Uploaded byBernd Ruecker
KanDDDinsky: Let your domain events flow
The document discusses modeling domain events and flows using state machines and explicit flows. It advocates modeling domain processes as flows that can be directly executed, tested, and monitored. Flows help separate domain logic from infrastructure and live within bounded contexts. Explicit flows and state machines improve developer productivity, operational visibility, and reduce tight coupling between services.
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KanDDDinsky: Let your domain events flow
- 1. Let your domainevents flow KanDDDinsky, Oct 20th, 2017, Berlin, Germany mail@bernd-ruecker.com martin.schimak@plexiti.com With thoughts from http://flowing.io @berndruecker | @martinschimak
- 2. Bernd Rücker Consultant &Dev. Advocate 10+ years workflow Co-founder Camunda http://bernd-ruecker.com/ Martin Schimak Developer & Trainer, 10+ years (de-)coding domain knowledge DDDesign, TDD/BDD, EDA http://plexiti.com/ http://flowing.io/
- 4. Simplified example: dash button Photoby 0xF2, available under Creative Commons BY-ND 2.0 license. https://www.flickr.com/photos/0xf2/29873149904/
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- 7. Looking into events… Checkout Payment Inventory Shipment DomainEvents are facts that happened in the pastGood Fetched Good Stored Read Model Write Model „The button blinks green if we can ship the item within 24 hours!“
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- 9. Peer-to-peer event flows Checkout Payment Inventory Shipment Payment received Order placed Goods fetched Pleasefetch the goods before waiting for payment Some customers can pay via invoice …
- 10. Some requirements don‘tfit anywhere… What are we missing? Order Checkout Payment Inventory Shipment
- 11. Commands can decreasecoupling Order Checkout Payment Inventory Shipment Order placed Retrieve payment Commands have an intent about what needs to happen in the future Please fetch the goods before waiting for payment Some customers can pay via invoice Payment received Retrieve payment
- 12. Good API designrespects responsibility boundaries Order Checkout Payment Inventory Shipment „A few smart god services tell anemic CRUD services what to do!” Sam Newman What is the payment service responsible for?
- 13. Some things inlife take time
- 14. A customer can updatean expired credit card within two weeks before we cancel his order „
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- 16. Pass around state as„routing slip“ Persist state with Entity, Actor, … State machine How to implement a Process Manager? DIY DIY
- 17. State machine Persistent thing (Entity,Actor, …) Routing slip CADENCE Baker
- 18. State machines solvesome hard developer problems Monitoring & Operations Handling of time & timeouts Retry Visibility & Reporting Versioning Compensation Message correlation & deduplication Performance & scalability
- 19. Leaving the aggregatescope?
- 20. State machines solvesome hard developer problems Monitoring & Operations Handling of time & timeouts Retry Visibility & Reporting Versioning Compensation Message correlation & deduplication Performance & scalability
- 21. Bpmn.createProcess("order").executable() //... .sendTask().name("Retrieve payment").camundaClass(RetrievePayme .receiveTask().name("Payment received").message("PaymentReceive //... { "name":"retrieve_payment", "tasks": [ { "name": "Retrieve Payment", "taskReferenceName": "payment", "type": "SIMPLE", ... Do you prefer coded or graphical DSLs? * BPMN - ISO notation for modeling and executing long-running processes and flows
- 22. Do you needa timeout?
- 23. Do you needa compensation? *
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- 25. Flows done right Developerfriendly Lightweight & composable BizDevOps
- 28. More complex flows- transparent and directly executable
- 29. Specifying and testinglong-running behaviour
- 30. A visual testreport for example #1 (Balance = 50, Amount = 70)
- 31. A visual testreport for example #3 (Balance = 50, Amount = 30)
- 32. The binding strategyuses the step only when required
- 33. Living documentation forlong-running behaviour
- 34. Explicit language helpin tackling complex event flows Ubiquitous Language Software Experts Domain Experts
- 35. Explicit flows helpsepatrate domain and infrastructure Ports and Adapters Application Domain Aggregates, Domain Events, Domain Services, etc … + the flow State machine
- 36. Flows live insidethe context boundaries
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- 39. Operational visibility inmonitoring – possibly end-to-end
- 41. Mitigate tight coupling Considercore capabilities Leverage state machines Decentralize
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- 43. Code online: https://github.com/flowing Slides &Blog: https://bernd-ruecker.com https://plexiti.com With thoughts from http://flowing.io @berndruecker | @martinschimak https://www.infoq.com /articles/microservice- event-choreographies
- 44. Images licensed fromiStock no attribution required All icons licensed from Noun Project no attribution required Images licensed under Creative Commons license Photo by 0xF2, available under Creative Commons BY-ND 2.0 license. https://www.flickr.com/photos/0xf2/2987 3149904/