Design principles and patterns for creating composable software components

Design principles for composable software components

Software design principles are abstract principles, advice, and guidelines that help you create better software. This section discusses the guiding principles that help you design complex software effectively, reduce the risk of errors, and improve our product’s maintainability, scalability, and adaptability.

Separation of concerns

The separation of concerns is one of the fundamental principles in software development and design. This principle, likely coined by Edsger W. Dijkstra in his 1974 paper “On the role of scientific thought,” illustrates how to manage complexities by separating the software system into distinct sections, ensuring that each section is responsible for a separate concern.

The separation principle generally states that you should avoid overlapping concerns in a design or code. Mia-Platform excels at separation of concerns by providing packaged business capabilities (PBC) that handle specific business concerns. This modular approach enhances code maintainability and promotes collaboration among development teams.

There are different techniques for achieving effective separation. We’ve listed a few below:

• Module-based design groups related concerns into separate modules with a well-defined interface.
• Data encapsulation hides the internal implementation of modules, exposing only their public interface.
• Dependency injection makes implicit dependencies explicit, providing the receiving object or function with its dependencies by external code (an “injector”), which it’s not aware of.
• Abstraction uses abstract interfaces to hide the concrete implementation of modules.

Abstraction

Designing composable and maintainable software components requires a strong understanding of abstraction. By concealing unnecessary complexities from the developers, abstraction simplifies component interactions and reduces the cognitive load on the developers. It provides users with well-defined and easy-to-use interfaces that they can build on without worrying about the intricacies.

For example, in file systems, users interact with files and directories through abstracted functions like open() and read() without understanding the intricate details of disk management. Abstraction promotes reusability, making it easier to compose and maintain complex software systems by providing a clean separation between what a component does and how it accomplishes it, simplifying interactions in the process.

Loose coupling

In computing and systems design, a loosely coupled system is one in which the components are independent or detached. Changes to one component do not affect other components, which makes the system more flexible and easier to maintain, ultimately promoting composability.

You can minimize coupling between components by doing the following:

• Use well-defined interfaces: Each component should expose a well-defined interface with which other components can interact. The interface should define the methods and properties that the component provides, but it should not reveal the implementation details of the component.
• Avoid sharing state: When possible, avoid sharing state between components. This autonomy among components enhances their reliability and promotes a more predictable and maintainable system.
• Use dependency injection: Dependency injection is a technique that allows you to pass dependencies into components at runtime. This lets you to decouple the components from their dependencies, making them more testable and maintainable.

Cohesion

Cohesion measures how strongly elements within a module work together to fulfill a single well-defined purpose. In highly cohesive systems, the elements have a great relationship with each other and are focused on a single goal, while low cohesion in systems means that the elements are loosely related and serve multiple purposes. A system’s level of cohesiveness is directly proportional to its software quality.

To improve the cohesiveness of a software system, you can take the following actions:

• Split the software system into smaller, more manageable units of functionality, design, and reuse;
• Apply design principles and standards that ensure consistency and compatibility throughout the system;
• Refactor and review the code to improve its design and structure.

Completeness

When components are considered complete, they encapsulate all the functionality and features required to perform their designated task or fulfill their intended purpose within a system. This autonomy enhances the component’s predictability, making it less likely to cause unexpected issues in the system.

To ensure completeness, you must define specifications stating the component’s purpose, inputs, outputs, and expected behavior. Additionally, reducing external dependencies, implementing robust error handling, and using modular design principles contribute to more complete components.

Best practices for creating composable software components

Composable software components facilitate the creation of flexible and adaptable systems. By following best practices and adhering to well-defined golden paths, organizations can take advantage of the benefits of composability. Here are some of these best practices:

• Use a component-based design approach: Break down systems into smaller, independent components that can quickly be composed and reused, making the systems modular, flexible, and maintainable.
• Use standard interfaces: Standard interfaces promote interoperability and streamline the integration of components into larger systems. The interfaces also make it easier for developers to understand and work with the components as they’ve likely encountered them before.
• Write comprehensive documentation: As with any system, comprehensive documentation ensures that people can effectively understand and use our software components. The documentation should include information about the component, its intended purpose, inputs, expected outputs, and how to interact.
• Test your components thoroughly: Testing each component can help identify and resolve defects or errors before integrating with other components. This helps minimize the risk of system failure and ensures the software system is reliable and efficient.

Patterns for orchestrating and assembling composable software components

It is imperative to adhere to the following patterns to achieve seamless creation and integration of composable software components:

Saga Orchestration

A saga is a sequence of transactions in which each transaction updates data within a service. There are mainly two ways of handling sagas, namely the choreographic approach, and the orchestration approach; both are analyzed in detail in this article.

Specifically, the orchestration approach involves a central component that manages the flow of the entire saga through commands to every other component; hence the term orchestrator. This approach facilitates the addition and removal of components that make up the saga, as it is sufficient to update the central orchestrator, without having to intervene directly on the other components as well. Mia-Platorm has developed and refined over the years a sagas orchestrator called Flow Manager: read the introductory blog post and documentation for further details.

Event-driven architecture

Event-driven architecture (EDA) refers to a system of loosely coupled microservices that exchange information between each other through the production and consumption of events. EDA makes it possible to exchange information in real-time or near real-time.

Event-driven architecture is mainly realized through the publish/subscribe (pub/sub) message queue. This flexible messaging pattern is used in distributed systems for asynchronous communication between components or services.

Microservices architecture

Microservice architecture, also known as microservices, is an architectural style that allows a large application to be separated into smaller independent parts that communicate over well-defined APIs. By promoting composability and reusability, microservices make it faster to develop applications and easier to scale.

Best practices involved in developing composable microservices include the following:

• Define clear boundaries between services.
• Design robust and versioned APIs for each service.
• Manage data independently for each service.
• Implement error handling and resilience strategies for each service.
• Prioritize scalability and performance for each service.
• Monitor, log, and secure each service.
• Document each service thoroughly.

API Composition

API composition is a high-level pattern to query microservices. It involves integrating and combining multiple APIs to create new functionalities or services. This approach enables software developers to leverage existing APIs as building blocks, promoting flexibility and rapid development.

Consider a scenario where we want to build a location-based service. We can compose APIs from different providers to achieve this. For example, we might combine Google Maps’ geocoding API for address-to-coordinates conversion with a weather service API for weather information at a specific location. This composition allows you to create a comprehensive, location-aware application.

Microfrontend Composition

Similar to how backend-side microservices work, frontend applications can also be unpacked into smaller, reusable and composable components. These components are known as microfrontends.
A comprehensive and innovative solution that addresses this need is Mia‑Platform Microfrontend Composer, a product that provides both no-code functionality and full editing capabilities for creating frontend applications. Underlying this product is micro-lc, the open source microfrontend orchestrator developed and maintained by Mia-Platform.

Case studies of successful composable software architectures

Composable architecture is revolutionizing the way we deliver software. Many successful companies have recognized the value of composability and reusability and have begun to adapt composable software architectures. This section discusses examples of a successful composable software architecture.

Netflix

Netflix uses composable architecture to power its streaming services. By adopting a microservice-based approach, this streaming service offers a seamless experience while continuously evolving its service.

• Leveraging the superpower of modularity, Netflix can independently create, deploy, and scale services to meet fluctuating user demands without affecting the overall user experience of the application.
• Composable architecture allows Netflix to reuse existing components to create new features and functionalities, accelerating innovation.

Shopify

Shopify’s adoption of a composable architecture approach catalyzed its remarkable success. However, composable commerce applications are significantly more complex than traditional monolithic applications for some of the following reasons:

• Complexity: Composability leads to complex workflows because integrating different components with different interfaces and data formats can be challenging to design and manage. Organizations like Shopify implement robust data governance frameworks that include standardized data formats and processing workflows to deal with this challenge.
• Testing and QA: Composable applications comprise various components developed by diverse teams, introducing complexity in predicting, testing, and verifying how well these parts will work together. To overcome this challenge, Shopify uses rigorous testing and QA practices. These practices include test automation, continuous integration, and delivery (CI/CD).
• Customization complexity: Shopify serves a diverse range of businesses, each with unique customization requirements, which can be complex to implement. To mitigate this issue, Shopify encourages developers to create custom applications, themes, and integrations through its robust partner ecosystem and API-driven development. This approach allows businesses to tailor their stores to their needs while leveraging the platform’s core capabilities.

The future of composable software development

Gartner’s projection that 60% of new custom business applications will be built using reusable components by 2025 reinforces the idea that composable applications are the future of software development. So, what are the trends to watch in this space?

• Low-code and no-code development: Low-code and no-code platforms make it easier for developers at any skill level to create, contribute, and deploy composable applications.
• Artificial intelligence (AI) and machine learning (ML): AI and ML technologies enable applications to learn, adapt, and provide more personalized and intelligent user experiences.
• Serverless computing: Serverless computing is becoming popular in composable software development, abstracting server management and allowing developers to focus on code, reducing overhead and enhancing scalability.

Preparing teams for the future of composable software development

To ensure our teams are ready for the future of composable software development, you should do the following:

• Invest in a multifaceted approach that prioritizes continuous learning and skill development through accessible training and resources;
• Leverage solutions like Mia-Platform to ease the transition to a more composable architecture;
• Cultivate a culture of innovation, adaptability, and collaboration by encouraging team members to explore new technologies and work cohesively.

Additionally, staying updated on industry trends and emerging technologies ensures your organization remains competitive in this ever-evolving landscape.

Summing it up

As the software development landscape evolves, it becomes imperative that we build modular and adaptable software to accelerate innovation and software delivery. This article draws from real-life examples and case studies to teach us some of the best practices, principles, and patterns that are the foundation for designing composable and scalable software.

Additionally, organizations can take advantage of Mia-Platform’s reusable and ready-to-use components to accelerate their software delivery process. Check out this white paper to understand more about what composable software can do for our future.