Hacker News Reader

Comment by bullen | Hacker News Reader

I made a MMO in 2001 and came to the conclusions that one thread per socket was not going to scale and thought I would mothball the project until that was solved in Java.

2023 and now we have virtual threads that replace blocking IO with non-blocking automatically! Haven't tested it yet though! But I am reviving the 2001 MMO now!

In between I made my own MMO backend that uses NIO, conclusion is event-based network and validation is the only way to scale action MMOs past 100 players.

Also you need to share memory atomically between cores, so Java or C.

View on HN

I feel like the Erlang/OTP would be perfect for the MMO use case. It’s what I’d try first if building from scratch.

No erlang cannot share memory between cores, it has to copy it.

I think binaries are refcounted and shared in Erlang? I'm not sure if this happens between schedulers/cores, though. They're also obviously immutable, so might not be what you mean by "sharing memory atomically".

Other than Erlang, Pony[1] might be an interesting choice. It allows sharing memory, even mutable memory, but it tracks the sharing in the type system. It's been a long time since I looked at it, and it definitely had a bunch of rough edges, but I really liked where the things were going. I hope it got even better since.

[1] https://www.ponylang.io/

For me C (1970) and Java (1990) are the only options for eternity.

I use some C++ features and dabble in js when I make HTML but really since Applet and Flash has been removed the browser is just a bloated waste of time.

Make your apps fast by allowing them to share memory without latency!

I have also coded Perl, VisualBasic, php and C# and I'm pretty sure this is it.

What we need now are VMs that can take any bytecode/instructionset and translate it to all others. For true crossplatform development. But that requires us to dump dynamic allocation. Arrays of 64 byte structures FTW!

> VMs that can take any bytecode/instructionset and translate it to all others

You're gonna love this: https://en.wikipedia.org/wiki/WebAssembly

I would if anything worked.

Still waiting for a Windows release of this: https://github.com/bytecodealliance/wasm-micro-runtime

Don't hold you breath.

Also needs Risc-V and ARM 32/64.

Erlang performance would be a big problem. It's subpar compared to C++ by an order of magnitude.

depends on the kind of game you are making. People made MMOs in the year 2000 when CPUs themselves were an order of magnitude slower.

Would an MMO backend be CPU bound though? I feel the use case of having a large numbers of active connections with the very distributed nature of passing events around between them all would be perfect for Erlang/OTP. Anything CPU intensive (like dungeon generation or similar) could be offloaded to another service if needed.

You want low latency action, and for that you need one CPU with all cores talking to all the memory without locking. Erlang can't do that, and neither can any other language; except C (Arrays of 64 byte Structures) and Java (Concurrency complete rewrite of the JVM in 1.5 that was adopted and failed for C++11 because you need a VM + GC for that model to be meaningful).

Does it really need to be low latency? It's not an FPS - so I don't think high tick rate is important. I'd rather have a wider synchronized global state and acceptable server side latency (<500ms) than instant server updates. The client can interpolate everything.

Then you are making a slideshow, not a game.

The whole point of games is real-time action.

It does not need to be violent, but it needs physics that give you the feeling of being there.

Multiplayer > VR

Lots of mmos have low tick rates. I believe Eve Online is once per second. Originally WoW was like 2.5/s. You don’t need high tick rates in MMOs (but you certainly have to design the game systems around expected server tick rate).

I have an MMO demo in Elixir!

I haven’t updated it in some time because busy from work but take a look:

http://rotb.io

Erlang/OTP seems perfect for a diablo-esque game where you have lots of instances with a handful of players each. But a giant shared world with thousands of players doesn't seem to play into its wheelhouse as much.

Reply on news.ycombinator.com