Class MeterRegistryFactory


public final class MeterRegistryFactory extends Object
Provides access to the MeterRegistry Helidon SE uses to collect meters and report their metrics.

In reality, we use a CompositeMeterRegistry to which we, by default, add a PrometheusMeterRegistry and to which the developer can add, via either configuration or builder, other MeterRegistry instances.

Using the factory

Use this factory in either of two ways:

  1. Access the singleton instance via getInstance() or getInstance(Builder). The factory remembers the factory instance, lazily instantiated by the most recent invocation of either method.
  2. A custom instance via create() or create(Config). Instances of the factory created this way are independent of the singleton created by getInstance() or getInstance(Builder).

Adding developer-requested registries

In Micrometer, different registries report their contents in different formats. Further, there is no common abstract method defined on MeterRegistry which all implementations override; each MeterRegistry has its own particular way of furnishing metrics output. By default, we use a PrometheusMeterRegistry to support Prometheus/OpenMetrics format. Developers can enroll other registries to support other formats. We need to know which registry to use in response to receiving an HTTP request for Micrometer metrics output.

To allow us to do this, when our code or developer's enrolls a registry, it also passes a function that accepts a ServerRequest and returns an Optional<Handler>. The function is expected to inspect the request, and if it wants to process that request (which means, if that registry should be used to respond to that request), it returns an Optional.of a Handler. The handler uses the registry-specific mechanism for retrieving formatted meter and metrics information and sets and returns the HTTP response. If the function decides that its corresponding meter registry is not suitable for that particular request, it returns an Optional.empty().

When a Micrometer request arrives, the Helidon code invokes the functions associated with all enrolled registries, in the order of enrollment. The first function that returns a non-empty Optional wins and must populate and return the ServerResponse.

  • Method Details

    • create

      public static MeterRegistryFactory create()
      Creates a new factory using default settings (no config).
      initialized MeterRegistryFactory
    • create

      public static MeterRegistryFactory create(Config config)
      Creates a new factory using the specified config.
      config - the config to use in initializing the factory
      initialized MeterRegistryFactory
    • getInstance

      public static MeterRegistryFactory getInstance()
      Returns the singleton instance of the factory.
      factory singleton
    • getInstance

      public static MeterRegistryFactory getInstance(MeterRegistryFactory.Builder builder)
      Creates and saves as the singleton a new factory.
      builder - the Builder to use in constructing the new singleton instance
      MeterRegistryFactory using the Builder
    • builder

      public static MeterRegistryFactory.Builder builder()
      Returns a new Builder for constructing a MeterRegistryFactory.
      initialized builder
    • meterRegistry

      public io.micrometer.core.instrument.MeterRegistry meterRegistry()
      Returns the MeterRegistry associated with this factory instance.
      the meter registry