[Proposal] Add contrib support for cloudevents/sdk-go

[alfredosa]

Package Name

contrib/cloudevents

Package Version(s)

2.4.0, latest

Describe the feature you'd like

I would like to propose adding a contrib package for the official CloudEvents Go SDK: https://github.com/cloudevents/sdk-go.

CloudEvents is a very popular framework now to work with events, in an abstracted way. dd-trace-go does not have a native way to propagate context through CloudEvents.

I propose adding contrib/cloudevents/sdk-go.v2 which would provide:

• Context Injection: functions to work and properly inject span context (mapping to W3C/TraceParent).
• Context Extraction: functions to extract said data
• Publisher Wrapper: aid with a wrapper and inject the context (as cloudevents extensions)
• Handler Wrapper: A function for cloudevents.Client or handler functions to automatically start spans on incoming events.

I would be happy to provide do the code, open a pr with proper testing for the contrib 👍

Is your feature request related to a problem?

Yes, this feature doesn't exist and I developed a package that can do this but I think it would benefit everyone using cloudevents

Describe alternatives you've considered

As described above, I created a package that has been working fine, but thought to raise this for the community! It would be nice to polish and make it like the other extensions a bit more robust

Additional context

Here is the rough implementation logic I am proposing (simplified from our internal code):

package cloudevents

// .... 
// Code not relevant for the discussion
// ....


// Relevant functions >
// InjectTraceContext injects Datadog trace context into a CloudEvent's extensions.
func InjectTraceContext(spanCtx ddtrace.SpanContext, event *cloudevents.Event) error {
	carrier := tracer.TextMapCarrier{}
	if err := tracer.Inject(spanCtx, carrier); err != nil {
		return err
	}
	// Transfer trace headers from carrier to CloudEvent extensions
	for key, value := range carrier {
		event.SetExtension(key, value)
	}
	return nil
}

// ExtractTraceContext extracts Datadog trace context from a CloudEvent's extensions.
func ExtractTraceContext(event cloudevents.Event) (ddtrace.SpanContext, error) {
	carrier := make(tracer.TextMapCarrier)
	for key, val := range extensions {
		// CloudEvents extensions are interfaces, ensure they are strings for the carrier
		if strVal, ok := val.(string); ok {
			carrier[key] = strVal
		}
	}
	return tracer.Extract(carrier)
}

// Test Example so you can see the full flow:
func TestTracingCloudEvents(t *testing.T) {
	mt := mocktracer.Start()
	defer mt.Stop()

	e := event.New()
	e.SetID("1234")
	e.SetType("com.example.test")
	e.SetSource("/test/source")

	ctx := t.Context()
	span, _ := tracer.StartSpanFromContext(ctx, "test.span")
	defer span.Finish()

	// Important here how we can use the event to inject the context.
	err := process.InjectTraceContext(span.Context(), &e)
	require.NoError(t, err, "Failed to inject trace context")

	// Now we can actually verify everything propagates properly.
	ext := e.Extensions()
	assert.Contains(t, ext, "traceparent", "Should contain W3C traceparent")
	assert.Contains(t, ext, "tracestate", "Should contain W3C tracestate")

	extractedCtx, err := process.ExtractTraceContext(e)
	require.NoError(t, err, "Failed to extract trace context")
	assert.NotNil(t, extractedCtx, "Should extract span context")

	t.Logf("Original Trace ID: %s", span.Context().TraceID())
	t.Logf("Extracted Trace ID: %s", extractedCtx.TraceID())
	assert.Equal(t, span.Context().TraceID(), extractedCtx.TraceID(), "Trace IDs should match")
}

We also have the:

• TraceWrapCloudEventsHandler
• Code for publishing.