Event sourcing your AngularJS applications

Editor's Notes

• #4: Why? I want to create better applications Most applications store the current state http://www.flickr.com/photos/celestinechua/9661913835
• #5: Levels of working with data Create Read Update Delete Command Query Responsibility Segregation Event-Sourcing
• #6: Data dumps and CRUD actions against database is very similar as seen from the front end
• #7: Most applications store the current state If you are lucky there is an audit trail of sorts http://www.flickr.com/photos/ell-r-brown/4011702143
• #8: http://www.flickr.com/photos/willowbl00/12459211923
• #9: http://www.flickr.com/photos/sukiweb/10223596316
• #10: The server is often just a simple gateway with just some validation logic
• #11: $resource and noSQL database make CRUD applications really easy
• #12: There is nothing wrong with a CRUD application if the problem domain is simple http://www.flickr.com/photos/juhansonin/5144239690
• #13: Command Query Responsibility Segregation
• #14: 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
• #15: Still storing just the current state Database structure is often normalized and optimized for updating Most application read far more frequently then update
• #16: 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
• #17: We are stil storing only the current state No trace of how we got there http://www.flickr.com/photos/danrocha/15602018982
• #18: Event sourcing doesn’t depend on CQRS but that structure is often used.
• #19: 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 http://www.flickr.com/photos/dragontomato/5174914835
• #20: 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/
• #21: 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
• #22: Events are never erased or updated An append only model http://www.flickr.com/photos/horiavarlan/4263326117
• #23: Events are projected out to the read model Observed facts = events Derived facts = projections http://www.flickr.com/photos/fotnmc/7172465908
• #24: Eventual consistency both good and bad Better scalability Harder to program the UI Block until done Fake it on the client Use long polling or push notifications http://www.flickr.com/photos/epsos/5732013768
• #25: Event Sourcing adds complexity Don’t do it where it doesn’t make sense It’s perfectly fine to use CRUD for static reference and ES for domain in the same app http://www.flickr.com/photos/10912969@N03/2046600021/
• #26: Sample application: https://github.com/mauricedb/Movies-GES Main technologies used: https://angularjs.org/ http://geteventstore.com/ http://redis.io/ http://www.asp.net/ https://www.flickr.com/photos/kevandotorg/6229660191
• #27: More info: Martin Fowler: http://martinfowler.com/eaaDev/EventSourcing.html Greg Young: http://goodenoughsoftware.net/ Daniel Whittaker: http://danielwhittaker.me/tag/event-sourcing/ João Bragança: https://github.com/thefringeninja/derp.inventory Damian Hickey: http://dhickey.ie/?tag=/Event-Sourcing https://www.flickr.com/photos/stevendepolo/4582437563/