Refactor And Do It Safely - Jakub Pilimon
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Refactor And Do It Safely by Jakub Pilimon at SpringOne Tour 2019
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Refactor And Do It Safely - Jakub Pilimon
- 1. JakubPilimon Refactor And Do It Safely Jakub Pilimon
- 3. JakubPilimon Jakub Pilimon Principal Technologist @Pivotal •Domain-Driven Design •Test-Driven Development •Architecture •Spring pillopl.github.io #dddbyexamples https://github.com/ddd-by-examples JakubPilimon
- 4. JakubPilimon WHAT THIS TALK IS NOT ABOUT
- 5. JakubPilimon
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- 7. JakubPilimon BIG BALL OF MUD
- 12. JakubPilimon IS THERE ANY BUSINESS VALUE LOST?
- 13. JakubPilimon OUR JOB AS ENGINEERS IS BRINGING VALUE, NOT JUST SATISFYING OUR AESTHETICS NEEDS
- 15. JakubPilimon –Michael C. Feathers “Code refactoring is the process of restructuring existing computer code —changing the factoring— without changing its observable behavior. (!!!)”
- 16. JakubPilimon NOBODY IS GOING TO PAY FOR THAT
- 18. JakubPilimon CREATE COMMON UNDERSTANDING “Introducing Event Storming” by Alberto Brandolini
- 19. JakubPilimon USE MEASURABLE DATA “Introducing Event Storming” by Alberto Brandolini
- 20. JakubPilimon USE MAGIC* *MAGIC = ENGINEERING
- 22. JakubPilimon TREAT REFACTORING AS A FEATURE THAT ENABLES YOU TO DELIVER FEATURES QUICKER
- 23. JakubPilimonJakubPilimon •Desirable observable behavior of 🦄 is the same as 💩 - it is refactoring • 🦄 is clean and ready for new requirements How it works
- 25. JakubPilimon HOW TO REFACTOR WITHOUT TESTS? “…without changing its observable behavior…”
- 26. JakubPilimon OBSERVABLE BEHAVIORS CAN BE EXPRESSED AS AUTOMATED TEST SCENARIOS *ALMOST ALWAYS
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- 31. JakubPilimon IF IT WAS EASY TO ADD UNIT TESTS IT WOULD NOT BE A BIG BALL OF MUD
- 33. JakubPilimon HOW TO FIND SCENARIOS TO TEST?
- 34. JakubPilimon LOOK AT THE WALL Place CollectOnly if books on Placed Book Hold Hold Collected Books Placed on Hold
- 35. JakubPilimonJakubPilimon Place Book On Hold Only if books on hold < 5 HoldExpir ed 4. Rule 2. Command Placed On Hold 1. Domain Event Collected Books View View 3. Query
- 36. JakubPilimonJakubPilimon Black-box testing of observable behaviors Collect Book Collected Books View Command API call queue listener db script executed… Query API call Excel sheet DB query Place Book On Hold Collected Books View Collect Book Placed on Hold Books View
- 37. JakubPilimonJakubPilimon Black-box testing of observable behaviors @Test public void patronCanHoldABook() { //given BookEntity book = fixtures.aCirculatingBookAvailableForLending(); //and BookHolderEntity patron = fixtures.aRegularPatron(); //when patronWantsToHoldBook(patron, book); //then assertThat(placedOnHoldsBooksBy(patron)).containsExactlyInAnyOrder(book); } Hold Book Books on Hold View Observable Behaviors!!!
- 38. JakubPilimonJakubPilimon Exploratory testing against present data sets Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Production copy/Staging Amy John
- 39. JakubPilimonJakubPilimon Reverse engineering from tests to business rules @Test public void patronCanHoldABook() { //given BookEntity book = bookFromDb(“Domain-Driven Design”); //and BookHolderEntity john = fromDb(“John”); //and BookHolderEntity amy = fromDb(“Amy”); //when assertThatExceptionIsThrown(()-> patronWantsToHoldBook(john, book)); //exception patronWantsToHoldBook(amy, book); //success //then assertThat(placedOnHoldsBooksBy(amy)).containsExactlyInAnyOrder(book); } Heuristics about rules 5 holds rule? Researcher can book Restricted books? John has overdue books? DDD Book is special? Why exception? Why success?
- 40. JakubPilimon How to make the transition? JakubPilimon Option #1: Climbing step by step (💩 slowly becomes 🦄) Option #2: Blue/Green refactoring (🦄 side by side with 💩)
- 41. JakubPilimonJakubPilimon • 💩 slowly becomes 🦄 •Observable effects of 💩 kept •Cannot easily rollback to 💩 from 🦄 •Need to dig in 💩 •Need to maintain one model Step by Step Refactoring
- 42. JakubPilimon
- 43. JakubPilimonJakubPilimon • 💩 remains untouched •Observable behavior of 💩 kept •Easy to rollback to 💩 from 🦄 • 🦄 feels a bit like a green field in 💩 •Need to maintain both 💩 🦄 •Need to somehow plugin 🦄 to the observable behaviors Blue/Green Refactoring
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- 45. JakubPilimon Place Book On Hold Collected Books View How it works Collect Book Placed on Hold Books View JakubPilimon How to plug in new model to observable behaviors?
- 46. JakubPilimon –Michael C. Feathers “A seam is a place where you can alter behaviour in your program without editing in that place”
- 47. JakubPilimon HOW TO LOOK FOR SEEMS? Collected Books View Place Book On Hold
- 48. JakubPilimon public List<BookDto> booksPlacedOnHoldBy(UUID patronId, List<BookDto> oldModel) { if (NewModelToggles.USE_NEW_MODEL.isActive()) { List<BookDto> newModel = newLendingModel.booksOnHoldBy(patronId)); reconciliation.compare(oldModel, newModel); return newModel; } return oldModel; } Anti-Corruption Layer @GetMapping("/holds/{holderId}") public ResponseEntity<List<BookDto>> getPlacedOnHoldBooks(UUID holderId) { List<BookDto> oldModel = bookHolderService.getBooks(holderId); return ResponseEntity.ok(lendingACL.booksPlacedOnHoldBy(holderId, oldModel)); } Collected Books View
- 49. JakubPilimon Switch between models while querying Collected Books View OR Uses Feature Toggles for Querying Query
- 50. JakubPilimon Anti-Corruption Layer @PostMapping("/books/collections") public ResponseEntity collect(BookRequest bookRequest) { oldModel.createCollectedBook(bookRequest.getBookId(), bookRequest.getDays()); lendingACL.collect(bookRequest); return ResponseEntity.ok().build(); } Place Book On Hold
- 51. JakubPilimon Parallel Operations For Commands Collect AND Command
- 52. JakubPilimon New model command failure cannot affect old model result! try/catch/log - might be your friend
- 53. JakubPilimon
- 54. JakubPilimon Dependencies between packages Old Lending Model New Lending Model
- 55. JakubPilimon public List<BookDto> booksPlacedOnHoldBy(UUID patronId, List<BookDto> oldModel) { if (NewModelToggles.RECONCILE_NEW_MODEL.isActive()) { List<BookDto> newModel = newLendingModel.booksOnHoldBy(patronId)); reconciliation.compare(oldModel, newModel); return oldModel; } if (NewModelToggles.RECONCILE_AND_USE_NEW_MODEL.isActive()) { List<BookDto> newModel = newLendingModel.booksOnHoldBy(patronId)); reconciliation.compare(oldModel, newModel); return newModel; } return oldModel; } Reconciliation in the ACL
- 56. JakubPilimon Reconciliation class Reconciliation<T> { private final Reaction reaction; public Diff<T> compare(Set<T> oldOne, Set<T> newOne) { Diff<T> difference = new Diff<>(oldOne, newOne); if (difference.exists()) { reaction.reactTo(difference); } return difference; } } interface Reaction { void reactTo(Diff diff); static Reaction logAndThanDisableToggle() { return new CompositeReaction(justLog(), diff -> disableToggle()); } static Reaction justLog() { return System.out::println; } }
- 57. JakubPilimon Add new model to a next seam Go to prod Switch toggle to old model Reconcile Gather feedback Switch toggle to new model
- 58. JakubPilimon Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Black-box testing of observable behaviors should pass against two models!
- 59. JakubPilimon Black-box testing of observable behaviors should pass against two models! @Test public void patronCanHoldABook() { //given BookEntity book = fixtures.aCirculatingBookAvailableForLending(); //and BookHolderEntity patron = fixtures.aRegularPatron(); //when patronWantsToHoldBookInNewModel(patron, book); //then assertThat(newModelPlacedOnHoldsBooksBy(patron)).containsExactlyInAnyOrder(book); } @Rule public TogglzRule togglzRule = TogglzRule.allDisabled(NewModelToggles.class); List<UUID> newModelPlacedOnHoldsBooksBy(BookHolderEntity aRegularPatron) { togglzRule.enable(NewModelToggles.RECONCILE_AND_USE_NEW_MODEL); //.. }
- 60. JakubPilimon Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Automated verification of two models @Test public void researcherCanPlaceOpenEndedHolds() { //given BookHolderEntity aResearcherPatron = fixtures.aResearcherPatron(); //when patronWantsToHoldBookForOpenEndedHold(aResearcherPatron, aCirculatingBook); //and List<UUID> oldModel = oldModelPlacedOnHoldsBooksBy(aResearcherPatron); List<UUID> newModel = newModelPlacedOnHoldsBooksBy(aResearcherPatron); //then assertThat(oldModel).containsExactlyInAnyOrderElementsOf(newModel); }
- 61. JakubPilimon Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Production copy/Staging Amy John JakubPilimon Exploratory testing against present data set after data migration from 💩 to 🦄 Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Production copy/Staging Amy John
- 63. JakubPilimon When we are sure… Collected Books View 3
- 64. JakubPilimon Dependencies between packages Old Lending Model New Lending Model BBOM
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- 66. JakubPilimon Modular monolith Is the system modular? Isthesystemdistributed? Big Ball Of Mud Distributed Big Ball Of Mud Modular Monolith Microservices
- 67. JakubPilimon • Always, ALWAYS! Test if ACL works correctly (returning correct models depending on the toggle settings) • Always test if ACL does reconciliation correctly! • Add test that checks that your feature toggle is disabled/ enabled by default • Go to production and reconcile very quickly (after 1st seam) • Make sure new model failures do not affect old model • With B/G Refactoring you are limited to programming language and database of BBOM JakubPilimon Lessons Learned