Issue Impossible to switch PHP settings from Nginx to FPM or FASTCGI Apache

[Jeromenamnam]

Hello everybody,
My Plesk is running great with Nginx, but for some heavy Php requests from my wordpress multisite, I'm getting a lot of timeout.
I noticed that when my server is running with FPM Apache or FastCGI Apache. Time Out for these request occurs less often.
Now, when I try to switch back to Apache FPM or FastCGI I'm getting the following error:

About the time out: 502 gateway timeout error in browser
and I'm noticing in the nginx error log the following info:

2018/12/27 18:14:05 [error] 6952#0: *1124395 upstream sent too big header while reading response header from upstream, client: 62.138.18.42, server: billykite.com, request: "GET /product/nutcase-little-nuttygen-3-silver-fly-48-52cm/?add_to_wishlist=21904 HTTP/1.1", upstream: "fastcgi://unix:///var/www/vhosts/system/MyWebsite.com/php-fpm.sock:", host: "MyWebsite.com"

"New configuration files for the Apache web server were not created due to the errors in configuration templates: Can not restart web server: . Detailed error descriptions were sent to you by email. Please resolve the issues and click here to generate broken configuration files once again or here to generate all configuration files. See the details in Configuration Troubleshooter"

If this can help:

root@stock:~# service apache2 status -l
● apache2.service - LSB: Apache2 web server
      Loaded: loaded (/lib/systemd/system/apache2.service; enabled)
  Drop-In: /lib/systemd/system/apache2.service.d
           └─forking.conf
   Active: inactive (dead) since Tue 2019-01-08 20:46:11 CET; 6min ago
  Process: 26669 ExecStop=/etc/init.d/apache2 stop (code=exited, status=0/SUCCESS)
  Process: 26651 ExecStart=/etc/init.d/apache2 start (code=exited, status=0/SUCCESS)

Jan 08 20:46:11 stock.ovh systemd[1]: Starting LSB: Apache2 web server...
Jan 08 20:46:11 stock.ovh apache2[26651]: Starting web server: apache2Action 'start' failed.
Jan 08 20:46:11 stock.ovh apache2[26651]: The Apache error log may have more information.
Jan 08 20:46:11 stock.ovh apache2[26651]: .
Jan 08 20:46:11 stock.ovh apache2[26669]: Stopping web server: apache2.
Jan 08 20:46:11 stock.ovh systemd[1]: Started LSB: Apache2 web server.

root@stock:~# apachectl configtest
Syntax OK


root@stock:~# netstat -tulpn | grep :80
tcp        0      0 51.75.205.128:80        0.0.0.0:*               LISTEN      700/nginx

So sorry about that, I think I'm mixing two question. there is probably a way to solve my nginx error and as well understand why Apache want start when switching php settings from nginx to FPM or FastCGI Apache.

Thanks a lot in advance for your help !

 

[Jeromenamnam]

This made my day to fix the Nginx error:
Websites hosted on Plesk server are unavailable with 502 Bad Gateway: upstream sent too big header while reading response header