Reactive Programming

Reactive programming focuses on non-blocking, asynchronous execution 
 The Reactive Manifesto 
 Responsive 
 
 The System responds in a timely manner 
 Responsiveness is the cornerstone of usability and utility 
 Reponsiveness also means problems may be detected quickly 
 Responsive systems provide rapid and consistent response times 
 Consistent behavior simplifies error handling, builds end user confidence, and encourages further interaction 
 
 Resilient 
 
 System stays responsive in the face of failure 
 Resilience is achieved by replication, containment, isolation, and delegation 
 Failures are contianed within each component 
 Parts of the system can fail, without compromising the system as a whole 
 Recovery of each component is delegated to another 
 High-availability is ensured by replication where necessary 
 
 Elastic 
 
 The System stays responsive under varying workload 
 Reactive Systems can react to changes in the input rate by changing the amount of resources allocated to service inputs 
 Reactive Systems achieve elaticity in a cost effective way on commodity hardware and software platforms 
 
 Message Driven 
 
 Reactive Systems rely on asynchronous message passing to establish a boundary between components
 
 This ensures loose coupling, isolation, and location transparency 
 
 
 Message passing enables load management, elasticity and flow control 
 Location transparent messaging makes management of failures possible 
 Non-blocking communication allows recipients to only consume resources while active leading to less system overhead 
 
 Features of Reactive Programming 
 
 Data Streams 
 Asyncronous 
 Non-blocking - Process what is availble and ask for a notificaiton when more is available 
 Backpressure - The ability of the client to throttle data 
 Failures as Messages - Exceptions are processed by a handler function 
 
 Reactive Streams 
 
 Reactive Streams API was started in 2013 by engineers from Netflix and other companies. It was officially released 2015 and is now part of Java 9 JDK
 
 
 spring-webflux is a whole new non-blocking API for Spring
 
 
 
 Spring Reactive Types 
 
 Mono - A publisher with 0 or 1 elements in datastream 
 Flux - A publisher with 0+ elements in datastream