title: nginx error message - what does "peer" refer to?
body: <p>In order to debug an nginx error case, I need to fully understand an error log message first. Our nginx writes the particular error log message from time to time.</p>
  
  <p><strong>Log message</strong> </p>
  
  <p>"<em>peer closed connection in SSL handshake (104: Connection reset by peer) while SSL handshaking to upstream</em>".</p>
  
  <p><strong>What is meant by "peer"?</strong></p>
  
  <p>I would like to know: Does "peer" refer to the upstream, meaning that the upstream closed the connection during ssl handshake, or does it refer to the client, meaning that the client closed connection while the load balancer and the webserver was internally during a handshake?</p>
  
  <p><strong>Setup</strong></p>
  
  <ul>
  <li>nginx loadbalancer</li>
  <li>2 webservers (upstreams) running IIS8</li>
  <li>Ssl provider: Comodo</li>
  </ul>