A Redis server implementation written from scratch in Rust using Tokio. This project implements a subset of Redis's functionality, focusing on core commands, data structures, replication, and pub/sub. This project was built as part of the Build your own Redis.

• Built with Tokio for async I/O and runtime
• Supports concurrent client connections (up to 10,000)
• Implements master-replica replication with PSYNC and RDB snapshots
• Pub/Sub messaging with channel-based communication
• Transaction support with command queueing
• RDB file persistence with expiry support
• Rate Limit to max 10,000 concurrent connections

• String: SET, GET, INCR
• List: LPUSH, RPUSH, LRANGE, LLEN, LPOP, BLPOP
• Stream: XADD, XRANGE, XREAD
• Sorted Set: ZADD, ZRANK, ZRANGE, ZCARD, ZSCORE, ZREM
• Geospatial: GEOADD, GEOPOS, GEODIST, GEOSEARCH
• Transactions: MULTI, EXEC, DISCARD
• Pub/Sub: SUBSCRIBE, UNSUBSCRIBE, PUBLISH
• Connection: PING, ECHO, AUTH
• Server: INFO, TYPE, WAIT, CONFIG, KEYS
• ACL: ACL WHOAMI, ACL GETUSER
• Replication: REPLCONF, PSYNC (master-slave replication)

• Bind to a port
• Respond to PING
• Respond to multiple PINGs
• Handle concurrent clients
• Implement the ECHO command
• Implement the SET & GET commands
• Expiry

• Create a list
• Append an element (RPUSH)
• Append multiple elements
• List elements with positive indexes (LRANGE)
• List elements with negative indexes
• Prepend elements (LPUSH)
• Query list length (LLEN)
• Remove an element (LPOP)
• Remove multiple elements
• Blocking retrieval (BLPOP)
• Blocking retrieval with timeout

• The TYPE command
• Create a stream (XADD)
• Validating entry IDs
• Partially auto-generated IDs
• Fully auto-generated IDs
• Query entries from stream (XRANGE)
• Query with -
• Query with +
• Query single stream using XREAD
• Query multiple streams using XREAD
• Blocking reads
• Blocking reads without timeout
• Blocking reads using $

• The INCR command
• The MULTI command
• The EXEC command
• Empty transaction
• Queueing commands
• Executing a transaction
• The DISCARD command
• Failures within transactions
• Multiple transactions

• Configure listening port
• The INFO command
• The INFO command on a replica
• Initial replication ID and offset
• Send handshake (REPLCONF, PSYNC)
• Receive handshake
• Empty RDB transfer
• Single-replica propagation
• Multi-replica propagation
• Command processing
• ACKs with no commands
• ACKs with commands
• WAIT with no replicas
• WAIT with no commands
• WAIT with multiple commands

• Subscribe to a channel
• Subscribe to multiple channels
• Enter subscribed mode
• PING in subscribed mode
• Publish a message
• Deliver messages
• Unsubscribe

• Respond to ACL WHOAMI
• Respond to ACL GETUSER
• The nopass flag
• The passwords property
• Setting default user password
• The AUTH command
• Enforce authentication
• Authenticate using AUTH

• RDB file config
• Read a key
• Read a string value
• Read multiple keys
• Read multiple string values
• Read value with expiry

• Create a sorted set
• Add members
• Retrieve member rank
• List sorted set members
• ZRANGE with negative indexes
• Count sorted set members
• Retrieve member score
• Remove a member

• Respond to GEOADD
• Validate coordinates
• Store a location
• Calculate location score
• Respond to GEOPOS
• Decode coordinates
• Calculate distance
• Search within radius

• Rust 1.70 or higher
• Cargo (comes with Rust)

To build the server, clone the repository and run:

cargo build --release

Run the server using:

cargo run --release -- [--port <port>] [--replicaof <master_host> <master_port>]

Or run the pre-built binary:

./target/release/codecrafters-redis [--port <port>] [--replicaof <master_host> <master_port>]

Options:

• --port: The port to listen on (default: 6379)
• --replicaof: Configure as a replica of the specified master (format: <host> <port>)

Examples:

# Run as master on default port 6379
cargo run --release

# Run as master on custom port
cargo run --release -- --port 6380

# Run as replica
cargo run --release -- --port 6380 --replicaof 127.0.0.1 6379

Connect to the server using any Redis client such as redis-cli:

redis-cli -p 6379

Once connected, you can use any of the supported commands:

SET mykey "Hello"
GET mykey
INCR counter
LPUSH mylist "item1" "item2"
XADD stream:1 * field1 value1
MULTI
SET key1 val1
SET key2 val2
EXEC
SUBSCRIBE channel1
PUBLISH channel1 "message"

The codebase has been refactored into a modular architecture for better maintainability and separation of concerns:

src/
├── main.rs                      # Server initialization and entry point
├── protocol/
│   ├── mod.rs                   # Protocol module exports
│   ├── state.rs                 # Redis state and server state management
│   ├── value.rs                 # RedisValue type definitions
│   └── replication.rs           # Replication handshake and sync logic
├── commands/
│   ├── mod.rs                   # Command module exports
│   └── handler.rs               # Command execution and routing
├── client/
│   ├── mod.rs                   # Client module exports
│   ├── normal_mode.rs           # Standard client connection handling
│   ├── subscribe_mode.rs        # Pub/Sub client connection handling
│   └── replica_mode.rs          # Replica-to-master connection handling
└── utils.rs                     # RESP protocol encoding/decoding utilities

Key Modules:

• protocol/ - Core Redis protocol types, state management, and replication logic
• commands/ - Command parsing, validation, and execution
• client/ - Different client connection modes (normal, subscribe, replica)
• utils.rs - Low-level RESP protocol utilities and configuration

cargo run -- --port 6379

To run tests install codecrafters cli:

curl https://codecrafters.io/install.sh | sh
codecrafters test