How to Deploy Micronaut on Platform.sh with MongoDB

To activate MongoDB and then have it accessed by the Micronaut application already in Platform.sh, it is necessary to modify two files.

1. Add the MongoDB service 

In your service configuration, include MongoDB with a valid supported version:

dbmongo:
    type: mongodb:3.6
    disk: 512

2. Grant access to MongoDb through a relationship 

In your app configuration, use the service name dbmongo to grant the application access to MongoDB via a relationship:

.platform.app.yaml
relationships:
    mongodatabase: "dbmongo:mongodb"

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 database into it’s own environment variables that can be used by Micronaut. On Platform.sh, custom environment variables can be defined programmatically in a .environment file using jq to do just that:

export MONGO_PORT=`echo $PLATFORM_RELATIONSHIPS|base64 -d|json_pp|jq -r ".mongodb[0].port"`
export MONGO_HOST=`echo $PLATFORM_RELATIONSHIPS|base64 -d|json_pp|jq -r ".mongodb[0].host"`
export MONGO_PASSWORD=`echo $PLATFORM_RELATIONSHIPS|base64 -d|json_pp|jq -r ".mongodb[0].password"`
export MONGO_USER=`echo $PLATFORM_RELATIONSHIPS|base64 -d|json_pp|jq -r ".mongodb[0].username"`
export MONGO_DATABASE=`echo $PLATFORM_RELATIONSHIPS|base64 -d|json_pp|jq -r ".mongodb[0].path"`
export MONGO_URL=mongodb://${MONGO_USER}:${MONGO_PASSWORD}@${MONGO_HOST}:${MONGO_PORT}/${MONGO_DATABASE}
export JAVA_OPTS="-Xmx$(jq .info.limits.memory /run/config.json)m -XX:+ExitOnOutOfMemoryError"

4. Connect to the service 

Commit that code and push. The application is ready and connected to a MongoDB instance.