Domain Events - czyli jak radzić sobie z rzeczywistością!

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1. Domain Events Czyli jak radzić sobie z rzeczywistością! Mateusz Stasch | 2016.04.11
2. Mateusz Stasch @mattstasch http://mattstasch.net
3. ?
5. Domain Events
6. Domain Events
7. UI Events Event Loop … Application Events EDA … … Domain Events
8. UI Events Event Loop … Application Events EDA … … Domain Events
9. Domain event is something that happened that domain experts care about. Anonymous
10. Domain(T0 ) Domain(T1 ) Operation E
11. NOW
12. C D E H
13. C D E H1 H2
14. C D E H1 H2 Ext. System
15. C D E H1 H2 Ext. System Sync Async
17. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { // Validation... var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); _mmeGateway.RegisterPayment(/*...*/); if (paymentDetails.CardType == CardType.Credit) { // Message generation... _mailGateway.Send(/*...*/); } /* Send to PDA... */ }
18. Business Logic PDA MME Mail
19. Business Logic PDA MME Mail Test Scope
20. Business Logic PDA MME Mail CBL * CPDA CMME CMail * * Test Scope
21. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { // Validation... var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); _mmeGateway.RegisterPayment(/*...*/); if (paymentDetails.CardType == CardType.Credit) { // Message generation... _mailGateway.Send(/*...*/); } /* Send to PDA... */ }
22. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { // Validation... var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); }
23. public class CardPaymentRegisteredEvent : Event { public CardPayment Details { get; set; } }
24. Business Logic PDA MME Mail
25. public class MmePaymentsHandler : IEventHandler<CardPaymentRegisteredEvent> { private MMEGateway _mmeGateway; /* ctor(MMEGateway Gateway)... */ public void Handle(CardPaymentRegisteredEvent @event) { if (@event.Details.CardType == CardType.Credit) { _mmeGateway.Send(/*...*/); } } }
26. public class MmePaymentsHandler : IEventHandler<CardPaymentRegisteredEvent> { private MMEGateway _mmeGateway; /* ctor(MMEGateway Gateway)... */ public void Handle(CardPaymentRegisteredEvent @event) { if (@event.Details.CardType == CardType.Credit) { _mmeGateway.Send(/*...*/); } } }
27. Event Bus Listen Business Logic Publish Listen PDA MME Listen Mail
28. Event Bus Listen Business Logic Publish Listen PDA MME Listen Mail
29. Event Bus Listen Business Logic Publish Listen PDA MME Listen Mail CBL + CPDA + CMME + CMail
30. public class MmePaymentsHandler : IEventHandler<CardPaymentRegisteredEvent> { private MMEGateway _mmeGateway; /* ctor(MMEGateway Gateway)... */ public void Handle(CardPaymentRegisteredEvent @event) { if (@event.Details.CardType == CardType.Credit) { _mmeGateway.Send(/*...*/); } } }
31. Event Bus Listen Business Logic Publish Listen PDA MME Listen Mail Listen … Listen …
32. Nie wiem ilu Was jest, kiedy i w jakiej kolejności wykonacie pracę oraz jaki będzie jej wynik
33. SendEmailEvent #1
34. SendEmailEvent Życzenie, nie fakt! #1
35. NOW #1
36. PaymentRejectedEvent Zrób coś, bo Payment został odrzucony! #1
37. Czas przeszły, tryb dokonany! #1
38. Fakt, a nie życzenie! #1
39. _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails, Case = caseToBePaid }); #2
40. _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails, Case = caseToBePaid }); #2
41. Zdarzenie powinno być małe* i serializowalne #2
42. 2 1 #3
43. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { caseToBePaid.MarkAsPaid(); } /* MME */ /* Mail */ /* Send to PDA... */ }
44. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { caseToBePaid.MarkAsPaid(); } /* MME */ /* Mail */ /* Send to PDA... */ }
45. Nie wiem ilu Was jest, kiedy i w jakiej kolejności wykonacie pracę oraz jaki będzie jej wynik #3
46. Nie polegaj na konkretnej implementacji! Infrastruktury zdarzeń. #3
47. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { _eventBus.Raise(new CasePaidEvent { Id = id }); } _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); } public void RegisterCashPayment(EntityId id /*...*/)
48. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { _eventBus.Raise(new CasePaidEvent { Id = id }); } _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); } public void RegisterCashPayment(EntityId id /*...*/)
49. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { _eventBus.Raise(new CasePaidEvent { Id = id }); } _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); } public void RegisterCashPayment(EntityId id /*...*/)
50. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); if (caseToBePaid.OutstandingBalance.IsZero) { _eventBus.Raise(new CasePaidEvent { Id = id }); } _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); } public void RegisterCashPayment(EntityId id /*...*/) Utrata kontroli
52. public void RegisterCardPayment(EntityId id, CardPayment paymentDetails) { var caseToBePaid = _caseDao.GetById(id); // It was not so simple... ;) caseToBePaid.Payments.Add(paymentDetails); caseToBePaid.RefreshOutstandingBalance(); _eventBus.Raise(new CardPaymentRegisteredEvent { Id = id, Details = paymentDetails }); } public void RegisterCashPayment(EntityId id /*...*/)
53. Jedno zdarzenie ma jedno źródło! #4
54. public void AddGood(EntityId id, Good good) { var @case = _caseDao.GetById(id); @case.AddGood(good); _mmeGateway.Send(/*...*/ @case.Balance); /* Other stuff */ } #5
55. public void AddGood(EntityId id, Good good) { var @case = _caseDao.GetById(id); @case.AddGood(good); _mmeGateway.Send(/*...*/ @case.Balance); /* Other stuff */ } #5
56. #5 public class GoodAddedEvent : IEvent { public EntityId Id { get; set; } public DateTimeOffset RaisedAt { get; set; } public Good Good { get; set; } public Money Balance { get; set; } }
57. #5 public class GoodAddedEvent : IEvent { public EntityId Id { get; set; } public DateTimeOffset RaisedAt { get; set; } public Good Good { get; set; } public Money Balance { get; set; } }
58. public void AddGood(EntityId id, Good good) { var @case = _caseDao.GetById(id); @case.AddGood(good); /* Raise Event */ _mailGateway.Send(/*...*/ @case.OutstandingBalance); /* Other stuff */ } #5
59. #5 Nie modeluj zdarzenia dla konkretnego handlera
60. ReCap • Fakt, a nie życzenie! • Obiekt zdarzenia powinien być mały • Nie polegaj na skutkach ubocznych swojej implementacji • Jedno zdarzenie ma jedno źródło • Nie modeluj zdarzenia dla jednego handlera • Nie używajcie EF-a.
61. Jaką logikę, przerzucić do handlera?
63. Refactoring  Powiadomienia(Maile, SMSy)  Integracje z zew. systemami o ile nie są krytyczne*  Eager Data Derivation  Generowanie dokumentów/raportów  Unieważnianie :D Cache
64. MVP Niestety na przykładzie EF-a
65. public interface IEvent { int Id { get; set; } Type EntityType { get; set; } } public interface IEventHandler<TEvent> where TEvent : IEvent { void Handle(TEvent @event); }
66. public interface IEventSource { IList<IEvent> Events { get; } }
67. this.Raise(new CasePaidEvent() {Id = id});
68. private void ApplyEvents() { var processed = new List<IEvent>(); for (;;) { var events = ChangeTracker.Entries<IEventSource>() .SelectMany(x => x.Entity.Events) .Except(processed) .ToList(); if (!events.Any()) break; foreach (var @event in events) { _eventDispatcher.Apply(@event); processed.Add(@event); } } } public override int SaveChanges() { ApplyEvents(); base.SaveChanges(); }
69. private void ApplyEvents() { var processed = new List<IEvent>(); for (;;) { var events = ChangeTracker.Entries<IEventSource>() .SelectMany(x => x.Entity.Events) .Except(processed) .ToList(); if (!events.Any()) break; foreach (var @event in events) { _eventDispatcher.Apply(@event); processed.Add(@event); } } } public override int SaveChanges() { ApplyEvents(); base.SaveChanges(); }
70. private void ApplyEvents() { var processed = new List<IEvent>(); for (;;) { var events = ChangeTracker.Entries<IEventSource>() .SelectMany(x => x.Entity.Events) .Except(processed) .ToList(); if (!events.Any()) break; foreach (var @event in events) { _eventDispatcher.Apply(@event); processed.Add(@event); } } } public override int SaveChanges() { ApplyEvents(); base.SaveChanges(); }
71. private void ApplyEvents() { var processed = new List<IEvent>(); for (;;) { var events = ChangeTracker.Entries<IEventSource>() .SelectMany(x => x.Entity.Events) .Except(processed) .ToList(); if (!events.Any()) break; foreach (var @event in events) { _eventDispatcher.Apply(@event); processed.Add(@event); } } } public override int SaveChanges() { ApplyEvents(); base.SaveChanges(); }
72. private void ApplyEvents() { var processed = new List<IEvent>(); for (;;) { var events = ChangeTracker.Entries<IEventSource>() .SelectMany(x => x.Entity.Events) .Except(processed) .ToList(); if (!events.Any()) break; foreach (var @event in events) { _eventDispatcher.Apply(@event); processed.Add(@event); } } } public override int SaveChanges() { ApplyEvents(); base.SaveChanges(); }
73. public class EventDispatcher : IEventDispatcher { /*...*/ public void Apply(IEvent @event) { // ... Call generic ApplyTyped } protected void ApplyTyped<TEvent>(TEvent @event) where TEvent : IEvent { var handlers = _scope.Resolve<IEnumerable<IEventHandler<TEvent>>>(); foreach (var eventHandler in handlers) { eventHandler.Handle(@event); } } }
74. public class EventDispatcher : IEventDispatcher { /*...*/ public void Apply(IEvent @event) { // ... Call generic ApplyTyped } protected void ApplyTyped<TEvent>(TEvent @event) where TEvent : IEvent { var handlers = _scope.Resolve<IEnumerable<IEventHandler<TEvent>>>(); foreach (var eventHandler in handlers) { eventHandler.Handle(@event); } } }
75. public void Apply(IEvent @event) { try { applyTypedMethod.MakeGenericMethod(@event.GetType()) .Invoke(this, new object[] { @event }); } catch (TargetInvocationException ex) { ex.InnerException.PreserveStackTrace(); throw ex.InnerException; } }
76. public class AgreementSubmitted : IEvent { public DateTime EffectiveDate { get; set; } public string Note { get; set; } public int Id { get; set; } public Type EntityType { get; set; } public AgreementSubmitted(int id, DateTime effectiveDate, string note) { Id = id; EffectiveDate = effectiveDate; Note = note; } }
77. public void Handle(AgreementSubmitted @event) { SendEmail(ApprovalRequestEmailCode, @event.Id, pa => pa.Administrators); }
78. Event Log jako Log Historia pewnego włamania...
79. public class EventPersister<TEvent> : IEventHandler<TEvent> where TEvent : IEvent { private readonly IEventStore _eventStore; public void Handle(TEvent @event) { _eventStore.Save(new EventEnvelope<TEvent>(@event)); } }
80. SELECT * FROM EventLog WHERE EntityType = 'NS.Case' AND Id = 302049 ORDER BY RaisedAt Id EntityType RaisedAt RaisedBy EventType Content 302049 Domain.Case 2016-01-01 20:54:43.104 56 Events.Case.Created {…} 302049 Domain.Case 2016-01-01 20:55:43.105 56 Events.Case.CardPaymentRegistered {…} 302049 Domain.Case 2016-03-01 15:01:13.554 76 Events.Case.GoodsCollected {…} 302049 Domain.Case 2016-03-01 15:01:13.555 1 Events.Case.Paid {} 302050 Domain.Case 2016-03-01 15:01:13.556 1 Events.Case.Closed {}
81. SELECT * FROM EventLog WHERE EntityType = 'NS.Case' AND Id = 302049 ORDER BY RaisedAt Id EntityType RaisedAt RaisedBy EventType Content 302049 Domain.Case 2016-01-01 20:54:43.104 56 Events.Case.Created {…} 302049 Domain.Case 2016-01-01 20:55:43.105 56 Events.Case.CardPaymentRegistered {…} 302049 Domain.Case 2016-03-01 15:01:13.554 76 Events.Case.GoodsCollected {…} 302049 Domain.Case 2016-03-01 15:01:13.555 1 Events.Case.Paid {} 302050 Domain.Case 2016-03-01 15:01:13.556 1 Events.Case.Closed {}
82. Event Sourcing Replay Entity(TN )
83. Event Storming
84. Pytania?
85. Dzięki! Domain Events Czyli jak radzić sobie z rzeczywistością! Mateusz Stasch | 2016.04.11