fix(tracing): record error on mux

The otellambda wrapper does not record an error when the invoked lambda
fails. We need to do it ourselves for now, otherwise the respective KPIs
will be skewed.

pkg/tracing/mux.go

@@ -6,6 +6,7 @@ import (
 	"github.com/aws/aws-lambda-go/lambda"
 	"go.opentelemetry.io/contrib/instrumentation/github.com/aws/aws-lambda-go/otellambda"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	"go.opentelemetry.io/otel/trace"
 )
@@ -27,6 +28,14 @@ type LambdaHandler struct {
 func (h *LambdaHandler) Invoke(ctx context.Context, payload []byte) ([]byte, error) {
 	span := trace.SpanFromContext(ctx)
 	span.SetAttributes(payloadKey.String(string(payload)))
+	resp, err := h.Handler.Invoke(ctx, payload)
+
+	// surprisingly, otellambda wrapper does not emit the error
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+	}
+
 	// nolint: wrapcheck
-	return h.Handler.Invoke(ctx, payload)
+	return resp, err
 }