Python Redis Server Clone 🚀

A fully functional, asynchronous Redis server built entirely from scratch in Python using only the standard library—absolutely no external dependencies required!

This project implements the RESP (REdis Serialization Protocol) and supports a wide array of advanced Redis features, making it a highly capable lightweight drop-in replacement for basic Redis operations.

🌟 Features

Core Capabilities

• RESP Protocol: Fully parses and serializes RESP arrays, bulk strings, simple strings, and integers.
• Concurrency: Handles multiple concurrent client connections using Python's asyncio event loop.
• Zero Dependencies: Built entirely with Python's built-in modules (asyncio, socket, os, hashlib, etc.).

Data Structures & Commands

• Strings: SET (with PX millisecond expiry), GET, TYPE, KEYS *.
• Lists: LPUSH, RPUSH, LPOP, LRANGE, LLEN, and blocking operations (BLPOP).
• Streams: XADD (with auto-ID generation), XRANGE, and XREAD (with blocking support).
• Sorted Sets: ZADD, ZRANK, ZRANGE, ZCARD, ZSCORE, ZREM.
• Geospatial: GEOADD, GEOPOS, GEODIST, GEOSEARCH (using custom Geohash bit-interleaving and Haversine distance calculations).

High Availability & Durability

• AOF Persistence (Append-Only File): * Writes mutating commands to disk in real-time.
  • Uses modern Multi-Part AOF architecture (manifest files + incremental .incr.aof logs).
  • Automatically recovers state from disk on startup.
• RDB Parsing: Can natively read, parse, and load pre-existing binary .rdb snapshot files.
• Replication: * Master/Replica architecture (--replicaof).
  • Handles PING, REPLCONF, and PSYNC handshakes.
  • Real-time command propagation and byte-offset tracking.
  • Synchronous replication support via the WAIT command.

Advanced Systems

• Transactions (Optimistic Locking): Supports MULTI, EXEC, DISCARD, WATCH, and UNWATCH to ensure atomic, connection-safe queue execution.
• Pub/Sub: Real-time messaging with SUBSCRIBE, PUBLISH, and UNSUBSCRIBE.
• Security (ACL): User authentication via AUTH, along with ACL WHOAMI, ACL GETUSER, and ACL SETUSER using SHA-256 password hashing.

🧠 Architecture & Design

handle_client: An asynchronous task spawned for every connected socket. Manages transaction states, queued commands, and connection-specific ACL authentication.

process_command: The core routing engine. Decodes RESP parts, modifies the global database dictionary, and triggers AOF writes or replication propagation.

background_conn: A dedicated listener for Replica servers to continuously ingest propagated bytes from the Master without blocking standard client requests.

dbfile_manager: A custom binary parser that decodes standard Redis .rdb files, handling complex length encodings, string conversions, and expiry timestamps byte-by-byte.