How to Deploy Micronoaut on Platform.sh with JPA
Contents:
To activate JPA and then have it accessed by the Micronoaut application already configured for Platform.sh, it is necessary to modify two files.
Note:
This guide only covers the addition of a service configuration to an existing Micronoaut project already configured to deploy on Platform.sh. Please see the deployment guide for more detailed instructions for setting up app containers and initial projects.
1. Add a SQL database service 
In your service configuration, include a SQL database service. Make sure to visit the documentation for that service to find a valid version. For PostgreSQL that would look like:
dbpostgres:
type: postgresql:13
disk: 2562. Grant access to the service through a relationship
To access the new service, set a relationship in your app configuration.
relationships:
postgresdatabase: "dbpostgres:postgresql"3. Export connection credentials to the environment
Connection credentials for services are exposed to the application container through the PLATFORM_RELATIONSHIPS environment variable from the deploy hook onward. Since this variable is a base64 encoded JSON object of all of your project’s services, you’ll likely want a clean way to extract the information specific to the databse into it’s own environment variables that can be easily used by Micronaut. On Platform.sh, custom environment variables can be defined programmatically in a .environment file using jq to do just that:
export JDBC_HOST=`echo $PLATFORM_RELATIONSHIPS|base64 -d|jq -r ".database[0].host"`
export JDBC_PORT=`echo $PLATFORM_RELATIONSHIPS|base64 -d|jq -r ".database[0].port"`
export DATABASE=`echo $PLATFORM_RELATIONSHIPS|base64 -d|jq -r ".database[0].path"`
export DATASOURCES_DEFAULT_PASSWORD=`echo $PLATFORM_RELATIONSHIPS|base64 -d|jq -r ".database[0].password"`
export DATASOURCES_DEFAULT_USERNAME=`echo $PLATFORM_RELATIONSHIPS|base64 -d|jq -r ".database[0].username"`
export DATASOURCES_DEFAULT_URL=jdbc:postgresql://${JDBC_HOST}:${JDBC_PORT}/${DATABASE}
export JAVA_OPTS="-Xmx$(jq .info.limits.memory /run/config.json)m -XX:+ExitOnOutOfMemoryError"
Tip:
Environment variable names are following the conversion rules of the Micronaut Documentation.
4. Connect to the service
Commit that code and push. The specified cluster will now always point to the PostgreSQL or any SQL service that you wish.