Exploring Projections and Processors in Event Sourcing

Projections und Prozessoren sind einer der Säulen, um mit Event Sourcing umzugehen. Dabei werden wir einsteigen, was diese Begriffe bedeuten und welche Probleme wir damit lösen möchten. Anschließend werden wir klassische Implementierungen betrachten und schauen, ob wir unsere Probleme damit lösen können oder eventuell sogar neue Probleme entstehen. Zu guter Letzt schauen wir uns einen anderen Lösungsansatz an, welche Vorteile es hat, aber auch welche Nachteile.

Links zu der library und github:

https://event-sourcing.patchlevel.io/latest/
https://github.com/patchlevel/event-sourcing

Transcript

2. David Badura Freelance Software Engineer @davidbadura david.badura@patchlevel.de
3. Event Bus Content
4. Challenge
5. • Build from events • Keep it up to date • Updating and rebuilding
6. • At least once • Error Handling • External Processing
7. Event Bus Solution?
8. Event Bus Event Bus
9. An event bus is a design pattern to facilitate communication between different parts of an application. It acts as a central hub where events (messages) are published and subscribed to, allowing decoupled components to communicate without direct references to each other.
14. Event Bus Schema
16. Event Bus Rebuild
18. Event Bus Error Handling
21. Transaction
24. Event Bus Outbox
28. Event Bus Many Listeners
30. Multiple Outbox Stores? Kafka? RabbitMQ Fanout?
31. Event Bus Event Bus
32. • id • aggregate • aggregate_id • playhead • event • payload • recorded_on • id • message ◦ aggregate ◦ aggregate_id ◦ playhead ◦ event ◦ payload ◦ recorded_on
33. • subscription_id • run_mode • status • position • …
34. Event Bus Subscription Engine
36. Event Bus Run Modes
37. From Beginning The subscriber will start from the beginning of the event stream and process all events. From Now Certain subscribers operate exclusively on post-release events, disregarding historical data. Once The subscribers are executed from the beginning to the end of the stream.
41. Event Bus Status / Lifecycle
43. Event Bus Blue-Green-Deployment
44. Active hotel_v1 hotel_v2 Active Active Detached New Booting Active Active Boot Setup Teardown Deployment Switch
45. Event Bus Retry Strategy
47. Event Bus Conclusion
48. Event Bus Demo