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by jitl 1130 days ago
You need to design your document to minimize these kinds of issues. You can treat properties in the document as a last-write-wins register to minimize “strange merge” consistency within that property.

For use cases with a central server, you can use server reconciliation to handle “true conflicts”, essentially doing layer of OT-style ops at the application level around CRDT structures provided by a library. See how Replicache suggests handling text for example. They provide a server reconciliation framework, and suggest you use a CRDT for text within that semantics.
1 comments
alserio 1130 days ago
Why not going full OT then? Complexity?
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jitl 1130 days ago
Yes, complexity! What I meant by OT-style operations is a command queue with optimistic updates on the client, and authoritative updates made by the server. This is an easy way to structure your application. "Full OT" means you need to be able to transform any operation type against any other operation of any type. It's quite complicated to implement your application's semantics in terms of operations while maintaining the M*M transform conditions.

Again, Replicache/Reflect.net is a very practical server-reconciliation based system that uses user-defined commands for application semantics, and delegates tricky merge situations to CRDTs; see https://reflect.net/#benefits:~:text=First%2DClass%20Text,st....

Notion also uses a command queue, but we don't use a CRDT for text - although I've been thinking about that for a long time

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josephg 1130 days ago
OT systems generally require a single, centralised server to be a party in between any two changes. CRDTs make it really easy to do multi-server deployments or peer-to-peer data replication. That is (basically) not possible using OT based systems.
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Rapzid 1130 days ago
Most people wanting to use CRDTs though want to use them in scenarios where a central authority is desirable for all sorts of other reasons.
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josephg 1130 days ago
Oh, absolutely. And OT based approaches work great here. CRDTs have the advantage that multi-server deployments are also easy, and modern CRDTs are increasingly faster and better optimized than most OT systems (certainly the ones I've worked on). But OT is a great approach.
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