Heroku's Logplex will record all of our application logs that are directed to Standard Output (STDOUT). By default, Rails applications write to a logfile instead of STDOUT. Heroku solves this by automatically injecting a gem into all Rails applications to ensure that the logs are correctly recorded. This gem also gives us the ability to change our logging level on the fly using a configuration variable. In this recipe, we will learn how to adjust a Ruby on Rails application's logging level without having to redeploy any code.
If we do not already have a Rails application, we can use a sample application from GitHub. Open up a terminal and run the following commands to get a Rails application up and running on Heroku:
$ git clone https://github.com/mscoutermarsh/unicorn-rails-heroku.git $ cd unicorn-rails-heroku $ heroku create $ git push heroku master $ heroku open