A compact Redis-compatible server implemented in Go. It supports core string/list/stream/zset/geo operations, basic ACL/auth, persistence via RDB loading, transactions, and a replication subset (INFO/PSYNC/REPLCONF/WAIT).

• RESP protocol support (arrays, bulk strings, integers, errors)
• String commands: PING, ECHO, SET (EX/PX), GET, INCR
• Lists: LPUSH, RPUSH, LRANGE, LPOP, LLEN, BLPOP
• Streams: XADD, XRANGE, XREAD (blocking)
• Sorted sets: ZADD, ZRANGE, ZCARD, ZREM, ZRANK, ZSCORE
• Geo: GEOADD, GEODIST, GEOPOS, GEOHASH, GEOSEARCH
• Pub/Sub: SUBSCRIBE, PUBLISH, UNSUBSCRIBE
• Transactions: MULTI, EXEC, DISCARD (with queued execution)
• ACL/Auth: AUTH, ACL subcommands
• Replication (subset): INFO replication, REPLCONF, PSYNC (FULLRESYNC), WAIT
• RDB load on startup with expiry handling

Build and run the server locally:

./your_program.sh

Run on a different port:

./your_program.sh --port 6380

Run as a replica (connects to master and starts syncing):

./your_program.sh --port 6380 --replicaof "localhost 6379"

• --dir and --dbfilename: load an RDB file on startup
• --requirepass: set a password for AUTH
• --replicaof "host port": start as replica and connect to master
• --port: listen port for the server (default 6379)

• app/
  • main.go: CLI flags and server startup
• internal/server/
  • server.go: TCP listener, client read/write loops
  • replication_client.go: replica handshake and replication stream apply
• internal/handler/
  • dispatcher.go: command dispatch, auth checks, transactions, replication propagation
  • command files: command implementations grouped by data type
• internal/store/
  • in-memory data structures and operations
• internal/resp/
  • RESP read/write + Encode helper
• internal/rdb/
  • RDB loader for string keys + expiries
• internal/replication/
  • replication state, offsets, ack tracking, command encoding

1. Server loop accepts TCP connections and creates a per-connection message channel.
2. RESP reader parses incoming requests into command + args.
3. Dispatcher enforces auth and pub/sub rules, then routes to a handler.
4. Handlers implement command logic using the in-memory store.
5. Replication (master) propagates write commands to replicas and tracks offsets/ACKs.
6. Replication (replica) performs handshake, receives FULLRESYNC RDB, then applies streamed commands.
7. Background expiration periodically cleans expired keys.

• MULTI starts a transaction and queues subsequent commands.
• EXEC executes queued commands and returns an array of responses.
• DISCARD clears the queue.
• EXEC returns an error if the transaction is marked dirty (e.g., unknown command queued).

• INFO replication exposes role, replid, offsets, and connected replicas.
• PSYNC ? -1 triggers FULLRESYNC with an empty RDB payload.
• REPLCONF handles listening-port, capa, and ACK messages.
• WAIT blocks until enough replicas have ACKed a target offset (or timeout).

On startup, if --dir and --dbfilename are provided, the server loads a Redis RDB file containing string keys and expiries. Expired keys are dropped during load.

• Go version: 1.24 (as used by CodeCrafters)
• Tests are not included; use codecrafters test or the challenge runner.

This is a learning-focused implementation and does not cover the full Redis command set or replication protocol. Only the parts required by the challenge stages are implemented.