Module io.prometheus.metrics.core
Package io.prometheus.metrics.core.exemplars

Class ExemplarSampler

java.lang.Object
io.prometheus.metrics.core.exemplars.ExemplarSampler
public class ExemplarSampler extends Object
The ExemplarSampler selects Spans as exemplars.

There are two types of Exemplars: Regular exemplars are sampled implicitly if a supported tracing library is detected. Custom exemplars are provided explicitly in code, for example if a developer wants to make sure an Exemplar is created for a specific code path.

Spans will be marked as being an Exemplar by calling SpanContext.markCurrentSpanAsExemplar(). The tracer implementation should set a Span attribute to mark the current Span as an Exemplar. This attribute can be used by a trace sampling algorithm to make sure traces with Exemplars are sampled.

The ExemplarSample is rate-limited, so only a small fraction of Spans will be marked as Exemplars in an application with a large number of requests.

See ExemplarSamplerConfig for configuration options.

  • Constructor Details

    • ExemplarSampler

      public ExemplarSampler(ExemplarSamplerConfig config)

    • ExemplarSampler

      public ExemplarSampler(ExemplarSamplerConfig config, io.prometheus.metrics.tracer.common.SpanContext spanContext)
      Constructor with an additional {code spanContext} argument. This is useful for testing, but may also be useful in some production scenarios. If spanContext != null that spanContext is used and SpanContextSupplier is not used. If spanContext == null SpanContextSupplier.getSpanContext() is called to find a span context.

  • Method Details

    • collect

      public io.prometheus.metrics.model.snapshots.Exemplars collect()

    • reset

      public void reset()

    • observe

      public void observe(double value)

    • observeWithExemplar

      public void observeWithExemplar(double value, io.prometheus.metrics.model.snapshots.Labels labels)