Event Sourcing 101 (Vienna, 21. 2. 2019)
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This document summarizes a presentation about event sourcing. Event sourcing involves storing a chronological record of events that describe state changes rather than storing the current state. Storing events allows reconstructing past states and enables complex queries. It is more optimized for writes than a traditional database but allows for many projections to optimize reads. Examples of companies using event sourcing include LinkedIn and BlaBlaCar. Advice includes not putting everything in one event stream and ensuring events represent real-world actions.
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Event Sourcing 101 (Vienna, 21. 2. 2019)
- 1. Event Sourcing 101 Wien, 21. 2. 2019 Jan Kuchař CTO @ Grifart
- 2. @honzakuchar, honza.kuchar@grifart.cz keen in domain driven design phpstan backer UX community member exploring event-sourcing
- 4. How do you store state of your application?
- 5. „Snapshot” of current state
- 6. „Snapshot” of current state in database 📗 👱 The book Tom 👨 Tom
- 7. „Snapshot” of current state in database 📗 👱 The book Tom Book has been inventorized: The Hitchhiker's Guide to the Galaxy ISBN 978-80-257-0030-3 👨 Tom
- 8. „Snapshot” of current state in database 📗 👱 The book Tom Book has been inventorized: The Hitchhiker's Guide to the Galaxy ISBN 978-80-257-0030-3 Lent to Tom 👨 Tom
- 9. „Snapshot” of current state in database 📗 👱 The book Tom Book has been inventorized: The Hitchhiker's Guide to the Galaxy ISBN 978-80-257-0030-3 Lent to Tom Tom returned 👨 Tom
- 10. „Snapshot” of current state in database 📗 👱 The book Tom Book has been inventorized: The Hitchhiker's Guide to the Galaxy ISBN 978-80-257-0030-3 Lent to Tom Tom returned 👨 Tom Lent to Jan
- 11. No. Title ISBN 1 The Hitchhiker's Guide to the Galaxy ISBN 978-80-257-0030-3 Books
- 12. No. Name 1 Jan 2 Tom Users
- 13. No. Lent to Date&Time 1 2 - Tom today 16:15 Books lent
- 14. No. Returned by Date&Time 1 2 - Tom today 16:18 Returns table
- 15. No. Lent to Date&Time 1 2 - Tom today 16:15 2 1 - Jan today 18:02 Books lent (2)
- 16. Which books are now lent?
- 17. Who was lent 30 mins before?
- 18. What is median value of lent length?
- 19. Complicated.
- 20. Storing snapshot of state - issues ~3rd normal form
- 21. Storing snapshot of state - issues ~3rd normal form easy to write, hard to read optimized for writes
- 22. Storing snapshot of state - issues ~3rd normal form easy to write, hard to read optimized for writes hard to get complex aggregation-based reports ∑
- 23. Storing snapshot of state - issues ~3rd normal form easy to write, hard to read optimized for writes hard to get complex aggregation-based reports ∑ only one point of view on data
- 24. Storing snapshot of state - issues ~3rd normal form easy to write, hard to read optimized for writes hard to get complex aggregation-based reports ∑ only one point of view on data well-known architecture
- 26. What does your model consist of?
- 28. Model all your state transitions explicitly.
- 29. Stuctural model is second. = your database table
- 30. Stuctural model is second. = your database table emphasis on behavirour
- 31. Store behaviour instead! Each individual action!
- 32. Serie of events stored on one „topic” is called event stream.
- 35. And there can be thousands of them
- 36. Campaign 1
- 38. Do you implictly delete your data?
- 39. Not me!
- 40. Published campaign version 1 In this time, published version 1 is available to sales team. Updated typo in title of campaign. Published campaign version 2 version 2 visible time
- 41. Published campaign version 1 In this time, published version 1 is available to sales team. Updated typo in title of campaign. Published campaign version 2 version 2 visible time Uploaded material has been discarded
- 42. Published campaign version 1 In this time, published version 1 is available to sales team. Updated typo in title of campaign. Published campaign version 2 version 2 visible time Uploaded material has been discarded Published campaign version 3 version 3 visible
- 43. You can still see discarded material if you open version 2.
- 44. Complain: However it is very hard to read from this model.
- 45. but what if…
- 46. DEMO
- 47. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 Campaign version Content Campaign 1 draft <html><body>… CampaignContentHasBeenUpdated content: new working draft content event stream of campaign 1
- 48. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 Campaign version Content Campaign 1 draft <html><body>… CampaignContentHasBeenUpdated content: new working draft content event stream of campaign 1
- 49. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 Campaign version Content Campaign 1 draft <html><body> new content CampaignContentHasBeenUpdated content: new working draft content event stream of campaign 1
- 50. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 event stream of campaign 1 Campaign version Content Campaign 1 draft <html><body> new content Campaign 1 1 <html><body> new content CampaignContentHasBeenUpdated content: new working draft content
- 51. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 event stream of campaign 1 Campaign version Content Campaign 1 draft new working draft content Campaign 1 1 <html><body> new content CampaignContentHasBeenUpdated content: new working draft content
- 52. CampaignContentHasBeen Updated content: <html><body>… MaterialUploaded {page1, page2, page3} CampaignContentHasBeenUpdated content: <html><body>new content CampaignHasBeenPublished versionNumber: 1 event stream of campaign 1 Campaign version Content Campaign 1 draft new working draft content Campaign 1 1 <html><body> new content CampaignContentHasBeenUpdated content: new working draft content Projection
- 53. then reading is just one hit in table
- 54. and you can have 100 projections if you want
- 55. each computing direrent point of view on your data
- 56. Optimize reads and writes separately (CQRS)
- 57. Scale to infinity
- 58. Event stream Event Serialized event HTTP read from HTTP cache HTTP Client reading event stream HTTP
- 59. Event stream Event Serialized event HTTP read from HTTP cache HTTP Client reading event stream HTTP 3rd party API
- 60. Event stream Event Serialized event HTTP read from HTTP cache HTTP Client reading event stream HTTP projection3rd party API
- 61. Event stream Event Serialized event HTTP read from HTTP cache HTTP Client reading event stream HTTP projection analytics engine 3rd party API
- 62. Who is using event sourcing?
- 63. LinkedIn
- 64. BlaBlaCar
- 65. 2 years of studying
- 66. Eric Evans Tackling complexity in heart of software
- 67. My resources library on this topic&related https://gitlab.grifart.cz/jkuchar1/ eventsourcing-cqrs-simple-app or http://bit.ly/event-sourcing-resources
- 68. Greg Young 8 hour workshop on youtube ❤
- 70. Do not put everything into one event-stream
- 71. Events are stored, think twice before writing code.
- 72. Mistakes happen.
- 73. Events needs to mean things in real-world.
- 74. @honzakuchar, honza.kuchar@grifart.cz Jan Kuchař CTO @ Grifart reach me at: honza.kuchar@grifart.cz @honzakuchar Questions?
- 75. Talk feedback What worked and what not?