Question

Hello I am working on an existing Drupal website for my client. He has this website working a little slow, and my client wants me to make changes to this website’s caching system, since it keeps crashing when the user count on the site goes up.

Now I need some advice on where to start to understand about this site’s caching system. I did do grep of a few Drupal’s caching functions and I saw boost and memcache files in there.

Answer 1

I don’t know which version of drupal you are running, but it shouldn’t make that much of a difference other then the modules available to you.

Basically Drupal has a cache API which works by storing whatever it wants to cache into the DB in the tables beginning with cache_, using cache_set and cache_get. If the site has a lot of traffic, the added overhead of the reads and writes to the DB can bring it down. Those functions will work with any of the caching modules that you replace the original one with, for example:

To over come this you can add various modules to change the cache, for example, using memcache module, to store the cache values in memory rather then in the DB. You will still need to configure a memcache instance on the server, and then set it up in the settings.php, but all of that is explained in the memcache readme.

There’s a very good chance that the site is suffering because of the views on the page. I would look at the views, and see if any are making queries that are very very slow. Views is always heavy on the DB. You might want to go through each of the views and change (or even enable) their cache timings and settings.

You might be suffering because you have a lot of logged in users on the site, and they will bypass a lot of the cache, so you could try the AuthCache module, which allows you to fine tune the block caching for logged in users.

You can also make some searches for High traffic sites and caching for drupal. I found quite a few when I was otimizing a site I was working on with ~100’000 visitors per day.