nest-healthCheck

Overview

• Healthchecks (Terminus) in NestJS
• Example: HTTP Healthcheck
• Advanced Health Indicators
• Integration with Application Lifecycle

Healthchecks (Terminus) in NestJS

1- Purpose of Healthchecks:: - Healthchecks are crucial in complex backend setups, often used in services and infrastructure components (like Kubernetes) to continually assess the health of an application. - They usually involve a special endpoint (e.g., /health/readiness) that returns an HTTP status code to indicate the application's health status.

2 - What is Terminus?: - Terminus is an integration in NestJS that provides health check functionalities. - It helps define what constitutes a "healthy" or "unhealthy" state for your service, with a set of predefined health indicators.

##Setting Up Terminus in NestJS 1- Installation: Install Terminus using npm: bash npm install --save @nestjs/terminus

2- Creating a Health Module: - Create a HealthModule in your NestJS application and import TerminusModule. - Use Nest CLI to generate the module and controller (nest g module health, nest g controller health).

3- Implementing Health Checks: - Health checks summarize the status of various health indicators. - Indicators could be for databases (like MongoDB), HTTP services, memory usage, etc. - Terminus offers predefined indicators such as HttpHealthIndicator, TypeOrmHealthIndicator, and more.

4- Setting Up a Health Controller: - Implement a health check in a controller. - Use decorators like @Get() and @HealthCheck() to define health check routes. - Configure your health indicators within the health check method.

Example: HTTP Healthcheck

• HTTPHealthIndicator: Checks the health of an HTTP endpoint.
• Setup:
  • Ensure @nestjs/axios is installed for HTTP requests.
  • Define a route in your controller that uses HttpHealthIndicator to ping a specified URL.
  • The health endpoint will return an "ok" status if the ping is successful.

Advanced Health Indicators

1- Database Health Indicators:

• For databases like MongoDB or SQL databases, use the corresponding health indicator (e.g., TypeOrmHealthIndicator).
• The health check typically runs a simple query to ensure the database is responsive.

2- Disk and Memory Health Indicators:

• Check the usage of disk space or memory and define thresholds for what's considered healthy.

3- Custom Health Indicators:

• You can create custom health indicators for specific use cases not covered by the predefined ones.

Integration with Application Lifecycle

• Graceful Shutdown: 1- Terminus can manage graceful shutdowns, which is especially useful in orchestrated environments like Kubernetes. 2- This helps in achieving zero downtime during deployments or when containers are

Conclusion Terminus integration in NestJS provides a structured and straightforward way to implement health checks for various aspects of your application. These health checks are essential for monitoring the application's state and ensuring its reliability, especially in complex and distributed architectures. By leveraging Terminus, you can define detailed health check mechanisms that align with the specific needs and configurations of your services.