feat(otel): adding support for OpenTelemetry logs

ddtrace/opentelemetry/log/correlation.go

@@ -0,0 +1,95 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2025 Datadog, Inc.
+
+package log
+
+import (
+	"context"
+	"encoding/binary"
+
+	"github.com/DataDog/dd-trace-go/v2/ddtrace/tracer"
+
+	oteltrace "go.opentelemetry.io/otel/trace"
+)
+
+// ddSpanWrapper wraps a Datadog span to implement the OTel Span interface minimally.
+// This allows DD spans to be visible to OTel APIs like trace.SpanFromContext.
+type ddSpanWrapper struct {
+	oteltrace.Span // Embed noop span for unimplemented methods
+	dd             *tracer.Span
+	spanContext    oteltrace.SpanContext
+}
+
+// SpanContext returns the OTel SpanContext derived from the DD span.
+func (w *ddSpanWrapper) SpanContext() oteltrace.SpanContext {
+	return w.spanContext
+}
+
+// IsRecording returns true if the span is recording.
+func (w *ddSpanWrapper) IsRecording() bool {
+	// DD spans are always recording if not finished
+	return true
+}
+
+// ddSpanContextToOtel converts a Datadog span context to an OTel SpanContext.
+func ddSpanContextToOtel(ddCtx *tracer.SpanContext) oteltrace.SpanContext {
+	// Convert DD trace ID (128-bit) to OTel TraceID
+	var traceID oteltrace.TraceID
+	traceID = ddCtx.TraceIDBytes()
+
+	// Convert DD span ID (64-bit) to OTel SpanID (64-bit)
+	var spanID oteltrace.SpanID
+	binary.BigEndian.PutUint64(spanID[:], ddCtx.SpanID())
+
+	// Create OTel span context
+	config := oteltrace.SpanContextConfig{
+		TraceID:    traceID,
+		SpanID:     spanID,
+		TraceFlags: oteltrace.FlagsSampled, // DD spans are sampled by default
+		Remote:     false,
+	}
+
+	return oteltrace.NewSpanContext(config)
+}
+
+// contextWithDDSpan wraps a Datadog span in an OpenTelemetry span context and adds it to the context.
+// This allows OpenTelemetry APIs like trace.SpanFromContext to find the Datadog span.
+//
+// If the context already has an OpenTelemetry span, it is preserved.
+// If there's a Datadog span in the context but no OpenTelemetry span, this creates a bridge.
+//
+// This function is internal and used automatically by ddAwareLogger.
+func contextWithDDSpan(ctx context.Context) context.Context {
+	// Check if there's already an OTel span in the context
+	if oteltrace.SpanFromContext(ctx).SpanContext().IsValid() {
+		// OTel span already present, no need to bridge
+		return ctx
+	}
+
+	// Check if there's a DD span in the context
+	ddSpan, ok := tracer.SpanFromContext(ctx)
+	if !ok {
+		// No DD span, return original context
+		return ctx
+	}
+
+	// Create an OTel span wrapper for the DD span
+	otelSpanCtx := ddSpanContextToOtel(ddSpan.Context())
+
+	// Verify the span context is valid
+	if !otelSpanCtx.IsValid() {
+		// Something went wrong with conversion, return original context
+		return ctx
+	}
+
+	wrapper := &ddSpanWrapper{
+		Span:        oteltrace.SpanFromContext(ctx), // Use existing (noop) span
+		dd:          ddSpan,
+		spanContext: otelSpanCtx,
+	}
+
+	// Add the wrapped span to the context
+	return oteltrace.ContextWithSpan(ctx, wrapper)
+}