title: Does Nginx have separate queuing mechanism for requests?
body: <p>Consider the following situation: you are deploying application that can serve 1 req./sec. What would happen if I send 10 request in 1 second? I wrote simple app to test that: <a href="https://github.com/amezhenin/nginx_slow_upstream" rel="noreferrer">https://github.com/amezhenin/nginx_slow_upstream</a> .
  This test shows that your requests will be served _in_exact_same_order_ they were sent.</p>
  
  <p>For now, this looks like Nginx have some kind of queue for requests, but my colleague(administrator) sayd that there is no any queues in Nginx. So I wrote another question about epoll here: <a href="https://stackoverflow.com/questions/19114001/does-epoll-preserve-the-order-in-which-fds-was-registered">Does epoll preserve the order in which fd&#39;s was registered?</a> . From that discussion I figured that epoll does preserves the order of requests.</p>
  
  <p>I have two questions:</p>
  
  <p>1) Is there any mistakes in reasoning/code above?</p>
  
  <p>2) Does Nginx have some sort of queue for requests on top of epoll? Or Nginx uses pure epoll functionality?</p>
  
  <p>Thank you, and sorry for my English :)</p>