Performance

Image Serving

Firstly, make sure your webserver is configured properly and nice URLs are enabled, so that images will be served straight from disk by the webserver instead of via PHP. If you're serving images via PHP, then your site might melt under the load of 5 concurrent users...

Server

While any web server should work, nginx has been found to work particularly well

Running PHP in FastCGI mode (eg via PHP-FPM) should reduce startup overhead a lot.

Software Cache

Install a key / value store like memcached or redis, and then add to shimmie.conf.php: define("CACHE_DSN", "memcache://127.0.0.1:11211"). A bunch of stuff will then get served from the high-speed cache instead of the SQL database.

HTTP Cache

Varnish makes everything better. The default behavior of "anons see cached pages that are up to two minutes old, logged in users get fresh data" is pretty close to perfect, though you may want to increase the TTL for some pages (image lists / search results may change often, individual images not so much)

Note that this behaviour works correctly because shimmie only sets a session cookie when a user is logged in, no cookie for anonymous users. If you modify shimmie to add new cookies (or you have ads on your site, which have their own cookies), you'll also need to modify the Varnish config to ignore them too.

Example varnish config file

Software tweaks

Board Config -> Advanced will show a bunch of extra settings which can make things faster at the expense of cutting down on the heavier features (for example, only showing the first 500 pages of search results, instead of all results)

CDN support

If serving images and thumbs from a set of mirrors, one can load balance by setting eg: the image url to http://mirror-{a=25,b=25,c=50}.mysite.com/_images/$hash/$id - $tags.$ext. Shimmie will then spread the load over those three servers, using a consistent hash for distribution (consistent meaning that if you add or remove a server from the list, as many URLs as possible will stay the same)

Data Store

Setting define("WH_SPLITS", 2); in shimmie.conf.php will store files as images/ab/cd/... instead of images/ab/..., which can reduce filesystem load when you have millions of images. Note that if you use this setting, you'll need to update the webserver config to match (or if using the docker image, just restart the container and it will automatically reconfigure the internal webserver)

Profiling

If you want to help make the software itself as fast as possible, a good starting place is to see what's slow right now: define()'ing TRACE_FILE to a filename and TRACE_THRESHOLD to a number of seconds will result in JSON event traces being dumped into that file whenever a page takes longer than the threshold to load. These traces can then be loaded into Perfetto and you'll get a breakdown of page performance by extension, event, database, and cache queries.