Spring application properties (map) from docker environment - spring

Question

I would like to configure my dockerized spring boot application using Docker Environments. The property is a map, which I configure it in application.yml like below.
spring:
kafka:
producer:
properties:
"schema.registry.url": http://schema-registry.com:8081
I tried the following, but it didn't worked,
environment:
- SPRING_KAFKA_PRODUCER_PROPERTIES_SCHEMA.REGISTRY.URL=http://schema-registry.com:8081
How can I configure this schema.registry.url parameter from docker environment ?

Answer 1

Well, first of all, I would require a little bit more of information about how do you use that containerized application: Do you deploy it with docker-compose? Does it forms part of a Docker Swarm?
Depending of this, the possible solutions can vary.
Docker Swarm
For example, if you are using Docker Swarm, you can define your application.yml as a template:
application.yml.template
spring:
kafka:
producer:
properties:
"schema.registry.url": {{ env "schema_registry" }}
Then, you will have to parse that template. For that, I will suppose you have located your Spring Boot executable JAR under /usr/app in the container and that your image is named springboot-app.
docker-compose.yml
version: "3.8"
services:
springboot-app:
image: springboot-app:latest
environment:
SPRING_KAFKA_PRODUCER_PROPERTIES_SCHEMA.REGISTRY.URL: 'http://schema-registry.com:8081'
configs:
- source: springboot-app.application.yml
target: /usr/app/config/application.yaml
mode: 0440
configs:
springboot-app.application.yml:
template_driver: golang
file: ./application.yml.template
So you can deploy now your Swarm with docker stack deploy -c docker-compose.yml springboot-app.
Or even better, if you are working in a production environment, you can separate the environment variables from the common configuration:
docker-compose.yml
version: "3.8"
services:
springboot-app:
image: springboot-app:latest
configs:
- source: springboot-app.application.yml
target: /usr/app/config/application.yaml
mode: 0440
configs:
springboot-app.application.yml:
template_driver: golang
file: ./application.yml.template
docker-compose.dev.yml
version: "3.8"
services:
springboot-app:
environment:
SPRING_KAFKA_PRODUCER_PROPERTIES_SCHEMA.REGISTRY.URL: 'http://schema-registry.com:8081'
And deploy it as docker stack deploy -c docker-compose.yml -c docker-compose.dev.yml springboot-app.
Docker Compose
Since you mentioned in a lately comment that you are using docker-compose, the way of working with isn't the same.
First of all, not all the properties in Spring can be overridden in the Docker Compose file, only the ones that you can pass to Maven at the time of building or starting the application.
Also, it seems you have wrongly defined the environment Property, since normally all those that you provide you should change the dots '.' by underscores '_', but anyway, since normally the configuration of a Kafka Producer goes further than just defining an URL, I would use the profiles feature of Spring.
You can create several profiles with the configuration combinations that you want, and inform Spring via Compose which one you want to use. Let's see an example.
application.yml
spring:
config:
activate:
on-profile: "development"
kafka:
producer:
properties:
"schema.registry.url": https://kafka-dev-endpoint.com
---
spring:
config:
activate:
on-profile: "production"
kafka:
producer:
properties:
"schema.registry.url": https://kafka-prod-endpoint.com
and finally then:
docker-compose.yml
environment:
- SPRING_PROFILES_ACTIVE=development
If you wanna check further, you have more information about that here: https://docs.spring.io/spring-boot/docs/current/reference/html/howto.html#howto-set-active-spring-profiles