What does “WARN Could not determine content-length of response body.” mean and how to I get rid of it?

Question

Since upgrading to Rails 3.1 I\'m seeing this warning message in my development log:

WARN Could not determine content-length of response body. Set co

Answer 1

You can also use Thin instead of the default Webrick. Add this to Gemfile gem 'thin'

then rails s thin will use thin, and the warning will disappear.