OpenTelemetryTracer#spanBuilder always sets parent to active span; how can developers create a root span (with no parent)?

[tjquinno]

Environment Details

• Helidon Version: 4.x
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

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Problem Description

The Helidon OpenTelemetryTracer#spanBuilder implementation of our neutral Tracer interface always sets the parent of the new span builder to the currently-active span (if there is one).

How can developers create a root OTel span (with no parent)?

Answer

OpenTelemetry's SpanBuilder type exposes the setNoParent() method which does exactly what you expect...it clears out any current parent setting for the span builder.

So developers using the Helidon tracing API can do the following _if they know they are using the Helidon OpenTelemetry implementation of the Helidon tracing API:

    Span rootSpan = tracer.spanBuilder("rootSpan")
            .update(builder -> builder.unwrap(io.opentelemetry.api.trace.SpanBuilder.class).setNoParent())
            .start();

The example code works only if the Helidon OpenTelemetry implementation is in use. The unwrap will fail (in fact it will probably not even compile) if you are using a different Helidon tracer provider.