Spring: Blocking vs non-blocking: R2DBC vs JDBC and WebFlux vs Web MVC

Spring Framework version 5, released in Sept 2017, introduced Spring WebFlux. A fully reactive stack. In Dec 2019 Spring Data R2DBC, a reactive relational database driver was released. In this blog post I'll show that at high concurrency, WebFlux and R2DBC perform better. They have better response times and higher throughput. As additional benefits, they use less memory and CPU per request processed and when leaving out JPA in case of R2DBC, your fat JAR becomes a lot smaller. At high concurrency using WebFlux and R2DBC is a good idea!

Running Reactive Spring Boot on GraalVM in Docker

GraalVM is an open source polyglot VM which makes it easy to mix and match different languages such as Java, Javascript and R. It has the ability (with some restrictions) to compile code to native executables. This of course offers great performance benefits. Recently, GraalVM Docker files and images have become available. See here.

Since Spring Boot is a popular Java framework and reactive (non blocking) RESTful services/clients implemented in Spring Boot are also interesting to look at, I thought; lets combine those and produce a Docker image running a reactive Spring Boot application on GraalVM.

I've used and combined the following

• Building a Reactive RESTful Web Service
• Spring Boot with Docker and Running Spring Boot in a Docker container on OpenJDK, Oracle JDK, Zulu on Alpine Linux, Oracle Linux, Ubuntu
• Oracle's GraalVM Docker images
• (my very own) Ubuntu Development VM (requires VirtualBox, Vagrant)

As a base I've used the code provided in the following Git repository here. In the 'complete' folder (the end result of the tutorial) is a sample Reactive RESTful Web Service and client.