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CQRS and Event Sourcing
- 1. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | CQRS & Event Sourcing Better Distributed Applications through CQRS, Event Sourcing, and Immutable Logs Inho Kang Principal Sales Consultant Infrastructure, Cloud Platform Confidential – Oracle Internal/Restricted/Highly Restricted
- 2. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Safe Harbor Statement The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle. Confidential – Oracle Internal/Restricted/Highly Restricted 2
- 3. .Net Developer CBD, SOA Methodology Consulting ITA/EA, ISP Consulting Oracle Corp. Middleware Open Source, Cloud Native Application OCAP Team DevRel innoshom@gamil.com
- 4. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Program Agenda Microservices Event Sourcing CQRS Reference Hands-On 1 2 3 4 Confidential – Oracle Internal/Restricted/Highly Restricted 4 4
- 5. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Microservice Confidential – Oracle Internal/Restricted/Highly Restricted 5
- 6. Middleware/App Server Transactions/Synchronous API Calls/Asynchronous Monolith Problem : 1. Scaling 2. Performance 3. Deploy 4. Down
- 7. User Interface Application Datastore Infrastructure Resulting SoftwareTypical Enterprise Organization Structure Head of IT Head of Operation Head of DBAs Head of Infrastructure Head of App Dev Head of UI Head of Development An Enormous Monolith Conway’s Law: Software reflects the structure of the organization that produced it
- 8. Build small product-focused teams – strict one team to one microservice mapping Many Small Microservices Resulting SoftwareMicroservices Organization Structure API Application Datastore Infrastructure API Application Datastore Infrastructure API Application Datastore Infrastructure API Application Datastore Infrastructure Product Lead Project Manager Sys Admin DBA JavaScript Developer Developer Developer Sys Admin Storage Admin Graphic ArtistNoSQL Admin Product Lead Project Manager Sys Admin DBA JavaScript Developer Developer Developer Sys Admin Storage Admin Graphic ArtistNoSQL Admin Product Lead Project Manager Sys Admin DBA JavaScript Developer Developer Developer Sys Admin Storage Admin Graphic ArtistNoSQL Admin Product Lead Project Manager Sys Admin DBA JavaScript Developer Developer Developer Sys Admin Storage Admin Graphic ArtistNoSQL Admin
- 9. Edge Load Balancer Zuul (Proxy Svc) Playback (Legacy Dev.) API (g/w) Middle Tier & Platform EVCache Cassandra
- 10. Reference: http://microservices.io http://microservices.io Patterns of Microserivce
- 13. Online Shopping Mall Order Customer ID CUSTOMER_ID STATUS TOTAL ID CREDIT_LIMIT ……. Order Table Customer Table
- 14. BEGIN TRANSACTION … SELECT ORDER_TOTAL FROM ORDERS WHERE CUSTOMER_ID = ? … SELECT CREDIT_LIMIT FROM CUSTOMERS WHERE CUSTOMER_ID = ? … INSERT INTO ORDERS … … COMMIT TRANSACTION Traditional First Challenge - ACID User Interface Application Datastore Infrastructure One Application Transaction
- 15. Consistency across multiple services Order Customer API Application Datastore Infrastructure Order Microservice API Application Datastore Infrastructure Customer Microservice First Challenge - ACID
- 16. 2-PC (Phase Commit) First Challenge - ACID
- 17. Rules of Distributed Computing Consistency Each node shows the same data at all times Availability Each node is available for writes at all times Partition Tolerance Able to handle network outages CAP Theorem C A P Theory Practice Pick One Partition Tolerance is non-negotiable because we have networks that can always fail Enterprise IT Systems: Often CP Microservice Systems: Often AP Each microservice can be CP, AP or CA but the system as a whole is always CP or AP Pick Any Two
- 18. First Challenge - BASE Basic Availability • The database appears to work most of the time. Soft-state • Stores don’t have to be write-consistent, nor do different replicas have to be mutually consistent all the time. Eventual consistency • Stores exhibit consistency at some later point (e.g., lazily at read time).
- 19. Traditional Second Challenge - Query User Interface Application Datastore Infrastructure One Application SELECT * FROM CUSTOMER c, ORDER o WHERE c.id = o.ID AND o.ORDER_TOTAL > 100000 AND o.STATE = 'SHIPPED' AND c.CREATION_DATE > ? Join Query
- 20. Event Driven Architecture Order Customer Message Broker (Pub/Sub) Order Created Event Order Created Event Credit Reserved ID CUSTOMER_ID STATUS TOTAL 900 202 NEW 1000 ID CREDIT_LIMIT ……. 202 5,000,000 Order Table Customer Table CUST_ID ORDER_ID AMOUNT 202 900 1000 Reserved_Credit Table Credit Reserved 1 2 3 4 Credit Limit Exceeded APPROVED CANCELLED Eventual Consistency
- 21. Order Service Customer Service Event Driven Architecture Message Broker Customer Order View Query Service Customer Created Customer Cancelled Customer Shipped …… Order Created Order Cancelled Order Shipped ….. Customer Order View Update Find Customer & Order Query
- 22. Event Driven Architecture - Example Profile WebApp Message Broker Database Search App Cache Monitoring App Newsfeed App Memcached HBASE/ CASSANDRA/ RDBMS ELASTICSEARCH/ SOLR
- 23. ACCOUNT_ID ACCOUNT_TYPE BALANCE 12345 A 5,000,000 23456 B 250,000 34567 C 3,500,000 … …. …. Account Table SEQ ACCOUNT_ID … UPDATE_DATE 1 12345 .. …. 2 23456 … … 3 34567 … … 4 5 Account History Table 입금 출금 최종 시점의 상태 정보만을 보관 잔고 정보가 맞지 않는 경우? 원인 파악은???
- 24. Event Sourcing = 데이터 저장의 새로운 Pattern Order event #1 @ T1 event #2 @ T2 event #3 @ T3 event #4 T4 “Capture all changes to an application state as a sequence of events” ”어플리케이션의 모든 상태 변화를 발생순서에 따라 이벤트로 보관한다.
- 26. https://martinfowler.com/eaaDev/EventSourcing.html “Capture all changes to an application state as a sequence of events” ”어플리케이션의 모든 상태 변화를 발생순서에 따라 이벤트로 보관한다. – Martin Fowler
- 27. Feature Immutable Append Only (No Update/Delete) Contents Event ID(Aggregate ID) Type Revision TimeStamp PayloadOrderCreated ItemAddedToOrder OrderShipped OrderDeliverred … ……. Event 속성
- 30. 장점 Event Driven Architecture를 구현하면서 Atomic한 데이터 Publish가 가능 – Event 자체가 Atomic Domain Event(Aggregate) 를 적용함으로써 Object–Relation 의 Impedance Mismatch 문제를 회피 특정 시점의 상태값을 조회할 수 있다. 단점 상대적을 낯선 스타일 – Learning Curve Event Store기반의 쿼리에 한계점으로 인해 CQRS가 필수 적용 분야 예시 추천(장바구니), 분석(Debugging), 감사(Audit) Netflix Download Service License
- 31. CQRS (Command and Query Responsibility Segregation) 명령과 쿼리의 역할 구분 CQS Bertrand Meyer가 “Object Oriented Construction”이란 책에서 거론한 개념으로, 모든 메소드는 한번의 액션에서 1) 상태를 변경하는 커맨드든 2) 데이터를 반환하는 쿼리든 한가지 액션만 취해야 한다는 것이다. 다시 말하자면 질문을 할때 대답을 변경하지 말라는 것이다. 이 개념이 Object로 확대되어, 상태를 변경하는 Command(CUD)와 Query(Read)를 분리해야 한다는 원칙
- 32. 단일 모델 모델 분리
- 33. CQRS (Command Query Responsibility Segregation) Problem : 최근 일주일간 장바구니 아이템 추가 중간에 주문을 취소한 주문만 조회 Solution - 명령과 조회의 책임을 분리 - 상태변경을 처리하는 Command Model과 데이터를 조회하는 Query Model을 분리 구현 - 조회에 위한 Materialized View을 미리 생성
- 34. API Gateway Message Broker Event Store Command Processor (Write Logic) API(Commands) Event View Store Materialized View (Read Logic) API(Query) Event Projection
- 35. From Early in 2016
- 36. Download Business Requirements ● Devices with downloads ● Downloads per studio
- 37. Working With Event Sourcing
- 38. Debugging ● Possibly the biggest win ● Current tooling is rudimentary { "Event" : "LicenseAcquiredEvent", "Event Time" : "2017-06-25 05:23:00 PM", "aggregateId" : "aggregateId1", "committed" : true, "eventTimeStamp" : 1498411380903, "eventOrderNumber" : 0 }
- 39. Event Sourcing
- 40. Domain Model
- 43. Added Red Event Added Blue Event Make Purple Command Command Handler Commands
- 46. Aggregate
- 48. Event Store Row ID Events
- 49. Event Store Row ID Events
- 50. Row ID Events e1 e2 e3 e5 e6 e7 e4 Event Store Aggregate id 1 Aggregate id 2
- 52. Aggregate Repository Event StoreQuery select * from events where rowId =
- 53. Aggregate Repository Event StoreResponse e1 e2 e3 e5 e6 e7e4
- 54. Aggregate Repository e1 e2 e3 e5 e6 e7e4 e1 Aggregate id 1 e2 e5 e6 Aggregate id 2 e3 e4 e7
- 55. Aggregate Repository Aggregate id 1 e2 e5 e6 Aggregate id 2 Aggregate 1 Aggregate 2 e3 e4 e7 e1
- 56. Aggregate Repository Aggregate id 2 Aggregate id 1 Aggreeg2ate 1 e5 e6 Aggre ate 2 3 e7
- 57. Aggregate Repository Aggregate id 2 Aggregate id 1 Aggreeg5ate 1 e6 Aggre ate 2 7
- 58. Aggregate Repository Aggregate 2 Aggregate id 2 Aggregate id 1 Aggreeg6ate 1
- 66. Aggregate Repository Event Store Update append events where rowId = e8 e9
- 67. Event Store Aggregate id 1 Aggregate id 2 Row ID Events e1 e2 e3 e5 e6 e7e4 e8 e9
- 69. Axonframework.org / AxonIQ.com Since 2010, 8 years Version : 3.x Many systems in production Focus on Messaging in Commands, Events and Queries Plug in Event Store JPA, JDBC and MongoDB OOTB Scalability with JGroups Eventuate.io vs RBMH Eventuate? Since 2015 Version : Still 0.x Focus of Event Sourcing and Event Publication Own Event Store implementation Scalability with Akka https://stackoverflow.com/questions/43136291/axon-framework-vs-eventuate-comparison
- 70. • Chris Richardson : http://Micoservice.io • http://www.slideshare.net/RichardHarvey7/micro-services-and-containers • Thought Works - Real Case : http://vvgomes.com/microservices-event- sourcing/ • Mastering Chaos : https://www.slideshare.net/JoshEvans2/mastering-chaos- a-netflix-guide-to-microservices • Scaling Event Sourcing for Netflix Downloads : https://www.infoq.com/presentations/netflix-scale-event-sourcing
- 71. CQRS is not a silver bullet...CQRS is not Event Sourcing...CQRS is not a good wife...but...CQRS can open many doors. - Greg Young
- 73. Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Confidential – Oracle Internal/Restricted/Highly Restricted 73
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