Caching With C

A minimal Redis-like cache server written in C.

This project is for people who want to understand how a networked cache works under the hood: sockets, select, RESP parsing, command dispatch, an in-memory key-value store, and TTL handling without hiding the interesting parts behind a framework.

Fork it if you want a compact C systems project that is still small enough to read in one sitting and practical enough to extend.

What It Does

• Accepts TCP clients with a single-threaded select loop
• Speaks the Redis Serialization Protocol subset used by normal Redis clients
• Supports PING, SET, GET, DEL, EXPIRE, and TTL
• Stores string keys and values in memory
• Deletes expired keys lazily when they are touched
• Includes focused C tests for the store, RESP parser, and command layer

Quick Start

Run these commands from the repository root:

cd server
make clean
make all
make test
./build/server 6379

In another terminal, talk to it with redis-cli:

redis-cli -p 6379 PING
redis-cli -p 6379 SET hello world
redis-cli -p 6379 GET hello
redis-cli -p 6379 EXPIRE hello 10
redis-cli -p 6379 TTL hello
redis-cli -p 6379 DEL hello

Expected replies:

PONG
OK
"world"
(integer) 1
(integer) 10
(integer) 1

Build And Test Rules

Use the Makefile in server/. The project intentionally keeps the build simple and explicit.

cd server
make all      # builds ./build/server
make test     # runs all test binaries
make clean    # removes generated build files

Before opening a pull request or sharing a fork, run:

cd server
make clean && make all && make test

The generated server/build/ directory is ignored by git. Do not commit compiled binaries.

Project Layout

server/
  Makefile
  src/
    main.c              # CLI entrypoint: ./server <port>
    headers/            # Public module interfaces
    core/
      server.c          # Socket lifecycle and select loop
      client.c          # Per-client input buffers
      resp.c            # RESP parser and response formatting
      commands.c        # Command dispatch and command behavior
      store.c           # In-memory key-value store with TTL
  tests/
    test_store.c
    test_resp.c
    test_commands.c

Protocol Scope

The server currently supports RESP arrays of bulk strings, which is what redis-cli sends for normal commands.

Supported commands:

• PING [message]
• SET key value
• GET key
• DEL key [key ...]
• EXPIRE key seconds
• TTL key

The following iterations will cover:

• Persistence
• Replication
• Authentication
• Transactions
• Inline Redis commands
• Advanced Redis data structures

Contributing

Keep changes small and testable.

For behavior changes, add or update a test in server/tests/ first, then run:

cd server
make clean && make all && make test

If that command does not pass, the change is not ready to share.