The Rails Analyzer Tools are a very useful way to keep tabs on the performance of your site. They were written by Eric Hodel and have been open-sourced to the community by the Robot Co-Op.

The problem is that you need to install and run SysLogLogger to make it work. If you have more than one Rails app on a box, or if you don’t have root access to the box, or if you are on a shared host, you are out of luck.

No longer!

Many speedy sites use memcached to save the results of expensive database queries and intense rendered templates. This is a basic introduction to using memcached with Rails. Thanks to Eric Hodel and Layton Wedgeworth who have answered many questions.

Yes, there is a hash in the sky

Memcached is a lightweight server process that stakes out a fixed amount of memory and makes it available as a quick access object cache.

Some of the things you can do with it are:

• Automatically cache a row from the database as an ActiveRecord object
• Explicitly render_to_string and save the results (works well for tag clouds)
• Manually store a complicated database query and retrieve it later

I thought there was some kind of fancy voodoo happening, but it turns out that it’s basically just a hash! You can put a key and value into the cache, and get it later. memcache-client also gives you a delete method.

Objects are serialized using Marshal, so it’s very fast.

@tags = Tag.find_all
Cache.put 'all_your_tags', @tags

Cache.put 'favorite_skateboarder', 'Tom Penny'
skateboarder = Cache.get 'favorite_skateboarder'

Cache.delete 'all_your_tags'