rest otel support (#943)

rest/handler/otelhandler.go

@@ -0,0 +1,36 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/tal-tech/go-zero/core/opentelemetry"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
+	oteltrace "go.opentelemetry.io/otel/trace"
+)
+
+func OtelHandler(path string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		if !opentelemetry.Enabled() {
+			return next
+		}
+
+		propagator := otel.GetTextMapPropagator()
+		tracer := otel.GetTracerProvider().Tracer(opentelemetry.TraceName)
+
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ctx := propagator.Extract(r.Context(), propagation.HeaderCarrier(r.Header))
+			spanCtx, span := tracer.Start(
+				ctx,
+				path,
+				oteltrace.WithSpanKind(oteltrace.SpanKindServer),
+				oteltrace.WithAttributes(semconv.HTTPServerAttributesFromHTTPRequest("", path, r)...),
+			)
+			defer span.End()
+
+			next.ServeHTTP(w, r.WithContext(spanCtx))
+		})
+	}
+}