Welcome to the (state) machine @ ExploreDDD 2019
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Stateless all the thing, they say. In the last few years weve been brainwashed: design stateless systems, otherwise they cannot scale, they cannot be highly available, and they are hard to maintain and evolve. In a nutshell stateful is bad. However complex software systems need to do collaborative processing, that is stateful by definition. Stateless myth busted! Collaborative domains deal with long running business transactions and need to interact with distributed resources. The traditional distributed transactions approach, even if tempting, is a time bomb. This is when Sagas come into play. Sagas allow to model complex collaborative domains without the need for distributed transactions and/or orchestration across multiple resources. Join Mauro on a journey that aims to disclose what sagas are, how they can be used to model a complex collaborative domain, and what role they play when it comes to designing systems with failure and eventual consistency in mind. (Its all right, I know where youve been)
Welcome to the (state) machine @ ExploreDDD 2019
- 1. welcome to the (state) machine Its all right, I know where youve been mauroservienti Mauro Servienti
- 2. All I want to do when I wake up in the morning is (cit. Rosanna, Toto, Toto IV) mauroservienti
- 4. buy ticket(s) stage dive :-) mauroservienti
- 5. All what they want to do is mauroservienti
- 7. display available tickets reserve ticket(s) charge my credit card ship ticket(s) mauroservienti
- 8. sometimes order doesnt matter sometimes it does! mauroservienti
- 9. Na誰ve way var seats = await DisplayAvailableSeats(); var selectedSeats = seats.Take(2); var reservation = await ReserveSeats(selectedSeats); var authorization = await AuthorizeCard(reservation); if (authorization.Succeeded) { await ChargeCard(authorization); await ShipTickets(reservation); } mauroservienti
- 10. Na誰ve way var seats = await DisplayAvailableSeats(); var selectedSeats = seats.Take(2); var reservation = await ReserveSeats(selectedSeats); var authorization = await AuthorizeCard(reservation); if (authorization.Succeeded) { await ChargeCard(authorization); await ShipTickets(reservation); } Remote requests mauroservienti Remote requests
- 11. Tickets Selection Credit Card Gateway/ACL Orders Manager Order Checked-out AuthorizeCard request/response Reservation ConfirmTickets request/response Credit Card Gateway/ACL ChargeCard request/response Shipping Gateway/ACL Shiptickets request/response mauroservienti Reservation SelectTickets request/response Process Managers
- 12. Tickets Selection Credit Card Gateway/ACL Orders Manager Checkout request AuthorizeCard request/response Reservation ConfirmTickets request/response Credit Card Gateway/ACL ChargeCard request/response Shipping Gateway/ACL Shiptickets request/response Some sort of orchestration is still required mauroservienti Reservation SelectTickets request/response Process Managers
- 13. Orchestration is not the only issue we should get rid of
- 14. Process Managers (a different point of view) New requirement: collect tickets at the venue OrderId ShippingId ShippingStatus Etc 12 1337 Delivered 58 1338 Pending Orders table mauroservienti
- 15. mauroservienti like a punch card Process Managers own the process
- 17. Process Managers, a retrospective. Violate Single Responsibility Principle Single Unit of Deployment Conflicting Changes/Merge Conflicts Contention/Performance Bottleneck mauroservienti
- 18. mauroservienti there is no Spoon Process Manager
- 21. sagas autonomy in collaborative domains mauroservienti
- 22. multiple workflows, each providing compensating actions for every step of the workflow where it can fail mauroservienti
- 23. multiple workflows, each providing compensating actions for every step of the workflow where it can fail mauroservienti
- 24. reserve ticket(s) charge my credit card ship tickets mauroservienti
- 25. Shipping Finance Tickets Ordering Saga mauroservienti ReservationReservation Checked-out Payment Authorized Order Created Payment Succeeded Available Tickets Select tickets Shopping Cart Proceed to checkout workflow workflow workflow
- 26. Shipping Finance Tickets Ordering Saga mauroservienti ReservationReservation Checked-out Payment Authorized Order Created Payment Succeeded Available Tickets Select tickets Shopping Cart Proceed to checkout Policy Policy Policy
- 27. Shipping Finance mauroservienti Reservation Available Tickets Select tickets Shopping Cart Proceed to checkout Policy Policy Policy Reservation Checked-out Payment Authorized Order Created Payment Succeeded Pivotal Events
- 28. mauroservienti Lets open the black box
- 29. Shipping ReservationPayment Gateway Finance Finance Initiate Payment Authorize Card Courier Gateway Tickets Ordering Saga mauroservienti Available Tickets Select tickets Reservation Shopping Cart Proceed to checkout Reservation Reservation Checked-out Payment Authorized Order CreatedFinance Payment Gateway Charge Card Payment Succeeded Delivery Pick-up
- 30. Sounds more complex than the na誰ve approach, doesnt it? mauroservienti
- 31. New requirement Collect tickets at the venue mauroservienti
- 32. Shipping ReservationPayment Gateway Finance Finance Initiate Payment Authorize Card Courier Gateway mauroservienti Available Tickets Select tickets Reservation Shopping Cart Proceed to checkout Reservation Reservation Checked-out Payment Authorized Order CreatedFinance Payment Gateway Charge Card Payment Succeeded Delivery Pick-up Shipping Policy
- 33. Order Created Payment Succeeded NY Batch Shipping at the Venue Policy Store for Venue Delivery Mark as Complete Courier Gateway Batch Delivery Pick-up Courier Gateway Delivery Pick-up Deliver Tickets Mark as Complete mauroservienti Shipping Policy Shipping Policy Delivery-Mode: - Collect-at-the-Venue - Ship-at-Home ? Is Collect-at-the-Venue?
- 34. Order Created Payment Succeeded NY Store for Venue Delivery Mark as Complete Courier Gateway Delivery Pick-up Deliver Tickets Mark as Complete mauroservienti Shipping Policy Shipping Policy Delivery-Mode: - Collect-at-the-Venue - Ship-at-Home ? Is Collect-at-the-Venue? Batch Shipping at the Venue Policy Courier Gateway Batch Delivery Pick-up Mark as Complete
- 35. multiple workflows, each providing compensating actions for every step of the workflow where it can fail mauroservienti
- 36. Shipping ReservationPayment Gateway Finance Finance Initiate Payment Authorize Card Courier Gateway Tickets Ordering Saga mauroservienti Available Tickets Select tickets Reservation Shopping Cart Proceed to checkout Reservation Reservation Checked-out Payment Authorized Order CreatedFinance Payment Gateway Charge Card Payment Succeeded Delivery Pick-up
- 37. Payment Gateway Finance Finance Initiate Payment Authorize Card Payment Policy mauroservienti Reservation Checked-out Payment Authorized Finance Payment Gateway Charge Card Payment Succeeded Do we need a Reservation Failed event?
- 38. Payment Gateway Finance Finance Initiate Payment Authorize Card Payment Policy mauroservienti Payment Authorized 48hrs to release money Reservation Checked-out
- 39. Reservation Checked-out Payment Gateway Finance Finance Initiate Payment Authorize Card Payment Policy mauroservienti Payment Authorized Finance Payment Gateway Charge Card Payment Succeeded 48hrs to release money Payment Gateway Release Money Reserved?N Y Do nothing Reservation Order Created 48hrs later Mark as Complete
- 40. Whats a timeout? void Handle(ReservationCheckedout evt) { Send(new AuthorizationRequest()); } void Handle(AuthorizationRequest msg) { var authId = await AuthorizeCard(); Reply(new AuthorizationResponse(authId)); } void Handle(AuthorizationResponse msg) { Publish(new PaymentAuthorized()); RequestTimeout(TimeSpan.FromHours(48)); } void Timeout() { if(NotReserved){ } } Payment Gateway Finance Authorize Card Payment Authorized 48hrs to release money Reservation Checked-out Reserved? Payment Gateway FinanceFinanceFinance
- 41. Whats a timeout? void Handle(ReservationCheckedout evt) { Send(new AuthorizationRequest()); } void Handle(AuthorizationRequest msg) { var authId = await AuthorizeCard(); Reply(new AuthorizationResponse(authId)); } void Handle(AuthorizationResponse msg) { Publish(new PaymentAuthorized()); RequestTimeout(TimeSpan.FromHours(48)); } void Timeout() { if(NotReserved){ } } Payment Gateway Finance Authorize Card Payment Authorized 48hrs to release money Reservation Checked-out Reserved? Payment Gateway FinanceFinanceFinance
- 42. Whats a timeout? void Handle(ReservationCheckedout evt) { Send(new AuthorizationRequest()); } void Handle(AuthorizationRequest msg) { var authId = await AuthorizeCard(); Reply(new AuthorizationResponse(authId)); } void Handle(AuthorizationResponse msg) { Publish(new PaymentAuthorized()); RequestTimeout(TimeSpan.FromHours(48)); } void Timeout() { if(NotReserved){ } } Payment Gateway Finance Authorize Card Payment Authorized 48hrs to release money Reservation Checked-out Reserved? Payment Gateway FinanceFinanceFinance
- 43. Sagas (a different point of view) OrderId ShippingId ShippingStatus Etc 12 1337 Delivered 58 1338 Pending Orders table Reservation Shipping Finance OrderId TicketId 12 ABC 58 ACD Reservations table OrderId Address 12 Milan, Italy 58 Paris, France Shipping table OrderId Status 12 Paid 58 Overdue Invoices table VS mauroservienti
- 44. Sagas (a different point of view) Reservation Shipping Finance Reservations table OrderId Address 12 Milan, Italy 58 Paris, France Shipping table OrderId Status 12 Paid 58 Overdue Invoices table mauroservienti Each service can evolve independently OrderId TicketId 12 ABC 58 ACD
- 45. Sagas Business Process is distributed Respect Single Responsibility Principle Simpler/not conflicting evolution Independent Units of Deployment Independent scale out mauroservienti
- 46. Every year is getting shorter never seem to find the time Sagas Demo bit.ly/eddd-state-machine Udi Dahan about Sagas go.particular.net/eddd-state-machine mauroservienti
- 47. Demos: bit.ly/eddd-state-machine Videos: go.particular.net/eddd-state-machine Pitfalls Monitor the (distributed) state mauroservienti
- 48. Demos: bit.ly/eddd-state-machine Videos: go.particular.net/eddd-state-machine Takeaways Behaviors define how to designs processes Follow the coupling, not the data Identify processes and chop them up by service mauroservienti
- 49. Demos: bit.ly/eddd-state-machine Videos: go.particular.net/eddd-state-machine Takeaways Behaviors define how to designs processes Use Delayed Messaging to model time Simplifies making decisions in an async world mauroservienti
- 50. there is no such thing as orchestration mauroservienti
- 51. @mauroservienti | #EDDD Mauro Servienti Solution Architect @ Particular Software the makers of NServiceBus mauro.servienti@particular.net @mauroservienti //github.com/mauroservienti //milestone.topics.it mauroservienti
- 52. @mauroservienti | #EDDD Demos: bit.ly/eddd-state-machine Videos: go.particular.net/eddd-state-machine mauroservienti
Editor's Notes
- Red Hot Chili Peppers, 1989 Ritmo tribale Litfiba
- Surface vs Highways
- tricked by domain experts, they talk about tickets ordering process
- Whats a collaborative domain? IKEA furniture and shipping at a retail shop