tiny-redis

A minimal, dependency-free Redis-compatible server written in Go, implementing the core Redis Serialization Protocol (RESP), deterministic AOF persistence, two-tier key eviction, and high-throughput concurrent connection handling.

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Technical Details

• Network Model: Goroutine-per-connection pattern using Go's net package listening on port :6379.
• Dual-Format Protocol Parser: Custom RESP deserializer that handles standard multibulk arrays (*<count>\r\n...) and inline plain-text commands (PING\r\n, SET foo bar\r\n) via bufio.Reader.
• Storage & Concurrency: In-memory map[string]Entry guarded by sync.RWMutex. Employs an optimistic read path (RLock) for cache hits and lazily escalates to an exclusive write lock (Lock) only when evicting expired entries.
• Key Expiration:
  • Passive: Checks TTL on read (GET, TTL) and eagerly deletes keys if the expiration timestamp has passed.
  • Active Sweeper: Background routine running on a 100ms ticker, randomly sampling keys in an adaptive 25ms time-capped loop to eliminate expired memory without starving concurrent queries.
• Deterministic Durability (AOF): Mutating commands (SET, DEL, EXPIRE) are committed to appendonly.aof using absolute millisecond UNIX timestamps (PEXPIREAT). This guarantees that expiration windows do not reset upon server restarts and accurately expire against wall-clock time.
• Graceful Shutdown: Intercepts SIGINT / SIGTERM signals to stop accepting new traffic, flushes all pending file buffers to disk via fsync, closes descriptors cleanly, and exits.

Clients (redis-cli / redis-benchmark / nc) 
       │  TCP (:6379)
       ▼
net.Listener.Accept() 
       │
       ├─► Goroutine (Client 1) ──► parseCommand() ──┐
       ├─► Goroutine (Client 2) ──► parseCommand() ──┼─► [sync.RWMutex] map[string]Entry
       └─► Goroutine (Client N) ──► parseCommand() ──┤          │
                                                     │          ▼
                          (Mutations: SET/PEXPIREAT) └──► AOF (appendonly.aof)
                                                                ▲
                                                         (Startup Replay)

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Benchmarks

Benchmarked using the official redis-benchmark utility with 50 concurrent connections across 100,000 requests:

redis-benchmark -p 6379 -c 50 -n 100000 -t ping,set,get -q

Command	Throughput (Requests/sec)	P50 Latency
PING (Inline)	105,820 req/s	0.215 ms
PING (RESP Multibulk)	114,155 req/s	0.215 ms
SET (with AOF write)	97,181 req/s	0.255 ms
GET (Concurrent RLock)	108,225 req/s	0.223 ms

Tested on Linux (x86_64) using the standard Go runtime over local loopback.

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Supported Commands

Command	Format	Return
PING	PING	+PONG\r\n
ECHO	ECHO <msg>	$<len>\r\n<msg>\r\n
SET	SET <key> <val> [EX seconds]	+OK\r\n
GET	GET <key>	$<len>\r\n<val>\r\n or $-1\r\n (null)
DEL	DEL <key> [key ...]	:<count>\r\n
EXPIRE	EXPIRE <key> <seconds>	:1\r\n (set) or :0\r\n (not found)
TTL	TTL <key>	:<seconds>\r\n, :-1\r\n (no expiry), or :-2\r\n (missing/expired)
CONFIG	CONFIG GET <param>	*2\r\n$<len>\r\n<param>\r\n$0\r\n\r\n (Benchmark support stub)
COMMAND	COMMAND	*0\r\n (Client negotiation stub)

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How to Run

1. Build and Start Server

# Run directly
go run main.go

# Or compile into a standalone binary
go build -o tiny-redis main.go
./tiny-redis

2. Connect with redis-cli

# Basic Key-Value operations
redis-cli -p 6379 set foo bar
redis-cli -p 6379 get foo

# Set with expiration (in seconds)
redis-cli -p 6379 set session token123 ex 30
redis-cli -p 6379 ttl session

# Update TTL on an existing key
redis-cli -p 6379 expire foo 60
redis-cli -p 6379 ttl foo

# Delete keys
redis-cli -p 6379 del foo session

# Verify crash-resilient persistence
# Stop the server with Ctrl+C, start it again, and retrieve your data:
redis-cli -p 6379 get foo

3. Run Benchmarks

redis-benchmark -p 6379 -c 50 -n 100000 -t ping,set,get -q

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License

MIT