refactor: migrate trace propagation from B3 to W3C TraceContext - switch OTel propagator from b3.New() to propagation.TraceContext{} - rename B3 header constants to generic internal context keys

- remove go.opentelemetry.io/contrib/propagators/b3 dependency                                                                - add amqpHeaderCarrier to inject W3C traceparent into AMQP message headers

constants/trace.go

@@ -1,11 +1,13 @@
 // Package constants define constant variable
 package constants
 
-// Assuming the B3 specification
+// Internal context keys for trace values set by StartTrace middleware.
+// These are gin/stdlib context keys only — actual W3C header propagation
+// (traceparent / tracestate) is handled automatically by the OTel propagator.
 const (
-	HeaderTraceID      = "X-B3-TraceId"
-	HeaderSpanID       = "X-B3-SpanId"
-	HeaderParentSpanID = "X-B3-ParentSpanId"
+	HeaderTraceID      = "trace-id"
+	HeaderSpanID       = "span-id"
+	HeaderParentSpanID = "parent-span-id"
 )
 
 // traceCtxKey is an unexported type for context keys to avoid collisions with other packages.

go.mod

@@ -22,7 +22,6 @@ require (
 	github.com/swaggo/gin-swagger v1.6.0
 	github.com/swaggo/swag v1.16.4
 	github.com/youmark/pkcs8 v0.0.0-20240726163527-a2c0da244d78
-	go.opentelemetry.io/contrib/propagators/b3 v1.43.0
 	go.opentelemetry.io/otel v1.43.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.43.0
 	go.opentelemetry.io/otel/sdk v1.43.0

go.sum

@@ -183,8 +183,6 @@ github.com/youmark/pkcs8 v0.0.0-20240726163527-a2c0da244d78/go.mod h1:aL8wCCfTfS
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
-go.opentelemetry.io/contrib/propagators/b3 v1.43.0 h1:CETqV3QLLPTy5yNrqyMr41VnAOOD4lsRved7n4QG00A=
-go.opentelemetry.io/contrib/propagators/b3 v1.43.0/go.mod h1:Q4mCiCdziYzpNR0g+6UqVotAlCDZdzz6L8jwY4knOrw=
 go.opentelemetry.io/otel v1.43.0 h1:mYIM03dnh5zfN7HautFE4ieIig9amkNANT+xcVxAj9I=
 go.opentelemetry.io/otel v1.43.0/go.mod h1:JuG+u74mvjvcm8vj8pI5XiHy1zDeoCS2LB1spIq7Ay0=
 go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.43.0 h1:88Y4s2C8oTui1LGM6bTWkw0ICGcOLCAI5l6zsD1j20k=

middleware/trace.go

@@ -14,7 +14,6 @@ import (
 	"modelRT/logger"
 
 	"github.com/gin-gonic/gin"
-	"go.opentelemetry.io/contrib/propagators/b3"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
@@ -25,7 +24,7 @@ import (
 )
 
 // InitTracerProvider creates an OTLP TracerProvider and registers it as the global provider.
-// It also registers the B3 propagator to stay compatible with existing B3 infrastructure.
+// It registers the W3C TraceContext propagator (traceparent header).
 // The caller is responsible for calling Shutdown on the returned provider during graceful shutdown.
 func InitTracerProvider(ctx context.Context, cfg config.ModelRTConfig) (*sdktrace.TracerProvider, error) {
 	opts := []otlptracehttp.Option{
@@ -52,18 +51,15 @@ func InitTracerProvider(ctx context.Context, cfg config.ModelRTConfig) (*sdktrac
 	)
 
 	otel.SetTracerProvider(tp)
-	otel.SetTextMapPropagator(b3.New())
+	otel.SetTextMapPropagator(propagation.TraceContext{})
 
 	return tp, nil
 }
 
-// StartTrace extracts upstream B3 trace context from request headers and starts a server span.
-// Typed context keys are also injected for backward compatibility with the existing logger
-// until the logger is migrated to read from the OTel span context (Step 6).
+// StartTrace extracts upstream W3C trace context from request headers and starts a server span.
 func StartTrace() gin.HandlerFunc {
 	tracer := otel.Tracer("modelRT/http")
 	return func(c *gin.Context) {
-		// Extract upstream trace context from B3 headers (X-B3-TraceId etc.)
 		ctx := otel.GetTextMapPropagator().Extract(
 			c.Request.Context(),
 			propagation.HeaderCarrier(c.Request.Header),

mq/publish_up_down_limit_event.go

@@ -11,8 +11,36 @@ import (
 	"modelRT/mq/event"
 
 	amqp "github.com/rabbitmq/amqp091-go"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
 )
 
+// amqpHeaderCarrier adapts amqp.Table to propagation.TextMapCarrier for trace context injection.
+type amqpHeaderCarrier amqp.Table
+
+func (c amqpHeaderCarrier) Get(key string) string {
+	val, ok := amqp.Table(c)[key]
+	if !ok {
+		return ""
+	}
+	str, _ := val.(string)
+	return str
+}
+
+func (c amqpHeaderCarrier) Set(key, value string) {
+	amqp.Table(c)[key] = value
+}
+
+func (c amqpHeaderCarrier) Keys() []string {
+	keys := make([]string, 0, len(c))
+	for k := range c {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+var _ propagation.TextMapCarrier = amqpHeaderCarrier{}
+
 // MsgChan define variable of channel to store messages that need to be sent to rabbitMQ
 var MsgChan chan *event.EventRecord
 
@@ -124,6 +152,10 @@ func PushUpDownLimitEventToRabbitMQ(ctx context.Context, msgChan chan *event.Eve
 				continue
 			}
 
+			// inject current trace context into AMQP headers so eventRT can restore the span chain
+			headers := amqp.Table{}
+			otel.GetTextMapPropagator().Inject(ctx, amqpHeaderCarrier(headers))
+
 			// send event alarm message to rabbitMQ queue
 			routingKey := eventRecord.Category
 			pubCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
@@ -135,6 +167,7 @@ func PushUpDownLimitEventToRabbitMQ(ctx context.Context, msgChan chan *event.Eve
 				amqp.Publishing{
 					ContentType: "text/plain",
 					Body:        recordBytes,
+					Headers:     headers,
 				})
 			cancel()