.NET Minimal API — Distributed System (Master / Followers)

This project demonstrates a simple distributed system built with .NET 8 Minimal API. It uses a master–followers architecture, where:

• The master node accepts write requests
• Updates are represented as JSON Patch operations
• The master applies the patch locally and propagates it to all followers
• Followers apply the same patch to keep state consistent
• A simple vector clock is used to prevent stale updates

Architecture Overview

• Master node — receives PATCH requests and broadcasts them
• Follower nodes — receive updates only from the master
• All nodes run the same application image
• Roles and topology are configured via appsettings.json and environment variables

Available Endpoints

• /
  Returns a simple status message: "Server started!"
• /get
  Returns the current JSON state stored on the node.
• /replace
  Applies a single JSON Patch operation to the current state.
  On the master node, the patch is also forwarded to all followers.
• /vclock
  Returns the current vector clock (logical timestamps per source).
• /test
  Simple HTML UI for manual testing of /replace and /get.

Example /replace request body

The request contains:

• Source — identifier of the request sender
• ID — monotonically increasing logical timestamp
• Payload — a single JSON Patch operation (RFC 6902)

{
    "Source": "Dyagilev",
    "ID": 1,
    "Payload": "{'op': 'add', 'path': '/hello', 'value': { 'name': 'Ginger' }}"
}

JSON Patch Examples

{
    "op": "add",
    "path": "/user",
    "value": { "name": "Alice" }
}

{
    "op": "replace",
    "path": "/user/name",
    "value": "Bob"
}

{
    "op": "remove",
    "path": "/user"
}

Setup and Run (Docker Compose)

The system is designed to run using Docker Compose. One container acts as the master, and multiple containers act as followers.

1. Clone the repository:

   git clone https://github.com/GeorgeD615/DistributedSystemAPI.git

2. Navigate to the project directory:

   cd DistributedSystemAPI

3. Build and start all services:

   docker compose up --build

4. Open the master node in a browser:

   http://localhost:3000

Ports Mapping

• Master: http://localhost:3000
• Follower 1: http://localhost:3001
• Follower 2: http://localhost:3002
• Follower 3: http://localhost:3003

Notes

• The system demonstrates eventual consistency
• JSON Patch operations are applied in order using logical clocks
• This project is intended for educational purposes