Maurice de Beijer
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Event-Sourcing your React-Flux applications
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Maurice de Beijer
- 1. React applications & Event Sourcing Maurice de Beijer Software Engineer Trainer ABL – The Problem Solver
- 2. Who am I? Maurice de Beijer The Problem Solver Microsoft Azure MVP Freelance developer/instructor Twitter: @mauricedb and @React_Tutorial Web:http://www.TheProblemSolver.nl E-mail: maurice.de.beijer@gmail.com
- 11. (Semi) Structured storage Database CRUD Server HTTP Browser
- 13. A React component to display data
- 14. Command Query Responsibility Segregation
- 15. Command Query Responsibility Segregation Database Query Service Browser Command Service Read Update
- 17. A command to draft a permit
- 19. A Redux Action Creator
- 29. The permit drafted event
- 33. Projecting a permit drafted event
- 34. The permit collection reducer
- 35. The single permit reducer
- 36. The React application startup
- 37. Connecting state to a component
Editor's Notes
- https://www.flickr.com/photos/25143217@N05/3468038614/
- https://www.flickr.com/photos/faceme/7466333558/
- https://www.flickr.com/photos/sierag
- Why? I want to create better applications Most applications store the current state http://www.flickr.com/photos/celestinechua/9661913835
- Deepwater Horizon Offshore Drilling Platform on Fire https://www.flickr.com/photos/ideum/4711481781
- https://www.flickr.com/photos/organikal/5597513455/
- http://www.flickr.com/photos/willowbl00/12459211923
- http://www.flickr.com/photos/sukiweb/10223596316
- The server is often just a simple gateway with just some validation logic
- There is nothing wrong with a CRUD application if the problem domain is simple http://www.flickr.com/photos/juhansonin/5144239690
- A basic React component to show a list of permits
- CQRS = Command Query Responsibility Segregation Use a different model to update information than the model you use to read information http://www.flickr.com/photos/usnavy/8220344431
- Still storing just the current state Database structure is often normalized and optimized for updating Most application read far more frequently then update
- Commands should be modeled after business actions A business user can understand command names and have a reasonable expectation of the outcome http://www.flickr.com/photos/micahdowty/4630801442
- A command to update/create a draft permit
- The JavaScript command to send to the server
- Using Flux Standard Actions
- We are still storing only the current state No trace of how we got there http://www.flickr.com/photos/danrocha/15602018982
- Event Sourcing is a very old idea that has become popular again over recent years. Events provide insight into how the system came to be in its current state The current state is a left fold of the events http://www.flickr.com/photos/dragontomato/5174914835
- https://www.flickr.com/photos/eisenbahner/4051462178/
- Fra Luca Bartolomeo de Pacioli (1447–1517) The Father of Accounting and Bookkeeping https://en.wikipedia.org/wiki/Luca_Pacioli
- Domain Event is something that has happened in the past The result of a Command to change something Very similar to the audit trail in a database http://www.flickr.com/photos/lendingmemo/11747440176/
- No longer storing the current state but all event leading up to it The current state is a left fold of all events The projection parts are not really part of ES but CQRS and usually combined
- Flux has a very similar and explicit way of working with data.
- Events are never erased or updated An append only model Updates may happen during application updates http://www.flickr.com/photos/horiavarlan/4263326117
- A permit aggregate root
- A domain event to describe the drafted permit
- Events are projected out to the read model Observed facts = events Derived facts = projections http://www.flickr.com/photos/fotnmc/7172465908
- https://en.wikipedia.org/wiki/File:Mercator_projection_SW.jpg
- https://en.wikipedia.org/wiki/File:Mollweide_projection_SW.jpg
- Projecting an event to the read model
- A Redux reducer function for a collection of permits. It calls another reducer for individual permits Very functional: Old State + Action = New State
- A Redux reducer function for a single permit.
- The Redux createStore() function creates the store based on the reduce functions. The React-Redux Provider connects the store state to the root App component.
- The React-Redux connect functions makes data from the store available as props for the child React component.
- https://www.flickr.com/photos/ell-r-brown/7160371456