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![Event [ɪˈvent]
Describes a fact, something that have happened.
Usually expressed in a past-tense form.
(e.g.: TalkStarted)](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-17-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-18-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Properties / Members
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-19-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Evolution functions
Change state
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-20-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Constructor
Change state
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-21-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Decision functions
Don’t change state
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-22-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-23-2048.jpg)
![public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Decision functions
Don’t change state
Event-Sourced business objects](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-24-2048.jpg)
![Event-Sourced business objects
public class Fund : EventSourcedAggregate
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public Fund(IEnumerable<Event> events)
{
foreach(var evt in events)
{
Apply(evt);
}
}
private Apply(FundRenamed event)
{
this.Name = event.FundNewName;
}
public IEnumerable<Event> Rename(string newName)
{
!// business logic and invariants checks HERE
!// Raise event(s)
return new[] { new FundRenamed(this.Id, newName) };
}
}
Decision functions
Don’t change state
Evolution functions
Change state](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-25-2048.jpg)
![Projection [prəˈjekSHən]
Deriving a current state from a stream of events](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-26-2048.jpg)
![Command [kəˈmɑːnd]
Triggers an action. Modify the state of the system
e.g.: RenameFund](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-43-2048.jpg)
![UTC [Utéçé;-)]
Universal Time Coordinated is the primary time standard by which the world
regulates clocks and time. It does not observe daylight saving time.](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-185-2048.jpg)
![Instant [ˈÇaAriiiv]
Describes “when something happened”. Can then be interpreted in a
particular time zone and calendar system.
e.g.: 2018-05-18T16:40:35Z (Z means UTC, i.e. +00h)](https://image.slidesharecdn.com/astimegoesbyv2-181107061957/75/As-time-goes-by-episode-2-186-2048.jpg)
Uploaded byThomas Pierrain
As time goes by (episode 2)
The document discusses the technical challenges of bi-temporal event sourcing, highlighting how it allows for tracking changes over time while maintaining an immutable history of events. Key challenges include retroactively altering events, forecasting future facts and projecting unsorted event streams. Solutions involve using different event types and managing multiple perspectives for operational and audit purposes.
More Related Content
Similar to As time goes by (episode 2)
As time goes by (episode 2)
- 1. As time goesby… Episode 2: technical challenges of bi-temporal Event Sourcing @tpierrain t
- 2. If you want towin… Tweet like hell on… #newCrafts
- 4.
- 5.
- 6. REQUIREMENTS — Understand their formerdecisions Fix their perception of the world retroactively
- 7. REQUIREMENTS — Understand their formerdecisions Fix their perception of the world retroactively (Re)produce reports in and from the past
- 8. REQUIREMENTS — Understand their formerdecisions Fix their perception of the world retroactively (Re)produce reports in and from the past Forecast ”events” in the future
- 9. REQUIREMENTS — Understand their formerdecisions Fix their perception of the world retroactively (Re)produce reports in and from the past Forecast ”events” in the future Strong audit trail
- 10. They needed atime machine
- 11.
- 12.
- 13. Remember your bankingaccount? Event Sourcing
- 14.
- 15. Final state ofthe world All changes since the beginning
- 16. All changes sincethe beginning = A list of events
- 17. Event [ɪˈvent] Describes afact, something that have happened. Usually expressed in a past-tense form. (e.g.: TalkStarted)
- 18. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Event-Sourced business objects
- 19. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Properties / Members Event-Sourced business objects
- 20. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Evolution functions Change state Event-Sourced business objects
- 21. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Constructor Change state Event-Sourced business objects
- 22. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Decision functions Don’t change state Event-Sourced business objects
- 23. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Event-Sourced business objects
- 24. public class Fund: EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Decision functions Don’t change state Event-Sourced business objects
- 25. Event-Sourced business objects publicclass Fund : EventSourcedAggregate { public Guid Id { get; private set; } public string Name { get; private set; } public Fund(IEnumerable<Event> events) { foreach(var evt in events) { Apply(evt); } } private Apply(FundRenamed event) { this.Name = event.FundNewName; } public IEnumerable<Event> Rename(string newName) { !// business logic and invariants checks HERE !// Raise event(s) return new[] { new FundRenamed(this.Id, newName) }; } } Decision functions Don’t change state Evolution functions Change state
- 26. Projection [prəˈjekSHən] Deriving acurrent state from a stream of events
- 27. Fund myFund =fundRepository.GetById(fundId, projectedAt); Event-Sourcing in motion Guid timestamp
- 28. Fund myFund =fundRepository.GetById(fundId, projectedAt); Now b7f3ddfb-2cb5…. Event-Sourcing in motion
- 29.
- 30. t FundCreated “super yield ” Jan1st 2016 Fund id: b7f3ddfb -2cb5…. Name: super yield Creation date: Jan 1st 2016 Management Company: Shares: Event-Sourcing in motion
- 31. t Jan 1st 2016 ManagementCompanyAssigned “BNP” Jan 30th 2016 Fund id:b7f3ddfb -2cb5…. Name: super yield Creation date: Jan 1st 2016 Management Company: BNP Shares: Event-Sourcing in motion
- 32. t Jan 1st 2016 Jan 30th 2016 FundRenamed “Yield2k22” Apr 1st 2016 Fund id: b7f3ddfb -2cb5…. Name: Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: Event-Sourcing in motion
- 33. t Jan 1st 2016 Jan 30th 2016 Apr1st 2016 ShareAdded “Part D” Jun 2nd 2016 Fund id: b7f3ddfb -2cb5…. Name: Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: Part D Event-Sourcing in motion
- 34. Fund id: b7f3ddfb -2cb5…. Name:Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: Part D End of Stream >> <<t Jan 1st 2016 Jan 30th 2016 Apr 1st 2016 Jun 2nd 2016 Event-Sourcing in motion
- 35. Projected at now Readyto work Fund id: b7f3ddfb -2cb5…. Name: Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: Part D
- 36. The beauty ofit Pick the projection date you want ;-)
- 37. Project same Fundat Apr 1st 2016 (same stream of events) Event-Sourcing in motion
- 38.
- 39. t FundCreated “super yield ” Jan1st 2016 Fund id: b7f3ddfb -2cb5…. Name: super yield Creation date: Jan 1st 2016 Management Company: Shares: Event-Sourcing in motion
- 40. t Jan 1st 2016 ManagementCompanyAssigned “BNP” Jan 30th 2016 Fund id:b7f3ddfb -2cb5…. Name: super yield Creation date: Jan 1st 2016 Management Company: BNP Shares: Event-Sourcing in motion
- 41. t Jan 1st 2016 Jan 30th 2016 FundRenamed “Yield2k22” Apr 1st 2016 Fund id: b7f3ddfb -2cb5…. Name: Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: Event-Sourcing in motion
- 42. t Jan 1st 2016 Jan 30th 2016 Apr1st 2016 Fund id: b7f3ddfb -2cb5…. Name: Yield 2k22 Creation date: Jan 1st 2016 Management Company: BNP Shares: We’re done here ;-) >> << Event-Sourcing in motion
- 43. Command [kəˈmɑːnd] Triggers anaction. Modify the state of the system e.g.: RenameFund
- 44. Commands are usedto take decisions and to raise events.
- 45. Commands are usedto take decisions and to raise events. Command (RenameFund) Aggregate (Fund X)
- 46. Commands are usedto take decisions and to raise events. Command (RenameFund) Events (FundRenamed) Events are used to restore/change the state of our aggregates. Aggregate (Fund X)
- 47. so far sogood? 😉
- 48.
- 49. Challenge #1 How tochange what can’t be changed?
- 50. Challenge #1 - Eventsare immutable (facts) - We save them in append-only streams (Event Store) t Q: How to retroactively change former mistaken events? Q: How to insert forgotten events in the past (in the middle of a stream)?
- 51. we don’t changeevents we just add more events
- 52. we don’t changeevents we just add more events
- 53.
- 54. “One more thing… Allour events have…”
- 55. createdAt validFrom !->when it applies 2 timestamps
- 56. createdAt validFrom !->when it applies 2 timestamps ( bi-temporal)
- 57.
- 58. Types of events validFrom createdAt Classicevent validFrom createdAt Retroactive event
- 59. Thus we canhide former events
- 60. Thus we canhide former events t Feb 1st 2016 Feb 3rd 2016 Feb 5th 2016 “new naaame” “initial name”
- 61. Thus we canhide former events t Feb 1st 2016 Feb 3rd 2016 Feb 5th 2016 “new naaame” “initial name” “fixed name ;-)”
- 62. Thus we canhide former events t Feb 1st 2016 Feb 3rd 2016 Feb 5th 2016 “new naaame” “initial name” “fixed name ;-)”
- 64.
- 65. Challenge #2 - EventStore stores “Events” ;-) - Events are things that have already happened (facts) t Q: How to store things that have to happen in an Event Store?
- 67. Let’s store ”aCommand (X) has just been Scheduled” events
- 68. validFromcreatedAt “Command Scheduled” event“CommandScheduled” event RenameFund (Cmd)
- 69.
- 70. 3 Types ofevents
- 71. 3 Types ofevents validFrom createdAt Classic event
- 72. 3 Types ofevents validFrom createdAt Classic event validFrom createdAt Retroactive event
- 73. 3 Types ofevents validFrom createdAt Classic event validFrom createdAt Retroactive event validFromcreatedAt “Command Scheduled” event C
- 74.
- 76. Challenge #3 How toproject unsorted streams of events?
- 77. Challenge #3 - Withretroactive events, we have unsorted streams of events - Some events may hide others - Past may change at any time. Future too t Q: How to implement projections in such environment?
- 78. Let’s review someoptions
- 79. 1 Forward-only projectionswith filters
- 80. 1 Forward-only projectionswith filters 2 Sort - then - Apply events
- 81. 1 Forward-only projectionswith filters 2 Sort - then - Apply events 3 Rebased Timelines with branches
- 82. 1 Forward-only projectionswith filters 2 Sort - then - Apply events 3 Rebased Timelines with branches too complicated
- 83. 1 Forward-only projectionswith filters 2 Sort - then - Apply events 3 Rebased Timelines with branches too complicated not compliant with bigstreams of events
- 84. 2 Sort -then - Apply events 3 Rebased Timelines with branches too complicated not compliant with bigstreams of events 1 Forward-only projections with filters
- 86. Challenge #4 How toprovide multiple visions of the same reality? (operational - audit-trail)
- 87. Challenge #4 - 1stream of events per aggregate instance - We need to provide both an operational mode and an audit mode t Q: How to provide various points of view in our reality?
- 88.
- 89.
- 90. / As AtAsOf "
- 91. / As AtAsOf As we should have known "
- 92. / As AtAsOf As we should have known Patches inside "
- 93. /As Of As weshould have known Patches inside As At As we knew (at the time) "
- 94. / As At Aswe knew (at the time) Audit trails As Of As we should have known Patches inside "
- 95. / As At Aswe knew (at the time) Audit trails As Of As we should have known Patches inside "
- 96. Since we havea model, let’s find some exemples
- 98. Our main usages(patches included) As Of - as we should have known
- 99. As Of -as we should have known Imagine a stream of 3 events for a Fund
- 100. 1.Let’s see howthose events have been saved over the time
- 101. As Of -as we should have known t Jan 1st 2016 Jan 1st 2017 Jun 1st 2017
- 102. As Of -as we should have known t Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name”
- 103. As Of -as we should have known t Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name”
- 104. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name”
- 105. 2. Let’s dosome As Of projections
- 106.
- 107. As Of -as we should have known Name: ??? Projection date Jun 1st 2017
- 108. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: ??? Projection date Jun 1st 2017
- 109. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: ??? Projection date Jun 1st 2017
- 110. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” ??? Name: Projection date Jun 1st 2017
- 111. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” 👍 Apply Name: “First name” -pending- Projection date Jun 1st 2017
- 112. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “official name”“First name” Projection date Jun 1st 2017 ??? Name: “First name” -pending-
- 113. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 👍 Apply Name: “Official name” -pending- “official name”“First name” Projection date Jun 1st 2017
- 114. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: “Official name” -pending- “official name”“First name” “patched name” Projection date Jun 1st 2017 ???
- 115. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 👎 Do NOT Apply Name: “Official name” -pending- “official name”“First name” “patched name” Projection date Jun 1st 2017
- 116. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: “official name” Projection date Jun 1st 2017
- 117. Same events /another projection date
- 118. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: ??? Projection date Apr 1st 2016
- 119. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: ??? Projection date Apr 1st 2016
- 120. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” Name: “First name” -pending- Projection date Apr 1st 2016 ???
- 121. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” 👍 Apply Name: “First name” -pending- Projection date Apr 1st 2016
- 122. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: “First name” -pending- “official name”“First name” Projection date Apr 1st 2016 ???
- 123. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: “First name” -pending- “official name”“First name” 👎 Do NOT Apply Projection date Apr 1st 2016
- 124. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: “patched name” -pending- “official name”“First name” “patched name” Projection date Apr 1st 2016 ???
- 125. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 Name: “patched name” -pending- “official name”“First name” “patched name” 👍 Apply Projection date Apr 1st 2016
- 126. As Of -as we should have known t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: “patched name” Projection date Apr 1st 2016
- 127.
- 128. As At -as we knew (at the time) " audit-trail use cases
- 129. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: ??? Projection date Apr 1st 2016 As At - as we knew (at the time) "
- 130. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: ??? Projection date Apr 1st 2016 As At - as we knew (at the time) "
- 131. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” Name: Projection date Apr 1st 2016 As At - as we knew (at the time) " ???
- 132. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” 👍 Apply Name: “First name” -pending- Projection date Apr 1st 2016 As At - as we knew (at the time) "
- 133. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: “First name” -pending- “official name”“First name” Projection date Apr 1st 2016 As At - as we knew (at the time) " ???
- 134. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: “First name” -pending- “official name”“First name” 👎 Do NOT Apply Projection date Apr 1st 2016 As At - as we knew (at the time) "
- 135. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “official name”“First name” Projection date Apr 1st 2016 As At - as we knew (at the time) " “patched name” Name: “First name” -pending- ???
- 136. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “official name”“First name” Projection date Apr 1st 2016 As At - as we knew (at the time) " 👎 Do NOT Apply “patched name” Name: “First name” -pending-
- 137. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: “First name” Projection date Apr 1st 2016 As At - as we knew (at the time) "
- 138. Same events /another projection date
- 139. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: ??? Projection date Jun 1st 2017 As At - as we knew (at the time) "
- 140. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” “official name” “patched name” Name: ??? As At - as we knew (at the time) " Projection date Jun 1st 2017
- 141. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” Name: As At - as we knew (at the time) " ??? Projection date Jun 1st 2017
- 142. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “First name” 👍 Apply Name: “First name” -pending- As At - as we knew (at the time) " Projection date Jun 1st 2017
- 143. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: “First name” -pending- “official name”“First name” As At - as we knew (at the time) " ??? Projection date Jun 1st 2017
- 144. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 Name: “official name” -pending- “official name”“First name” As At - as we knew (at the time) " Projection date Jun 1st 2017 👍 Apply
- 145. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “official name”“First name” As At - as we knew (at the time) " “patched name” ??? Projection date Jun 1st 2017 Name: “official name” -pending-
- 146. t Apr 1st 2016 Jan 1st 2016 Jan1st 2017 Jun 1st 2017 “official name”“First name” As At - as we knew (at the time) " 👎 Do NOT Apply “patched name” Projection date Jun 1st 2017 Name: “official name” -pending-
- 147. As At -as we knew (at the time) " Projection date Jun 1st 2017 Name: “official name”t Apr 1st 2016 Jan 1st 2016 Jan 1st 2017 Jun 1st 2017 “First name” “official name” “patched name”
- 148.
- 150. Challenge #5 How toproduce a report for March 1st like if we had made it June 1st?
- 151. Challenge #5 - Wedon’t want to suffer from hindsight bias - We need to understand how we had perceived the world in the past - We should not see some events that happened after a viewpoint t
- 152. Q: How toproduce a report for March 1st, like if we had made it June 1st?
- 153. Name: ??? t Q: How toproduce a report for March 1st, like if we had made it June 1st? ??? Feb 2nd 2016 Feb 1st 2016 Feb 28th 2016 March 1st 2016 Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016
- 154. t “name 1” “name 2” “name5” Feb 2nd 2016 Feb 1st 2016 Feb 28th 2016 March 1st 2016 Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016 Q: How to produce a report for March 1st, like if we had made it June 1st? Name: ??? ???
- 155. t Feb 2nd 2016 Feb 1st 2016 Feb28th 2016 March 1st 2016 “name 1” “name 2” “name 5” Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016 Q: How to produce a report for March 1st, like if we had made it June 1st? Name: ??? Date of the report Report target date
- 156. t Feb 2nd 2016 Feb 1st 2016 Feb28th 2016 March 1st 2016 “name 1” “name 2” “name 5” Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016 Q: How to produce a report for March 1st, like if we had made it June 1st? Date of the report Report target date Apply all events created before June 1st (viewPoint) Don’t apply events created after June 1st (viewPoint)
- 157. t Feb 2nd 2016 Feb 1st 2016 Feb28th 2016 March 1st 2016 “name 5” Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016 Q: How to produce a report for March 1st, like if we had made it June 1st? Date of the report Report target date Apply all events created before June 1st (viewPoint) “name 1” “name 2” Don’t apply events created after June 1st (viewPoint)
- 158. t Feb 2nd 2016 Feb 1st 2016 Feb28th 2016 March 1st 2016 “name 5” Feb 3rd 2016 Jul 1st 2016 Jun 1st 2016 Q: How to produce a report for March 1st, like if we had made it June 1st? Date of the report Report target date Apply all events created before June 1st (viewPoint) “name 1” “name 2” Don’t apply events created after June 1st (viewPoint)
- 159. which bring us 2new concepts
- 160.
- 161. Fund myFund =fundRepository.GetAsOUntil(fundId, projectedAt, viewPoint); AsOf Until Guid March 1st 2016 June 1st 2016
- 162. In code wetrust
- 169.
- 172. Challenge #6 Retroactive commands vs. Retroactive events?
- 173. Challenge #6 - Eventsare facts - Commands are used to take decisions and to raise events - Command may fail t Q: What should we do with ’retroactive’?
- 175. a) Apply aretroactive command to a aggregate projected in the past? (may fail)
- 176. a) Apply aretroactive command to a aggregate projected in the past? (may fail) b) Create an event in the past for an aggregate?
- 177. a) Apply aretroactive command to a aggregate projected in the past? (may fail) b) Create an event in the past for an aggregate? c) The answer C
- 178. c) There isno silver bullet
- 179. But we’ve mostlypicked the option a) Apply a retroactive command to a aggregate projected in the past? (may fail) so far
- 181. Challenge #7 Is U.T.C.enough?
- 182. tChallenge #7 - Westore instants in our Event Store (createdAt, validFrom timestamps) - Some events are applied on an entire “day” (e.g. June 8th)
- 183. t Q: Which timestampsshould we pick to describe a “day”? Challenge #7 - We store instants in our Event Store (createdAt, validFrom timestamps) - Some events are applied on an entire “day” (e.g. June 8th)
- 184. t Q: Which timestampsshould we pick to describe a “day”? Q: Is UTC enough to store all instants? Challenge #7 - We store instants in our Event Store (createdAt, validFrom timestamps) - Some events are applied on an entire “day” (e.g. June 8th)
- 185. UTC [Utéçé;-)] Universal TimeCoordinated is the primary time standard by which the world regulates clocks and time. It does not observe daylight saving time.
- 186. Instant [ˈÇaAriiiv] Describes “whensomething happened”. Can then be interpreted in a particular time zone and calendar system. e.g.: 2018-05-18T16:40:35Z (Z means UTC, i.e. +00h)
- 187. Istanbul (+03) What doesJune 8th even mean?
- 188. What does June8th even mean? Paris (+02) Istanbul (+03)
- 189. UTC (+00) Paris (+02) Istanbul(+03) What does June 8th even mean?
- 190. UTC (+00) Jun 8th2018 00h (+ 03h) Paris (+02) Istanbul (+03) Jun 8th 2018 23h59 (+ 03h) What does June 8th even mean?
- 191. UTC (+00) Jun 8th2018 00h (+ 03h) Jun 7th 2018 21h (+ 00h) Paris (+02) Istanbul (+03) Jun 8th 2018 23h59 (+ 03h) Jun 8th 2018 21h59 (+ 00h) What does June 8th even mean?
- 192. UTC (+00) Paris (+02) Istanbul(+03) Jun 8th 2018 00h (+ 02h) Jun 8th 2018 23h59 (+ 02h) Jun 8th 2018 23h59 (+ 03h) Jun 8th 2018 21h59 (+ 00h) Jun 8th 2018 00h (+ 03h) Jun 7th 2018 21h (+ 00h) What does June 8th even mean?
- 193. UTC (+00) Paris (+02) Istanbul(+03) Jun 8th 2018 00h (+ 02h) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 23h59 (+ 02h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 23h59 (+ 03h) Jun 8th 2018 21h59 (+ 00h) Jun 8th 2018 00h (+ 03h) Jun 7th 2018 21h (+ 00h) What does June 8th even mean?
- 194. UTC (+00) Paris (+02) Istanbul(+03) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 21h59 (+ 00h) Jun 7th 2018 21h (+ 00h) Event 1 ? Should event 1 be involved in a June 8th projection?
- 195. UTC (+00) Paris (+02) Istanbul(+03) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 21h59 (+ 00h) Jun 7th 2018 21h (+ 00h) Event 1? only if it’s June 8th - Paris time
- 196. June 8th Paris!!= June 8th Istanbul
- 197. UTC (+00) Paris (+02) Istanbul(+03) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 21h59 (+ 00h) Jun 7th 2018 21h (+ 00h) June 8th Paris time !!= June 8th Istanbul time
- 198. UTC Time ismandatory to store & compare events UTC (+00) Paris (+02) Istanbul (+03) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 21h59 (+ 00h) Jun 7th 2018 21h (+ 00h)
- 199. UTC is mandatorybut not enough UTC (+00) Paris (+02) Istanbul (+03) Jun 7th 2018 22h (+ 00h) Jun 8th 2018 21h59 (+ 02h) Jun 8th 2018 21h59 (+ 00h) Jun 7th 2018 21h (+ 00h)
- 200. We need UTCTime + time zone of the event
- 201. time zone ofthe event?
- 202. Time zone ofthe action that originated the event? time zone of the event?
- 203. Time zone ofthe action that originated the event? Time zone associated with the topic (i.e. a Fund)? time zone of the event?
- 205.
- 206.
- 207. Without concrete examplesand a model, you’re dead.
- 208. And more thanever…
- 209. y.a.g.n.i you ain’t gonnaneed it
- 211. Would you d ar e t o destroy it?
- 212.
- 213.
- 214.
- 215. (White paper ongoing) @tpierrain(use case driven) Thank you!
- 216.
- 217.
- 218. 7 SPEAKERS, 5TALKS ORIGINAUX DE 15-20 MIN EN QUOI NOUS INTÉRESSER AUX PROBLÈMES DU MÉTIER NOUS A RENDU PLUS EFFICACE LE MARDI 26 JUIN, CHEZ DOMAIN FROM THE TRENCHES
- 219.
- 220.
- 221. As At #2- as we knew at the time
- 222. As At #2- as we knew at the time
- 223. As At #2- as we knew at the time “Patched name” will be <<discarded>> by the following FundRenamed event
- 224.
- 225. As Of #2- as we should have known “Patched name” is not <<discarded>> by the following FundRenamed event (“official name”)
- 226. As Of #2- as we should have known But then it is replaced by the new one ( “OfficialName”)
- 229. You want tobe ahead of what is done in software? You understand there are bigger issues than just coding We are looking for people who are daring, curious, sharing, but who especially like team work recruits