DNDS

A service that handles real-time notifications for a social media platform when users create new posts.

Features

• gRPC endpoint for receiving new post events
• Concurrent notification processing using Go routines and worker pools
• GraphQL API for retrieving user notifications
• Automatic retry with exponential backoff for failed notifications
• Metrics endpoint for monitoring system performance

Architecture

The service consists of the following components:

1. gRPC Service: Receives new post events and queues notifications for followers.
2. Notification Queue: Processes notifications concurrently using a worker pool.
3. GraphQL API: Provides an endpoint to retrieve user notifications.
4. In-Memory Store: Stores user, post, and notification data.

Technical Details

• Language: Go
• API Protocols: gRPC, GraphQL
• Concurrency: Goroutines, Channels, Worker Pool
• Error Handling: Retry logic with exponential backoff

Setup Instructions

Prerequisites

• Go 1.22+
• Protocol Buffer Compiler (protoc)
• Git

Installation

1. Clone the repository

   git clone https://github.com/suyashXD/DNDS.git
   cd DNDS

2. Install dependencies

   go mod download

3. Generate protocol buffer code

   protoc --go_out=. --go_opt=paths=source_relative \
       --go-grpc_out=. --go-grpc_opt=paths=source_relative \
       internal/grpc/proto/notification.proto

4. Build the service

   go build -o notification-service.exe ./cmd/server/

5. Run the service

   ./notification-service.exe

Docker

Alternatively, you can use Docker:

# Build the image
docker build -t notification-service .

# Run the container
docker run -p 50051:50051 -p 8080:8080 notification-service

Usage

The service exposes the following endpoints:

gRPC API (Port 50051)

The gRPC service implements the following RPC:

rpc PublishPost(Post) returns (NotificationResponse)

Example using a gRPC client:

post := &proto.Post{
    AuthorId: "user1",
    Content: "Hello world!",
    CreatedAt: time.Now().Unix(),
}
response, err := client.PublishPost(context.Background(), post)

GraphQL API (Port 8080)

The GraphQL API is available at http://localhost:8080/graphql and provides the following query:

query {
  getNotifications(userId: "user1") {
    id
    content
    createdAt
    status
  }
}

Metrics API

Metrics are available at http://localhost:8080/metrics and return JSON with the following information:

• total_sent: Total number of notifications delivered
• failed_attempts: Number of failed delivery attempts
• total_retries: Number of retried deliveries
• avg_delivery_time: Average time to deliver a notification
• queue_size: Current number of notifications in the queue
• worker_count: Number of active workers

Assumptions

• All data is stored in memory for simplicity
• Sample user and follower data is pre-populated
• A 10% random failure rate is simulated for demonstration purposes
• Notifications are kept simple with minimal content

Future Improvements

• Replace in-memory storage with a persistent database
• Add authentication/authorization
• Implement rate limiting
• Scale horizontally with multiple instances