My Own Redis-like server

This document provides a comprehensive guide and overview for the Command Server, a server application designed to handle a variety of commands sent by clients over a TCP/IP network. It supports operations like setting and getting key-value pairs, manipulating sorted sets, and handling timeouts and idle connections.

Overview

The Command Server listens for incoming TCP connections on a specified port, accepting commands from clients, processing them, and sending back responses. Supported operations include basic key-value storage, sorted set manipulations, and advanced features like key expiration and idle connection handling.

Requirements

• A Unix-like operating system (Linux, macOS)
• C++ compiler (e.g., g++, clang++)
• GNU Make or another build system (optional, for building the project)

Building

To compile the Command Server, navigate to the project directory and use the following command:

g++ -Wall -Wextra -O2 -g server.cpp -o server
g++ -Wall -Wextra -O2 -g client.cpp -o client

Ensure all dependencies, including the C++ standard library and POSIX threads, are correctly linked.

Features

• TCP Network Communication: Listens on a specified port for incoming connections.
• Command Processing: Supports a variety of commands for manipulating key-value pairs and sorted sets.
• Non-Blocking I/O: Utilizes non-blocking sockets and a custom event loop for efficient I/O operations.
• Connection Handling: Manages idle connections with timeouts to free up resources.
• Concurrency: Implements a thread pool for offloading certain operations, enhancing scalability and performance.
• Key Expiration: Supports setting expiration times on keys for automatic deletion.

Running the Server

To start the server, run:

./server

The server will listen on port 1234 by default. Ensure no other service is using this port or modify the source code to use a different port.

Supported Commands

• SET key value: Sets the value for a key.
• GET key: Retrieves the value for a key.
• DEL key: Deletes a key.
• PEXPIRE key milliseconds: Sets an expiration time on a key.
• PTTL key: Gets the remaining time to live (in milliseconds) of a key.
• KEYS: Lists all keys.
• ZADD zset score member: Adds a member to a sorted set, or updates its score if it already exists.
• ZREM zset member: Removes a member from a sorted set.
• ZSCORE zset member: Retrieves the score associated with the member in a sorted set.
• ZQUERY zset score member offset limit: Queries members in a sorted set based on score and name, with pagination support.

Command Syntax and Usage

1. SET key value

Sets the value for a key. If the key already exists, its value is overwritten.

./client SET mykey somevalue

2. GET key

Retrieves the value for a key. If the key does not exist, the server responds with (nil).

./client GET mykey

3. DEL key

Deletes a key. If the key is successfully deleted, the server responds with (int) 1, otherwise (int) 0.

./client DEL mykey

4. PEXPIRE key milliseconds

Sets an expiration time on a key in milliseconds. After the expiration time, the key is automatically deleted. The server responds with (int) 1 if the timeout was set successfully, otherwise (int) 0.

./client PEXPIRE mykey 5000

5. PTTL key

Gets the remaining time to live (in milliseconds) of a key. The server responds with the remaining time or (int) -1 if the key does not have an expiration time.

./client PTTL mykey

6. KEYS

Lists all keys stored on the server. The server responds with an array of keys.

./client KEYS

7. ZADD zset score member

Adds a member to a sorted set zset, or updates its score if it already exists. The server responds with (int) 1 if the member is a new addition, otherwise (int) 0.

./client ZADD myzset 1 member1

8. ZREM zset member

Removes a member from a sorted set zset. The server responds with (int) 1 if the member was removed, otherwise (int) 0.

./client ZREM myzset member1

9. ZSCORE zset member

Retrieves the score associated with the member in a sorted set zset. If the member exists, the server responds with (dbl) score, otherwise (nil).

./client ZSCORE myzset member1

10. ZQUERY zset score member offset limit

Queries members in a sorted set zset based on score and name, with pagination support using offset and limit. The server responds with an array of members and their scores.

./client ZQUERY myzset 0 member1 0 10

To use these commands, you can write a client in your preferred programming language that establishes a TCP connection to the server and sends these commands as plain text strings followed by a newline character. The server's response will also be in plain text, following the formats described above.

Customization

• Port Configuration: To change the listening port, modify the addr.sin_port assignment in the main function.
• Thread Pool Size: Adjust the size of the thread pool in the main function for optimal performance based on your hardware and workload.

Limitations

• The server assumes a little-endian byte order for network communication.
• There is a fixed maximum message size limit for sending and receiving data.
• It is designed primarily for demonstration purposes and may require modifications for production use.