Uninitialized constant ActiveSupport Dependencies Mutex NameError

Question

When I want to create a Ruby on Rails project  I get the message below    usr lib ruby gems 1 8 gems activesupport-2 3 8 lib active support dependencies rb 55  uninitialized constant ActiveSupport  Dependencies  Mutex  NameError      from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  gem original require      from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  require      from  usr lib ruby gems 1 8 gems activesupport-2 3 8 lib active support rb 57     from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  gem original require      from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  require      from  usr lib ruby gems 1 8 gems rails-2 3 8 lib rails generator rb 31     from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  gem original require      from  usr local lib site ruby 1 8 rubygems custom require rb 36 in  require      from  usr lib ruby gems 1 8 gems rails-2 3 8 bin rails 15     from  usr bin rails 19 in  load      from  usr bin rails 19   What has gone wrong  How do I to fix it

User · Answer

In case you can t upgrade to Ruby on Rails 2 3 11  and to expand on douglasr s answer   thread must be required at the top of boot rb  For example   require  thread     Don t change this file    Configure your app in config environment rb and config environments   rb

User · Answer

This is an incompatibility between Rails 2 3 8 and recent versions of RubyGems  Upgrade to the latest 2 3 version  2 3 11 as of today

User · Answer

I was able to fix this by downgrading RubyGems to 1 5 3  since it happens with RubyGems 1 6 0  and Rails  lt  2 3 11   gem update --system 1 5 3   If you had previously downgraded to an even earlier version and want to update to 1 5 3  you might get the following when trying to run that   Updating RubyGems ERROR   While executing gem      RuntimeError      No gem names are allowed with the --system option   If you get that error  then update  so that it lets you specify the version  and then downgrade again   gem update --system gem update --system 1 5 3

User · Answer

Try updating your Ruby on Rails version to v3 0 5   gem install rails --version 3 0 5   or v2 3 11   gem install rails --version 2 3 11   If this isn t a new project you ll have to upgrade your application accordingly  If it was a new project  just delete the directory you created it in and create a new project again

User · Answer

update the rubygems  gem update --system

User · Answer

If you want to keep your version same like rails will be 2 3 8 and gem version will be latest  You can use this solution Latest gem with Rails2 x  in this some changes in boot rb file and environment rb file   require  thread  in boot rb file at the top   and in environment rb file add the following code above the initializer block   if Gem  Version new Gem  VERSION   gt   Gem  Version new  1 3 7    module Rails    class GemDependency      def requirement        r   super         r    Gem  Requirement default    nil   r      end    end  end end

User · Answer

I have faced this problem in many occassions when I try to start an old rails 2 3 5 project after having worked with rails 3   In my case to solve the problem  I must do a rubygems update to version 1 4 2  this is   sudo gem update --system 1 4 2

User · Answer

If you re using Radiant CMS  simply add  require  thread    to the top of config boot rb    Kudos to Aaron s and nathanvda s responses

User · Answer

I m posting my solution for the other sleep-deprived souls out there   If you re using RVM  double-check that you re in the correct folder  using the correct ruby version and gemset   I had an array of terminal tabs open  and one of them was in a different directory  typing  rails console  produced the error because my default rails distro is 2 3 x   I noticed the error on my part  cd d to the correct directory  and my  rvmrc file did the rest   RVM is not like Git   In git  changing branches in one shell changes it everywhere   It s literally rewriting the files in question   RVM  on the other hand  is just setting shell variables  and must be set for each new shell you open   In case you re not familiar with  rvmrc  you can put a file with that name in any directory  and rvm will pick it up and use the version gemset specified therein  whenever you change to that directory   Here s a sample  rvmrc file   rvm use 1 9 2 turtles   This will switch to the latest version of ruby 1 9 2 in your RVM collection  using the gemset  turtles    Now you can open up a hundred tabs in Terminal  as I end up doing  and never worry about the ruby version it s pointing to

User · Answer

As mentioned this occurs when using RubyGems 1 6 0 with Ruby on Rails version earlier than version 3  My app is using Ruby on Rails 2 3 3 vendored into the  vendor of the project   No doubt an upgrade of Ruby on Rails to a newer 2 3 X version may also fix this issue  However  this problem prevents you running Rake to unvendor Ruby on Rails and upgrade it   Adding require  thread  to the top of environment rb did not fix the issue for me  Adding require  thread  to  vendor rails activesupport lib active support rb did fix the problem

User · Answer

You can also likely get around this issue by requiring  thread  in your application as such   require  thread    As per the RubyGems 1 6 0 release notes

[ruby-on-rails] Uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

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