Event Sourcing 101 (Vienna, 21. 2. 2019)
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What is event sourcing and how can that help me to build scalable and auditable application?
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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?