With Rails 2.1 cache_erb_fragment has been replaced by write_fragment. This breaks a plugin I really enjoy to use: timed_fragment_cache by Richard Livsey.
It basically allows you to specify an expiry for the fragments you cache, e.g. inside memcache, by adding a “meta” fragment for the fragment you store containing the expiry time.
Some usage examples – pretty self-explaining:
In your view:
<%- cache 'my_key', 1.hour.from_now do -%> ... <%- end -%>
With extensive queries – your view …:
<%- cache 'some_posts' -%>