• Simple Python Redis — v1 A custom, multithreaded Redis-compatible server built from scratch using Python. Version: v1

This project implements a functional subset of the Redis server, supporting the RESP (Redis Serialization Protocol), concurrent client handling, and data structures like Streams and Lists.

• Overview This project is a deep dive into backend engineering and systems design. It mimics the behavior of a real Redis instance, allowing standard Redis clients (like redis-cli) to connect, store data, and perform simple operations.

It demonstrates:

Socket Programming: Handling raw TCP connections.

Concurrency: Managing multiple clients simultaneously using threading.

Protocol Design: Parsing and encoding the RESP format.

Medium Logic: Implementing blocking operations and monotonic stream IDs.

• Features (v1) ✅ Core Commands PING: Health check for the server.

SET / GET: Key-value storage with PX (millisecond) expiry support.

INCR: Atomic integer incrementing.

TYPE: Identifies the underlying data structure (string, list, or stream).

✅ List & Blocking Operations LPUSH / RPUSH: Add elements to the head or tail of a list.

LPOP / LRANGE: Retrieve and view list elements.

BLPOP: Blocking pop operation that waits until data is available.

✅ Stream Processing XADD: Append entries to a stream with auto-generated (*) or custom IDs.

XRANGE: Query a range of entries from a stream.

XREAD: Synchronous or Blocking read from one or more streams.

✅ Transactions MULTI / EXEC / DISCARD: Standard Redis transaction block. Commands are queued and executed atomically.

• Architecture The engine is built around three core pillars:

The Global Data Store: A thread-safe dictionary managing strings, lists, and RedisStream objects.

The Command Processor: A robust parser that translates RESP arrays into executable logic.

The Condition Manager: Uses threading.Condition to handle the signaling required for blocking commands like BLPOP and XREAD.

• Build & Run Requirements Python 3.8+

No external dependencies (Standard Library only!)

Run the Server Bash python redis_server.py Connect with Redis CLI Bash redis-cli -p 6379 127.0.0.1:6379> SET name shinaayl PX 5000 OK 127.0.0.1:6379> GET name "shinaayl"

• Limitations (v1) In-Memory Only: No persistence (RDB/AOF) yet; data is lost on restart.

Memory Management: Does not yet implement LRU (Least Recently Used) eviction policies.

Security: No AUTH or password protection.

Single-threaded Core Logic: While networking is multithreaded, the data store access uses a global lock via LIST_CONDITION.

• Example Session & Pro-Tips Stream ID Generation A key feature of this implementation is handling the complex ID logic of Redis Streams.

Bash

Auto-generate ID based on current server time

127.0.0.1:6379> XADD mystream * sensor-id 1234 temperature 22.5 "1714772800000-0"

Explicit ID validation (must be greater than the last ID)

127.0.0.1:6379> XADD mystream 0-1 speed 50 (error) ERR The ID specified in XADD must be greater than 0-0

• Pro-Tip: When testing Streams, use XADD . The server will automatically generate a millisecond-based timestamp for you. If you provide a timestamp but use * for the sequence number (e.g., XADD mystream 1000- ...), the server logic automatically increments the sequence number for that specific millisecond!

• Purpose Understanding Network Protocols (TCP/RESP).

Learning how Blocking I/O and thread synchronization work.

Practicing the implementation of complex, stateful data structures.

• Future Improvements (v2) Persistence: Implement AOF (Append Only File) to save data to disk.

Pub/Sub: Add PUBLISH and SUBSCRIBE for real-time messaging.

Sorted Sets: Implement the ZSET type using Skip Lists.

Cluster Support: Basic replication between master and slave instances.