Simple Redis Clone in Python

A Redis-compatible in-memory database built from scratch in Python. Supports replication, blocking reads, lists, streams, sorted sets, and pub/sub.

Features

• Core Commands: PING, ECHO, SET, GET, INCR

• Lists: LPUSH, RPUSH, LPOP, BLPOP, LRANGE, LLEN

• Streams: XADD, XRANGE, XREAD

• Sorted Sets: ZADD, ZRANGE, ZRANK, ZCARD, ZSCORE, ZREM

• Pub/Sub: SUBSCRIBE, PUBLISH, UNSUBSCRIBE

• Replication: Implements REPLCONF, PSYNC, and WAIT

• Config & Introspection: CONFIG GET, INFO replication, KEYS

• Full RESP Protocol support

Installation

Clone the repository:

git clone https://github.com/YOUR_USERNAME/redis-clone.git cd redis-clone

Usage

Start the server:

• If on Windows, install and type wsl and enter first.

python3 -m app.main

• 

Connect with redis-cli:

redis-cli -p 6379

Commands Usage

Basic Commands

• PING # -> +PONG
• ECHO "Hello" # -> "Hello"
• SET key value [PX 1000] # -> +OK
• GET key # -> "value"
• INCR key # -> (integer) 1

Lists

• LPUSH mylist "a" # -> (integer) 1
• RPUSH mylist "b" # -> (integer) 2
• LRANGE mylist 0 -1 # -> ["a", "b"]
• LLEN mylist # -> (integer) 2
• LPOP mylist # -> "a"
• BLPOP mylist 0 # -> ["mylist", "b"] # Blocks if empty

Streams

• XADD mystream * field value # -> "1689851248173-0"
• XRANGE mystream - + # -> list of entries
• XREAD STREAMS mystream 0 # -> list of new entries
• XREAD BLOCK ms STREAMS mysteam id #-> Read entries from stream (blocking supported)

Pub/Sub

• SUBSCRIBE channel # -> "subscribe"
• PUBLISH channel "Hello" # -> (integer) number of subscribers
• UNSUBSCRIBE channel # -> "unsubscribe"

Sorted Sets

• ZADD myzset 1 "one" # -> (integer) 1
• ZRANGE myzset 0 -1 # -> ["one"]
• ZCARD myzset # -> (integer) 1
• ZRANK myzset "one" # -> (integer) 0
• ZSCORE myzset "one" # -> "1"
• ZREM myzset "one" # -> (integer) 1

Other Commands

• TYPE key # -> "string" | "list" | "stream" | "zset"
• KEYS * # -> ["key1", "key2"]
• CONFIG GET dir|dbfilename # -> ["dir", "/tmp" | "dbfilename", "dump.rdb"]
• INFO replication # -> replication info
• WAIT numreplicas timeout # -> Wait for replicas to acknowledge

Basic Commands Demo:

• 

Replication Setup

Start the primary:

python3 app/main.py --port 6379

Start a replica:

python3 app/main.py --port 6380 --replicaof localhost 6379

Replication supports:

• PSYNC for initial data sync

• REPLCONF for replica handshake

• WAIT to ensure writes propagate to replicas

Tech Stack

• Language: Python 3

• Networking: TCP Sockets

• Protocol: RESP (Redis Serialization Protocol)

Roadmap

Add RDB/AOF persistence

Improve async I/O for concurrency

Support pattern-based pub/sub

Acknowledgment

Inspired by the Redis architecture and built to deeply understand data structures, networking, and replication internals.