Error:

upstream timed out (110: Connection timed out) while reading response header from upstream

What causes

• The upstream timeout error generally triggers when the upstream takes too much to answer the request and NGINX thinks the upstream already failed in processing the request. [0]

• proxy_read_timeout – Defines a timeout for reading a response from the proxied server. Default is 60 seconds.

Solution

...

location ~ / {
  ...  
  proxy_connect_timeout      140;
  proxy_send_timeout         180;
  proxy_read_timeout         180;
  ...
}

...