Hands-On Reactive Programming in Spring 5

Monitoring reactor flows

In Project Reactor 3.2, reactive types Flux and Mono obtained a metrics() operator. This reports operational metrics regarding the stream when called. The metrics() operator behaves similarly to the log() operator. It cooperates with the name() operator to build a target metric name and add a tag. For example, the following code demonstrates how to add metrics to an outgoing SSE stream:

@GetMapping(
       path = "/temperature-stream",
       produces = MediaType.TEXTEVENTSTREAMVALUE)
public Flux<Temperature> events() {
  return temperatureSensor.temperatureStream()                       // (1)
      .name("temperature.stream")                                    // (2)
      .metrics();                                                    // (3)
}

Here, the temperatureSensor.temperatureStream() returns Flux<Temperature> (1), while the name("temperature.stream") ...