Question

Is there a way to cache per-request data in Rails? For a given Rails/mongrel request I have the result of a semi-expensive operation that I’d like to access several times later in that request. Is there a hash where I can store and access such data?

It needs to be fairly global and accessible from views, controllers, and libs, like Rails.cache and I18n are.

I’m ok doing some monkey-patching if that’s what it takes.

• Memcached doesn’t work because it’ll be shared across requests, which I don’t want.
• A global variable similarly doesn’t work because different requests would share the same data, which isn’t what I want.
• Instance variables don’t work because I want to access the data from inside different classes.

Answer 1

Try PerRequestCache. I stole the design from the SQL Query Cache.

Configure it up in config/environment.rb with:

config.middleware.use PerRequestCache

then use it with:

PerRequestCache.fetch(:foo_cache){ some_expensive_foo }