WARN Could not determine content-length of response body – Ruby on Rails

Hey everyone

I was going through my development logs today and noticed that the following line was appearing everywhere:

WARN Could not determine content-length of response body. Set content-length of the response or set Response#chunked = true

While nothing appeared to be wrong, it made the logs a lot harder to read. A stackoverflow post indicates that this is a webrick issue that can be avoided by switching to thin. This is also the recommended option for heroku. In order to use thin, you simply need to add it to your Gemfile:

#Gemfile

#Added gems
gem 'therubyracer' #JavaScript
gem 'thin' #Instead of webrick

Run bundle install

chris@chris-VirtualBox:~/calendar$ bundle install
Fetching gem metadata from https://rubygems.org/...........
Fetching gem metadata from https://rubygems.org/..
Using rake (10.0.2) 
Using i18n (0.6.1) 
Using multi_json (1.4.0) 
Using activesupport (3.2.9) 
Using builder (3.0.4) 
Using activemodel (3.2.9) 
Using erubis (2.7.0) 
Using journey (1.0.4) 
Using rack (1.4.1) 
Using rack-cache (1.2) 
Using rack-test (0.6.2) 
Using hike (1.2.1) 
Using tilt (1.3.3) 
Using sprockets (2.2.2) 
Using actionpack (3.2.9) 
Using mime-types (1.19) 
Using polyglot (0.3.3) 
Using treetop (1.4.12) 
Using mail (2.4.4) 
Using actionmailer (3.2.9) 
Using arel (3.0.2) 
Using tzinfo (0.3.35) 
Using activerecord (3.2.9) 
Using activeresource (3.2.9) 
Using bcrypt-ruby (3.0.1) 
Using bundler (1.2.3) 
Using coffee-script-source (1.4.0) 
Using execjs (1.4.0) 
Using coffee-script (2.2.0) 
Using rack-ssl (1.3.2) 
Using json (1.7.5) 
Using rdoc (3.12) 
Using thor (0.16.0) 
Using railties (3.2.9) 
Using coffee-rails (3.2.2) 
Installing daemons (1.1.9) 
Installing eventmachine (1.0.0) with native extensions 
Using jquery-rails (2.1.4) 
Using libv8 (3.3.10.4) 
Using pg (0.14.1) 
Using rails (3.2.9) 
Using sass (3.2.3) 
Using sass-rails (3.2.5) 
Using therubyracer (0.10.2) 
Installing thin (1.5.0) with native extensions 
Using uglifier (1.3.0) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

And finally start thin:

chris@chris-VirtualBox:~/calendar$ rails s thin
=> Booting Thin
=> Rails 3.2.9 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
>> Thin web server (v1.5.0 codename Knife)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:3000, CTRL+C to stop

If you’d prefer to keep using Webrick, the following patch is said to resolve the issue:
https://bugs.ruby-lang.org/attachments/2300/204_304_keep_alive.patch