How to make `thin` webserver print log to STDOUT

Well Thin explicitly does not log anything by default unless you specify it do so by passing options

-D or --debug and -V or --trace 

But having said that this would only track the request / response header of but not rails specific log since your are booting the rails as a rack app perhaps

I guess you need to start rails in ssl mode you can find couple of documentation over here and here

FYI to use thin as backend adapter in rails all you do is add gem 'thin' to the Gemfile and start rails it would start rails using thin adapter but you cant pass thin options like you do for when starting thin

i think that you need to tell rails to use STDOUT for logging instead of logging to log/development.log by putting config.logger = Logger.new(STDOUT) in your app/config/environments/development.rb.