SOA-C03 practice question: Load balancer and Route 53 health checks (1 of 2)

Reliability and Business Continuity A free question from our original SOA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.

A dental chain moved its patient portal behind an Application Load Balancer.

The target group uses the default health check settings with the path /. The application sends unauthenticated requests to / a 302 redirect to /login.

Every target is marked unhealthy, and the ALB access logs show the health check requests arriving at the instances.

What should a CloudOps engineer do so that healthy targets are reported correctly?

Choose one answer.

A. Raise the healthy threshold count and the health check interval so that targets have more time to answer the checks.
B. Allow inbound traffic from the load balancer's security group in the instances' security group on the application port.
C. Change the health check protocol to TCP so that the load balancer only checks that the application port is open.
D. Change the health check path to a lightweight page, such as /health, that returns HTTP 200.

Show the answer and explanation

Answer: D

A. Wrong: The targets answer quickly, but with a 302 that does not match the success codes. More time or more checks would still produce unhealthy results. Learn more: Health checks for Application Load Balancer target groups (opens in a new tab)
B. Wrong: The access logs show the requests reaching the instances, so the network path already works. The responses fail the health check because of their status code. Learn more: Security groups for your Application Load Balancer (opens in a new tab)
C. Wrong: Application Load Balancer target groups support only HTTP and HTTPS health checks. TCP health checks are available for Network Load Balancer target groups. Learn more: Health checks for Application Load Balancer target groups (opens in a new tab)
D. Right: Correct. ALB health checks expect the configured success codes, which default to 200. A dedicated health page that returns 200 lets the load balancer see healthy targets, and the success codes could also be changed to include 302. Learn more: Health checks for Application Load Balancer target groups (opens in a new tab)

Explanation

An ALB marks a target healthy only when the health check response code matches the success codes, which default to 200. A redirect on the health check path fails every check even though the application works. Pointing the check at a page that returns 200, or adding 302 to the success codes, fixes it.

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Health checks for Application Load Balancer target groups

SOA-C03 practice question: Load balancer and Route 53 health checks (1 of 2)

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