502 Bad Gateway error is shown after login to Plesk or performing any actions: Connection reset by peer

Symptoms

• While accessing Plesk or performing any actions the following error is shown:

  502 Bad Gateway

• The following error message appears in /var/log/sw-cp-server/error_log:

  recv() failed (104: Connection reset by peer) while reading response header from upstream, client: 203.0.113.2, server: , request: "POST <some url>

  OR

  [error] 17434#0: *4954 upstream sent too big header while reading response header from upstream, client: 203.0.113.2, server: , request: "GET /modules/xovi/index.php/log-analyzer/index/id/2 HTTP/1.1", upstream: "fastcgi://unix:/var/run/sw-engine.sock:", host: "example.com:8443", referrer: "https://example.com:8443/"

Cause

Low FastCGI buffer limits.

Resolution

1. Connect to the server via SSH.

2. Open /etc/sw-cp-server/config with a text editor:

   # vi /etc/sw-cp-server/config

3. Increase FastCGI buffer limits using the editor:

   fastcgi_buffers 32 32k;
   fastcgi_buffer_size 64k;

4. Restart sw-cp-server and sw-engine services:

   # service sw-cp-server restart && service sw-engine restart