Tuesday, February 11, 2025
I never got the memo on “copyover servers”
There’s only so much you can do with builder rights on someone else’s MUD. To really change the game, you needed to be able to code, and most MUDs were written “real languages” like C. We’d managed to get a copy of Visual C++ 6 and the CircleMUD source code, and started messing about. But the development cycle was pretty frustrating — for every change, you had to recompile the server, shut it down (dropping everyone’s connections), bring it back up, and wait for everyone to log back in.
Some MUDs used a very cool trick to avoid this, called “copyover” or “hotboot”. It’s an idiom that lets a stateful server replace itself while retaining its PID and open connections. It seemed like magic back then: you recompiled the server, sent the right command, everything froze for a few seconds, and (if you were lucky) it came back to life running the latest code. The trick is simple but I can’t find a detailed write-up, so I wanted to write it out while I thought of it.
Via Lobsters, How Copyover MUD Servers Worked | Blog | jackkelly.name
Somehow, in all my years of programming (and the few years I was looking into the source code of various MUDs back in the early 90s) I never came across this method of starting an updated version of a server without losing any network connections. In hindsite, it's an obvious solution—it just never occured to me to do this.
