502 Bad Gateway error showing after login to Plesk or performing any action.

[Almas Qazi]

While performing any action in Plesk it shows below error.

502 bad Gateway

Cause:

Too small fastcgi_buffers limits.

Solutions: Please refer below steps.

Step 1:

We can increase fastcgi_buffers limit as follows.

Below are the error logs.

2020/02/16 12:20:11 [crit] 3114#0: *3 connect() to unix:/var/run/sw-engine.sock failed (2: No such file or directory) while connecting to upstream, client: 115.112.36.86, server: , request: "GET /admin/notifications/list?filter[older]=0 HTTP/1.1", upstream: "fastcgi://unix:/var/run/sw-engine.sock:", host: "example.com:8443", referrer: "https://example.com:8443/smb/web/php-settings/id/867" 
 2020/02/16 12:20:11 [crit] 3114#0: *4 connect() to unix:/var/run/sw-engine.sock failed (2: No such file or directory) while connecting to upstream, client: 115.112.36.86, server: , request: "GET /smb/task/task-progress HTTP/1.1", upstream: "fastcgi://unix:/var/run/sw-engine.sock:", host: "example.com:8443", referrer: "https://example.com:8443/smb/web/php-settings/id/867"

Then we need to open below file.

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

Then find below values and make changes.

Before:

fastcgi_buffers 16 16k;
fastcgi_buffer_size 32k;

After:

fastcgi_buffers 32 32k;
fastcgi_buffer_size 64k;

Step 2:

Then we have to restart sw-cp-server and sw-engine service as below.

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