Bitcask

What is Bitcask?

Bitcask is an append-only log-structured key-value storage engine. Unlike traditional databases that update data in place, Bitcask writes every change to the end of a data file. This ensures high write throughput by utilizing sequential I/O.

To maintain fast reads, it keeps an in-memory "KeyDir" a hash map that stores the location (offset and size) of the most recent value for every key in the data file.

Key Features

• Append-only Storage: High-speed sequential writes.
• In-Memory Indexing: lookups for any key.
• Crash Recovery: Automatically rebuilds the in-memory index by scanning the .bc file on startup.

Supported Commands

• SET key value: Stores a string value associated with a key.
• GET key: Retrieves the most recent value for a key.
• RECOVERY: Automatically triggered on initialization if a database file is detected.

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Getting Started

Prerequisites

• Go 1.21+ installed on your machine.

Installation

Clone the repository and navigate to the project root:

git clone https://github.com/ganimtron-10/bitcask.git
cd bitcask

Running the Application

You can run the interactive CLI directly from the cmd directory:

go run cmd/main.go

Example Usage

Once the program is running, you can interact with it via the command line:

1. Set a value:

>>> set user_123 John
OK

2. Get a value:

>>> get user_123
John

3. Testing Recovery:

• Exit the program (Ctrl+C).
• Notice a .db file has been created in your directory.
• Run go run cmd/main.go again.
• Run get user_123 immediately; the data is recovered and available!