W-JAX 2017: Spring Boot Microservices mit Domain Events

Domain Events sind ein zentraler Aspekt des taktischen Domain-driven Designs und zudem noch die Basis für die Implementierung lose gekoppelter Microservices, die auf asynchrones Event Processing ausgelegt sind. In diesem Vortrag werden wir uns mit dem Konzept der Domain Events beschäftigen und kennen lernen, wie sie modelliert und genutzt werden können, um eine lose Kopplung ohne synchrone Kommunikation von Microservices erreichen zu können.
Weiterhin werden wir das Konzept anhand eines konkreten Beispiels in die Praxis umsetzen. Hierbei werden wir Technologien wie Spring Boot, Spring Cloud Stream (Rabbit/Kafka) und Cloud Foundry verwenden, um anhand von Events und unterschiedlichen Modellierungsstilen von Events die Vor- und Nachteile des Ansatzes kennen zu lernen.

Transcript

1. Spring Boot Microservices with Domain Events 
 Michael Plöd - innoQ @bitboss
2. Your Trainer: Michael Plöd > Principal Consultant at innoQ > Regular Conference Speaker > Domain-Driven Design Practitioner since 2006 > Twitter: @bitboss > GitHub: https://github.com/mploed
3. „After inserting data into“ „We need to check the status of“ „When we have called System X“ „If that happens“ „After the customer has“ „Notify me if“
4. Ubiquitous Language?
5. !Domain Events are something that happened that Domain Experts care about
6. ! Model information about activity in the domain as a series of discrete events.
7. Events are easy to grasp Events have a simple semantic Events can be placed 
 on a timeline
8. An event is something 
 that happened in the past t now Event Event Event Event Event
9. The names of the events are part of the
 Ubiquitous Language D D D
10. ShipmentDeliveredEvent
 CustomerVerifiedEvent CartCheckedOutEvent CreateCustomerEvent
 WillSaveItemEvent
 DoStuffEvent
11. Triggers of Events Documents Time Applications User Actions Other Events
12. ! A Domain Event is always immutable
13. Scope your events based on
 Aggregates D D D
14. Commands can change business object 
 state. Which can result in one or more Events being published Command Business
 Object Event Event Event
15. Command Event ShipOrderCommand OrderShippedEvent DecideCreditApplicationCommand CreditDecisionPositive
 CreditDecisionNegative AddCommentCommand CommentAdded LockCreditApplication CreditApplicationLocked
16. Options for Event Payload Options Full Payload The event carries complete Entitiy-Graphs or Aggregates Mix The event contains data that is usually of interest to many other contexts. For special purposes there is also a URL to a RESTful HTTP Ressource Empty The event is empty or contains only minimal data and is being used to trigger pulling from a feed (eg. Atom) REST URL The event only carries a URL to a RESTful HTTP Ressource
17. CustomerCreatedEvent { "eventId": "4567854", "eventTimetamp": „12398989343", "eventType": "CustomerCreatedEvent", "customerName": "Michael", "customerLastName": "Plöd", "customerNumber": "34ed2345", "address" : { "street": "Kreuzstr. 16", "postCode": "80331", "city": "München" } } Full Payload Events contain full object graphs Consumers do have all the data
 they need „Invitation“ to a high degree of
 coupling between event and
 consumer
18. CustomerCreatedEvent { "eventId": "4567854", "eventTimetamp": „12398989343", "eventType": "CustomerCreatedEvent", "url": "http://123.03.24.23/event/2" } REST URL Events only contain a URL to a REST resource for the event data If consumers need the data they can obtain it but don’t have to Synchronous communication, but 
 no service discovery
19. CustomerCreatedEvent { "eventId": "4567854", "eventTimetamp": „12398989343", "eventType": "CustomerCreatedEvent", } Empty Events contain no data at all Consumers would usually 
 consume an (ATOM) Feed Consumers need to know the 
 Source of the Feed
20. CustomerCreatedEvent { "eventId": "4567854", "eventTimetamp": „12398989343", "eventType": "CustomerCreatedEvent", "customerLastName": "Plöd", "customerNumber": "34ed2345", "url": "http://123.03.24.23/event/2"
 } MIX Events contain some data Additional data can be obtained 
 by calling as REST Resource Good compromise in many 
 occasions
21. An event is something 
 that happened in the past t now Event Event Event Event Event
22. Let’s reuse the ESB from the failed SOA project
23. NO
24. NO
25. NO
26. ! Prefer dumb pipes with smart endpoints as a suitable message broker architecture
27. Event Sourcing is an architectural pattern in which the state of the application is being determined by a sequence of events
28. Case Study https://github.com/mploed/event-driven-spring-boot
29. Start Application Enter
 Credit Details Enter Financial Situation Scoring Credit Decision
30. Credit
 Application
 Number
 Generated Application
 Process Credit Decision Credit Application Credit
 Details
 Entered Financial
 Situation
 Entered
31. Credit
 Application
 Entered Credit Application Customer Scoring Customer Created
32. Scoring Positive Scoring Scoring Negative Credit Decision Application Declined Application Approved
33. https://github.com/mploed/event-driven-spring-boot
34. THANK YOU I’ll post links to slides and code on Twitter
 Michael Plöd - innoQ @bitboss