Why Nginx send traffic to the next upstream on 504 error

[stmx38]

Maxim, thank you for reply!

Some additional question here:
1. If we will remove 'timeout' will Nginx send traffic to the next upstream
on 502 error?
2. More general question related the the Q.1. When Nginx interpret reply as
502 - on timeout, if yes - on which one? We have a lot of timeouts defined
in the main config:
----
  client_header_timeout 30s;
  client_body_timeout   30s;
  send_timeout          65s;

  proxy_connect_timeout 5s;
  proxy_send_timeout    65s;
  proxy_read_timeout    65s;
----

Thanks!

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,289020,289025#msg-289025