Nginx: [emerg] host not found in upstream

1

Hi everybody;
for unknown reason nginx stopped
when I try
systemctl status nginx.service

i got this issue:

    ● nginx.service - A high performance web server and a reverse proxy server
       Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
       Active: failed (Result: exit-code) since Fri 2020-04-17 13:28:38 EET; 7s ago
     Docs: man:nginx(8)
      Process: 28887 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; 
      (code=exited, status=1/FAILURE)

  : Starting A high performance web server and a reverse proxy server...
: nginx: [emerg] host not found in upstream "frappe-bench-socketio-server" in /etc/nginx/conf.d/ssl.conf:35
: nginx: configuration file /etc/nginx/nginx.conf test failed
   : nginx.service: Control process exited, code=exited status=1
: nginx.service: Failed with result 'exit-code'.
 : Failed to start A high performance web server and a reverse proxy server.

also sudo nginx

result this issue:

nginx: [emerg] host not found in upstream "frappe-bench-socketio-server" in /etc                                                                                        
/nginx/conf.d/ssl.conf:35
`

and this is line 35 in ssl.conf

 proxy_pass http://frappe-bench-socketio-server;