Redis Clone - Python Implementation

A Python implementation of a Redis-like in-memory database server, built as part of the CodeCrafters Redis Challenge. This project implements a subset of Redis commands and the RESP (Redis Serialization Protocol) for client-server communication.

Features

Core Commands

• PING - Health check command
• ECHO - Echo back the provided message
• SET - Set a key-value pair with optional expiration
• GET - Retrieve a value by key
• CONFIG GET - Get configuration parameters
• KEYS - List all keys matching a pattern

List Commands

• LPUSH - Push elements to the left of a list
• RPUSH - Push elements to the right of a list
• LPOP - Remove and return the leftmost element
• RPOP - Remove and return the rightmost element
• LRANGE - Get a range of elements from a list
• LLEN - Get the length of a list
• TYPE - Get the data type of a key

Advanced Features

• RESP Protocol - Full implementation of Redis Serialization Protocol
• RDB Support - Load initial data from Redis dump files
• Expiration - Support for key expiration with PX (milliseconds)
• Asynchronous I/O - Built with Python's asyncio for high performance
• Graceful Shutdown - Proper signal handling for clean server shutdown

Project Structure

├── app/
│   ├── __init__.py
│   ├── main.py              # Server entry point and connection handling
│   ├── redis_command.py     # Command implementations and handler
│   ├── redis_parser.py      # RESP protocol parser and serializer
│   └── rdb_reader.py        # RDB file format reader
├── codecrafters.yml         # CodeCrafters configuration
├── Pipfile                  # Python dependencies
├── your_program.sh         # Local execution script
├── example.bash            # Example client commands
└── README.md               # This file

Installation

Prerequisites

• Python 3.8+
• pipenv (for dependency management)

Setup

1. Clone the repository:

   git clone <repository-url>
   cd codecrafters-redis-python

2. Install dependencies:

   pipenv install

Usage

Running the Server

Local Development

# Run the server locally
./your_program.sh

# Or directly with pipenv
pipenv run python3 -m app.main

With Custom Configuration

# Run on a different port
pipenv run python3 -m app.main --port 6380

# Load data from RDB file
pipenv run python3 -m app.main --dir /path/to/data --dbfilename dump.rdb

Connecting to the Server

Using telnet

telnet localhost 6379

Using redis-cli (if available)

redis-cli -p 6379

Example Commands

Basic Operations

# Health check
*1\r\n$4\r\nPING\r\n

# Echo a message
*2\r\n$4\r\nECHO\r\n$11\r\nHello World\r\n

# Set a key-value pair
*3\r\n$3\r\nSET\r\n$5\r\nmykey\r\n$10\r\nHello Redis\r\n

# Get a value
*2\r\n$3\r\nGET\r\n$5\r\nmykey\r\n

# Set with expiration (5 seconds)
*5\r\n$3\r\nSET\r\n$5\r\nmykey\r\n$10\r\nHello Redis\r\n$2\r\nPX\r\n$4\r\n5000\r\n

List Operations

# Push to list
*3\r\n$5\r\nLPUSH\r\n$4\r\nmylist\r\n$5\r\nworld\r\n
*3\r\n$5\r\nLPUSH\r\n$4\r\nmylist\r\n$5\r\nhello\r\n

# Get list range
*4\r\n$6\r\nLRANGE\r\n$4\r\nmylist\r\n$1\r\n0\r\n$1\r\n-1\r\n

# Pop from list
*2\r\n$4\r\nLPOP\r\n$4\r\nmylist\r\n

Architecture

Core Components

1. RESP Parser/Serializer (redis_parser.py)

   • Parses incoming RESP protocol messages
   • Serializes responses back to RESP format
   • Handles different RESP data types (Simple Strings, Errors, Integers, Bulk Strings, Arrays)

2. Command Handler (redis_command.py)

   • Implements all Redis commands as separate classes
   • Uses abstract base class pattern for extensibility
   • Handles command validation and execution

3. RDB Reader (rdb_reader.py)

   • Reads Redis dump files for initial data loading
   • Supports basic RDB format parsing

4. Main Server (main.py)

   • Asynchronous TCP server using asyncio
   • Handles multiple concurrent connections
   • Implements graceful shutdown with signal handling

Configuration

The server can be configured via command-line arguments:

• --port <port>: Specify the port to listen on (default: 6379)
• --dir <directory>: Directory containing RDB files
• --dbfilename <filename>: Name of the RDB file to load

Limitations

This is a learning implementation and has some limitations compared to the full Redis:

• Limited command set (no hashes, sets, sorted sets)
• No persistence beyond RDB loading
• No replication or clustering
• No authentication or security features
• Limited configuration options

Contributing

This project is part of the CodeCrafters Redis Challenge. For the full challenge experience, visit codecrafters.io.

License

This project is for educational purposes as part of the CodeCrafters challenge.

References

• Redis Protocol Specification
• RESP Protocol
• CodeCrafters Redis Challenge