Nginx, PHP-FPM, and Cloudflare, oh my!

I use my Linode to host a number of things (this blog and Kristina’s, my website and Kristina’s, an IRC session via tmux and irssi for a friend and me, and probably another thing or two I’m forgetting). Kristina started up a travel blog a few months ago which I’m also hosting on it, and shortly after that point I found that maybe once every two weeks or so my website and our blogs weren’t running anymore. I looked into it and it was being caused by Linux’s Out-Of-Memory Killer, which kicks in when the system is critically low on memory and needs to free some up, killing the Docker container that my website runs in as well as MariaDB.

The main cause was Apache and MariaDB using up entirely too much memory for my little 2GB Linode, it was evidently just sitting on this side of stable with two WordPress blogs but adding a third seems like it tipped it over the edge. The reason MariaDB and my website’s Docker container were being killed is because although Apache was using up a heap of memory it was spread over a number of worker threads, so individually none of those were high, and MariaDB and my website were the largest on the list. There’s lots of tweaks you can do, several of which I tried, but all that happened was that it delayed the inevitable rather than entirely resolving it. Apache is powerful but low-resource-usage it ain’t. The primary low-resource-usage alternative to Apache is Nginx, so I figured this weekend I’d have a crack at moving over to that.

Overall it was pretty straightforward, this guide from Digital Ocean was a good starting point, the bits where it fell short was mostly just a case of looking up all of the equivalent directives for SSL, mapping to filesystem locations, etc. (I have ~15 years of history of hosted images I’ve posted on the Ars Technica  forums and my old LiveJournal—which is now this blog—and wanted to make sure those links all kept working). 

One difference is with getting WordPress going… WordPress is all PHP, and Apache by default runs PHP code inside the Apache process itself via mod_php, whereas when you’re using Nginx you have to be using PHP-FPM or similar which is an entirely separate process that runs on the server and that Nginx talks to to process the PHP code. I mostly followed this guide, also from Digital Ocean though there were a couple of extra gotchas I ran into when getting it fully going with Nginx for WordPress:

  • Edit /etc/nginx/fastcgi_params and add a new line with this content or you’ll end up with nothing but an empty blank page: fastcgi_param PATH_TRANSLATED $document_root$fastcgi_script_name;
  • Remember to change the ownership of the WordPress installation directory to the nginx user instead of  apache
  • The default settings for PHP-FPM assume it’s running on a box with significantly more than 2GB of RAM; edit /etc/php-fpm.d/www.conf and change the line that says pm = dynamic to be pm = ondemand; with ondemand PHP-FPM will spin up worker processes as needed but will kill off idle ones after ten seconds rather than leaving them around indefinitely.

Additionally, Nginx doesn’t support .htaccess files so if you’ve got WordPress set up to use any of the “pretty”-type links, you’ll end up with 404s when you try to view an individual post instead. The fix is to put the following into the server block at the bottom:

location / {
  try_files $uri $uri/ /index.php?$args;

So it’ll pass the correct arguments to WordPress’ index.php file. You’ll also want to block access to any existing .htaccess files as well:

location ~ /\.ht {
  deny all;

The last thing I did with this setup was to put the entirety of my website, Kristina’s, and our respective blogs behind Cloudflare. I had great success with their DNS over HTTPS service, and their original product is essentially a reverse proxy that caches static content (CSS, Javascript, images) at each of their points of presence around the world so you’ll load those from whichever server is geographically closest to you. For basic use it’s free, and includes SSL, you just need to point your domain’s nameservers at the ones they provide. The only thing I needed to do was to set up another DNS record so I could actually SSH into my Linode, because now the host resolves to Cloudflare’s servers which obviously don’t have any SSH running!

Overall, the combination of Nginx + PHP-FPM + Cloudflare has resulted in remarkably faster page loads for our blogs, and thus far significantly reduced memory usage as well. ?

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