Metrics Plugin

Overview

The Metrics plugin controls which metrics library Pinot uses to collect and expose internal metrics. All Pinot components (broker, server, controller, minion) use the PinotMetricsFactory SPI to create metric registries, counters, gauges, meters, timers, and JMX reporters.

Pinot ships with three metrics implementations:

Implementation	Class	Description
Dropwizard	DropwizardMetricsFactory	Based on Dropwizard Metrics (formerly Codahale). This is the default.
Yammer	YammerMetricsFactory	Based on Yammer Metrics, used in older Pinot versions.
Compound	CompoundPinotMetricsFactory	A meta-implementation that fans metrics out to multiple registries simultaneously. Useful for comparing or migrating between metrics libraries.

Configuration

To configure which metrics factory Pinot uses, set the following property in the component configuration (broker, server, controller, or minion):

pinot.<component>.metrics.factory.className=org.apache.pinot.plugin.metrics.dropwizard.DropwizardMetricsFactory

Replace <component> with broker, server, controller, or minion.

Dropwizard Configuration

The Dropwizard metrics plugin supports an optional JMX domain property:

pinot.metrics.dropwizard.domain=org.apache.pinot.common.metrics

If not set, the default domain org.apache.pinot.common.metrics is used.

Yammer Configuration

The Yammer metrics plugin does not require any additional configuration beyond setting the factory class name.

Compound Metrics Configuration

The Compound metrics factory reports to multiple metrics registries at once. This is useful for comparing behavior between different implementations during a migration.

pinot.<component>.metrics.factory.className=org.apache.pinot.plugin.metrics.compound.CompoundPinotMetricsFactory

The following additional properties control how the Compound factory discovers sub-factories:

Property Suffix	Values	Description
compound.algorithm	CLASSPATH (default), SERVICE_LOADER, LIST	How to discover sub-factories.
compound.ignored	Comma-separated class names	Metrics factory classes to exclude.
compound.list	Comma-separated class names	Explicit list of factory classes (used with LIST algorithm).

SPI Interface

To write a custom metrics plugin, implement the PinotMetricsFactory interface:

public interface PinotMetricsFactory {
  void init(PinotConfiguration metricsConfiguration);
  PinotMetricsRegistry getPinotMetricsRegistry();
  PinotMetricName makePinotMetricName(Class<?> klass, String name);
  <T> PinotGauge<T> makePinotGauge(Function<Void, T> condition);
  PinotJmxReporter makePinotJmxReporter(PinotMetricsRegistry metricsRegistry);
  String getMetricsFactoryName();
}

Key Methods

Method	Description
init(PinotConfiguration)	Initializes the factory with Pinot configuration.
getPinotMetricsRegistry()	Returns the singleton metrics registry instance.
makePinotMetricName(Class, String)	Creates a metric name scoped to a class.
makePinotGauge(Function)	Creates a gauge metric backed by the provided function.
makePinotJmxReporter(PinotMetricsRegistry)	Creates a JMX reporter for the given registry.
getMetricsFactoryName()	Returns a human-readable name for the factory.

Writing a Custom Metrics Plugin

To implement a custom metrics plugin:

1. Create a class that implements PinotMetricsFactory.

2. Annotate it with @AutoService(PinotMetricsFactory.class) and @MetricsFactory.

3. Implement wrapper classes for the Pinot metric types (PinotCounter, PinotGauge, PinotMeter, PinotTimer, PinotMetricsRegistry, PinotJmxReporter).

4. Package it as a Pinot plugin (see Write Custom Plugins).

5. Place the plugin JAR in the Pinot /plugins directory.

A custom metrics plugin could be useful for integrating with monitoring systems such as Prometheus, Micrometer, or OpenTelemetry.