My server configuration looks like this: Nginx1 (proxycache) <---------> Nginx2 <-> PHP-FPM

When PHP-FPM fails because of the process is down ( errorconnect to unix:/run/php/php7.0-fpm.sock failed: No such file or directory while connecting to upstream) or because of pm.max_children has been reached Nginx2 returns a 404. I have looked if this behavior is set anywhere in my configuration but it looks it's the default.

If Nginx1 gets a 502 error code from Nginx2 will show the stale version of the page and that's why I want it to return a 502 code. I know I can configure Nginx to use the stale version when it gets a 404 from upstream but it there is no way to differentiate that from a normal 404 when a file gets deleted.

  • What is your complete nginx confuguration? – Tero Kilkanen May 29 '18 at 18:06

Usually this happens if you configure php to display errors:

 php_admin_value[display_errors] = On

nginx considers the error msg a valid page and changes the http status code.

Ref: https://stackoverflow.com/questions/11421240/why-does-display-errors-change-the-http-status-code

  • that looks correct, but it seems to me that it should be logged as a bug with PHP - displaying errors shouldn't interfere with the protocol, look what it does to nginx – Sum1sAdmin May 28 '18 at 9:33
  • 1
    I will review this but I'm referring to situations when php-fpm is not processing the request, not when there is an error in the PHP code (like the question you mention), so I don't think the PHP configuration matters. One of the tests I do is literally executing service php7.0-fpm stop. In that case Nginx2 returns a 404 ( ( errorconnect() to unix:/run/php/php7.0-fpm.sock failed (2: No such file or directory)) and I want it to return a 502. – brainsqueezer May 28 '18 at 9:45

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