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Ensure that a given process is only running once. Helpful for ensure that scheduled tasks do not overlap if they run longer than the scheduled interval.

Prior attempts simply used a pid file, and checked if the process specified was still running (by calling Process.kill(0, pid)), but since the system reuses PID's you can get false positives. This project uses a locked pid file to ensure that the process is truly still running. So basically, if the file is locked the process is still running.

Supported Rubies

This process is currently tested in nearly every ruby version supported by Travis-CI

  • MRI versions 1.8.7, 1.9.2, 1.9.3, 2.0.0
  • JRuby running in either 1.8 or 1.9 mode
  • Rubinius running in either 1.8 or 1.9 mode


Add this line to your application's Gemfile:

gem 'singleton_process'

And then execute:

$ bundle

Or install it yourself as:

$ gem install singleton_process


The basic usage is quite simple: just supply a process name (will show up in ps ax output) and call #lock.'long_running_process').lock

If you just want to exit if you can't lock call #lock_or_exit'long_running_process').lock_or_exit # will call Kernel.exit if it is already running.

By default the lock file will be removed when the process exits, but if you need to clear the lock earlier you can call #unlock.

process ='long_running_process')
# your process here

If you want only a specific block of code to be locked call #run! with the block.'long_running_process_name').run! do
  # some long running code here


  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