Spring boot actuator 2 metrics from custom function

Question

I am in the spring-boot-actuator world mow...

How can I add my own metrics coming from a custom function from my @Service class?

I would expect to have something like

meterRegistry.registerNewGauge(
    "animals_count",
    "cats",
    animalCounterService::countCatsFromDatabase
);

currently i can only find easy metrics like

meterRegistry.counter("animals_count").increment();

but that doesn't help much when I have to aggregate things like database entries. I need a more flexible one. I also found something like MeterBinder.bindTo but that didn't worked. No error, nothing in metrics. I am searching now for months without any success.

thanks

Answer 1

I'm assuming you're using Micrometer for metrics, right?

If so, you can create a gauge and bind it to any object that provides a method that returns double like this:

@Service
public class MyService {
...
   public double calculateValueForGauge() {...}
}

MyService service = ...// get from spring
MeterRegistry registry = ... // get from spring


// here is how you can create a gauge and bind it to an arbitrary method of your service
Gauge.builder("some.name.goes.here, service, (service) -> service.calculateValueForGauge())
          .register(registry);

For example you can place the code of gauge registration to the listener that will be called when the application context is started:

@EventListener
public void onApplicationStarted(ApplicationReadyEvent event) {
  // register gauges here
}