Proxy support

[GillesSchippers]

Hey there,
Love the work you have done to make this a fascinating project. I have been using this plugin to make my experience managing my Minecraft servers way better especially when (re)starting multiple servers at once so that they wait for each other to finish starting in a scaffolding like pattern.
I am wondering if something like this could be done for any proxy software out there like Velocity and wonder how much different the code would have to be to make that possible.

[GillesSchippers]

I am not strong on my Java knowledge so unless I get my dev environment working I can't do much myself I'm afraid

[AgentOak]

Proxies like Velocity have a completely different plugin API. The only shareable code would be the system package which offers a higher-level interface to the notify socket, but the way it's implemented (going through libsystemd) isn't great anyway. It'd be better to write to the socket directly, which Java finally supports since Java 16.

Basically all one has to do is write READY=1 to the socket when the service is fully started/reloaded, WATCHDOG=1 periodically, RELOADING=1 before reloading and STOPPING=1 before stopping. Bukkit/Spigot/Paper API suits this very poorly, even lacking events for server started/stopping/reloading which is just mindblowing, hence much of what this plugin does is trying to infer what's actually happening from downstream events, even parsing the stack trace to find known method names.

Velocity appears to have a much more sensible API and the socket messages cleanly map to available events.

[punkeel]

It'd be better to write to the socket directly, which Java finally supports since Java 16.

That is unfortunately not entirely accurate – Java 16 added UNIX domain socket support, but it only supports SOCK_STREAM, whereas systemd notify requires SOCK_DGRAM. In addition, systemd may use abstract namespace sockets, which Java NIO also cannot address directly.

Netty supports both natively, and I implemented this approach in a quick Hytale plugin proof of concept: HySystemdNotifier.