Summary of Understanding the Differences Between Modularity and Granularity - Mark Richards

Summary of "Understanding the Differences Between Modularity and Granularity" by Mark Richards

In this session, Mark Richards discusses the key differences between Modularity and Granularity in software architecture, emphasizing their implications for system design and implementation. He outlines the importance of understanding both concepts to effectively transition from monolithic systems to modular architectures, such as Microservices.

Main Ideas:

Definitions:
- Modularity: The practice of breaking systems into separate parts or modules, which can lead to distributed architectures.
- Granularity: The size of these parts or modules, which can significantly impact system performance and maintainability.
Key Quote: "Leverage Modularity but beware of Granularity," highlighting that while Modularity is beneficial, inappropriate Granularity can lead to problems.
Drivers for Modularity:
- Maintainability: Easier to locate and modify code within smaller modules compared to a large monolithic codebase.
- Testability: Smaller modules allow for more focused testing, leading to quicker identification of issues.
- Deployability: Smaller services can be deployed more frequently with less risk, allowing for agile responses to changes.
- Scalability: Modular systems can scale specific components as needed, rather than scaling the entire application.
- Availability: Fault tolerance is improved; if one service fails, others can continue to operate.
Approaches to Breaking Apart Systems:
- Component-Based Decomposition: Involves controlled iterative refactoring of components to form services, suitable for systems with well-defined architectural components.
- Tactical Forking: A faster approach where teams replicate the existing codebase and remove unnecessary parts, but may lead to messy code and dependencies.
Granularity Considerations:
- Disintegration Drivers: Factors that suggest a service should be broken apart, including functionality, code volatility, scalability, fault tolerance, and security.
- Integration Drivers: Factors that suggest keeping services together, such as transactional integrity, data dependencies, and orchestration requirements.
Best Practices:
- Start with coarser-grained services and refine them as more is learned about their functionality and interactions.
- Balance the need for Modularity with the challenges posed by Granularity to avoid operational issues.

Methodology/Instructions:

Assess the Need for Modularity:
- Identify the drivers (maintainability, testability, deployability, scalability, availability) to justify breaking apart a monolith.
Choose an Approach:
- Use Component-Based Decomposition if architectural components are well-defined.
- Use Tactical Forking for rapid development but be aware of potential code management issues.
Evaluate Granularity:
- Analyze the service's functionality, code volatility, scalability needs, fault tolerance, and security requirements.
- Consider both disintegration and integration drivers to determine the appropriate size for services.

Speakers/Sources Featured:

Mark Richards: The primary speaker and expert on software architecture.
Venkat Subramaniam: Mentioned as a speaker in the context of a humorous anecdote related to design discussions.

This session provides valuable insights into the architectural decisions involved in transitioning to modular systems and the careful consideration required to manage Granularity effectively.

Notable Quotes

— 03:48 — « That cat was right, this is a really bad design. »

— 07:56 — « I can ignore them and hope that somebody else fixes them. »

— 08:10 — « This is the problem in reality that occurs. »

— 26:56 — « Tactical forking says no, we are going to replicate the code and delete the stuff we don't need. »

— 39:50 — « The saving money piece is not a huge argument but it also depends on the type of deployment environment we're in. »