title: How do you choose your HTTP server in Sinatra?
body: <p>I am running a Sinatra application locally.</p>
  
  <p>Ever since I installed Thin, my Sinatra app always uses it as the web server.  However, I have been having performance issues with Thin serving the large amount of static files required by my application, and I would like to switch to either Mongrel or WEBrick.</p>
  
  <p>I cannot seem to figure out how to switch my application over to Mongrel or WEBrick.  Even when I put <code>require 'mongrel'</code> or <code>require 'webrick'</code> at the top of my app.rb, upon a <code>ruby app.rb</code>, Sinatra still starts with Thin.</p>
  
  <p>So, my question is: how do you specify the web server for Sinatra to use in development mode?  Also, how could I do so in production mode?</p>