Health checks

To monitor the application, we need to know whether the application is running correctly or not. We can perform health checks to monitor the application. Normally, a health check is an endpoint that returns the health status of the application. This status can be Healthy, Degraded, or Unhealthy.

A health check is a critical part of the microservice architecture. In the microservice architecture, one API service may have multiple instances and also have dependencies on other services. A load balancer or orchestrator can be used to distribute the traffic to different instances. If one instance is unhealthy, the load balancer or orchestrator can stop sending traffic to the unhealthy instance. For example, Kubernetes – a popular container orchestrator – can use health checks to determine whether a container is healthy or not. If a container is not live, Kubernetes will restart the container.

We won’t discuss the details of Kubernetes in this book...