Reactive Summit 2020 - How state helps you to stay reactive
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The document discusses long running processes and transactions in distributed systems. It describes the challenges of using event-driven architectures without coordination. It presents orchestration and choreography patterns for implementing long running workflows across multiple services. Orchestration with a workflow engine provides capabilities for coordination, state management, and handling failures compared to event-driven choreography alone. Graphical models like BPMN can be used to define and document orchestration workflows.
Reactive Summit 2020 - How state helps you to stay reactive
- 1. @berndruecker How State Helps you to Stay Reactive Orchestration, Conversations and the Saga Pattern
- 2. Setting the scene. Example Checkout Payment Inventory Shipment @berndruecker
- 4. But there is also trouble in reactive land! Event chains that implement processes How to implement long running behavior
- 7. The danger is that it's very easy to make nicely decoupled systems with event notification, without realizing that you're losing sight of that larger-scale flow, and thus set yourself up for trouble in future years. https://martinfowler.com/articles/201701-event-driven.html @berndruecker
- 8. The danger is that it's very easy to make nicely decoupled systems with event notification, without realizing that you're losing sight of that larger-scale flow, and thus set yourself up for trouble in future years. https://martinfowler.com/articles/201701-event-driven.html @berndruecker
- 9. The danger is that it's very easy to make nicely decoupled systems with event notification, without realizing that you're losing sight of that larger-scale flow, and thus set yourself up for trouble in future years. https://martinfowler.com/articles/201701-event-driven.html @berndruecker
- 10. Phil Calcado at QCon NYC 2019
- 11. Notification Checkout Payment Inventory Shipment Pinball Machine Architecture „What the hell just happened?“ @berndruecker
- 12. Peer-to-peer event chains Checkout Payment Inventory Shipment Order placed Payment received Goods shipped Goods fetched Fetch the goods before the payment @berndruecker
- 13. Peer-to-peer event chains Checkout Payment Inventory Shipment Fetch the goods before the payment Goods fetched Order placed Payment received Goods shipped @berndruecker
- 14. What we wanted Photo by Lijian Zhang, under Creative Commons SA 2.0 License and Wikimedia Commons / CC BY-SA 4.0 @berndruecker Choreography
- 16. Order Decide about responsibility Checkout Payment Inventory ShipmentPayment received Order placed Retrieve payment @berndruecker This is choreography This is orchestration
- 17. Order Decide about responsibility Checkout Payment Inventory Shipment Order placed Retrieve payment It can still be messaging! @berndruecker
- 18. Order Checkout Payment Inventory Shipment Stateful orchestration This orchestration requires state @berndruecker
- 21. mail@berndruecker.io @berndruecker http://berndruecker.io/ Bernd Ruecker Co-founder and Chief Technologist of Camunda
- 23. Glue code (e.g. Java) https://github.com/berndruecker/flowing- retail/blob/master/kafka/java/order- zeebe/src/main/java/io/flowing/retail/kafka/or der/flow/FetchGoodsAdapter.java
- 24. Using a workflow engine Workflow Engine Scheduler Durable State Glue Code Whatever you need… Workflow Definition Workflow Engine: Is stateful Can wait Can retry Can escalate Can compensate Provides visibility
- 25. Now it is easy to change the process flow @berndruecker
- 26. Long Running Capabilities Solve Problems Long Running Technical Process Automation
- 27. Long Running Capabilities Solve Problems Long Running Technical Business Process Automation
- 30. Example Order Payment If the credit card was rejected, the customer can provide new details Credit Card Retrieve Payment Rejected Rejected @berndruecker
- 31. Payment failed Who is responsible? Order Payment If the credit card was rejected, the customer can provide new details Credit Card Retrieve Payment Rejected Payment received @berndruecker
- 32. Payment failed Long running services Order Payment Credit Card Retrieve Payment Rejected Payment received @berndruecker
- 33. Long running services Order Payment Credit Card @berndruecker
- 35. Extending Payment Options begin commit {local TX} Customer Credit Service begin commit {local TX} Credit Card Service @berndruecker
- 36. Distributed transactions using compensation * Compensation @berndruecker
- 37. Long Running Capabilities Solve Problems Long Running Technical Business Transactions, Saga Process Automation
- 38. Compensation – the classical example Saga book hotel book car book flight cancel hotel cancel car 1. 2. 3. 5.6. In case of failure trigger compensations book trip
- 39. 2 alterntive approaches: choreography & orchestration @berndruecker
- 41. Event-driven choreography Hotel Flight Car Trip Trip failed Trip requested Hotel booked Car booked Request trip Flight failed Car canceled Hotel canceled Perform undo (cancel car booking) Perform undo (cancel hotel) @berndruecker
- 42. If your transaction involves 2 to 4 steps, choreography might be a very good fit. However, this approach can rapidly become confusing if you keep adding extra steps in your transaction as it is difficult to track which services listen to which events. Moreover, it also might add a cyclic dependency between services as they have to subscribe to one another’s events. Denis Rosa Couchbase https://blog.couchbase.com/saga-pattern-implement-business-transactions-using-microservices-part/ @berndruecker
- 43. Implementing changes in the process Hotel Flight Car Trip Trip failed Trip requested Hotel booked Car booked Request trip Flight failed Car canceled Hotel canceled We have a new basic agreement with the car rental agency and can cancel for free within 1 hour – do that first! @berndruecker
- 44. Implementing changes in the process Hotel Flight Car Trip Trip failed Trip requested Hotel booked Car booked Request trip Flight failed Car canceled Hotel canceled You have to adjust all services and redeploy at the same time! We have a new basic agreement with the car rental agency and can cancel for free within 1 hour – do that first! @berndruecker
- 46. Orchestration Hotel Flight Car Trip Trip booked Request trip Book hotel Hotel booked Car booked Flight booked Book car Book flight We have a new basic agreement with the car rental agency and can cancel for free within 1 hour – do that first! You have to adjust one service and redeploy only this one! @berndruecker
- 47. Describe orchestration with BPMN Trip Trip booked Request trip @berndruecker
- 49. The workflow is domain logic as part of the service Trip @berndruecker
- 50. The workflow is domain logic as part of the service Trip Payment Payment could be one step in the Trip Saga @berndruecker
- 52. Clemens Vasters Architect at Microsoft http://vasters.com/archive/Sagas.html
- 53. Clemens Vasters Architect at Microsoft http://vasters.com/archive/Sagas.html
- 54. BPMN Business Process Model and Notation ISO Standard @berndruecker
- 55. Living documentation for long-running behaviour @berndruecker
- 56. Visual HTML reports for test cases @berndruecker
- 58. Consistency decisions need to be elevated to the business level!
- 59. Long Running Capabilities Solve Problems Long Running Technical Business Transactions, Saga Visibility Process Automation
- 60. Recap • You need capabilities for long running behavior for technical and business reasons • Workflow engines are a great fit – make sure you use a developer friendly one • Balance Orchestration (coordination) and choreography (reactive) @berndruecker
- 61. Want to learn more? https://learning.oreilly.com/get-learning/?code=PPAER20