An overview of a domain-driven CI/CD design pattern

DDD constitutes a software design approach that endeavors to develop software systems that are capable of accurately reflecting the complexities of a particular domain. This approach is predicated on the invaluable input of domain experts, who possess a profound understanding of the unique intricacies and challenges of the domain in question. The comprehensive nature of this approach is instrumental in the development of software systems that are optimally suited to meet the needs of the domain.

In essence, DDD emphasizes organizing code in a manner that aligns with business problems and uniformly uses the same business terms or ubiquitous language throughout the development process. This approach to software development enables developers to build solutions that accurately represent the business domain and support effective communication between technical and non-technical stakeholders.

When utilizing DDD in building applications, problems are described as domains, while independent problem areas are referred to as bounded contexts. Each of them correlates to a microservice and it relates to a common language to discuss these problems. By using the correlation between a microservice and its bounded context, it becomes easier for developers to identify and define the entities, value objects, and aggregates that model the domain. The following figure represents a bounded context in CI/CD:

Figure 8.1 – A bounded context in several stages of CI/CD

This diagram captures the essence of a domain-driven CI/CD design pattern:

• Domain layer: Represents DDD concepts such as ubiquitous language, a shared kernel, and bounded contexts
• CI layer: Encompasses the CI stages, from static analysis to the creation of deployable artifacts
• CD layer: Encompasses the continuous deployment stages, including configuration, environment provisioning, system tests, and release to production

Furthermore, DDD patterns help developers understand the complexity of the domain, which is instrumental in developing a domain model for each bounded context. The domain model provides a clear picture of the domain, and this makes it easier to manage the deployment of individual microservices. Each bounded context can be developed, tested, and deployed independently, which aligns well with the principles of CI/CD.

Some of the benefits of using a domain-driven CI/CD design pattern are as follows:

• It improves communication and collaboration between developers, domain experts, and stakeholders by using a common language and shared understanding of the domain.
• It reduces software’s complexity and technical debt by focusing on the core domain and its logic, avoiding unnecessary dependencies and coupling between different domains or bounded contexts.
• It increases software’s quality and reliability by applying DDD patterns and practices, such as entities, value objects, aggregates, domain services, domain events, and repositories, to code and tests.
• It enables faster and safer software delivery by automating the CI/CD pipeline and using domain-specific tools and techniques, such as feature toggles, canary releases, blue-green deployments, and chaos engineering.
• Scalability can help align CI/CD processes with domain boundaries, so it becomes easier to scale individual components independently. This approach allows teams to focus on specific domains, making it simpler to manage and scale services as needed without affecting an entire system.
• Domain-driven CI/CD design patterns emphasize clear separation of concerns and well-defined boundaries. This approach simplifies the identification and resolution of issues within specific domains, leading to more efficient troubleshooting and enhanced maintenance. Additionally, it fosters better collaboration among teams, as each team can work within its domain without conflicting with other parts of a system.

A domain-driven CI/CD design pattern is not a prescriptive or rigid methodology but, rather, a flexible and adaptable approach that can be applied to different domains and scenarios. It requires close collaboration between the technical and domain teams, as well as a continuous feedback loop to refine the domain model and the delivery process.

However, it’s essential to note that DDD should only be applied when implementing complex microservices with significant business rules. Simpler responsibilities such as CRUD (Create, Read, Update, and Delete) services can be managed with simpler approaches. Although DDD provides benefits such as maintainability, it is recommended only for complex domains where the model provides clear benefits in formulating a common understanding of the domain.

In the next section, we will take a look at the challenges of implementing regulations in CI/CD pipelines, based on the DDD patterns.