Allow configuration of container host via Spring Boot property (e.g. spring.docker.compose.host)

[julien92]

Context

We are currently migrating our GitHub Actions CI pipeline from GitHub-hosted runners to self-hosted
runners that run as pods inside our Kubernetes infrastructure.

We use spring-boot-docker-compose (introduced in Spring Boot 3.1) as part of our pipeline to
manage application containers.

However, our environment is a Docker-in-Docker (DinD) setup. This means the services launched by
docker-compose are not accessible via localhost, but only through the Docker bridge IP (
172.17.0.1, for example).

Currently, spring-boot-docker-compose assumes services are reachable on localhost, and has no
mechanism to distinguish between:

• Docker on local VM (e.g., Docker Desktop or normal Docker engine)
• Docker-in-Docker (common in CI/CD or Kubernetes runners)

This leads to connection issues in pipelines when services are not reachable via localhost.

Proposal

We propose that spring-boot-docker-compose supports a new Spring Boot property to explicitly
define the service host IP that Spring Boot should use when accessing the container from outside.

For example:

spring:
  docker:
    compose:
      host: 172.17.0.1

This would let users explicitly tell Spring Boot what host to use when generating dynamic service
URLs, particularly in CI/CD environments where assumptions about localhost do not hold.

This approach allows the property to be overridden using:

• Spring profiles (e.g., application-ci.yaml)
• Environment variables (e.g., SPRING_DOCKER_COMPOSE_HOST=172.17.0.1)
• Command line arguments (e.g., --spring.docker.compose.host=172.17.0.1)

Benefits

• Works seamlessly in Docker-in-Docker environments.
• Avoids hardcoding workaround logic in build scripts or dynamic property sources.
• Keeps docker-compose.yml clean and environment-agnostic.
• Improves compatibility with pipelines that use Spring Boot Docker Compose support.

Thank you for considering this improvement.