refactor: production architecture hardening and song fetch reliability

[hey-Zayn]

Summary by CodeRabbit

• New Features

  • Added /api/health endpoint reporting service status, environment details, and database/cache connection states.

• Bug Fixes

  • Improved error handling in stats retrieval with proper exception propagation.
  • Enhanced Redis reconnection strategy with configurable timeouts and retry limits for improved reliability.

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Project	Deployment	Actions	Updated (UTC)
music-app	Ready	Preview, Comment	Mar 29, 2026 1:01am
music-app-9r1o	Ready	Preview, Comment	Mar 29, 2026 1:01am

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e3eed00f-46d5-47da-8327-61e0a440f34d

📥 Commits

Reviewing files that changed from the base of the PR and between 982cf98 and a296c1f.

📒 Files selected for processing (3)

• backend/src/controllers/stats.controller.js
• backend/src/index.js
• backend/src/lib/redis.js

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📝 Walkthrough

Walkthrough

The pull request updates error handling in the stats controller to propagate exceptions through Express middleware, adds a health check endpoint monitoring MongoDB and Redis connectivity, and configures Redis connection timeouts with exponential backoff retry strategy.

Changes

Cohort / File(s)	Summary
Error Handling backend/src/controllers/stats.controller.js	Modified getStats catch block to forward exceptions via next(error) for centralized Express error handling instead of silent failure.
Server Startup & Health Monitoring backend/src/index.js	Added async startServer wrapper ensuring HTTP server starts only after successful database connection. New GET /api/health endpoint returns service status, environment, MongoDB readiness state, document count, and Redis connection state.
Redis Connection Configuration backend/src/lib/redis.js	Updated Redis client socket configuration with 5000ms connection timeout and exponential backoff retry strategy (capped at 500ms) that fails after retry limit exceeded.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant Server
    participant MongoDB
    participant Redis
    
    rect rgba(100, 150, 200, 0.5)
    Note over Server,Redis: Server Startup
    Server->>MongoDB: connectDB()
    activate MongoDB
    MongoDB-->>Server: connection ready
    deactivate MongoDB
    Server->>Server: listen(PORT)
    end
    
    rect rgba(150, 200, 100, 0.5)
    Note over Client,Redis: Health Check Request
    Client->>Server: GET /api/health
    Server->>MongoDB: check readyState
    Server->>MongoDB: Song.countDocuments()
    MongoDB-->>Server: count
    Server->>Redis: check isOpen
    Server-->>Client: {status, environment, mongodb, songs, redis}
    end

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A health check hops along the way,
With Redis retries that never stray,
Errors now flow through middleware's care,
Database connection waits with flair!

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch Live-0

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