Feed Service

Microservice responsible for post management, feed generation, and social feed-related operations.

📋 Overview

The Feed Service handles all post and feed-related functionality including:

• Post creation and management
• Feed generation with pagination
• Interest-based post discovery
• Post interest management
• Like/unlike functionality

🏗️ Architecture

API Gateway → Composite Service → Feed Service → Feed Database (Cloud SQL)

• Port: 8003
• Database: MySQL (Cloud SQL or local)
• Authentication: Trusts x-firebase-uid header from API Gateway
• Deployment: Can run on Cloud Run or Compute Engine VM

🚀 Setup

Prerequisites

• Python 3.9+
• MySQL 8.0+
• Firebase service account key

Installation

1. Install dependencies

   pip install -r requirements.txt

2. Set up database

   mysql -u root -p feed_db < ../DB-Service/initFeed.sql

3. Configure environment variables Create a .env file:

   DB_HOST=127.0.0.1
   DB_USER=root
   DB_PASS=your_password
   DB_NAME=feed_db
   FIREBASE_SERVICE_ACCOUNT_PATH=./serviceAccountKey.json

4. Add Firebase service account key

   • Download from Firebase Console
   • Place as serviceAccountKey.json in service directory

5. Run the service

   uvicorn main:app --host 0.0.0.0 --port 8003

🔧 Environment Variables

Variable	Description	Default	Required
DB_HOST	Database host address	127.0.0.1	Yes
DB_USER	Database username	root	Yes
DB_PASS	Database password	-	Yes
DB_NAME	Database name	feed_db	Yes
FIREBASE_SERVICE_ACCOUNT_PATH	Path to Firebase service account JSON	./serviceAccountKey.json	No

📡 API Endpoints

Post Management

GET /posts

Get all posts with pagination and filtering

Query Parameters:

• skip: Number of posts to skip (default: 0)
• limit: Number of posts to return (default: 10, max: 100)
• interest_id: Filter by interest ID
• created_by: Filter by creator user ID
• search: Search in title and body

Headers:

• x-firebase-uid: Firebase user ID (injected by API Gateway)

Response:

{
  "items": [
    {
      "post_id": 1,
      "title": "My First Post",
      "body": "This is my first post!",
      "created_by": 1,
      "created_at": "2024-01-01T00:00:00",
      "likes_count": 5,
      "interests": [
        {"interest_id": 1, "interest_name": "Technology"}
      ],
      "_links": {
        "self": {"href": "/posts/1"},
        "collection": {"href": "/posts"}
      }
    }
  ],
  "total": 50,
  "skip": 0,
  "limit": 10
}

ETag Support: Returns ETag header for caching

GET /posts/{post_id}

Get post by ID

Response:

{
  "post_id": 1,
  "title": "My First Post",
  "body": "This is my first post!",
  "created_by": 1,
  "created_at": "2024-01-01T00:00:00",
  "updated_at": "2024-01-01T00:00:00",
  "likes_count": 5,
  "interests": [...],
  "_links": {...}
}

POST /posts

Create a new post

Request Body:

{
  "title": "My First Post",
  "body": "This is my first post!",
  "interest_ids": [1, 2, 3]
}

Response:

• 201 Created with post data

PUT /posts/{post_id}

Update a post (full update)

Request Body:

{
  "title": "Updated Post Title",
  "body": "Updated post body",
  "interest_ids": [1, 2]
}

ETag Support: Requires If-Match header for optimistic locking

PATCH /posts/{post_id}

Partially update a post

Request Body:

{
  "title": "Updated Title"
}

ETag Support: Requires If-Match header

DELETE /posts/{post_id}

Delete a post

ETag Support: Requires If-Match header

Post Interests

GET /posts/{post_id}/interests

Get interests for a post

POST /posts/{post_id}/interests

Add interests to a post

Request Body:

{
  "interest_ids": [1, 2, 3]
}

DELETE /posts/{post_id}/interests/{interest_id}

Remove interest from a post

Post Likes

POST /posts/{post_id}/like

Like a post

Response:

{
  "post_id": 1,
  "likes_count": 6,
  "liked": true
}

DELETE /posts/{post_id}/like

Unlike a post

Response:

{
  "post_id": 1,
  "likes_count": 5,
  "liked": false
}

Feed Endpoints

GET /posts/feed

Get personalized feed for current user

Query Parameters:

• skip: Number of posts to skip (default: 0)
• limit: Number of posts to return (default: 10, max: 100)

Response: Returns posts from users the current user follows, ordered by creation date.

🔐 Authentication

This service does not perform Firebase authentication directly. It trusts the x-firebase-uid header injected by the API Gateway middleware.

🗄️ Database Schema

Posts Table

• post_id (INT, PRIMARY KEY, AUTO_INCREMENT)
• title (VARCHAR)
• body (TEXT)
• created_by (INT, FOREIGN KEY to Users)
• created_at (TIMESTAMP)
• updated_at (TIMESTAMP)

PostInterests Table (Many-to-Many)

• post_id (INT, FOREIGN KEY)
• interest_id (INT, FOREIGN KEY)

PostLikes Table

• post_id (INT, FOREIGN KEY)
• user_id (INT, FOREIGN KEY)
• created_at (TIMESTAMP)
• PRIMARY KEY (post_id, user_id)

Interests Table

• interest_id (INT, PRIMARY KEY)
• interest_name (VARCHAR, UNIQUE)

🐳 Docker Deployment

Build Image

docker build -t feed-service .

Run Container

docker run -p 8003:8003 \
  -e DB_HOST=your_db_host \
  -e DB_USER=your_db_user \
  -e DB_PASS=your_db_password \
  -e DB_NAME=feed_db \
  feed-service

☁️ GCP Deployment

Cloud Run Deployment

The service can be deployed to Cloud Run with:

• VPC Connector for database access
• Private IP connection to Cloud SQL
• Environment variables configured via deployment script

Compute Engine VM Deployment

The service can also run on a Compute Engine VM:

• Direct VPC connection to Cloud SQL
• Systemd service for auto-start
• No external IP required

See ../GCP_DEPLOYMENT_GUIDE.md for details.

🧪 Testing

Health Check

curl http://localhost:8003/

Get Posts

curl -H "x-firebase-uid: your-firebase-uid" \
     http://localhost:8003/posts

Create Post

curl -X POST \
     -H "x-firebase-uid: your-firebase-uid" \
     -H "Content-Type: application/json" \
     -d '{
       "title": "Test Post",
       "body": "Test post body",
       "interest_ids": [1]
     }' \
     http://localhost:8003/posts

Like Post

curl -X POST \
     -H "x-firebase-uid: your-firebase-uid" \
     http://localhost:8003/posts/1/like

📚 API Documentation

Interactive API documentation available at:

• Swagger UI: http://localhost:8003/docs
• ReDoc: http://localhost:8003/redoc
• OpenAPI JSON: http://localhost:8003/openapi.json

🔍 Error Handling

The service returns standard HTTP status codes:

• 200 OK: Successful request
• 201 Created: Post created
• 400 Bad Request: Invalid request data
• 401 Unauthorized: Missing or invalid x-firebase-uid header
• 404 Not Found: Post not found
• 409 Conflict: ETag mismatch (optimistic locking)
• 412 Precondition Failed: ETag required but not provided
• 500 Internal Server Error: Server error

🎯 Features

• HATEOAS: All responses include _links for navigation
• ETag Support: Optimistic locking for updates
• Pagination: Skip/limit for large result sets
• Filtering: By interest, creator, search
• Like System: Users can like/unlike posts
• Interest Tags: Posts can be tagged with interests

📝 Notes

• The service uses MySQL connector with dictionary cursor for JSON-like responses
• ETag is generated from post data for optimistic locking
• Like counts are calculated dynamically from PostLikes table
• All datetime fields use ISO 8601 format

🤝 Contributing

When adding new endpoints:

1. Add route to routers/posts.py
2. Use get_firebase_uid_from_header() helper for authentication
3. Add proper error handling and ETag support
4. Update this README with endpoint documentation