Demonstration of reactive programming with Spring Boot 2.2

1. Infinite Streams, Hot Fluxes, Live Queries
and Tail-able Cursors with Brian Matthews
2nd May, 2019
@bmatthews68

2. Our Partners

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12. And the most important people… YOU!

13. Ladies and Gentlemen, tonight's speaker...
19:00
Infinite Streams, Hot Fluxes, Live Queries,
and Tail-able Cursors
~ 20:00
Refreshments
20:30
Look, no HTTP! @bmatthews68

14. No speaker leaves empty handed

15. Group Photo time...

16. Ladies and Gentlemen, tonight's speaker...
19:00
Infinite Streams, Hot Fluxes, Live Queries,
and Tail-able Cursors
~ 20:00
Refreshments
20:30
Look, no HTTP! @bmatthews68

17. Infinite Streams, Hot
Fluxes, Live Queries and
Tail-able Cursors
Reactive Data Access with Spring WebFlux

18. Reactive
• Non-blocking (usually asynchronous)
• Event loop driven
• Back-pressure
• Declarative programming model
• Error propagation
• High efficiency
• Suitable for I/O bound workloads

19. Reactor & WebFlux
• WebFlux added to Spring 5
• Annotation driven
• Functional (WebFlux.fn)
• WebFlux built on top of Project Reactor
• Project Reactor implements Reactive Streams specification

20. Reactor
• Interoperable with RxJava 2
• Two publishers
• Mono<T> - zero or one element
• Flux<T> - zero or more elements
• Cold Flux
• Requires subscriber
• Replays data from start every time
• Hot Flux
• No subscriber required
• No historical data

21. Two Rules
• Nothing happens until you subscribe
• Never block!

22. NoSQL databases
• Spring Data currently ships with reactive data access support
for
• Cassandra (template & repositories)
• Couchbase (template & repositories)
• MongoDB (template & repositories)
• Redis (template only)

23. JDBC?
• JDBC is synchronous/blocking
• ADBA is asynchronous but not reactive
• Based on CompletableFuture<T>
• No back-pressure
• Java 9 Flow API

24. R2DBC
• Started as experimental project
• Supported databases
• H2
• Postgres
• SQL Server
• MySQL requires Kotlin runtime
• Definitely not ready for production

25. Live Queries
• Query returns available data but keeps the cursor open to stream
new additions
• So its just a Hot Flux
• Called a tail-able cursor in MongoDB
• But doesn’t work with an initially empty result set :(
• Cassandra and Couchbase just return a Flux<T> and its fine for
Server Sent Events
• Solution is to use an infinite stream with a timer to simulate a tail-
able cursor

26. Demo
https://gitlab.com/buralo/wtc

27. Q&A
brian@buralo.com
@bmatthews68

28. Look no HTTP!
RSocket

29. RSocket
• Efficient binary protocol
• Multiplexed & bi-directional
• Reactive (non-blocking, asynchronous, back-pressure)
• Framing protocol
• Payload encoding - JSON, Protobuf, roll-your-own
• Interaction models - oneway, request/response, request/stream, channel
• Language agnostic - Java, C++, Javascript, Kotlin, Flow
• Transport agnostic - TCP, WebSocket, HTTP/2, Aeron/UDP

30. RSocket & Spring
• Built with Project Reactor
• Integrated with Spring since
• Spring 5.2.0 M1
• Spring Boot 2.2.0 M2

31. Demo
https://gitlab.com/buralo/wtc

32. Q&A
brian@buralo.com
@bmatthews68