Gitlab Container Registry Deployment for M324

Overview

Created a multi-stage GitLab CI pipeline to automatically build and publish Docker images for three services used in the M324 project: the .NET backend, the Java backend, and the Ticket System service. This work removed the need for manual local builds and enabled faster, more consistent deployments.

Objectives

• Build Docker images for multiple services using GitLab CI
• Produce multi-architecture images (amd64 + arm64) using Docker buildx
• Tag images with a semantic version and with latest
• Push all generated images to the GitLab Container Registry
• Enable teams to pull and run prebuilt images directly without rebuilding

Pipeline Structure

Three build stages were added:

• build_dotnet
• build_java
• build_ticketsystem

Each stage uses the Docker-in-Docker service and buildx to produce multi-arch images.

Example: build_ticketsystem stage

build_ticketsystem:
  stage: build
  image: docker:24.0
  services:
    - docker:dind
  variables:
    DOCKER_HOST: "tcp://docker:2375"
  script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" "$DOCKER_REGISTRY"
    - docker buildx create --use
    - >
      docker buildx build --platform linux/amd64,linux/arm64 \
      -t "$DOCKER_REGISTRY/$DOCKER_REPOSITORY/ticketsystem:$SEMANTIC_VERSION" \
      -t "$DOCKER_REGISTRY/$DOCKER_REPOSITORY/ticketsystem:latest" \
      Code/ticketsystem --push

The Java and .NET stages use the same pattern, building from their respective directories.

Benefits

• No more manual local builds — images are always available prebuilt
• Multi-arch support ensures compatibility with x86 servers and ARM devices
• Consistent versioning through semantic version + latest
• Faster deployment since servers can pull prebuilt images immediately

Using the GitLab Container Registry

Login

docker login registry.gitlab.com

Use your GitLab username + Personal Access Token.

Pull an Image

Example for the .NET image:

docker pull registry.gitlab.com/tbz_git_projects/m324-devops-prozesse-mit-tools-unterstuetzen/m324-devops-g2/dotnet

Images can then be:

• Run locally using docker run
• Referenced directly in docker-compose.yml files

Summary

This pipeline adds automated multi-architecture builds, semantic versioning, and registry publishing for all core services in the M324 project — enabling faster deployments, cleaner workflows, and consistent environments across the team.