CQRS & Event Sourcing Explained with Examples
•
6 gefällt mir•1,580 views
This document discusses CQRS and event sourcing patterns. It begins with an overview of CQRS, explaining how separating commands and queries can help with consistency in distributed systems. It then covers event sourcing, where all state changes are stored as a sequence of events. Benefits of event sourcing include preserving history and ability to replay events to reset state. The document provides examples of how CQRS and event sourcing could be applied to a domain like a rock-paper-scissors game.
Empfohlen
Weitere ähnliche Inhalte
Ähnlich wie CQRS & Event Sourcing Explained with Examples
Ähnlich wie CQRS & Event Sourcing Explained with Examples (20)
Kürzlich hochgeladen
Kürzlich hochgeladen (20)
CQRS & Event Sourcing Explained with Examples
- 2. Who am I? @jankronquist
- 4. Outline CQRS! Event sourcing! Design & Code!! Functional programming
- 5. CQRS
- 6. Consistency User A User B Get Get Buy! Buy! ! One ticket left! One ticket left! User C Get Buy! ! One ticket left! User D Get No tickets!
- 7. Consistency User A User B Get Get Buy! Buy! ! One ticket left! One ticket left! User C Get Buy! ! One ticket left! User D Get No tickets!
- 8. Eventual Consistency User A User B Get Get Buy! Buy! ! One ticket left! One ticket left! User C Get Buy! ! One ticket left! User D Get No tickets! Buy! ! One ticket left!
- 9. CQRS Command Query Responsibility Segregation! Commands - action that will modify state! Queries - anything that view state! The handling of commands and queries are separated
- 10. ProjectionProjection Common CQRS Architecture API Aggregate Message Bus Projection Commands Queries EventsEvents Not possible to view!
- 11. Micro Service Architecture API Gateway Service A Message Bus Service B Request Request MessageMessage
- 12. Validation vs Business rules Validation! Correct structure! Ranges, lengths, types! Rules! Should we do this?! What should happen When creating the command When executing the command
- 13. CQRS scalability Queries! Add more nodes for linear scalability!! Commands! Partitioning! Process asynchronously
- 14. Event sourcing
- 15. Event vs Command Event - Something that has happened! UserCreatedEvent! FriendRequestReceivedEvent! TicketSoldEvent! Command - Something we want to happened! CreateUserCommand! SendFriendRequestCommand! BuyTicketCommand
- 16. Event sourcing All changes recorded as Events! Order (time) is preserved! The event log is THE persistent source
- 17. Aggregates Unit of consistency! Example: user, meeting, order, product, game MeetingCreated AttendeeAdded A AttendeeAdded B AttendeeRemoved A AttendeeAdded C Attendees:A Attendees:A & B Attendees: B Attendees: B & C Event Stream
- 18. Application Service Aggregate Command Handler Event Handler Inside the aggregate Command Handler Command Old events Event Handler New events Event Store
- 19. Event Sourcing Benefits History of changes! Reset & replay! Persisting changes is simple & fast
- 20. Example domain
- 21. Rock - Paper - Scissors
- 24. Lizard - Spock?
- 25. http://rps.com The future Facebook of Rock Paper Scissors! Millions of users! Many games per user
- 26. Lets design!
- 27. Playing the game Player A Player B Server rock paper Player B: paper Player A: rock Game 123 Game 123 winner: Player B loser: Player A CREATED WAITING GAME WON GAME TIED any move other move (victory) other move (tie) T