all web servers have a normal stop function. What do you mean by kill-9?

do you just unplug the computer when you turn it off?

if there is something similar to nginx between your service and users, directly change the nginx configuration, direct the service to an upgrade prompt page, make sure that no new requests come in, and then shut down the service directly after all the old requests have been processed. If the service is directly connected to the user, you can change the dns. Of course, the safest way is to change the code of the service, use something like a global variable as a tag, and then the administrator changes the tag when upgrading. Once the service detects that the tag has been changed, it rejects the new request, but continues to process the old request.