wal-kv

A persistent key-value store in Rust, backed by a write-ahead log (WAL).

This project is a from-scratch implementation of a durable key-value store. It uses a write-ahead log to ensure that all operations are atomic and durable, basically this means that the database can recover its state perfectly after a crash.

Features

• Durability: Every write is flushed to disk using fsync before the in-memory state is updated, guaranteeing that no acknowledged write is ever lost.
• Crash Recovery: On startup, the store replays the log to restore the in-memory HashMap to its last known state.
• Log Compaction: A compaction mechanism is implemented to reclaim disk space by removing obsolete log entries. The process uses an atomic rename to ensure the database is never in a corrupt state.
• Memory Efficient: The log is read using a streaming iterator, ensuring constant memory usage regardless of the log's size on disk.

How to Run

1. Clone the repository:

   git clone https://github.com/RedlineDevs/wal-kv.git
   cd wal-kv

2. Run the demo: The main.rs file contains a demonstration of the store's lifecycle: setting values, recovering from a "crash" (restart), and performing log compaction.

   cargo run

Example Output

$ cargo run
Set 2 entries
Recovered 2 entries after restart
Log file size before compaction: 3631 bytes
Log file size after compaction: 36 bytes
Compaction test passed