Are Thread.current[] values and class level attributes safe to use in rails?

I have a particular problem I'm trying to solve in a rails 3 app, and the two common solutions that I'm seeing are these:

Thread.current[:something] = value

and

class Foo
  cattr_accessor :bar
end

Foo.bar = value

Are these methods of data storage (and the corresponding retrieval) safe across multiple users making a request to my rails app, at the same time?

I'm concerned about Thread.current, because a web server could use a single thread to serve up multiple requests, right? Or is there something in the way rails handles threads to prevent problems when using Thread.current? I see Acts As Current uses Thread.current to store the current user, so that gives me hope... but I want authoritative confirmation.

I'm also concerned about class level attributes in a production environment, because I would expect rails to cache class objects in memory, for performance reasons. Does a class level attribute get re-used across requests? or is it safe due to something that rails does to handle class attributes across requests? again, i would like authoritative 开发者_JAVA技巧confirmation of this.

... this app uses Ruby 1.9.2@p180, with Rails 3.0.9

Safe enough to store the time zone of the current request:

https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/time/zones.rb