Redis Clone in Go(ongoing project)

A Redis-compatible server built from scratch in Go to learn Redis internals: the RESP protocol, event-driven I/O, key expiry, object encoding, eviction, and AOF persistence.

Features implemented

RESP protocol

• Custom encoder/decoder supporting simple strings (+), errors (-), integers (:), bulk strings ($), and arrays (*).
• Unit tests in core/resp_test.go.

Commands

Command	Description
PING [message]	Health check / echo
SET key value [EX seconds]	Set a string value, with optional expiry
GET key	Get a string value
DEL key [key ...]	Delete one or more keys
EXPIRE key seconds	Set a TTL on an existing key
TTL key	Get remaining TTL in seconds
INCR key	Increment an integer-encoded key
BGREWRITEAOF	Force a full AOF rewrite

Two server implementations

• Sync server (server/sync_tcp.go) - plain net.Listen, handles one connection fully before accepting the next (no concurrency).
• Async server (server/async_tcp.go, wired up in main.go) - raw non-blocking sockets + a kqueue event loop (BSD/macOS) for multiplexing many client connections on a single thread.

Key expiry

• Passive expiry on read (checked in Get).
• Active expiry cron in the async server's main loop: every 1s, samples up to 20 keys with a TTL and deletes expired ones, repeating while at least 25% of the sample was expired (mirrors Redis's active-expire cycle).

Object encoding

• Values carry a type + encoding byte, mirroring Redis's tryObjectEncoding: integer strings are encoded as int, short strings (<=44 bytes) as embstr, longer strings as raw.

Eviction

• When the key count reaches KeysLimit (default 1000), an arbitrary key is evicted before the next write.

AOF persistence

• BGREWRITEAOF (also triggered automatically after every SET) dumps the full dataset to an AOF file as RESP-encoded SET commands.
• On each new client connection, the async server replays the AOF file to rebuild state.

Configuration

• --host / --port CLI flags (default 0.0.0.0:7379).
• KeysLimit and AOFFile path are set in config/config.go.

Getting started

go run main.go --port 7379

Then connect with any RESP client, e.g.:

redis-cli -p 7379

Requirements

• Go 1.26+
• macOS or another BSD (the async server uses kqueue; no Linux/epoll or Windows backend yet)

Project layout

• core/ - RESP codec, command evaluation, storage, expiry, eviction, AOF
• server/ - sync and async TCP server implementations
• config/ - runtime configuration