title: What does "trust proxy" actually do in express.js, and do I need to use it?
body: <p>I am writing an express app that sits behind an nginx server.  I was reading through express's documentation and it mentioned the 'trust proxy' setting. All it says is</p>
  
  <blockquote>
    <p>trust proxy Enables reverse proxy support, disabled by default</p>
  </blockquote>
  
  <p>I read the little article here that explains Secure Sessions in Node with nginx. </p>
  
  <p><a href="http://blog.nikmartin.com/2013/07/secure-sessions-in-nodejs-with-nginx.html">http://blog.nikmartin.com/2013/07/secure-sessions-in-nodejs-with-nginx.html</a></p>
  
  <p>So I am curious.  Does setting 'trust proxy' to true only matter when using HTTPS?  Currently my app is just HTTP between the client and nginx.  If I set it to true now, are there any side-effects/repercussions I need to be aware of? Is there any point to setting it true now?</p>