A comprehensive API health checker built with TypeScript and Express.js that monitors the health of HTTP endpoints, databases, and system resources.

• 🌐 HTTP Health Checks: Monitor REST APIs, websites, and web services
• 🗄️ Database Health Checks: Support for PostgreSQL, MySQL, MongoDB, and Redis
• 🖥️ System Health Checks: Monitor CPU, memory, and disk usage
• 📊 Metrics Collection: Track uptime, response times, and success rates
• 🔄 Periodic Monitoring: Automated health checks with configurable intervals
• 🚨 Retry Logic: Configurable retry attempts with backoff
• 📝 Structured Logging: Winston-based logging with health check events
• 🛡️ Security: Helmet.js security headers and CORS support
• ⚙️ Configuration: JSON file and environment variable configuration

1. Install dependencies:

   npm install

2. Build the project:

   npm run build

3. Start the server:

   npm start

   For development with auto-reload:

   npm run dev

4. Access the API:

   • Health status: GET http://localhost:3000/api/health
   • Detailed health: GET http://localhost:3000/api/health/detailed
   • API documentation: GET http://localhost:3000/

• GET /api/health - Quick health status overview
• GET /api/health/detailed - Detailed health status with all check results

• GET /api/health/checks - List all registered health checks
• GET /api/health/checks/:id - Get specific health check status
• POST /api/health/checks/:id/execute - Execute a health check manually
• POST /api/health/checks - Register a new health check
• DELETE /api/health/checks/:id - Unregister a health check
• PUT /api/health/checks/:id/toggle - Enable/disable a health check

• GET /api/health/metrics - Get metrics for all health checks
• GET /api/health/metrics/:id - Get metrics for a specific health check

# Server configuration
PORT=3000
HOST=0.0.0.0
NODE_ENV=development

# Health check defaults
HEALTH_CHECK_TIMEOUT=5000
HEALTH_CHECK_INTERVAL=30000
MAX_RETRIES=3

# Logging
LOG_LEVEL=info
LOG_FORMAT=json

# Configuration directory
HEALTH_CHECKS_CONFIG_DIR=./config

You can define health checks using environment variables:

# HTTP check example
HEALTH_CHECK_API_URL=https://api.example.com/health
HEALTH_CHECK_API_NAME="API Service"
HEALTH_CHECK_API_METHOD=GET
HEALTH_CHECK_API_TIMEOUT=5000
HEALTH_CHECK_API_INTERVAL=30000

Health checks can be defined in JSON files in the config/ directory:

{
  "id": "api-service",
  "name": "API Service Health",
  "type": "http",
  "enabled": true,
  "interval": 30000,
  "timeout": 5000,
  "retries": 3,
  "metadata": {
    "url": "https://api.example.com/health",
    "method": "GET",
    "expectedStatusCodes": [200],
    "headers": {
      "Authorization": "Bearer token"
    }
  }
}

{
  "id": "postgres-main",
  "name": "PostgreSQL Main Database",
  "type": "database",
  "enabled": true,
  "interval": 60000,
  "timeout": 8000,
  "retries": 2,
  "metadata": {
    "connectionString": "postgresql://user:password@localhost:5432/maindb",
    "databaseType": "postgresql",
    "query": "SELECT 1 as health_check"
  }
}

{
  "id": "system-performance",
  "name": "System Performance Check",
  "type": "system",
  "enabled": true,
  "interval": 120000,
  "timeout": 15000,
  "metadata": {
    "checks": [
      { "type": "memory", "threshold": 85 },
      { "type": "cpu", "threshold": 90 },
      { "type": "disk", "threshold": 90, "path": "/" }
    ]
  }
}

• Monitor REST APIs and web endpoints
• Support for custom headers and authentication
• Configurable expected status codes and response body validation
• Follow redirects option

• PostgreSQL: Connection and query execution
• MySQL: Connection and query execution
• MongoDB: Connection and ping operations
• Redis: Connection and ping operations

• Memory: Monitor RAM usage percentage
• CPU: Monitor CPU load average
• Disk: Monitor disk usage by path

• healthy - Check passed successfully
• degraded - Check passed but performance is poor (slow response)
• unhealthy - Check failed
• unknown - Check status could not be determined

• 200 - All checks healthy
• 206 - Some checks degraded (partial content)
• 503 - One or more checks unhealthy (service unavailable)
• 500 - Internal server error

• npm run build - Build the TypeScript project
• npm run dev - Start development server with auto-reload
• npm start - Start production server
• npm test - Run tests
• npm run lint - Run ESLint
• npm run format - Format code with Prettier

src/
├── checkers/          # Health check implementations
│   ├── http.ts       # HTTP endpoint checker
│   ├── database.ts   # Database connectivity checker
│   └── system.ts     # System resource checker
├── routes/           # Express routes
│   └── health.ts     # Health check API routes
├── services/         # Core services
│   ├── health-check-orchestrator.ts  # Main orchestrator
│   └── logger.ts     # Logging service
├── types.ts          # TypeScript type definitions
└── index.ts          # Application entry point

MIT License - see LICENSE file for details.