Let's start with the app.yml file under src/main/docker, which can be found inside your gateway application.
As we saw at the beginning of this chapter, the file starts with the Docker version that it supports:
version: '2'
This is followed by the services section, where various services, applications, or components that we will kick start with this Docker Compose file are defined.
Under the services section, we have a name for the service – in our case, store-app – followed by the image that is used as the container. This image is generated with the help of JIB from our Gradle build.
This is followed by a series of environment variables that our application will depend on, including the following:
