SpringOne Platform 2017 David Julia, Pivotal; Simon P Duffy, Pivotal "The scene: A complex procedure cost estimation system with hundreds of unknown business rules hidden in a monolithic application. A rewrite is started. If our system gives an incorrect result, the company is financially on the hook. A QA team demanding month-long feature freezes for testing. A looming deadline to cut over to the new system with severe financial penalties for missing the date. Tension is high. The business is nervous, and the team isn’t confident that it can replace the system without introducing costly bugs. Does that powder-keg of a project sound familiar? Enter Project X: At a pivotal moment in the project, the team changed their approach. They’d implement a unique, data-driven variation of the strangler pattern. They’d run their system in production alongside the legacy system, while collecting data on their system’s accuracy, falling back to the legacy system when answers differed. True to Lean Software development, they would amplify learning and use data to drive their product decisions. The end result: An outstanding success. Happy stakeholders, business buy-in to release at will, a vastly reduced QA budget, reusable microservices, and one heck of a Concourse continuous delivery pipeline. We achieved all of this, while providing a system that was provably better than the legacy subsystem we replaced. This talk will appeal to engineers, managers, and product managers. Join us for a 30 minute session where we review this case study and learn how you too can: Build statistically significant confidence in your system with data-driven testing Strangle the Monolith safely Take a Lean approach to legacy rewrites Validate your system’s accuracy when you don’t know the legacy business rules Leverage Continuous Delivery in a Legacy Environment Get Business and QA buy-in for Continuous Delivery Articulate the business value of data-driven product decisions"

1. A Data Driven Approach
Dec 6, 2017
Simon Duffy, Staff Product Manager | Pivotal Labs
David Julia, Director | Pivotal Labs

4. Additional business features
Cost Estimator for medical procedures
Financial Penalties for inaccurate estimations

5. 3rd Party Web UI
Monolith
Source
System 1
Source
System 2
Source
System 3
… Source
System N

6. Main Member-Facing
Web UI
Account
Customization
Member Store
Secure Messages
...etc.
Member Liability
Estimator SOAP
Service Component
Source System
1
Source System
2
Source System
3
… Source
System N

7. Main Member-Facing
Web UI
Account
Customization
Member Store
Secure Messages
...etc.
Member Liability
Estimator SOAP
Service Component
Source System
1
Source System
2
Source System
3
… Source
System N

9. The expert leads the way

10. Complex flows create anxiety

11. External QA test team with competing priorities
Generating mocks and test cases is time consuming
Testing is not Production. Period.

13. ♥
Strangler Fig Hollow Inside of Strangler Fig

17. +
=
☺

18. 3rd Party Web UI
Monolith
Source
System 1
Source
System 2
Source
System 3
Project X
3rd Party Web UI
1 week

20. 3rd Party Web UI
Monolith
Source
System 1
Source
System 2
Source
System 3
Project X
3rd Party Web UI
Monolith
Source System
1
Source System
2
Source System
3
Project X
Calculation Module
2 weeks

21. Web App UI
Monolith
Source System
1
Source System
2
Source System
3
Project X
Calculation Module
3 weeks

24. ✖ ✖

26. Web App UI
Monolith
Source System
1
Source System
2
Source System
3
Project X
Calculation Module
4 weeks

27. Web App UI
Monolith
Project X
Calculation Module
Source System
1
Source System
2
Source System
3
5 weeks

30. Project X
3rd Party Web UI
Source System
1
Source System
2
Source System
3
Project X
Calculation Module
13 weeks

33. V100
Project X
Calculation
Module
Production
Baseline
Extractor
Extract
v100
15 weeks

34. Build & Test
Deploy to
Staging
Baseline
Variance Test
Deploy to Prod
Take New
Baseline

35. Build & Test
Deploy to
Staging
Baseline
Variance
Test
Deploy to
Prod
Take New
Baseline
V101
Project X
Calculation
Module
v100
Baseline
Variance
Test
Staging

38. Build integrity in -> Continuous delivery
You can’t always analyze a problem before acting.... Accept it and lean in!
Value based business metrics > team activity metrics
Automated testing can include “What’s the business impact?”
Pragmatism > perfection, especially in rewrites/app modernization

40. Consumer
Legacy System
Proxy
New System

41. Consumer request
Execute legacy app Execute new app
Route
old or
new

42. You want to decompose a system, and you know the logic inside it.
OR
You can redefine the business rules in the new system that you are writing.
This is probably lower cost!

43. Consumer request
Execute new app
Log request
Orchestrate calls to
old and new
Log responses
Execute legacy app
Analyse results

44. You want to decompose a system, and don’t know the logic inside it.
AND
The output of your new system ought to match the monolith.