OTel logs correlation breaks for transactions-mapped spans

[AlexanderWert]

When does the problem occur?

When receiving an OTel span S that is being mapped to a transaction (e.g. root span, or SpanKind = SERVER) and in addition an OTel log event L that is correlated to that span S (i.e. the log event has the OTLP field SpanID pointing to that span).

Problem

Correlation on the span / transaction breaks.

Reason

In the above situation we map the OTel span S to a transaction document. Thus, the OTLP field SpanID is being mapped to the transaction.id field in the internal model.

When receiving the corresponding log event L, the log event points to S through an OTLP SpanID field. However, since the log event L does not carry the characteristics of the span S (but only the SpanID) we cannot decide whether the OTLP field SpanID on the log event needs to be mapped to a span.id or a transaction.id field. As a result the SpanID OTLP field is always being mapped to the span.id field (even for associated transaction documents).