OTLP with Spring Boot

Metrics

Micrometer knows how to export metrics in OTLP format. For that, add the io.micrometer:micrometer-registry-otlp dependency. This is documented here. The management.otlp.metrics.export.url property can be used to set the OTLP collector url.

Traces

When you add "Distributed Tracing" on start.spring.io, you get the Brave tracer by default. Brave doesn't know how to speak OTLP (yet). To export traces in OTLP, replace the io.micrometer:micrometer-tracing-bridge-brave dependency with io.opentelemetry:opentelemetry-exporter-otlp. This switches the tracer from Brave to OpenTelemetry, which knows how to speak OTLP. To export traces in OTLP format, add the io.opentelemetry:opentelemetry-exporter-otlp dependency. This is documented here. The management.otlp.tracing.endpoint property must be used to set the OTLP collector url.

Logs

To export logs via OTLP, you have to first install the OpenTelemetry logback appender. For that, add the io.opentelemetry.instrumentation:opentelemetry-logback-appender-1.0:2.7.0-alpha dependency. Then add the io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender to the logback-spring.xml configuration. The appender needs to be provided with an OpenTelemetry instance. The class OpenTelemetryAppenderInitializer takes care of that. This is documented here. The management.otlp.logging.endpoint property must be used to set the OTLP collector url.

Testing it yourself

There's a OTLP collector included in this repo, which you can run with Docker Compose:

cd collector/
docker compose up

and then run the application:

./gradlew bootRun

And open http://localhost:8080/ in the browser.

You should now see some logs show up in the collector/file-exporter folder and in the output of Docker Compose.