Refactor and Do It Safely - Jakub Pilimon
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Refactor and Do It Safely with 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 ā¢Domain-Driven Design ā¢Test-Driven Development ā¢Architecture ā¢Spring pillopl.github.io #dddbyexamples https://github.com/ddd-by-examples JakubPilimon
- 4. JakubPilimon WHAT THIS TALK IS NOT ABOUT
- 5. JakubPilimon
- 6. JakubPilimon
- 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 āMichael C. Feathers āCode refactoring is the process of restructuring existing computer code āchanging the factoringā without changing its observable behavior. (!!!)ā
- 16. JakubPilimon NOBODY IS GOING TO PAY FOR THAT
- 18. JakubPilimon CREATE COMMON UNDERSTANDING āIntroducing Event Stormingā by Alberto Brandolini
- 19. JakubPilimon USE MEASURABLE DATA āIntroducing Event Stormingā 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 ā¢Desirable observable behavior of š¦ is the same as š© - it is refactoring ā¢ š¦ is clean and ready for new requirements How it works
- 25. JakubPilimon HOW TO REFACTOR WITHOUT TESTS? āā¦without changing its observable behaviorā¦ā
- 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 Book On CollectOnly if books on Placed Book Hold Hold Collected Books Placed on Hold Books
- 35. JakubPilimonJakubPilimon Place Book On Hold Only if books on hold < 5 HoldExpire d 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 executedā¦ 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(āDomain-Driven Designā); //and BookHolderEntity john = fromDb(āJohnā); //and BookHolderEntity amy = fromDb(āAmyā); //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 (š© slowly becomes š¦) Option #2: Blue/Green refactoring (š¦ side by side with š©)
- 41. JakubPilimonJakubPilimon ā¢ š© slowly becomes š¦ ā¢Observable effects of š© kept ā¢Cannot easily rollback to š© from š¦ ā¢Need to dig in š© ā¢Need to maintain one model Step by Step Refactoring
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- 43. JakubPilimonJakubPilimon ā¢ š© remains untouched ā¢Observable behavior of š© kept ā¢Easy to rollback to š© from š¦ ā¢ š¦ feels a bit like a green ļ¬eld in š© ā¢Need to maintain both š© š¦ ā¢Need to somehow plugin š¦ to the observable behaviors Blue/Green Refactoring
- 44. JakubPilimon
- 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 āMichael C. Feathers āA seam is a place where you can alter behaviour in your program without editing in that placeā
- 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 veriļ¬cation 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 š© to š¦ Place Book On Hold Collected Books View Collect Book Placed on Hold Books View Production copy/Staging Amy John
- 63. JakubPilimon When we are sureā¦ Collected Books View 3
- 64. JakubPilimon Dependencies between packages Old Lending Model New Lending Model BBOM
- 65. JakubPilimon
- 66. JakubPilimon Modular monolith Is the system modular? Isthesystemdistributed? Big Ball Of Mud Distributed Big Ball Of Mud Modular Monolith Microservices
- 67. JakubPilimon ā¢ Always, ALWAYS! Test if ACL works correctly (returning correct models depending on the toggle settings) ā¢ Always test if ACL does reconciliation correctly! ā¢ Add test that checks that your feature toggle is disabled/ enabled by default ā¢ Go to production and reconcile very quickly (after 1st seam) ā¢ Make sure new model failures do not affect old model ā¢ With B/G Refactoring you are limited to programming language and database of BBOM JakubPilimon Lessons Learned