Going Reactive With Spring Data
Why Reactive?
In a nutshell, reactive programming is about non-blocking, event-driven applications that scale with a small number of threads with back pressure as a key ingredient that aims to ensure producers to not overwhelm consumers.
The main goal of Reactive Streams is to govern the exchange of stream data across an asynchronous boundary — think passing elements on to another thread or thread-pool — while ensuring that the receiving side is not forced to buffer arbitrary amounts of data.
Relevant Projects
Reactive Streams
Common interfaces and a TCK.
Allows for interoperation of various implementations
Implementations
RxJava
Akka
Project Reactor
+ other more specialized
Flow API
Semantically equivalent to Reactive Streams.
Part of the JDK.
Rules of Reactive Streams apply.
Which to pick?
Ask the developer of RxJava.
Spring Framework 5.0
Reactive server side web framework based on Project Reactor.
Spring Data - Kay Release
Reactive Persistence API for
MongoDB
Cassandra
Redis
Uses Reactor by Default, but supports RxJava as well.
Threads in Servlet Apps
1 Thread per CPU Core
Overload → Network based Time Out
With I/O
1 T/Core + 1/Connection (???)
Works only with full/even load.
Assymetric Load → Wasted Resources
Overload → Network based Time Out
Reactive Streams
The Contract
Backpressure
Publisher may only send what requested.
Processor
Combines Subscriber and Publisher
Functional Processors
map: transform events
flatmap: many elements from one
filter
Controlling Processors
buffer n elements
stop after some time
work on a special Thread-Pool
Reactor
Publisher → Mono, Flux
Processors → methods on Mono & Flux
reactive Spring Data
Lets play!
What about JDBC?
Nobody wants to push JPA through Reactive Streams
Spring Data JDBC
Oracle Works on Async SQL-API
Not Flow/Reactive Stream based
Mailing List: jdbc-spec-discuss@openjdk.java.net
Spring will take a look
The idea of a reactive JDBC template
There are APIs
Run on Thread Pools
Jens Schauder
Dad, Board&Roleplaying Gamer, Runner, Freeletics Masochist
+
JUG Organizer
The Demo Repositories
From this talk
From the long version of this talk
Similar to the first but better documented
better for self study