Constructing an OpenTelemetry Span from a String TraceID

To establish the parent-child relationship between spans, the headers must be utilized in situations where context propagation is not viable. In this scenario, a trace ID and span ID are contained within the message broker's headers, which allows the subscriber to create a new span with the parent trace ID.

Solution

The following steps can be taken to construct a context or span on the subscriber side using the trace ID:

1. Define a function with the trace ID as an argument:

func constructNewSpanContext(traceID string) (spanContext trace.SpanContext, err error) {
    traceID, err := trace.TraceIDFromHex(traceID)
    if err != nil {
        return trace.SpanContext{}, err
    }
    return trace.NewSpanContext(trace.SpanContextConfig{
        TraceID: traceID,
    }), nil
}

2. Inside the channel, call the function to construct the span context:

spanContext, err := constructNewSpanContext(request.TraceID)
if err != nil {
    log.Fatal(err)
}

3. Enrich a context with the constructed span context:

requestContext := context.Background()
requestContext = trace.ContextWithSpanContext(requestContext, spanContext)

4. Create a new span using the enriched context:

requestInLoopSpan, _ := otel.Tracer("requestInLoop").Start(requestContext, "requestInLoopSpan")

By following these steps, you can successfully construct a new span on the subscriber side using the trace ID extracted from the message headers, ensuring the hierarchical relationship between the spans.