Skip to content


Subversion checkout URL

You can clone with
Download ZIP
A lock-free logger for Ruby 2.0
Latest commit 0cbc317 @steveklabnik Merge pull request #4 from Dangeranger/patch-1
fix rdoc for


Build Status Code Climate Coverage Status

Ruby's stdlib Logger wraps all IO in mutexes. Ruby 2.0 doesn't allow you to request a lock in a trap handler because that could deadlock. This gem fixes this issue by giving you a lock-free logger class.

If you've ever seen log writing failed. can't be called from trap context, you're in the right place!


Add this line to your application's Gemfile:

gem 'mono_logger'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mono_logger


It's simple, just use MonoLogger anywhere you'd use Logger:

require 'logger'

logger =
logger.level = Logger::WARN

logger.debug("Created logger")"Program started")
logger.warn("Nothing to do!")

Turns into

require 'mono_logger'

logger =
logger.level = MonoLogger::WARN

logger.debug("Created logger")"Program started")
logger.warn("Nothing to do!")

That's it! No more errors!


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request


MIT. See LICENSE.txt for more details.

Something went wrong with that request. Please try again.