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.github/copilot-instructions.md

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+# GitHub Copilot Instructions for Sunbird Telemetry Service
+
+## Project Overview
+This is a Node.js microservice that provides APIs for Sunbird telemetry. The service is built with Express.js and uses Kafka for message dispatching.
+
+## Technology Stack
+- **Node.js**: v22.15
+- **Framework**: Express.js v4.16
+- **Message Queue**: Kafka (using kafka-node v5.0.0)
+- **Clustering**: express-cluster for multi-process support
+- **Logging**: Winston with Cassandra and daily rotate file transports
+
+## Project Structure
+```
+src/
+├── app.js              # Main Express application setup
+├── routes/             # API route definitions
+├── service/            # Business logic layer
+├── dispatcher/         # Kafka message dispatchers
+├── test/               # Test files (mirrors src structure)
+├── envVariables.js     # Environment configuration
+└── package.json        # Dependencies and scripts
+```
+
+## Development Setup
+
+### Prerequisites
+- Node.js v22.15
+- Kafka and Zookeeper running locally
+
+### Installation
+```bash
+cd src
+npm ci
+```
+
+### Running the Service
+```bash
+node app.js
+```
+Note: The `package.json` does not define a `start` script. Run the application directly with Node.js.
+
+### Working Directory
+Always run npm commands from the `src/` directory, as that's where `package.json` is located.
+
+## Code Style and Quality
+
+### ESLint Configuration
+- **Environment**: Node.js, ES2021
+- **Indentation**: 2 spaces
+- **Quotes**: Single quotes
+- **Semicolons**: Required
+- **Rules**:
+  - `no-console`: warn
+  - `no-debugger`: error
+  - `no-unused-vars`: warn
+
+### Linting
+```bash
+npm run lint          # Check for issues
+npm run lint:fix      # Auto-fix issues
+```
+
+**Important**: Always run linting before committing code. The CI pipeline will fail PRs with linting errors.
+
+## Testing
+
+### Test Framework
+- **Test Runner**: Mocha
+- **Assertions**: Chai (with chai-http for HTTP testing)
+- **Mocking/Stubbing**: Sinon
+- **Coverage**: NYC (Istanbul)
+- **Reporting**: Mochawesome
+
+### Test Structure
+- Tests are located in `src/test/` directory
+- Test files follow the pattern `*.spec.js`
+- Tests mirror the source structure (e.g., `service/telemetry-service.js` → `test/service/telemetry-service.spec.js`)
+
+### Test Patterns
+```javascript
+// Standard test structure
+const chai = require('chai');
+const sinon = require('sinon');
+const expect = chai.expect;
+
+describe('Feature Name', () => {
+  beforeEach(() => {
+    // Setup stubs and mocks
+    // Clear require cache if testing different configurations
+  });
+
+  afterEach(() => {
+    // Restore stubs
+  });
+
+  it('should describe expected behavior', () => {
+    // Test implementation
+  });
+});
+```
+
+### Running Tests
+```bash
+npm test                    # Run all tests with coverage
+npm run test-with-coverage  # Run tests and upload to Codacy
+```
+
+## API Development Guidelines
+
+### Express Application Structure
+- The application uses clustering with configurable thread count
+- CORS is enabled for all origins
+- Body size limit is 5MB
+- Keep-alive timeout is set to 5 minutes (300,000ms)
+
+### Creating New Routes
+1. Define routes in `src/routes/` directory
+2. Implement business logic in `src/service/` directory
+3. Keep routes thin - delegate to service layer
+4. Follow existing patterns for consistency
+
+### Environment Variables
+- Configuration is centralized in `src/envVariables.js`
+- Use environment variables for all configurable values
+- Never hardcode credentials or sensitive data
+
+## Kafka Integration
+
+### Dispatcher Pattern
+- Kafka dispatchers are in `src/dispatcher/` directory
+- Use kafka-node library for Kafka interactions
+- Follow the existing dispatcher patterns for consistency
+
+## CI/CD
+
+### Pull Request Checks
+- **Linting**: Must pass ESLint checks
+- **Dependencies**: Installed via `npm ci` for deterministic builds
+- **Node Modules Caching**: GitHub Actions caches dependencies for faster builds
+
+### Workflow Location
+- `.github/workflows/pull_request.yml`: Runs on all PRs
+
+### Before Submitting PRs
+1. Run `npm run lint:fix` to fix auto-fixable issues
+2. Run `npm test` to ensure tests pass
+3. Ensure working directory is `src/` when running npm commands
+
+## Docker
+
+### Image Building
+- Uses multi-stage builds (see `Dockerfile` and `Dockerfile.Build`)
+- Images are published to GitHub Container Registry (GHCR)
+- Automated builds trigger on tag creation
+
+### Image Naming
+- Repository: `ghcr.io/project-sunbird/sunbird-telemetry-service`
+- Tag format: `{TAG_NAME}_{COMMIT_HASH}_{RUN_NUMBER}`
+
+## Best Practices
+
+### Code Organization
+- Keep functions small and focused
+- Use clear, descriptive variable names
+- Follow the single responsibility principle
+- Maintain consistent error handling patterns
+
+### Error Handling
+- Use Express error handling middleware
+- Log errors appropriately with Winston
+- Return meaningful HTTP status codes
+
+### Performance
+- Leverage clustering for multi-core utilization
+- Use appropriate caching strategies
+- Monitor Kafka consumer lag
+
+### Security
+- Never commit credentials or secrets
+- Validate and sanitize all inputs
+- Use latest security patches for dependencies
+- Follow OWASP best practices for web services
+
+## Common Tasks
+
+### Adding a New Dependency
+```bash
+cd src
+npm install <package-name>
+```
+
+### Updating Dependencies
+```bash
+cd src
+npm update
+npm audit fix  # Fix security vulnerabilities
+```
+
+### Debugging
+- Set `node_env=test` to run in single-process mode for easier debugging
+- Use debug logs with the Winston logger
+- Check Kafka consumer status if messages aren't processing
+
+## Additional Resources
+- [Sunbird Documentation](https://github.com/project-sunbird)
+- [Express.js Documentation](https://expressjs.com/)
+- [Kafka Node Documentation](https://www.npmjs.com/package/kafka-node)
+
+## Questions or Issues?
+For questions or issues, please open an issue in the GitHub repository or refer to the project documentation.