Health checks in containers in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a health check in a containerized microservice?

A health check verifies if a containerized microservice is running correctly and ready to serve requests. It helps orchestrators decide if the container should keep running or be restarted.

beginner

Name the two common types of health checks used in containers.

Liveness check: Determines if the container is alive or stuck. Readiness check: Determines if the container is ready to accept traffic.

intermediate

Why should readiness checks be separate from liveness checks?

Readiness checks control traffic routing and prevent sending requests to containers not ready yet. Liveness checks detect if a container is broken and needs restart. Separating them avoids unnecessary restarts.

beginner

What happens if a liveness check fails in a container orchestrator like Kubernetes?

The orchestrator considers the container unhealthy and restarts it to recover from failure or stuck state.

beginner

Give an example of a simple readiness check for a web service container.

A readiness check can be an HTTP GET request to an endpoint like /health or /ready that returns status 200 if the service is ready to accept requests.

Which health check type ensures a container is ready to receive traffic?

A Readiness check

B Liveness check

C Startup check

D Performance check

Readiness checks confirm if the container is ready to accept requests, controlling traffic routing.

What action does Kubernetes take when a liveness check fails?

A Restarts the container

B Routes traffic away from the container

C Scales up the service

D Ignores the failure

Kubernetes restarts containers that fail liveness checks to recover from unhealthy states.

Why is it important to have separate readiness and liveness checks?

A To reduce network traffic

B To avoid restarting containers unnecessarily

C To improve logging

D To speed up container startup

Separating checks prevents restarting containers that are alive but not ready to serve traffic.

Which of these is a common method for implementing a readiness check?

A Checking CPU usage

B Monitoring memory leaks

C Sending an HTTP GET request to a health endpoint

D Verifying disk space

Readiness checks often use HTTP requests to specific endpoints that return status indicating readiness.

If a container is alive but not ready, what should happen?

A It should be deleted

B It should receive traffic normally

C It should be restarted immediately

D Traffic should be withheld until ready

Traffic should be withheld until the container signals readiness to avoid errors.

Explain the difference between liveness and readiness health checks in containers.

Think about when a container should be restarted versus when it should receive traffic.

Describe how health checks improve reliability in a microservices architecture using containers.

Consider what happens when a service fails or is not ready.