From a9ccfe85dcc09abde8d11e96210b2f31fba1671d Mon Sep 17 00:00:00 2001
From: Nicholas Wiersma <nick@wiersma.co.za>
Date: Fri, 13 Sep 2019 07:24:50 +0200
Subject: [PATCH] Fixed bug with prometheus label names

---
 prometheus/prometheus.go      | 10 +++++-----
 prometheus/prometheus_test.go | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/prometheus/prometheus.go b/prometheus/prometheus.go
index 904346f..17e16e2 100644
--- a/prometheus/prometheus.go
+++ b/prometheus/prometheus.go
@@ -68,7 +68,7 @@ func (s *Prometheus) Handler() http.Handler {
 
 // Inc increments a count by the value.
 func (s *Prometheus) Inc(name string, value int64, rate float32, tags ...string) {
-	lblNames, lbls := formatTags(tags)
+	lblNames, lbls := formatTags(tags, s.fqn)
 
 	key := createKey(name, lblNames)
 	m, ok := s.counters[key]
@@ -99,7 +99,7 @@ func (s *Prometheus) Dec(name string, value int64, rate float32, tags ...string)
 
 // Gauge measures the value of a metric.
 func (s *Prometheus) Gauge(name string, value float64, rate float32, tags ...string) {
-	lblNames, lbls := formatTags(tags)
+	lblNames, lbls := formatTags(tags, s.fqn)
 
 	key := createKey(name, lblNames)
 	m, ok := s.gauges[key]
@@ -125,7 +125,7 @@ func (s *Prometheus) Gauge(name string, value float64, rate float32, tags ...str
 
 // Timing sends the value of a Duration.
 func (s *Prometheus) Timing(name string, value time.Duration, rate float32, tags ...string) {
-	lblNames, lbls := formatTags(tags)
+	lblNames, lbls := formatTags(tags, s.fqn)
 
 	key := createKey(name, lblNames)
 	m, ok := s.timings[key]
@@ -161,13 +161,13 @@ func createKey(name string, lblNames []string) string {
 }
 
 // formatTags create a prometheus Label map from tags.
-func formatTags(t []string) ([]string, prometheus.Labels) {
+func formatTags(t []string, fqn *FQN) ([]string, prometheus.Labels) {
 	t = tags.Deduplicate(tags.Normalize(t))
 
 	names := make([]string, 0, len(t)/2)
 	lbls := make(prometheus.Labels, len(t)/2)
 	for i := 0; i < len(t); i += 2 {
-		key := t[i]
+		key := fqn.Format(t[i])
 		names = append(names, key)
 		lbls[key] = t[i+1]
 	}
diff --git a/prometheus/prometheus_test.go b/prometheus/prometheus_test.go
index 40c6a51..e044d30 100644
--- a/prometheus/prometheus_test.go
+++ b/prometheus/prometheus_test.go
@@ -77,6 +77,20 @@ func TestPrometheus_Timing(t *testing.T) {
 	assert.Contains(t, rr.Body.String(), "test_test_test_count{test=\"test\"} 1")
 }
 
+func TestPrometheus_ConvertsLabels(t *testing.T) {
+	l := &testLogger{}
+	s := prometheus.New("test.test", l)
+
+	s.Inc("test", 2, 1.0, "test-label", "test")
+
+	rr := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/metrics", nil)
+	s.Handler().ServeHTTP(rr, req)
+
+	assert.Equal(t, "msg=", l.Render())
+	assert.Contains(t, rr.Body.String(), "test_test_test{test_label=\"test\"} 2")
+}
+
 func TestPrometheus_Close(t *testing.T) {
 	l := &testLogger{}
 	s := prometheus.New("test.test", l)