How to set the size of the event-event pool in Spring Webflux / WebClient?

Question

In an infrastructure with multiple reactors , such as Vert.X, we can set the number of event loop threads, for example:

final VertxOptions vertxOptions = new VertxOptions();
vertxOptions.setEventLoopPoolSize(16);
final Vertx myVertx = Vertx.vertx(vertxOptions);

How to make equivalent in Spring Boot 2 WebFlux / WebClient?

Answer 1

You have two options:

• Override the ReactiveWebServerFactorybean using a customizer that applies the event loop resource configuration:

  @Bean
  public ReactiveWebServerFactory reactiveWebServerFactory() {
      NettyReactiveWebServerFactory factory = new NettyReactiveWebServerFactory();
      factory.addServerCustomizers(builder -> builder.loopResources(LoopResources.create("my-http", 16, true)));
  
      return factory;
  }
  

• Or use an environment variable -Dreactor.ipc.netty.workerCount=16. By default, this value is set to Math.max(availableProcessors(), 4).