title: How to run Rails multi-threaded in development?
body: <p>I am working on a multiple projects that talk to each other sometimes and I've run into an issue where app </p>
  
  <ol>
  <li>A calls B (<code>request 1</code>, still running)</li>
  <li>B calls A (<code>request 2</code>)</li>
  <li>based on <code>request 2</code>'s result, B responds to request 1</li>
  </ol>
  
  <p>This requires me running multi-threaded rails in development mode.</p>
  
  <p>I know I can set it up using puma or something like that but ... Isn't there really a simpler way?</p>
  
  <p>I would like to avoid changing anything in the project (adding gems, config files..).</p>
  
  <p>Something like <code>rails s --multi</code> would be nice, can't <code>webrick</code> just run with multiple threads or spawn more processes?</p>
  
  <p>Can I perhaps install a standalone gem to do what I need and run something like <code>thin run . -p 3</code>?</p>