Overwrite type/unit labels when already set

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

storage/remote/otlptranslator/prometheusremotewrite/helper.go

@@ -554,21 +554,12 @@ func createLabels(name string, baseLabels []prompb.Label, extras ...string) []pr
 func addTypeAndUnitLabels(labels []prompb.Label, metadata prompb.MetricMetadata, settings Settings) []prompb.Label {
 	unitNamer := otlptranslator.UnitNamer{UTF8Allowed: settings.AllowUTF8}
 
-	var hasTypeLabel, hasUnitLabel bool
-	for _, l := range labels {
-		if l.Name == "__type__" {
-			hasTypeLabel = true
-		}
-		if l.Name == "__unit__" {
-			hasUnitLabel = true
-		}
-	}
-	if !hasTypeLabel {
-		labels = append(labels, prompb.Label{Name: "__type__", Value: strings.ToLower(metadata.Type.String())})
-	}
-	if !hasUnitLabel {
-		labels = append(labels, prompb.Label{Name: "__unit__", Value: unitNamer.Build(metadata.Unit)})
-	}
+	labels = slices.DeleteFunc(labels, func(l prompb.Label) bool {
+		return l.Name == "__type__" || l.Name == "__unit__"
+	})
+
+	labels = append(labels, prompb.Label{Name: "__type__", Value: strings.ToLower(metadata.Type.String())})
+	labels = append(labels, prompb.Label{Name: "__unit__", Value: unitNamer.Build(metadata.Unit)})
 
 	return labels
 }

storage/remote/otlptranslator/prometheusremotewrite/helper_test.go

@@ -966,3 +966,58 @@ func TestGetPromExemplars(t *testing.T) {
 		require.Error(t, err)
 	})
 }
+
+func TestAddTypeAndUnitLabels(t *testing.T) {
+	testCases := []struct {
+		name           string
+		inputLabels    []prompb.Label
+		metadata       prompb.MetricMetadata
+		expectedLabels []prompb.Label
+	}{
+		{
+			name: "overwrites existing type and unit labels and preserves other labels",
+			inputLabels: []prompb.Label{
+				{Name: "job", Value: "test-job"},
+				{Name: "__type__", Value: "old_type"},
+				{Name: "instance", Value: "test-instance"},
+				{Name: "__unit__", Value: "old_unit"},
+				{Name: "custom_label", Value: "custom_value"},
+			},
+			metadata: prompb.MetricMetadata{
+				Type: prompb.MetricMetadata_COUNTER,
+				Unit: "seconds",
+			},
+			expectedLabels: []prompb.Label{
+				{Name: "job", Value: "test-job"},
+				{Name: "instance", Value: "test-instance"},
+				{Name: "custom_label", Value: "custom_value"},
+				{Name: "__type__", Value: "counter"},
+				{Name: "__unit__", Value: "seconds"},
+			},
+		},
+		{
+			name: "adds type and unit labels when missing",
+			inputLabels: []prompb.Label{
+				{Name: "job", Value: "test-job"},
+				{Name: "instance", Value: "test-instance"},
+			},
+			metadata: prompb.MetricMetadata{
+				Type: prompb.MetricMetadata_GAUGE,
+				Unit: "bytes",
+			},
+			expectedLabels: []prompb.Label{
+				{Name: "job", Value: "test-job"},
+				{Name: "instance", Value: "test-instance"},
+				{Name: "__type__", Value: "gauge"},
+				{Name: "__unit__", Value: "bytes"},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			result := addTypeAndUnitLabels(tc.inputLabels, tc.metadata, Settings{AllowUTF8: false})
+			require.ElementsMatch(t, tc.expectedLabels, result)
+		})
+	}
+}