CookieDebugger

Easily debug ActionDispatch::Cookies::CookieOverflow error in your rails app by having the key size information in your logs

CookieDebugger (total size: 17 bytes) from url: http://localhost:3000/ | Cookie: [username=8] | Session: [calculation=4098] [_csrf_token=43] [session_id=32] [session_key_one=3]

I had a problem to reproduce CookieOverflow error on my local machine. I made a blog post about the problem with debugging cookies on production here.

Install the gem and add to the application's Gemfile by executing:

$ bundle add cookie_debugger

or manually by adding gem 'cookie_debugger' into your Gemfile.

Create a new file in the config/initializers folder

# config/initializers/my_cookie_debugger.rb

module MyCookieDebugger
  def log_error(request, wrapper)
    if wrapper.exception.class == ActionDispatch::Cookies::CookieOverflow
      # put information in standard logger(visible in logs file)
      # cat log/development.log | grep CookieDebugger
      logger(request).public_send(:error, ::CookieDebugger::Debug.call(request))

      # or send a message to slack or whatever
      # ::Notify::Slack::Channel::Error.call(message: ::CookieDebugger::Debug.call(request))
    end

    super(request, wrapper)
  end
end

ActionDispatch::DebugExceptions.prepend(MyCookieDebugger)

Then restart the app and check the logs in your console or via bash command:

cat log/development.log | grep CookieDebugger

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

The gem is available as open source under the terms of the MIT License.