contrib/gin-gonic/gin: set error tag only for 5xx (#449)

contrib/gin-gonic/gin/gintrace.go

@@ -3,6 +3,7 @@ package gin // import "gopkg.in/DataDog/dd-trace-go.v1/contrib/gin-gonic/gin"
 
 import (
 	"fmt"
+	"net/http"
 	"strconv"
 
 	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
@@ -42,11 +43,14 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 		// serve the request to the next middleware
 		c.Next()
 
-		span.SetTag(ext.HTTPCode, strconv.Itoa(c.Writer.Status()))
+		status := c.Writer.Status()
+		span.SetTag(ext.HTTPCode, strconv.Itoa(status))
+		if status >= 500 && status < 600 {
+			span.SetTag(ext.Error, fmt.Errorf("%d: %s", status, http.StatusText(status)))
+		}
 
 		if len(c.Errors) > 0 {
 			span.SetTag("gin.errors", c.Errors.String())
-			span.SetTag(ext.Error, c.Errors[0])
 		}
 	}
 }

contrib/gin-gonic/gin/gintrace_test.go

@@ -2,6 +2,7 @@ package gin
 
 import (
 	"errors"
+	"fmt"
 	"html/template"
 	"net/http/httptest"
 	"testing"
@@ -85,29 +86,63 @@ func TestError(t *testing.T) {
 	// setup
 	router := gin.New()
 	router.Use(Middleware("foobar"))
-	wantErr := errors.New("oh no")
+	responseErr := errors.New("oh no")
 
-	// a handler with an error and make the requests
-	router.GET("/err", func(c *gin.Context) {
-		c.AbortWithError(500, wantErr)
+	t.Run("server error", func(*testing.T) {
+		defer mt.Reset()
+
+		// configure a handler that returns an error and 5xx status code
+		router.GET("/server_err", func(c *gin.Context) {
+			c.AbortWithError(500, responseErr)
+		})
+		r := httptest.NewRequest("GET", "/server_err", nil)
+		w := httptest.NewRecorder()
+		router.ServeHTTP(w, r)
+		response := w.Result()
+		assert.Equal(response.StatusCode, 500)
+
+		// verify the errors and status are correct
+		spans := mt.FinishedSpans()
+		assert.Len(spans, 1)
+		if len(spans) < 1 {
+			t.Fatalf("no spans")
+		}
+		span := spans[0]
+		assert.Equal("http.request", span.OperationName())
+		assert.Equal("foobar", span.Tag(ext.ServiceName))
+		assert.Equal("500", span.Tag(ext.HTTPCode))
+		assert.Equal(fmt.Sprintf("Error #01: %s\n", responseErr), span.Tag("gin.errors"))
+		// server errors set the ext.Error tag
+		assert.Equal("500: Internal Server Error", span.Tag(ext.Error).(error).Error())
 	})
-	r := httptest.NewRequest("GET", "/err", nil)
-	w := httptest.NewRecorder()
-	router.ServeHTTP(w, r)
-	response := w.Result()
-	assert.Equal(response.StatusCode, 500)
 
-	// verify the errors and status are correct
-	spans := mt.FinishedSpans()
-	assert.Len(spans, 1)
-	if len(spans) < 1 {
-		t.Fatalf("no spans")
-	}
-	span := spans[0]
-	assert.Equal("http.request", span.OperationName())
-	assert.Equal("foobar", span.Tag(ext.ServiceName))
-	assert.Equal("500", span.Tag(ext.HTTPCode))
-	assert.Equal(wantErr.Error(), span.Tag(ext.Error).(error).Error())
+	t.Run("client error", func(*testing.T) {
+		defer mt.Reset()
+
+		// configure a handler that returns an error and 4xx status code
+		router.GET("/client_err", func(c *gin.Context) {
+			c.AbortWithError(418, responseErr)
+		})
+		r := httptest.NewRequest("GET", "/client_err", nil)
+		w := httptest.NewRecorder()
+		router.ServeHTTP(w, r)
+		response := w.Result()
+		assert.Equal(response.StatusCode, 418)
+
+		// verify the errors and status are correct
+		spans := mt.FinishedSpans()
+		assert.Len(spans, 1)
+		if len(spans) < 1 {
+			t.Fatalf("no spans")
+		}
+		span := spans[0]
+		assert.Equal("http.request", span.OperationName())
+		assert.Equal("foobar", span.Tag(ext.ServiceName))
+		assert.Equal("418", span.Tag(ext.HTTPCode))
+		assert.Equal(fmt.Sprintf("Error #01: %s\n", responseErr), span.Tag("gin.errors"))
+		// client errors do not set the ext.Error tag
+		assert.Equal(nil, span.Tag(ext.Error))
+	})
 }
 
 func TestHTML(t *testing.T) {