The blog post advocates for a layered approach to structuring Go applications, emphasizing separation of concerns and dependency inversion. It proposes organizing code into distinct layers – domain, service, handler – with each layer depending only on the layers beneath it. The domain layer houses core business logic and entities, the service layer orchestrates domain operations and handles application-specific logic, and the handler layer interacts with external systems like databases and HTTP requests. This layered structure promotes testability, maintainability, and clearer understanding of the codebase by enforcing boundaries and reducing dependencies between different parts of the application. This approach differs from strictly hexagonal architecture, allowing the service layer to orchestrate domain logic, and focuses on practical application over strict adherence to architectural patterns.
This blog post, titled "Layered Design in Go," by Jerf, explores the effective application of layered architecture within Go projects. The author argues that while Go's package system offers a mechanism for organizing code, it doesn't inherently enforce the stricter separation and dependency rules that a true layered architecture demands. He emphasizes that layering is about managing dependencies to improve code maintainability, testability, and adaptability.
The post begins by defining layered architecture, explaining how each layer should only depend on the layers beneath it, never those above. This creates a clear hierarchy where higher layers utilize the services provided by lower layers, but lower layers remain unaware of the existence or functionalities of the layers above them. This unidirectional dependency flow is crucial for the benefits of layered architecture.
Jerf then delves into the practical implementation of this concept in Go, highlighting that simply using packages isn't enough. He advocates for a conscious and disciplined approach to structuring dependencies. He proposes using separate directories within the project to represent different layers, such as "presentation," "application," and "infrastructure." This physical separation reinforces the logical separation of concerns that layered architecture promotes.
Furthermore, the post discusses the complexities and nuances that can arise when implementing layered architecture, specifically addressing the handling of data transfer between layers. Jerf recommends using simple data structures, like structs, for inter-layer communication, rather than sharing complex objects directly. This avoids tight coupling and maintains the desired separation. He also touches upon the potential for code duplication when strictly adhering to layered design, suggesting that some duplication might be acceptable if it avoids compromising the architectural boundaries.
The author illustrates these concepts with a detailed example involving a hypothetical "bank account" service. He demonstrates how the various operations related to a bank account, like depositing or withdrawing funds, can be organized into different layers based on their responsibilities. This concrete example helps clarify the practical implications of the theoretical concepts discussed.
Finally, the post concludes by reiterating the importance of discipline and careful planning when implementing layered architecture in Go. It's not a silver bullet, but when applied correctly, it can significantly improve the overall structure, maintainability, and testability of a Go project by clearly defining dependencies and responsibilities within the codebase. The key takeaway is that developers need to go beyond simply using packages and actively enforce the dependency rules of layered design to reap its benefits.
Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=43740992
Hacker News users generally praised the article for its clear explanation of layered architecture in Go, particularly appreciating the focus on dependency inversion and the practical "domain" layer example. Some debated the merits of layered architecture in general, with a few suggesting alternative approaches like hexagonal architecture or Clean Architecture, noting potential drawbacks like increased boilerplate. A recurring theme was the importance of considering the project's complexity before adopting a layered approach, with simpler projects potentially not needing such strict structure. Others shared related experiences and alternative approaches to organizing Go code, highlighting the "package by feature" method and discussing the challenges of maintaining large, complex codebases. Several commenters also appreciated the author's clear and concise writing style.
The Hacker News post titled "Layered Design in Go" (linking to an article about the same topic) generated several comments discussing the merits and drawbacks of the layered architecture approach in Go, along with alternative suggestions and experiences.
Several commenters appreciate the clarity and simplicity presented in the article. One user found the article a helpful reminder of good software engineering principles, applicable beyond just Go. Another agreed with the author's focus on dependency inversion, highlighting its crucial role in building testable and maintainable software. The conciseness of the article was also praised.
A recurring theme in the comments is the discussion of alternative approaches to layered architecture, particularly hexagonal architecture (also known as ports and adapters). Commenters pointed out the benefits of hexagonal architecture in terms of decoupling business logic from external dependencies, ultimately improving testability and flexibility. Some argued that while layered architecture might be suitable for simpler projects, hexagonal architecture offers greater advantages for more complex applications.
A few comments also delved into the specifics of dependency injection in Go. One commenter suggested using a "wire" tool for compile-time dependency injection, while others discussed the pros and cons of using interfaces for dependency injection. A point was raised about the potential overhead of interfaces in Go and the consideration of using concrete types for dependencies in performance-sensitive scenarios.
The discussion also touched upon the trade-offs between strict layering and practicality. One commenter argued that rigid adherence to layered architecture can sometimes lead to unnecessary abstraction and complexity. The idea of allowing some controlled violation of layering for pragmatic reasons was also proposed.
A few commenters shared their own experiences with layered and hexagonal architectures, offering real-world examples of where each approach proved beneficial. These anecdotal comments provided valuable context to the more theoretical discussions.
Overall, the comments on Hacker News presented a balanced view of layered architecture in Go. While acknowledging its simplicity and usefulness in certain contexts, the commenters also highlighted potential limitations and explored alternative architectural patterns like hexagonal architecture. The discussion was constructive and insightful, offering practical advice and diverse perspectives on software design in Go.