Add information on required mapping of /

[ryanmcfall]

What can we improve?

In chapter 5, the book talks about deploying a Spring Boot app using CDK and uses the authors' Todo app as a sample. I wanted to try this but use my own app in place of the Todo app. So I replaced the URL to the docker image and tried to build / deploy.

It look me a long time to discover that the load balancing service periodically checks the health of the deployed app by accessing the URL /, and that if this fails enough times, the deployment fails. My app didn't have a mapping for this URL. Once I added it, deployment was smooth.

Version

1.12

Suggested Changes

Add a note about the requirement for the root URL to be mapped by the application being deployed. This probably also belongs in the chapter 1 example that uses CloudFormation directly as well.

[rieckpil]

Thanks for this finding, we'll adjust the book 👍

[rieckpil]

That's indeed not optimal, what I would suggest is to map the health check to the Actuator endpoint (/actuator/health or info) to have it consistent across all apps.