Rails - cannot run app: Unable to load the EventMachine C extension;

Question

When I run an app on Lion OS X, I get this error:

Unable to load the EventMachine C extension; To use the pure-ruby reactor, require \'em/pure_ruby\'
/Users/         


        

Answer 1

In my case this fixed it:

• $ gem uninstall eventmachine
• at the prompt tell it to uninstall all versions (it tells you about dependencies)
• $ bundle install

I was reading through this https://github.com/eventmachine/eventmachine/issues/333. There were problems with eventmachine, so making sure I got the newest version seemed a good idea.

Answer 2

For me, compiling eventmachine from sources with tweaked config helped. Try:

Uninstall eventmachine if it's already installed:

gem uninstall eventmachine

Fetch eventmachine sources:

git clone https://github.com/eventmachine/eventmachine.git
cd eventmachine

Edit ext/extconf.rb and ext/fastfilereader/extconf.rb files by adding CONFIG['CXX'] = "g++" right after require 'mkmf'

Compile and install gem:

rake gem
gem install pkg/eventmachine-1.0.3.gem

Now eventmachine should work just fine :)

Answer 3

The easiest fix as the message says is just to require 'em/pure_ruby'. I think you can put this in the config/inlitializers folder, you can call the file event_machine.rb

But it won't have the same performance as the C extension.

Answer 4

Providing another solution as I just wasted hours tracking this issue down. I was doing bundle install --deployment and then committing the result to a separate branch in git so I could deploy this branch straight to servers without having to do bundle install again.

The problem is that eventmachine has a .gitignore file in it which tells git to ignore all *.so files. Because of this when I was committing, the .so files didn't commit, and wouldn't show up as untracked in a git status. Also since the gemspec was present, bundle thought the package was completely installed.

My solution was to add a command as part of the build process to go and whack all the .gitignore files in the gems before committing.

Answer 5

You may find various errors while installing gems or trying to find solution to your ruby application installation failing due to ruby-devel was not installed.

I just installed on my Kali linux with

sudo apt-get install ruby-dev

and everything resolved. I was trying to install bettercap.

This answer helped: https://stackoverflow.com/a/4502672/6503117