How to restart Apache without disconnecting user
If you have made changes to the apache configuration (httpd.conf), you would need to restart Apache to re-read the new configuration.
However, you don't need to disconnect user immediately, you can tell the Apache's parent process to advise their children to exit after they have finished their current request. So users will not experience a sudden disconnect.
To do so, use the graceful flag
apachectl -k graceful