MeowDB : Redis-like Database Server

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This project implements a Redis-like database server in C, supporting basic operations such as create, insert, select, update, and delete. The server uses a tree-based data structure to store key-value pairs and handles client connections using sockets.

This project is based on a tutorial taught by Dr. Birch (Youtube | Website)

Features

• Create: Add a new key-value pair to the database.
• Insert: Insert or update a key-value pair.
• Select: Retrieve the value associated with a key.
• Update: Modify the value of an existing key.
• Delete: Remove a key-value pair from the database.
• Hello: A simple command to test the server connection.

Technical Details

Data Structures

• Tree: The database uses a tree structure to store key-value pairs. Each node in the tree can be either a TreeNode or a TreeLeaf.
  • TreeNode: Represents a node in the tree, containing pointers to child nodes and a path.
  • TreeLeaf: Represents a leaf in the tree, containing a key, value, and size.

Server Architecture

• Client Connection: The server handles client connections using sockets. Each client connection is managed in a separate process using fork().
• Command Handlers: The server supports multiple commands, each handled by a specific function. The command handlers are defined in an array of CmdHandler structures.

Networking Details

The server listens on a specified port (default: 6969) for incoming client connections. When a client connects, the server forks a new process to handle the client's requests. The server supports the following commands:

• create <key> <value>: Create a new key-value pair.
• insert <key> <value>: Insert or update a key-value pair.
• select <key>: Retrieve the value associated with a key.
• update <key> <value>: Update the value of an existing key.
• delete <key>: Delete a key-value pair.
• hello: Test the server connection.

Compilation and Execution

To compile and run the server, use the following commands:

$ make
$ ./Meow [port]

Replace [port] with the desired port number. If no port is specified, the server will use the default port 6969.

Example Queries and Results

Here are some example queries and their expected results:

1. Create a new key-value pair:

   create mykey myvalue

   Result:

   Key 'mykey' created with value 'myvalue'.
   

2. Insert or update a key-value pair:

   insert mykey newvalue

   Result:

   Key 'mykey' updated with value 'newvalue'.
   

3. Select a value by key:

   select mykey

   Result:

   Value for 'mykey': newvalue
   

4. Delete a key-value pair:

   delete mykey

   Result:

   Key 'mykey' deleted.
   

5. Test the server connection:

   hello

   Result:

   Hello from the Cache server!
   

UML Diagram

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classDiagram
    class Client {
        +int socket
        +char ip[16]
        +int16 port
    }

    class TreeNode {
        +Tag tag
        +TreeNode* north
        +TreeNode* west
        +TreeLeaf* east
        +int8 path[256]
    }

    class TreeLeaf {
        +Tag tag
        +union u_tree* west
        +TreeLeaf* east
        +int8 key[128]
        +int8* value
        +int16 size
    }

    class CmdHandler {
        +int8* command
        +CommandCallback handler
    }

    Client --> CmdHandler : uses
    TreeNode --> TreeLeaf : contains