Posted over 5 years ago. Visible to the public.

Fixing "uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)"

RubyGems 1.6.0 has undergone some changes which may cause Rails 2.x applications to break with an error like this one (e.g. when running script/server):
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

Fix it by adding the following not only to your environment.rb but also into your script/server file, in both cases before boot.rb is required.
require 'thread'

If you still get the error above you can also add require 'thread' in your boot.rb after the RAILS_ROOT constant was defined.
RAILS_ROOT = "#{File.dirname(FILE)}/.." unless defined?(RAILS_ROOT)
require 'thread'

Does your version of Ruby on Rails still receive security updates?
Rails LTS provides security patches for old versions of Ruby on Rails (3.2 and 2.3).

Author of this card:

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Ulrich Berkmueller
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We are makandra and do test-driven, agile Ruby on Rails software development.
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Posted by Ulrich Berkmueller to makandropedia