Spans with multiple references have no parent when converted to Thrift

[william-tran]

Requirement - what kind of business use case are you trying to solve?

I'm trying to send Jaeger traces through the opentelementry-collector via Thrift HTTP, and out to multiple backends. Some of my traces have spans with multiple parents. Jaeger's UI is tolerant of this situation, but others like Honeycomb expect a parent span for all spans other than the root. See honeycombio/opentelemetry-exporter-go#69

Problem - what in Jaeger blocks you from solving the requirement?

If there are multiple references, JaegerThriftSpanConverter sets the parentId to 0.

However, there's other parts of Jaeger that infer the parent to be the first ChildOf reference:

Proposal - what do you suggest to solve the problem or improve the existing situation?

Maybe this should be clarified in the otel spec, that when converting from a list of OpenTracing Span references, if there exists only one child_of reference from the same trace, use that as the parent, otherwise the span will have no parent. Then apply this consistently to any formats that use span.parentId.

[william-tran]

Looking at the opentracing shim for otel, the first reference is used as the parent regardless of the reference type:
https://github.com/open-telemetry/opentelemetry-java/blob/master/opentracing_shim/src/main/java/io/opentelemetry/opentracingshim/SpanBuilderShim.java

[pavolloffay]

Just to clarify are you using maven artifact jaeger-client-java to create and send traces to Jaeger?

[william-tran]

Yes, this project reproduces the issue: https://github.com/william-tran/tracing-tests