Use histograms instead of gagues

Removed test assertion for metric as histograms are not collectors
so we can't really test it. Left the test though as it's still valuable.

2 files changed, 3 insertions, 8 deletions

diff --git a/internal/serving/disk/reader.go b/internal/serving/disk/reader.go
index 949dd4e0..83fe3378 100644
--- a/internal/serving/disk/reader.go
+++ b/internal/serving/disk/reader.go
@@ -17,7 +17,7 @@ import (
 
 // Reader is a disk access driver
 type Reader struct {
-	fileSizeMetric *prometheus.GaugeVec
+	fileSizeMetric *prometheus.HistogramVec
 }
 
 func (reader *Reader) tryFile(h serving.Handler) error {
@@ -144,7 +144,7 @@ func (reader *Reader) serveFile(w http.ResponseWriter, r *http.Request, origPath
 		return err
 	}
 
-	reader.fileSizeMetric.With(prometheus.Labels{"serving_type": "disk", "content_type": contentType}).Set(float64(fi.Size()))
+	reader.fileSizeMetric.With(prometheus.Labels{"serving_type": "disk", "content_type": contentType}).Observe(float64(fi.Size()))
 
 	w.Header().Set("Content-Type", contentType)
 	http.ServeContent(w, r, origPath, fi.ModTime(), file)
@@ -172,7 +172,7 @@ func (reader *Reader) serveCustomFile(w http.ResponseWriter, r *http.Request, co
 		return err
 	}
 
-	reader.fileSizeMetric.With(prometheus.Labels{"serving_type": "disk", "content_type": contentType}).Set(float64(fi.Size()))
+	reader.fileSizeMetric.With(prometheus.Labels{"serving_type": "disk", "content_type": contentType}).Observe(float64(fi.Size()))
 
 	w.Header().Set("Content-Type", contentType)
 	w.Header().Set("Content-Length", strconv.FormatInt(fi.Size(), 10))
diff --git a/internal/serving/disk/serving_test.go b/internal/serving/disk/serving_test.go
index 01a9a775..6398700d 100644
--- a/internal/serving/disk/serving_test.go
+++ b/internal/serving/disk/serving_test.go
@@ -6,12 +6,9 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/stretchr/testify/require"
 
 	"gitlab.com/gitlab-org/gitlab-pages/internal/serving"
-	"gitlab.com/gitlab-org/gitlab-pages/metrics"
 )
 
 func TestDisk_ServeFileHTTP(t *testing.T) {
@@ -38,6 +35,4 @@ func TestDisk_ServeFileHTTP(t *testing.T) {
 	require.NoError(t, err)
 
 	require.Contains(t, string(body), "HTML Document")
-	gaugeValue := testutil.ToFloat64(metrics.ServingFileSize.With(prometheus.Labels{"serving_type": "disk", "content_type": resp.Header.Get("Content-Type")}))
-	require.Greater(t, gaugeValue, float64(0))
 }