Brownfield Development Strategies

We're probably familiar with the book "Working Effectively with Legacy Code" by my friend Michael Feathers. This is a great book that explains how to keep legacy code running. But how do we handle re-architecting legacy applications? This presentation gives some valuable techniques to enable your rearchitecting efforts.

Transcript

1. BROWNFIELD DEVELOPMENT STRATEGIES Craig Berntson HealthEquity
2. Author - Continuous Integration in .NET - .NET Curry Technical Speaker - North America - Europe .NET Architect / Engineer - HealthEquity
3. TODAY’S AGENDA ❑ Define Brownfield ❑ Issues and challenges ❑ Traditional development ❑ Layering ❑ Modern approaches
4. BROWNFIELD vs GREENFIELD vs LEGACY Concern Greenfield Brownfield Legacy Project state Early development, new features New features and/or production maintenance Primarily maintenance. No new features Code maturity All code actively worked on Some new code; All code maintained for defects Little code developed except for defects Architectural review Reviewed and modified at all levels and times Only when significant changes requested Rarely if ever Practices and processes Developed as work progresses Mostly in place, but may not be working for the team/project Focused on critical defects Project team Newly formed Mix of old and new with fresh ideas and historical biases Very small, maintains status quo Unit Tests Close to 100% coverage May have some None
5. WHAT IS BROWNFIELD? Existing codebase Potential for improvement Contamination Brownfield Application Development in .NET
6. ISSUES YOU MAY ENCOUNTER ❑ Pain points ❑ Friction ❑ Challenge assumptions ❑ Client’s expectations ❑ Boss’s expectations ❑ Rewrite decisions
7. CHALLENGES ❑ Technical factors ❑ Political factors ❑ Team morale ❑ Client morale ❑ Management morale ❑ Agent for change
8. ECOSYSTEM ❑ Version control ❑ Continuous integration ❑ Automated testing ❑ Software metrics and code analysis ❑ Defect management
9. METHODOLOGY INDIVIDUALS AND INTERACTIONS WORKING SOFTWARE CUSTOMER COLLABORATION RESPONDING TO CHANGE
10. AGILE PRINCIPLES ❑ Satisfy the customer ❑ Welcome change requirements ❑ Deliver working software frequently ❑ Business people and developers work together ❑ Build projects around motivated people ❑ Face-to-face conversation ❑ Working software is primary measure of success ❑ Sustainable development ❑ Technical excellence ❑ Simplicity ❑ Self-organizing teams ❑ Reflect then tune and adjust
11. DEVELOPMENT TEAM ❑ Agile ❑ Cross-functional ❑ Keep it small ❑ Open-minded ❑ Passion to learn ❑ Empowered ❑ Failure is acceptable ❑ Work/Life balance ❑ Dedicated
12. DOS Windows Web Mobile Cloud
15. TIERS - PHYSICAL Presentation Tier Business Logic Tier Data Access Tier Database
16. LAYERS - LOGICAL Views Controllers Service Layer Domain Model Repository Layer Etc. Presentation Tier Business Logic Tier
17. ANTICORRUPTION LAYER ❑ Well defined contract ❑ Changes in one layer don’t affect calling code ❑ Expose only minimum required interface ❑ Decouples layers ❑ “Seams”
18. SEAMS User Interface Layer Service Layer Domain Model Repository Layer Seam Seam Seam
19. VERTICAL LAYERS Presentation Layer Presentation Validation Layer De/Serialization Layer Application Service Layer Logging Layer Data Access Translation Layer Data Interface Layer Data Access Layer Performance Monitoring Layer User Validation and Authorization Layer Exception & Error Handling Layer
20. Presentation Tier Domain Logic Tier Data Access Tier VERTICAL FUNCTIONALITY Customer Management Order Entry Inventory Management Invoicing
21. TRADITIONAL APPROACH – DATABASE CENTRIC User Interface Database
22. MODERN APPROACH – USER CENTRIC Database Domain User Experience User
23. Person’s perceptions and responses resulting from the use and or anticipated use of a product, system, or service - International Organization for Standardization (ISO)
24. UX HONEYCOMB Valuable Useful Desirable Accessible Credible Findable Usable http://semanticstudios.com/user_experience_desig
25. UX IS MORE THAN UI How screen is laid out Flow from textbox to textbox Flow from screen to screen Is data logically grouped Keyboard vs mouse navigation Verbiage, fonts, colors Whitespace Accessibility Sound
27. You should focus on the domain, rather that the database, the servers, and the programming language. - “Brownfield Application Development in .NET”
28. In a data-driven approach, the attributes of an object are discovered first and then responsibilities are meted out as a function of which object holds which data. A behavioral approach mandates the assignment of responsibilities first. Only when you are satisfied with the distribution of responsibilities among your objects are you ready to make a decision about what they need to know to fulfill those responsibilities and which parts of that knowledge they need to keep as part of their structure. - “Object Thinking”
29. Responsibilities are not functions, although there is a superficial resemblance. Perhaps the easiest way to differentiate between a responsibility and a function is to remember that the former reflects expectations in the domain – the problem space – while the latter reflects an implementation detail in the solution space – the computer program. - “Object Thinking”
30. User Interface Database Database Domain User Experience User TRADITIONAL vs MODERN
31. DOMAIN DRIVEN User Interface Layer Service Layer Domain Layer Repository Layer Seam Seam Seam
32. SUB-DOMAINS Product Database Order Entry Inventory Management • Sale price • Item ID • Manufacturer • Description • Order Quantity • Item ID • Manufacturer / Reseller • In-stock Quantity • Reorder Quantity • Lead time
34. MICROSERVICES Order Entry Address Verification Shipping Calculator
35. MICROSERVICES ADVANTAGES ❑ Small, defined functionality ❑ Web API & JSON ❑ Less chance of introducing bugs ❑ Called asynchronously ❑ Easy to deploy ❑ Accessible to entire enterprise / application
36. SERVERLESS ❑ You don’t allocate server ❑ Small units of code ❑ Cloud infrastructure handles scaling automatically ❑ Azure Functions / AWS Lambdas ❑ Best used for glue code vs. business code
37. Web UI External Interfaces DB Controllers Use Cases Entities Enterprise Business Rules Application Business Rules Interface Adapters Frameworks & Drivers
38. REVIEW ❑ Define Brownfield ❑ Issues and challenges ❑ Traditional development ❑ Layering ❑ Modern approaches
39. CONTACT / QUESTIONS cberntson@healthequity.com @craigber www.dotnetcurry.com www.speakerdeck.com/craigber