Websites hosted in Plesk show a "502 Bad Gateway" error: no resolver defined to resolve example.com

Symptoms

• Websites show a "502 Bad Gateway" error. The following error message appears in /var/log/nginx/error.log:

  CONFIG_TEXT: [error] 20109#0: *945 no resolver defined to resolve example.com, client: 192.168.0.1, server: , request: "GET / HTTP/1.1", host: "example.com"

• $host is used instead of a server IP address for proxy_pass value under location / in the file /etc/nginx/plesk.conf.d/server.conf:

  # grep -B2 7080 /etc/nginx/plesk.conf.d/server.conf | grep -B2 proxy_pass
  
  location / {
  proxy_pass http://$host:7080;

Cause

No resolver is specified in the nginx configuration.

Resolution

1. Connect to the Plesk server via SSH.

2. Open the file /etc/nginx/nginx.conf in any text editor. In this example, we are using the vi editor:

   # vi /etc/nginx/nginx.conf

3. Add resolver under the http section:

   CONFIG_TEXT: http {
   resolver 127.0.0.1;

4. Save the changes and close the file.

5. Restart nginx:

   # service nginx restart