app.yaml vs appengine-web.xml which one to use?

Question

I am using Google App Engine flexible to deploy my spring boot app. I see the configuration can be specified by app.yaml or appengine-web.xml. However, my questions are,

1. Which configuration file should I use for the Spring boot app, yaml or xml?
2. If xml, should I create web/WEB-INF/ folder and place the appengine-web.xml under that?
3. Also, if xml how to specify the "flex" environment choice (via which property) in the xml?

Thanks in advance.

Answer 1

You need to use both files.

The app.yaml file covers configurations applicable to all flexible environment apps/services, regardless of the language they're written in, like:

• the flex environment and other General settings
• Network settings
• Health checks
• Service scaling settings

The web.xml config file has a very specific coverage, which doesn't overlap the app.yaml file's coverage:

The web.xml file is only used when deploying a Java app to a runtime that includes the Jetty9/servlet3 server. For more details, see the Java 8 / Jetty 9.3 Runtime.

As for your #2 question, you may have been looking at the standard env docs (check the docs/standard or docs/flexible strings in the doc's URL). From web.xml:

This file is named web.xml, and resides in the app's WAR under the WEB-INF/ directory. web.xml is part of the servlet standard for web applications.