DOC-3321: Add SSL certificate rotation instructions for Nginx [4.3]

modules/admin-portal/pages/components/nginx.adoc

@@ -69,10 +69,47 @@ Click btn:[Self Signed] to fill in the information to generate a self-signed cer
 
 image::ssl-uploading.png[]
 
-Since configuration change requires restarting the server service, a pop-up box will appear to confirm whether to restart the service.
+For configuration changes made through the Admin Portal, a pop-up box will appear asking whether to restart the service.
 After clicking the btn:[OK] button, the configuration changes and server restart process will take several moments.
 You will be notified after all the process is completed.
 
+=== Gracefully rotating the Nginx SSL certificate
+
+To rotate the Nginx SSL certificate and key without interrupting active connections, update the certificate and key configuration, apply the changes, and then gracefully reload Nginx.
+
+. Update the Nginx SSL certificate and key:
++
+[source,console]
+----
+gadmin config set Nginx.SSL.Cert @/path/to/certificate.pem
+gadmin config set Nginx.SSL.Key @/path/to/key.pem
+gadmin config set Nginx.SSL.Enable true
+----
+
+. Apply the configuration changes:
++
+[source,console]
+----
+gadmin config apply -y
+----
+
+. Gracefully reload Nginx on all nodes:
++
+[source,console]
+----
+nginx_path=$(gadmin config get System.AppRoot)/nginx/sbin/nginx
+prefix_path=$(gadmin config get System.LogRoot)/nginx
+conf_path=$(gadmin config get System.DataRoot)/configs/nginx/conf/nginx.conf
+grun nginx "$nginx_path -p $prefix_path -c $conf_path -s reload"
+----
+
+[IMPORTANT]
+====
+Do not run `gadmin restart -y nginx` when rotating the certificate if you need to preserve active connections. Use the `grun` command above to perform a graceful Nginx reload.
+====
+
+. Verify that Nginx is serving the new certificate.
+
 [WARNING]
 ====
 Downgrading from HTTPS to HTTP (turning off SSL) will cause a user authentication failure.