SigNoz is an open-source APM. It helps developers monitor their applications & troubleshoot problems, an open-source alternative to DataDog, NewRelic, etc.

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I don't think function level data is available ... AFAIK opentelemetry get data of standard client libraries used in the application. Have a look at <https://github.com/open-telemetry/opentelemetry-java-instrumentation> and  <https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/supported-libraries.md>

Would be great to know your thoughts on this