Health checks in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a health check in the context of NGINX?

A health check is a process where NGINX regularly tests backend servers to see if they are working properly before sending traffic to them.

beginner

How does NGINX decide to stop sending traffic to a backend server?

NGINX stops sending traffic to a backend server if the health check fails, meaning the server did not respond correctly or on time.

intermediate

Which NGINX directive is used to enable active health checks?

The directive 'health_check' inside the 'upstream' block enables active health checks in NGINX Plus.

intermediate

What is the difference between active and passive health checks in NGINX?

Active health checks send regular test requests to servers. Passive health checks watch real traffic and mark servers unhealthy if errors happen.

intermediate

Write a simple NGINX upstream block with a health check enabled for two backend servers.

upstream backend { server backend1.example.com; server backend2.example.com; health_check; }

What happens if a backend server fails a health check in NGINX?

A NGINX stops sending traffic to that server.

B NGINX restarts the server automatically.

C NGINX sends more traffic to that server.

D NGINX ignores the failure and continues.

If a backend server fails a health check, NGINX marks it as unhealthy and stops sending traffic to it.

Which NGINX version supports active health checks natively?

A NGINX Open Source

B NGINX Plus

C Both versions

D Neither version

Active health checks are a feature of NGINX Plus, the commercial version.

What type of request does an active health check usually send?

A A special test request like HTTP GET to a health endpoint

B A normal user request

C A database query

D A DNS lookup

Active health checks send special HTTP requests to a health endpoint to verify server status.

What is passive health checking based on?

A Server uptime logs

B Regular test requests sent by NGINX

C Manual server checks

D Monitoring real user traffic and errors

Passive health checks observe real traffic and mark servers unhealthy if errors occur.

Where do you configure health checks in NGINX?

A Inside the server block

B Inside the location block

C Inside the upstream block

D In the http block only

Health checks are configured inside the upstream block where backend servers are defined.

Explain how NGINX uses health checks to improve reliability.

Think about how NGINX decides which servers to send traffic to.

Describe how to configure a simple active health check in NGINX Plus.

Focus on the configuration syntax inside the upstream block.