Celeris

A lightweight Redis-compatible in-memory data store written in C++. Supports strings, lists, and hashes, full Redis Serialization Protocol (RESP) parsing, multi-client concurrency, and periodic disk persistence.

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Description

Name: my_redis_server
Default Port: 6379

This project implements a Redis clone in C++, providing common Redis commands over a plain TCP socket using the RESP protocol. It supports:

• Common Commands: PING, ECHO, FLUSHALL
• Key/Value: SET, GET, KEYS, TYPE, DEL/UNLINK, EXPIRE, RENAME
• List: LGET, LLEN, LPUSH/RPUSH (multi-element), LPOP/RPOP, LREM, LINDEX, LSET
• Hash: HSET, HGET, HEXISTS, HDEL, HKEYS, HVALS, HLEN, HGETALL, HMSET

Data is automatically dumped to dump.my_rdb every 300 seconds and on graceful shutdown; at startup, the server attempts to load from this file.

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Repository Structure

├── include/                # Public headers
│   ├── RedisCommandHandler.h
│   ├── RedisDatabase.h
│   └── RedisServer.h
├── src/                    # Implementation files
│   ├── RedisCommandHandler.cpp
│   ├── RedisDatabase.cpp
│   ├── RedisServer.cpp
│   └── main.cpp            # Entry point
├── Concepts,UseCases&Tests.md    # Design concepts and command use cases
├── Makefile                # Build rules
├── README.md               # This documentation
└── test_all.sh             # Bash script for all tests

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Installation

This project uses a simple Makefile. Ensure you have a C++17 (or later) compiler.

• make
• make clean

# from project root
make

Or compile manually:

g++ -std=c++17 -pthread -Iinclude src/*.cpp -o my_redis_server

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Usage

After compiling the server, you can run it and use with client.

Running the Server

Start the server on the default port (6379) or specify a port:

./my_redis_server            # listens on 6379
./my_redis_server 6380       # listens on 6380

On startup, the server attempts to load dump.my_rdb if present:

Database Loaded From dump.my_rdb
# or
No dump found or load failed; starting with an empty database.

A background thread dumps the database every 5 minutes.

To gracefully shutdown and persist immediately, press Ctrl+C.

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Using the Server

You can connect with the standard redis-cli or custom RESP client my_redis_cli.

# Using redis-cli:
redis-cli -p 6379

# Example session:
127.0.0.1:6379> PING
PONG

127.0.0.1:6379> SET foo "bar"
OK

127.0.0.1:6379> GET foo
"bar"

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Supported Commands

Common

• PING: PING → PONG
• ECHO: ECHO <msg> → <msg>
• FLUSHALL: FLUSHALL → clear all data

Key/Value

• SET: SET <key> <value> → store string
• GET: GET <key> → retrieve string or nil
• KEYS: KEYS * → list all keys
• TYPE: TYPE <key> → string/list/hash/none
• DEL/UNLINK: DEL <key> → delete key
• EXPIRE: EXPIRE <key> <seconds> → set TTL
• RENAME: RENAME <old> <new> → rename key

Lists

• LGET: LGET <key> → all elements
• LLEN: LLEN <key> → length
• LPUSH/RPUSH: LPUSH <key> <v1> [v2 ...] / RPUSH → push multiple
• LPOP/RPOP: LPOP <key> / RPOP <key> → pop one
• LREM: LREM <key> <count> <value> → remove occurrences
• LINDEX: LINDEX <key> <index> → get element
• LSET: LSET <key> <index> <value> → set element

Hashes

• HSET: HSET <key> <field> <value>
• HGET: HGET <key> <field>
• HEXISTS: HEXISTS <key> <field>
• HDEL: HDEL <key> <field>
• HLEN: HLEN <key> → field count
• HKEYS: HKEYS <key> → all fields
• HVALS: HVALS <key> → all values
• HGETALL: HGETALL <key> → field/value pairs
• HMSET: HMSET <key> <f1> <v1> [f2 v2 ...]

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Design & Architecture

• Concurrency: Each client is handled in its own std::thread.
• Synchronization: A single std::mutex db_mutex guards all in-memory stores.
• Data Stores:
  • kv_store (unordered_map<string,string>) for strings
  • list_store (unordered_map<string,vector<string>>) for lists
  • hash_store (unordered_map<string,unordered_map<string,string>>) for hashes
• Expiration: Lazy eviction on each access via purgeExpired(), plus TTL map expiry_map.
• Persistence: Simplified RDB: text‐based dump/load in dump.my_rdb.
• Singleton Pattern: RedisDatabase::getInstance() enforces one shared instance.
• RESP Parsing: Custom parser in RedisCommandHandler supports both inline and array formats.

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Concepts & Use Cases

Refer to Concepts,UseCases&Tests.md for a detailed description of the underlying concepts (TCP sockets, RESP, data structures, etc.) and real‑world usage scenarios for each command.

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Testing

You can verify functionality interactively or via scripts. See the test examples in Concepts,UseCases&Tests.md or use the provided test_all.sh script for end‑to‑end validation.

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Performance Measurement

You can benchmark the performance using redis-benchmark -c 50 -n 100000. This command simulates a workload of 50 simultaneous clients sending a total of 100,000 requests to the Redis server. This allows you to evaluate the performance of your Redis instance under a specific level of load and concurrency. The benchmark will typically measure and report metrics such as requests per second (throughput) and latency for various Redis commands.

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