Reddit Clone - Distributed Actor System with REST API

Team Members

• Anup Sedhain (UF ID - 92896347)
• Dinank Bista (UF ID - 41975568)

Project Overview

This project implements a distributed Reddit-like platform combining two key architectural components:

1. A REST API interface for client-server communication
2. An Actor-based backend system using Proto.Actor framework in Go

The system enables users to create communities (subreddits), share content, and interact through comments and votes, all while maintaining data consistency across concurrent operations.

Architecture

Core Components

1. Actor System

The backend is built on several specialized actors:

- EngineActor    // Coordinates system operations
- PostActor      // Manages posts and voting
- SubredditActor // Handles subreddit operations
- CommentActor   // Manages comments and replies
- UserActor      // Handles user operations

2. REST API Layer

The system exposes RESTful endpoints that follow Reddit-like API patterns:

Authentication:
- POST /register
- POST /login

Content:
- POST /post
- GET  /post/:postId
- POST /comment
- GET  /feed

Communities:
- POST /subreddit
- GET  /subreddits
- POST /subreddit/:name/join

Data Management

1. Post Management

type PostActor struct {
    posts map[string]*messages.Post           // PostId -> Post
    subredditPosts map[string][]string       // SubredditName -> []PostId
    votes map[string]map[string]bool         // PostId -> UserId -> IsUpvote
}

2. User State

type UserActor struct {
    karma map[string]int           // UserId -> Karma
    joinedSubreddits map[string][]string  // UserId -> []SubredditName
}

Implementation Details

1. REST API Implementation

Authentication Flow

1. Registration

   • Username/password validation
   • Account creation
   • Initial state setup

2. Login

   • Credential verification
   • JWT token generation
   • Session management

Content Operations

1. Post Creation

   • Authorization check
   • Content validation
   • Actor message dispatch
   • Response handling

2. Comment Management

   • Nested comment support
   • Vote tracking
   • Real-time updates

2. Actor System Implementation

Message Flow

Client Request -> REST Handler -> Engine Actor -> Specialized Actor -> Response

State Management

• Isolated actor states
• Concurrent access control
• Message-based updates
• Real-time consistency

Testing Framework

1. Test Scenarios

We validate the system using three distinct user personas:

Techie (Technical User)

• Creates programming content
• Participates in technical discussions
• Tests post creation and editing

Gamer (Gaming Enthusiast)

• Manages gaming communities
• Creates gaming-related content
• Tests cross-posting capabilities

MovieBuff (Entertainment Fan)

• Manages movie discussions
• Tests content interaction
• Demonstrates multi-subreddit usage

2. Test Flow

1. User Creation and Authentication
2. Subreddit Creation and Joining
3. Content Creation and Interaction
4. Search and Feed Generation
5. Edit and Delete Operations

API Endpoints Detail

Authentication

POST /register
- Request: {username, password}
- Response: {token, userId}

POST /login
- Request: {username, password}
- Response: {token}

Content Management

POST /post
- Auth: Required
- Request: {title, content, subredditName}
- Response: {postId, success}

POST /comment
- Auth: Required
- Request: {postId, content}
- Response: {commentId, success}

Community Operations

POST /subreddit
- Auth: Required
- Request: {name, description}
- Response: {subredditId, success}

POST /subreddit/:name/join
- Auth: Required
- Response: {success}

Discovery

GET /feed
- Auth: Required
- Response: {posts[], subreddits[]}

GET /search?q=query
- Auth: Required
- Response: {posts[], relevance}

Performance Analysis

1. Metrics

• Average response time: 2.5s for content operations
• Authentication operations: ~10μs
• Search operations: 2.7s
• Concurrent user handling: 96.5% success rate

2. Load Testing Results

• Successful requests: 96.5%
• Failed requests: 3.5%
• Error distribution analysis
• Concurrent user capacity

Technical Insights

1. Message-Based Communication

The system implements comprehensive message passing:

type Post struct {
    PostId        string
    Title         string
    Content       string
    AuthorId      string
    SubredditName string
    Timestamp     int64
    ActorPID      *actor.PID
}

2. Voting System

Reddit-like voting mechanism:

func (state *PostActor) handleVote(msg *messages.Vote) *messages.VoteResponse {
    if _, exists := state.posts[msg.TargetID]; !exists {
        return &messages.VoteResponse{Success: false, Error: "Post not found"}
    }

    if state.votes[msg.TargetID] == nil {
        state.votes[msg.TargetID] = make(map[string]bool)
    }

    previousVote, hasVoted := state.votes[msg.TargetID][msg.UserID]
    if hasVoted {
        if previousVote == msg.IsUpvote {
            delete(state.votes[msg.TargetID], msg.UserID)
        } else {
            state.votes[msg.TargetID][msg.UserID] = msg.IsUpvote
        }
    } else {
        state.votes[msg.TargetID][msg.UserID] = msg.IsUpvote
    }

    return &messages.VoteResponse{Success: true}
}

Running the System

Prerequisites

• Go 1.16 or higher
• Proto.Actor framework
• Git

How to run this program

1. Build and run the main server:

   go build -o reddit
   ./reddit

   This will start the server on port 8080

2. Run the test script:

   go run script/test_script.go

   This will execute the test scenarios with different user personas

Setup Instructions

1. Clone the repository
2. Install dependencies: go mod tidy
3. Start the server: go run main.go
4. Run tests: go run test_script.go

Future Enhancements

1. Security

• Public key-based digital signatures
• Enhanced authentication
• Rate limiting
• Content verification

2. Features

• Media content support
• Real-time notifications
• Enhanced search capabilities
• Content recommendation system

3. Performance

• Database integration
• Caching layer
• Load balancing improvements
• Response time optimization

Conclusion

This project demonstrates a practical implementation of a distributed system using the Actor model with REST API integration. Its modular design and message-passing architecture provide a solid foundation for a scalable social platform. The implementation successfully showcases key concepts of distributed systems and concurrent programming while maintaining clean REST principles.

How to run this program

1. Build and run the main server:

   go build -o reddit or  go build
   ./reddit or go run main.go

   This will start the server on port 8080. Now in a separate terminal run the test script

2. Run the test script:

   go run script/test_script.go

   This will execute the test scenarios with different user personas

Setup Instructions

1. Clone the repository
2. Install dependencies: go mod tidy

Demo Video Link