theme. If you’re website DocRoot is at /var/www/drupal6/ then we just added more file system stats. This adds 3 stats per request. This is an incredibly common Apache/Drupal setup. It’s the end result of countless guides out there.

/var/www/drupal6/sites/example.com/themes/yourtheme/images/layout/header.png

Two .htaccess files will be in this path unless you create your own. I’ll be assuming you added one in /var/www/ because this is common.

Requests / Hour NGINX FS Stats NGINX FS Reads Apache FD Stats Apache FS Reads Comment
144,000 144,000 144,000 1,296,000 576,000 40 req/sec
324,000 324,000 324,000 2,916,000 1,296,000 90 req/sec
576,000 576,000 576,000 51,840,000 2,304,000 160 req/sec

Conclusion

Stop using .htaccess. It’s horrible for performance. NGINX is designed to be efficient. Adding something like this destroys that.