Introduction

Microservice architecture is an approach to designing an application as independent, small services. Each service performs a specific function and can be scaled, developed, and deployed independently. This feature makes microservice architecture particularly ideal for dynamic and fast-growing applications such as e-commerce platforms. The ability to develop, test, and deploy each service independently speeds up software development processes, simplifies scaling, and reduces integration errors.

In this article, we will explore how multiple microservices can be managed under a centralized structure using GitLab Submodules, how it can streamline CI/CD processes, and how teams can work efficiently on large projects.

1. Microservice Architecture and Management Challenges

While microservice architecture offers significant advantages, it also presents some management challenges:

• Independent Services and Management Challenges: Each microservice is developed and managed independently, which can complicate integration between services.
• Managing Dependencies: Dependencies between services can become complex, making updates more difficult.
• Code Duplication and Inconsistencies: Without a centralized place for shared components, code duplication and inconsistencies can occur.
• Team Collaboration: Working on different microservices by different teams can be challenging without a centralized management structure.

GitLab Submodules provide an effective solution to overcome these challenges. By using submodules, independent microservices can be managed under a central repository, and dependencies between services can be organized.

2. What is GitLab Submodules and How Does It Work?

GitLab Submodules is a feature that allows you to add another Git repository as a submodule within your Git repository. This feature helps create a structure where independent microservices are grouped under a central repository.

Basic Git Submodule Commands:

1. Adding a submodule:

git submodule add https://gitlab.com/my-projects/catalog-service.git services/catalog-service

2. Cloning the submodule:

git clone --recurse-submodules

3. Updating the submodule:

git submodule update --remote --merge

4. Removing a submodule:

git submodule deinit -f
git rm -f
rm -rf .git/modules/

3. Using GitLab Submodules in Your Microservice Architecture

3.1 Architectural Structure

Here’s an example directory structure for a microservice architecture using GitLab Submodules:

ecommerce-platform/
│── services/
│ ├── catalog-service/ (Git Submodule)
│ ├── category-service/ (Git Submodule)
│ ├── order-service/ (Git Submodule)
│── shared-libraries/ (Git Submodule)
│── .gitmodules
│── docker-compose.yml
│── README.md

Each microservice is added as a submodule, which can be developed and updated independently. The central repository manages the dependencies for all microservices.

3.2 Managing Microservices with Submodules

• Independent Development: Each microservice is developed independently as its own submodule.
• Centralized Management: The central repository manages the dependencies and integration of services.
• Independent CI/CD: Each service can have its own CI/CD pipeline.

4. Using Submodules in GitLab CI/CD Pipelines

4.1 GitLab CI/CD Pipeline Structure

GitLab CI/CD can be configured to automatically build, test, and deploy projects that contain submodules. You can add the following commands to your .gitlab-ci.yml file:

stages:
- build
- test
- deploy
before_script:
- git submodule update --init --recursive
build:
stage: build
script:
- cd services/catalog-service
- dotnet build
test:
stage: test
script:
- cd services/category-service
- dotnet test
deploy:
stage: deploy
script:
- docker-compose up -d

4.2 Using Docker with Submodules

To run microservices with submodules on Docker, the following commands can be used in the Dockerfile:

FROM mcr.microsoft.com/dotnet/aspnet:8.0
WORKDIR /app
COPY . .
RUN git submodule update --init --recursive
RUN dotnet restore
RUN dotnet publish -c Release -o out
ENTRYPOINT ["dotnet", "MyService.dll"]

In the docker-compose.yml file, each microservice can be defined with its own container:

version: '3.4'
services:
gateway:
build:
context: ./gateway-service
ports:
- "5000:5000"
catalog:
build:
context: ./services/catalog-service
ports:
- "5001:5001"

5. Team Management and Version Control

5.1 Team Management

GitLab Submodules allow teams to work independently on different microservices. The central repository ensures that all services work in harmony.

5.2 Version Control

Each microservice can have its own version control. Submodules are pinned to specific commits, ensuring that each service’s version is controlled. This reduces the risk of incompatibility between services and makes version transitions more manageable.

git submodule update --remote --merge

6. Alternative Methods and Comparison

There are various repository management strategies for microservice architecture:

GitLab Submodules offer a balance between monorepo and polyrepo. With submodules, microservices can be managed independently, while a central repository manages the dependencies.

Conclusion

GitLab Submodules provides an efficient solution for managing microservices in a centralized manner, making it an excellent choice for large projects. With this approach:

• Independent development and a modular structure are achieved.
• CI/CD processes become more modular and efficient.
• Team collaboration becomes easier.

Offering a powerful alternative between monorepo and independent repository management, Submodules enable more efficient management of microservices, especially in large-scale projects, by reducing management complexity and allowing independent teams to work more effectively.

This approach provides a flexible and universally applicable management solution for microservices architectures. The advantages of GitLab Submodules can be adapted to various microservice structures, offering efficient solutions tailored to specific needs.