Ember

A small Redis-compatible in-memory server written in Rust. I built it to learn how Redis works under the hood and to get more comfortable with async Rust (Tokio), the RESP wire protocol, and structuring a network service.

More Redis features will be added over time.

What works today

• TCP server on 127.0.0.1 (default port 6379, overridable with --port).
• Concurrent clients via Tokio tasks.
• In-memory store backed by Arc<Mutex<...>> for shared mutable state.
• RESP support for simple strings, bulk strings, arrays, integers, null, and booleans.
• Redis-like commands (implemented subset):
  • Core: PING, ECHO, SET, GET, DELETE
  • Expiration: SET ... EX|PX, EXPIRE key milliseconds [NX|XX|GT|LT]
  • Lists: LPUSH, RPUSH, LRANGE
  • Transactions: MULTI, EXEC, DISCARD
  • Persistence: SAVE
• Expiration handling with both lazy expiration checks and a periodic active expiration cycle.
• RDB snapshot persistence:
  • Loads snapshot from snapshots/client-0001.rdb on startup (if present)
  • Saves snapshot atomically when SAVE is called

You can talk to it with redis-cli like a real Redis instance for these commands.

Requirements

• A recent Rust toolchain (rustup recommended) that supports the edition declared in Cargo.toml.

Build and run

cargo build --release
cargo run --release

Custom port:

cargo run --release -- --port 1234

Optional: enable logs (uses env_logger), e.g.:

RUST_LOG=info cargo run --release

Try it

With another terminal and redis-cli installed:

redis-cli -p 6379 PING
redis-cli -p 6379 ECHO hello
redis-cli -p 6379 SET mykey "hello world"
redis-cli -p 6379 GET mykey
redis-cli -p 6379 SET temp value EX 10
redis-cli -p 6379 EXPIRE temp 5000 NX
redis-cli -p 6379 DELETE mykey

redis-cli -p 6379 LPUSH mylist a b c
redis-cli -p 6379 RPUSH mylist d e
redis-cli -p 6379 LRANGE mylist 0 -1

redis-cli -p 6379 <<'EOF'
MULTI
SET txkey one
GET txkey
EXEC

redis-cli -p 6379 SAVE

Stack

• Tokio — async runtime, TCP, I/O
• bytes — buffering
• anyhow — error handling
• log / env_logger — logging

Roadmap

The goal is to keep expanding Redis compatibility: richer data types (hashes, sets, sorted sets, streams), replication, pub/sub, stricter protocol and reply compatibility, and more complete persistence behavior.

License

This project is licensed under the MIT License.

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Educational project; not a production Redis replacement.