Micrometer filter is ignored with CompositeMeterRegistry - spring-boot

Question

I use Spring Boot 2.1.2.RELEASE, and I try to use Micrometer with CompositeMeterRegistry. My goal is to publish some selected meters to ElasticSearch. The code below shows my sample config. The problem is, that the filter is completely ignored (so all metrics are sent to ElasticSearch), although I can see in the logs that it was processed ("filter reply of meter ..." lines).
Strangely, if I define the MeterFilter as a Spring bean, then it's applied to ALL registries (however, I want it to be applied only on "elasticMeterRegistry").
Here is a sample configuration class:
#Configuration
public class AppConfiguration {
#Bean
public ElasticConfig elasticConfig() {
return new ElasticConfig() {
#Override
#Nullable
public String get(final String k) {
return null;
}
};
}
#Bean
public MeterRegistry meterRegistry(final ElasticConfig elasticConfig) {
final CompositeMeterRegistry registry = new CompositeMeterRegistry();
registry.add(new SimpleMeterRegistry());
registry.add(new JmxMeterRegistry(new JmxConfig() {
#Override
public Duration step() {
return Duration.ofSeconds(10);
}
#Override
#Nullable
public String get(String k) {
return null;
}
}, Clock.SYSTEM));
final ElasticMeterRegistry elasticMeterRegistry = new ElasticMeterRegistry(elasticConfig, Clock.SYSTEM);
elasticMeterRegistry.config().meterFilter(new MeterFilter() {
#Override
public MeterFilterReply accept(Meter.Id id) {
final MeterFilterReply reply =
id.getName().startsWith("logback")
? MeterFilterReply.NEUTRAL
: MeterFilterReply.DENY;
log.info("filter reply of meter {}: {}", id.getName(), reply);
return reply;
}
});
registry.add(elasticMeterRegistry);
return registry;
}
}
So, I expect ElasticSearch to receive only "logback" metrics, and JMX to receive all metrics.
UPDATE:
I have played with filters and found a "solution", but I don't really understand why the code above doesn't work.
This works:
elasticMeterRegistry.config().meterFilter(new MeterFilter() {
#Override
public MeterFilterReply accept(Meter.Id id) {
final MeterFilterReply reply =
id.getName().startsWith("logback")
? MeterFilterReply.ACCEPT
: MeterFilterReply.DENY;
log.info("filter reply of meter {}: {}", id.getName(), reply);
return reply;
}
});
The difference is: I return ACCEPT instead of NEUTRAL.
Strangely, the following code does not work (ES gets all metrics):
elasticMeterRegistry.config().meterFilter(
MeterFilter.accept(id -> id.getName().startsWith("logback")));
But this works:
elasticMeterRegistry.config().meterFilter(
MeterFilter.accept(id -> id.getName().startsWith("logback")));
elasticMeterRegistry.config().meterFilter(
MeterFilter.deny());
CONCLUSION:
So, it seems that instead of NEUTRAL, the filter should return ACCEPT. But for meters not starting with "logback", my original filter (with NEUTRAL) returns DENY. Then why are those metrics published to ElasticSearch registry?
Can someone explain this?

Answer 1

This is really a composite of questions. I'll just point out a few points.
For the MeterRegistry bean you defined, Spring Boot will auto-configure an ElasticMeterRegistry bean as there's no ElasticMeterRegistry bean. Instead of creating a CompositeMeterRegistry bean on your own, just define a custom ElasticMeterRegistry bean which is applied the MeterFilter you want and let Spring Boot create one (CompositeMeterRegistry bean) for you.
For MeterFilterReply, ACCEPT will accept the meter immediately, DENY will deny the meter immediately, and NEUTRAL will postpone the decision to next filter(s). Basically meters will be accepted unless there's any DENY.