Distributed Key-Value Store in C++ with Bully Leader Election

📌 Overview

This project is a distributed key-value (KV) store written in C++. It evolves over five phases—each improving on scalability, durability, and fault tolerance. By the final phase, it supports leader election using the Bully algorithm, enabling robust coordination across a distributed system.

Development is structured into Git branches, one per phase, allowing easy progression and experimentation.

🏗 Project Phases & Branches

Phase 1 — Basic Key-Value Store

Branch: main Implements a simple thread-safe, in-memory key-value store.

Key Features:

• GET, SET, DEL operations
• Command-line or API interface

Phase 2 — Logging Support

Branch: append_log Introduces write-ahead logging to persist changes and enable recovery.

Key Features:

• Log every write operation

Phase 3 — Networking Layer

Branch: networking Adds TCP networking to serve remote clients.

Key Features:

• TCP-based server-client model
• Message parsing and framing
• Concurrent client handling

Phase 4 — Replication & Refactoring

Branch: replication Enables data replication across follower nodes.

Key Features:

• Synchronous/asynchronous replication
• Modular server-client refactor
• Redundancy for fault tolerance

Phase 5 — Leader Election via Bully Algorithm

Branch: leader-election Implements dynamic leader election based on node priorities.

Key Features:

• Bully election protocol
• Automatic failover and re-election
• Leader coordination for write operations

🛠️ How to Build

Ensure CMake is installed and a C++17-compatible compiler is available.

mkdir build
cd build
cmake ..
cmake --build .

🚀 How to Run

For Local Operation (e.g., main, append_log)

./kvstore

For Networked Operation (e.g., networking)

Start server:

./kvstore_server

For Replicated Networked Operation (e.g., replication, leader-election)

Start server:

./kvstore_server <PORT> <PEER1>:<PORT>,<PEER2>:<PORT2>,<PEERN>:<PORTN>

Start client:

./kvstore_client <IP_ADDRESS> <PORT>

📂 Branch Overview

Phase	Branch Name	Description
1	main	In-memory key-value store
2	append_log	Adds persistent write-ahead logging
3	networking	Enables client-server networking
4	replication	Adds replication and modularizes codebase
5	leader-election	Introduces leader election (Bully algorithm)

🔧 Technologies Used

• C++17
• CMake
• POSIX Sockets
• Multithreading (std::thread, std::mutex)
• File I/O Logging

🧩 Potential Future Work

• Consensus protocol integration (e.g., Raft)
• HTTP/REST interface
• Dynamic service discovery
• Cluster rebalancing

🤝 Contributing

Contributions are welcome! Each phase is independently accessible via its respective branch. Ensure code is tested and adheres to existing structure.

📄 License

This project is licensed under the MIT License.