y-crdt VS Matrix-CRDT

Definitely agree that would be valuable. In fact our multiplayer state synchronization aspect is largely implemented in TypeScript (there's a TS element to the stack as well), and is built on top of YJS – there is a Rust implementation of YJS already though, which would likely be a great start for anyone looking to build something similar purely in Rust: https://github.com/y-crdt/y-crdt

We are working on a plugin API, which will allow people to build functionality that leverages the multiplayer data model – but within the app rather than as standalone applications.

It sounds like you want a Conflict-Free Replicated Data Type, CRDT for short. There are some Rust libraries you can use, but y-crdt seems very feature-complete, a port of Yjs.

I've found reliably persistence on the backend irritating with yjs. Seems like the official path is to fork their example library and edit it. (The example is insufficient because, for example, it will silently eat data if the onchange webhook fails).

yrs initially looks tempting but it's unsound at it's core. (The plan is to port the API directly from JS, use unsafe to silence the borrow checker, then gradually fix specific instances of undefined behavior if they cause actual real world issues.[1] I don't this this is an approach that can work. That's a shame because a lot of impressive work has gone into yrs.)

[1]: https://github.com/y-crdt/y-crdt/issues/233

So exciting! Strangely enough, a couple of hours before this release, we just managed to wrap our heads around Yjs after playing with it on and off for a few weeks!

For anyone not up to date with the world of CRDTs, Seph Gentle's two blog posts have become legendary:

* https://josephg.com/blog/crdts-are-the-future/

* https://josephg.com/blog/crdts-go-brrr/

these are also worth checking out:

* https://github.com/y-crdt/y-crdt (rust implementation started by the creator of Yjs, Kevin Jahns)

* https://github.com/y-crdt/ypy (python bindings for the rust implementation)

* https://github.com/josephg/diamond-types (Seph Gentle's rust implementation of YATA, the algorith behind Yjs)

I found the concept of conflict-free relational data types (CRDTS) interesting as it allows you to have fully offline experiences while also having a conflict-free syncing experience. I was looking for some good libraries and came across automerge and yrs, but both had some rough APIs as they're primarily low-level libraries that are wrapped by TypeScript APIs.

Yrs (Yjs on Rust) maintainer here: we actually had some idea about building extension to Postgres ;) See: https://github.com/y-crdt/y-crdt/issues/220

Hi everyone! Author here. I'm happy to answer questions.

I wrote this a couple years ago. Since then I've been working on my own CRDT called Diamond Types[1], which uses a lot of these ideas to be bonkers fast. I've built several OT based collaborative editing systems, and diamond types is much faster than any of them - though rust and wasm might be the real MVPs here. I wrote a follow-up to this article last year when I got that working, talking about how some of the optimizations work. That article is here[2].

A fair bit has changed since I wrote that article. Yjs has started a rewrite in rust (called yrs[3]). And Automerge has apparently dramatically improved performance based on some of the ideas I talk about in this article. Oh, and diamond types has been rewritten from the ground up. Its now about 5x faster than it was last year, by completely changing the internal structure. But thats a story for another day.

Unfortunately I still only support collaborative text editing. Adding full JSON support comes soon, after I document some more of the tricks I'm doing. Its really fun work!

Why do I only support collaborative text editing? Because I care about performance, and text CRDT performance is hard because you have so many individual changes. (One for each keystroke!). Making text editing fast means everything is fast. But we've still got to do the work. To make that happen, my plan is to add full JSON editing support to diamond types using shelf[4]. Shelf is a super simple CRDT which fits in 100 lines of javascript.

[1] https://github.com/josephg/diamond-types/

[2] https://josephg.com/blog/crdts-go-brrr/

[3] https://github.com/y-crdt/y-crdt/tree/main/yrs

[4] https://github.com/dglittle/shelf

Another interesting and peculiar approach would be to use Matrix, which is chat and collaboration framework that is completely decentralised. Essentially, in this way Scrivano would translate pen input into chat messages that are sent to other users who receive them in real time. One advantage of this approach is that the collaborative notes will remain accessible even after you go offline and multiple users will be able to collaborate on a single note just like they would in a group chat. There are already apps that make use of this idea (e.g. see Matrix-CRDT or TheBoard), but when I tried this it last time didn't work very well and I'm not sure whether this is a limitation of the service or of the specific implementation I tried.

1. This is complicated. There is a notion of power_level, which you can set to different events. So you can set "send message" to power level 30, and any user with a "power level" of 30 or more will be able to send messages. Those power levels (and the required level to send an event) are granted by the room creator.

There is, however, no power_level associated with reading messages. I think you need to be joined to a room to send messages, and to be joined, you need to be able to read messages by design. So the "inbox" model doesn't seem representable to me. But maybe I'm missing something!

2. Yes. Events can refer to prior events to modify them, e.g. you can "edit" a previous message by appending a new message of type "msg.edit" (made up type, not sure what the exact it), specifying the old message id, and the new text. For matrix-based CRDT, see Matrix-CRDT[1], a Yjs backend using Matrix.

[1]: https://github.com/YousefED/Matrix-CRDT

Have you checked out Matrix? It's specifically a protocol (they've used OpenWhisper) but people are using it like a social media platform (specifically like IRC). There's even people doing google docs like services. I'm going to link a HN thread from that last link because others are just talking about Matrix and that'll likely be helpful to you.

Show HN: Matrix-CRDT – real-time collaborative apps using Matrix as backend\ (2 comments)