P2PDocs: Building a Decentralized Collaborative Editor
A Distributed Systems Course Project at the University of Udine
Course: Distributed Systems Team: Alessandro De Biasi, Alessandro Minisini, Nazareno Piccin GitHub: Repository Link | Stack: Elixir, Node.js, Docker
📚 Project Overview
As part of our Distributed Systems course, we designed P2PDocs, a peer-to-peer collaborative text editor. The goal was to implement and evaluate core distributed algorithms:
- Conflict-Free Replicated Data Types (CRDTs) for conflict resolution
- Causal Broadcast for ordered message delivery
🔍 Key Technical Contributions
1. LSEQ CRDT Implementation
To achieve intention preservation (ensuring edits respect user intent across peers), we adopted the LSEQ strategy:
- Position vectors as rational numbers for dense ordering
- Peer-ID tagging to break ties in concurrent edits
- AVL Order-Statistic Tree for O(log n) insertions/deletions
2. Network Layer
- Echo-Wave Protocol: Reliable operation propagation in dynamic topologies
- Neighbor Handshake: State synchronization for joining peers
- Crash Recovery: ETS (Erlang Term Storage) for persistence
3. Validation & Testing
- Unit Tests: ExUnit for module correctness
- Multi-Node Tests: Dockerized network partitions and merges:
./start_n_instances_for_tests.sh 5 # Launch 5 peers ./disconnect.sh 2 # Simulate node failure
🔮 Future Work
Suggestions from our final report:
- Add Markdown support
- Implement real-time cursor tracking
- Optimize vector clock size
📚 Learn More
For a detailed technical deep dive, including:
- Full CRDT implementation details
- Network protocol design choices
- System validation methodology (unit/integration tests)
Check out the Project Report in the repository.
Explore the Code: GitHub | Connect: LinkedIn