Forum: Ruby on Rails Volatile cache keys with Rails and Redis

Does Rails automatically set an EXPIRE attribute on keys when working 
with
Redis, or will an old key sit there forever if it's never manually 
cleared
out? This is mostly a concern when using ActiveModel's "cache_key":

<%= cache @post do %>

The cache-key will be something like views/posts/744-20120613070958 . 
When
the post is updated, and therefore gets a new cache-key, what happens to
the old one? Will it just sit there forever? Do I need to add an
`expires_in` option to every cache call, just to make sure it gets 
cleaned
up every once in a while?

<%= cache @post, expires_in: 1.month do %>

Thanks,
Bryan

The idea is that your cache system should expire the oldest items in the
cache automatically when it hits its pre-configured size limit.