OTLP

The Prometheus Java client library allows you to push metrics to an OpenTelemetry endpoint using the OTLP protocol.

To implement this, you need to include prometheus-metrics-exporter as a dependency

implementation 'io.prometheus:prometheus-metrics-exporter-opentelemetry:1.0.0'

<dependency>
    <groupId>io.prometheus</groupId>
    <artifactId>prometheus-metrics-exporter-opentelemetry</artifactId>
    <version>1.0.0</version>
</dependency>

Initialize the OpenTelemetryExporter in your Java code:

OpenTelemetryExporter.builder()
    // optional: call configuration methods here
    .buildAndStart();

By default, the OpenTelemetryExporter will push metrics every 60 seconds to localhost:4317 using grpc protocol. You can configure this in code using the OpenTelemetryExporter.Builder, or at runtime via io.prometheus.exporter.opentelemetry.* properties.

In addition to the Prometheus Java client configuration, the exporter also recognizes standard OpenTelemetry configuration. For example, you can set the OTEL_EXPORTER_OTLP_METRICS_ENDPOINT environment variable to configure the endpoint. The Javadoc for OpenTelemetryExporter.Builder shows which settings have corresponding OTel configuration. The intended use case is that if you attach the OpenTelemetry Java agent for tracing, and use the Prometheus Java client for metrics, it is sufficient to configure the OTel agent because the Prometheus library will pick up the same configuration.

The examples/example-exporter-opentelemetry folder has a docker compose with a complete end-to-end example, including a Java app, the OTel collector, and a Prometheus server.