I’m working on a JavaScript editor that lets multiple people edit at once, like Google Docs. But I’m stuck on a tricky problem.
Here’s the issue:
Two users, Alice and Bob, are editing the same document. There’s a 10ms delay between them. The document starts as ‘xyz123’.
Alice adds ‘abc’ at the start (time: 001ms).
Bob adds ‘hello’ between ‘xyz’ and ‘123’ (time: 005ms).
They both expect ‘abcxyzhello123’. But because of the delay, they end up with different results.
I’ve thought of a few ways to fix this:
- Track insertion points
- Send context with edits
- Undo and redo conflicting edits
- Include timestamp info with edits
- Give each character a unique ID
None of these seem perfect. How does Google Docs handle this? Are there other smart ways to solve this editing collision problem?
As someone who’s dabbled in building collaborative tools, I can tell you Google Docs’ magic isn’t just one trick. It’s likely a cocktail of clever algorithms and optimizations.
From my experience, they’re probably using a variation of Operational Transformation (OT) at its core. But here’s the kicker - they’ve likely built layers upon layers of custom logic on top of it.
One thing that’s often overlooked is the importance of efficient data structures. I bet they’re using some seriously optimized structures to represent the document state. This allows for lightning-fast updates and conflict resolution.
Another crucial aspect is intelligent client-side prediction. This creates the illusion of instant updates, even when there’s network lag. It’s a game-changer for user experience.
Don’t underestimate the power of a well-designed centralized server either. It’s the unsung hero, quietly keeping everything in sync behind the scenes.
Remember, Google’s been at this for years. They’ve likely ironed out countless edge cases we mere mortals haven’t even thought of yet. It’s not just about the algorithm - it’s about years of refinement and optimization.
google uses operational transformation (OT) for this. it’s a complex algorithm that merges changes from multiple users in real-time. basically, it transforms operations to account for concurrent edits. there’s also newer approaches like conflict-free replicated data types (CRDTs) that some collaborative editors use. both have pros/cons, but OT is prob what gdocs uses.
Having worked on similar projects, I can say that Google Docs likely employs a combination of techniques to achieve seamless collaboration. While Operational Transformation (OT) is often cited, Google’s approach is likely more sophisticated. They probably use a custom algorithm that incorporates elements of OT, CRDTs, and other proprietary methods.
Key to their system is likely a centralized server that acts as the source of truth, resolving conflicts and maintaining consistency across all clients. This server would apply a set of rules to determine the ‘correct’ order of operations when conflicts occur.
Additionally, Google’s implementation likely includes optimizations for network latency, intelligent client-side prediction, and efficient data structures for representing the document state. These elements combined create the illusion of real-time collaboration, even in less-than-ideal network conditions.