zenith

A Redis-protocol-compatible in-memory server written in Go. It speaks both RESP2 and RESP3 and works with standard Redis client libraries (verified against redis-py 8.0.1 and node-redis 6.0.1).

Run

go build -o zenith .
./zenith --addr :6379

Then point any Redis client at it:

redis-cli -p 6379
# or
python3 -c "import redis; r=redis.Redis(port=6379); print(r.ping())"

Architecture

main.go              entrypoint / flag parsing
resp/                RESP2 + RESP3 wire protocol
  resp.go            reader: parses *N $L bulk arrays + inline commands
  writer.go          writer: encodes replies, downgrades RESP3 -> RESP2
store/               in-memory keyspace (per-DB, mutex-guarded)
  db.go              keyspace, expiry, generic key ops
  string.go         string type + counters
  list.go           list type
  set_hash.go       set + hash types
  zset.go           sorted set (score-ordered)
server/              networking + command dispatch
  server.go          TCP listener
  engine.go          16 logical DBs + pub/sub registry
  conn.go            per-connection state, read loop, subscriber impl
  pubsub.go          channel + pattern subscriptions
  dispatch.go        command table, arity checks, MULTI/EXEC/WATCH
  cmd_conn.go        PING ECHO SELECT HELLO CLIENT CONFIG INFO ...
  cmd_key.go         DEL EXISTS TYPE KEYS EXPIRE TTL SCAN RENAME ...
  cmd_string.go      SET GET INCR APPEND GETRANGE SETRANGE MSET ...
  cmd_list.go        LPUSH RPUSH LPOP LRANGE LREM LTRIM ...
  cmd_sethash.go     SADD SMEMBERS SUNION / HSET HGETALL HDEL ...
  cmd_zset.go        ZADD ZRANGE ZRANGEBYSCORE ZRANK ZINCRBY ...
  cmd_pubsub.go      SUBSCRIBE PSUBSCRIBE PUBLISH ...

Implemented

• Protocol: RESP2 and RESP3, including the HELLO handshake with version negotiation, AUTH/SETNAME options, and RESP3-native maps, sets, doubles, booleans, nulls, and push frames.
• Keys: DEL, UNLINK, EXISTS, TYPE, KEYS, SCAN, RENAME, RENAMENX, RANDOMKEY, EXPIRE, PEXPIRE, EXPIREAT, PEXPIREAT, TTL, PTTL, PERSIST. Lazy expiry on access.
• Strings: SET (NX/XX/GET/EX/PX/EXAT/PXAT/KEEPTTL), GET, GETSET, GETDEL, SETNX, SETEX, PSETEX, MSET, MGET, MSETNX, APPEND, STRLEN, INCR/DECR/INCRBY/ DECRBY/INCRBYFLOAT, GETRANGE, SETRANGE.
• Lists: LPUSH/RPUSH(+X), LPOP/RPOP (with count), LLEN, LINDEX, LSET, LRANGE, LTRIM, LREM.
• Sets: SADD, SREM, SISMEMBER, SCARD, SMEMBERS, SUNION, SINTER, SDIFF.
• Hashes: HSET, HMSET, HSETNX, HGET, HMGET, HDEL, HLEN, HEXISTS, HGETALL, HKEYS, HVALS.
• Sorted sets: ZADD (NX/XX/GT/LT/CH/INCR), ZSCORE, ZINCRBY, ZCARD, ZREM, ZRANGE, ZREVRANGE, ZRANGEBYSCORE, ZRANK, ZREVRANK, ZCOUNT, WITHSCORES.
• Pub/Sub: SUBSCRIBE, UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH with glob pattern matching.
• Transactions: MULTI, EXEC, DISCARD, WATCH, UNWATCH (queueing + EXECABORT).
• Server/conn: SELECT (16 DBs), DBSIZE, FLUSHDB, FLUSHALL, INFO, CONFIG GET/SET, TIME, CLIENT, COMMAND, RESET, QUIT.

NOT implemented (honest scope)

This is the core of Redis, not all of it. Missing:

• Persistence: no RDB snapshots, no AOF. Data is in-memory only.
• Replication & cluster: no replicas, no cluster mode / hash slots.
• Scripting: no EVAL / Lua / FUNCTION.
• Other types/features: no streams, HyperLogLog, geo, bitfields, bitmap ops, blocking ops (BLPOP/BRPOP), keyspace notifications, or ACLs.
• SCAN is non-incremental: it returns all matching keys in one pass with cursor 0. Correct for clients that loop until cursor 0, but not a true incremental cursor.

Tests

test_resp2.py and test_advanced.py exercise the server with redis-py (RESP2 + RESP3). nodeclient/test.js cross-verifies with node-redis. Combined: 70 redis-py checks + 17 node-redis checks, all passing.