GoRedis

A small Redis server clone written in Go.

It implements a subset of the Redis wire protocol and supports a handful of commands (PING, SET, GET, DEL, EXISTS, HELLO, COMMAND, CLIENT) backed by an in-memory key-value store. It's compatible with redis-cli and the official go-redis client.

Architecture

TCP client
    |
    v
acceptLoop()  -- accepts connections, spawns one goroutine per peer
    |
    v
Peer.readLoop() -- parses RESP values off the wire, turns them into
    |               typed Commands, sends them as Messages
    v
msgCh (channel) ---------------------+
addPeerCh / delPeerCh (channels) ----+--> loop() -- the ONLY goroutine
                                      |     that touches shared state
                                      v
                              handleMessage()
                                      |
                                      v
                              KV store (map + RWMutex)

Only one goroutine (loop()) ever reads or writes the peers map and the KV store. Every connection's goroutine talks to it exclusively through channels — this is why there's no manual locking needed around peers, and why a select (rather than a simple channel range) is required once more than one channel needs watching at once.

Project layout

File	Responsibility
main.go	Parses flags, boots the Server
server.go	Server/Config structs, acceptLoop, loop (the event loop), handleMessage
peer.go	Peer type wrapping a connection
message.go	Message — couples a parsed Command with the Peer it came from
command.go	Command types (SetCommand, GetCommand, etc.) and RESP-array-to-command parsing
kv.go	KV — the in-memory store (map[string]string + RWMutex)
resp.go	RESP reader: parses bulk strings and arrays off a bufio.Reader
resp_writer.go	RESP writer: simple strings, errors, bulk strings, integers, RESP3 maps
server_test.go	Integration test using the real go-redis client
peer_test.go	Raw-socket smoke test for the HELLO handshake

Supported commands

Command	Behavior
PING	Replies PONG
SET key val	Stores a value
GET key	Returns the value, or a null bulk string if missing
DEL key	Deletes a key, returns 1/0 for found/not-found
EXISTS key	Returns 1/0
HELLO	Returns a minimal RESP3 map (handshake used by real Redis clients)
COMMAND	Returns an empty array (satisfies clients that probe this on connect)
CLIENT ...	Acknowledges with OK (subcommands like SETNAME aren't actually implemented)

Running it

go run . -listenAddr :5001

-listenAddr defaults to :5001 if omitted.

Talk to it with redis-cli:

redis-cli -p 5001
> SET foo bar
OK
> GET foo
"bar"
> DEL foo
(integer) 1

Or raw RESP over nc:

printf '*3\r\n$3\r\nSET\r\n$3\r\nfoo\r\n$3\r\nbar\r\n' | nc localhost 5001

Running the tests

go test -v ./...

Note: peer_test.go's TestHelloCommand expects a server already running on :5001 — start one in a separate terminal first. server_test.go's TestOfficialRedisClient starts its own server, so it doesn't need this.

Possible next steps

• EXPIRE/TTL support (requires a background goroutine sweeping expired keys)
• INCR/DECR
• Multi-key DEL
• Pub/sub, using the now-tracked peers map to broadcast messages
• Persistence to disk (e.g. periodic snapshot via encoding/gob)
• A Dockerfile (multi-stage build) and docker-compose.yml for running the server and a test client as separate containers