Prometheus middleware should not call c.Error() as it causes double e…

…rror logging.

Handle status code properly when next returns an error

prometheus/prometheus.go

@@ -22,6 +22,7 @@ package prometheus
 
 import (
  "bytes"
+ "errors"
  "net/http"
  "os"
  "strconv"
@@ -364,7 +365,7 @@ func (p *Prometheus) Use(e *echo.Echo) {
 
 // HandlerFunc defines handler function for middleware
 func (p *Prometheus) HandlerFunc(next echo.HandlerFunc) echo.HandlerFunc {
- return func(c echo.Context) (err error) {
+ return func(c echo.Context) error {
  if c.Path() == p.MetricsPath {
  return next(c)
  }
@@ -375,18 +376,22 @@ func (p *Prometheus) HandlerFunc(next echo.HandlerFunc) echo.HandlerFunc {
  start := time.Now()
  reqSz := computeApproximateRequestSize(c.Request())
 
- if err = next(c); err != nil {
- c.Error(err)
- }
+ err := next(c)
 
- status := strconv.Itoa(c.Response().Status)
- url := p.RequestCounterURLLabelMappingFunc(c)
+ status := c.Response().Status
+ if err != nil {
+ var httpError *echo.HTTPError
+ if errors.As(err, &httpError) {
+ status = httpError.Code
+ }
+ if status == 0 || status == http.StatusOK {
+ status = http.StatusInternalServerError
+ }
+ }
 
  elapsed := float64(time.Since(start)) / float64(time.Second)
- resSz := float64(c.Response().Size)
-
- p.reqDur.WithLabelValues(status, c.Request().Method, url).Observe(elapsed)
 
+ url := p.RequestCounterURLLabelMappingFunc(c)
  if len(p.URLLabelFromContext) > 0 {
  u := c.Get(p.URLLabelFromContext)
  if u == nil {
@@ -395,11 +400,15 @@ func (p *Prometheus) HandlerFunc(next echo.HandlerFunc) echo.HandlerFunc {
  url = u.(string)
  }
 
- p.reqCnt.WithLabelValues(status, c.Request().Method, p.RequestCounterHostLabelMappingFunc(c), url).Inc()
- p.reqSz.WithLabelValues(status, c.Request().Method, url).Observe(float64(reqSz))
- p.resSz.WithLabelValues(status, c.Request().Method, url).Observe(resSz)
+ statusStr := strconv.Itoa(status)
+ p.reqDur.WithLabelValues(statusStr, c.Request().Method, url).Observe(elapsed)
+ p.reqCnt.WithLabelValues(statusStr, c.Request().Method, p.RequestCounterHostLabelMappingFunc(c), url).Inc()
+ p.reqSz.WithLabelValues(statusStr, c.Request().Method, url).Observe(float64(reqSz))
+
+ resSz := float64(c.Response().Size)
+ p.resSz.WithLabelValues(statusStr, c.Request().Method, url).Observe(resSz)
 
- return
+ return err
  }
 }
 

prometheus/prometheus_test.go

@@ -134,3 +134,37 @@ func TestMetricsPushGateway(t *testing.T) {
  })
  unregister(p)
 }
+
+func TestMetricsForErrors(t *testing.T) {
+ e := echo.New()
+ p := NewPrometheus("echo", nil)
+ p.Use(e)
+
+ e.GET("/handler_for_ok", func(c echo.Context) error {
+ return c.JSON(http.StatusOK, "OK")
+ })
+ e.GET("/handler_for_nok", func(c echo.Context) error {
+ return c.JSON(http.StatusConflict, "NOK")
+ })
+ e.GET("/handler_for_error", func(c echo.Context) error {
+ return echo.NewHTTPError(http.StatusBadGateway, "BAD")
+ })
+
+ g := gofight.New()
+ g.GET("/handler_for_ok").Run(e, func(r gofight.HTTPResponse, rq gofight.HTTPRequest) { assert.Equal(t, http.StatusOK, r.Code) })
+
+ g.GET("/handler_for_nok").Run(e, func(r gofight.HTTPResponse, rq gofight.HTTPRequest) { assert.Equal(t, http.StatusConflict, r.Code) })
+ g.GET("/handler_for_nok").Run(e, func(r gofight.HTTPResponse, rq gofight.HTTPRequest) { assert.Equal(t, http.StatusConflict, r.Code) })
+
+ g.GET("/handler_for_error").Run(e, func(r gofight.HTTPResponse, rq gofight.HTTPRequest) { assert.Equal(t, http.StatusBadGateway, r.Code) })
+
+ g.GET(p.MetricsPath).Run(e, func(r gofight.HTTPResponse, rq gofight.HTTPRequest) {
+ assert.Equal(t, http.StatusOK, r.Code)
+ body := r.Body.String()
+ assert.Contains(t, body, fmt.Sprintf("%s_requests_total", p.Subsystem))
+ assert.Contains(t, body, `echo_requests_total{code="200",host="",method="GET",url="/handler_for_ok"} 1`)
+ assert.Contains(t, body, `echo_requests_total{code="409",host="",method="GET",url="/handler_for_nok"} 2`)
+ assert.Contains(t, body, `echo_requests_total{code="502",host="",method="GET",url="/handler_for_error"} 1`)
+ })
+ unregister(p)
+}