Zache: A Simple Ruby In-Memory Cache

A month ago I stumbled upon a problem: I wasn’t able to find a Ruby gem which would do in-memory caching with the capability to expire on timeout. After some quick research I decided to implement my own and called it Zache (as in “zero cache,” since there is no back end). Here is how it works:

First, you create the cache:

require 'zache'
zache = Zache.new

Then you fetch the value by the key, also providing the block which will be executed if the key is absent or expired:

x = zache.get(:x, lifetime: 15) do
  # Something very slow and expensive, which
  # we only want to execute once every 15 seconds.
end

Here, :x is the key and 15 is the number of seconds it will stay in the cache, until it expires.

It’s important to notice that the key won’t be deleted from the cache automatically. It will stay there until the next call to get(:x). Only at that moment will it be marked as “expired.” In order to clean up the cache, you can call zache.clean() and all expired keys will be deleted.

You can do it regularly in a separate thread, for example, every minute:

Thread.start do
  sleep 60
  zache.clean
end

Also, Zache, of course, is thread-safe.

The gem is in this GitHub repository. Feel free to report bugs, if you find them, or help us with additional features.