Somebody please clone Cloudflare Durable Objects
I’ve been looking into how to build a Figma-like realtime multiplayer editor. These two articles go into a lot of detail about the efforts Figma had to expend to achieve it:
https://www.figma.com/blog/rust-in-production-at-figma/
https://www.figma.com/blog/how-figmas-multiplayer-technology-works/
While I was working on a series of prototypes based on the posts above, Cloudflare dropped a new product: Durable Objects, an extension of their Workers platform.
https://blog.cloudflare.com/introducing-workers-durable-objects/
As Paul puts it in this piece about the Durable Objects advantage:
Durable Objects provide a way to reliably connect two clients to the same object. Each object has a (string) name that is used when connecting to it, which typically corresponds to a “room” or “document ID” in the application itself.
In practice, this means that two clients can establish WebSocket connections using the same document ID, and the infrastructure will guarantee that they are connected to the same Durable Object instance.
This is the difference that makes Durable Objects so compelling for multiplayer use cases, but it’s also the reason that the Durable Object abstraction hasn’t been slapped on top of other FaaS platforms – it is a radical departure from core assumptions made by their scheduling and routing systems.
https://digest.browsertech.com/archive/browsertech-digest-cloudflares-durable/
The Durable Objects killer feature is the global uniqueness of each object, and the ability to address the object from a known string.
For example, say I have a “customer” object in my database and I want to associate a realtime session with each customer, e.g. for the purpose of adding realtime updates to the CRM interface for that customer.
A client can send a request to Cloudflare asking:
connect me via Websocket to the Object identified by
"session:customer_<id>"
and when two clients make that same request with the same <id> on opposite sides of the world, both their Websockets will end up connected to the same Durable Object instance somewhere in Cloudflare.
I’ve been wishing another cloud provider would build similar functionality, but as Paul notes, it’s not simple. While edge workers (especially JavaScript ones) are fairly commoditised now, building on Durable Objects is still significant vendor lock-in.
Jamsocket deserves an honorable mention for building open-source tooling to self-host something very similar: