From ca06bbe2536d9f40c5c1da171a272564a0784b3d Mon Sep 17 00:00:00 2001
From: David Ashpole <dashpole@google.com>
Date: Wed, 26 Jul 2023 20:19:52 +0000
Subject: [PATCH] do not append _total if the metric already ends in _total

---
 CHANGELOG.md                          |  1 +
 exporters/prometheus/exporter.go      | 42 +++++++++++++++------------
 exporters/prometheus/exporter_test.go | 29 ++++++++++++++++++
 3 files changed, 53 insertions(+), 19 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 691ed9e8c4f8..2c446acd2891 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - If a Reader's AggregationSelector return nil or DefaultAggregation the pipeline will use the default aggregation. (#4350)
 - Log a suggested view that fixes instrument conflicts in `go.opentelemetry.io/otel/sdk/metric`. (#4349)
 - Fix possible panic, deadlock and race condition in batch span processor in `go.opentelemetry.io/otel/sdk/trace`. (#4353)
+- Do not append _total if the counter already ends in total `go.opentelemetry.io/otel/exporter/prometheus`. (#4373)
 
 ## [1.16.0/0.39.0] 2023-05-18
 
diff --git a/exporters/prometheus/exporter.go b/exporters/prometheus/exporter.go
index 04f26e7cb4af..b6d3fa27341d 100644
--- a/exporters/prometheus/exporter.go
+++ b/exporters/prometheus/exporter.go
@@ -189,10 +189,11 @@ func (c *collector) Collect(ch chan<- prometheus.Metric) {
 		}
 
 		for _, m := range scopeMetrics.Metrics {
-			typ, name := c.metricTypeAndName(m)
+			typ := c.metricType(m)
 			if typ == nil {
 				continue
 			}
+			name := c.getName(m, typ)
 
 			drop, help := c.validateMetrics(name, m.Description, typ)
 			if drop {
@@ -336,17 +337,23 @@ var unitSuffixes = map[string]string{
 }
 
 // getName returns the sanitized name, prefixed with the namespace and suffixed with unit.
-func (c *collector) getName(m metricdata.Metrics) string {
+func (c *collector) getName(m metricdata.Metrics, typ *dto.MetricType) string {
 	name := sanitizeName(m.Name)
+	addCounterSuffix := !c.withoutCounterSuffixes && *typ == dto.MetricType_COUNTER
+	if addCounterSuffix {
+		// Remove the _total suffix here, as we will re-add the total suffix
+		// later, and it needs to come after the unit suffix.
+		name = strings.TrimSuffix(name, counterSuffix)
+	}
 	if c.namespace != "" {
 		name = c.namespace + name
 	}
-	if c.withoutUnits {
-		return name
-	}
-	if suffix, ok := unitSuffixes[m.Unit]; ok {
+	if suffix, ok := unitSuffixes[m.Unit]; !c.withoutUnits && ok {
 		name += suffix
 	}
+	if addCounterSuffix {
+		name += counterSuffix
+	}
 	return name
 }
 
@@ -403,27 +410,24 @@ func sanitizeName(n string) string {
 	return b.String()
 }
 
-func (c *collector) metricTypeAndName(m metricdata.Metrics) (*dto.MetricType, string) {
-	name := c.getName(m)
-
+func (c *collector) metricType(m metricdata.Metrics) *dto.MetricType {
 	switch v := m.Data.(type) {
 	case metricdata.Histogram[int64], metricdata.Histogram[float64]:
-		return dto.MetricType_HISTOGRAM.Enum(), name
+		return dto.MetricType_HISTOGRAM.Enum()
 	case metricdata.Sum[float64]:
-		if v.IsMonotonic && !c.withoutCounterSuffixes {
-			return dto.MetricType_COUNTER.Enum(), name + counterSuffix
+		if v.IsMonotonic {
+			return dto.MetricType_COUNTER.Enum()
 		}
-		return dto.MetricType_GAUGE.Enum(), name
+		return dto.MetricType_GAUGE.Enum()
 	case metricdata.Sum[int64]:
-		if v.IsMonotonic && !c.withoutCounterSuffixes {
-			return dto.MetricType_COUNTER.Enum(), name + counterSuffix
+		if v.IsMonotonic {
+			return dto.MetricType_COUNTER.Enum()
 		}
-		return dto.MetricType_GAUGE.Enum(), name
+		return dto.MetricType_GAUGE.Enum()
 	case metricdata.Gauge[int64], metricdata.Gauge[float64]:
-		return dto.MetricType_GAUGE.Enum(), name
+		return dto.MetricType_GAUGE.Enum()
 	}
-
-	return nil, ""
+	return nil
 }
 
 func (c *collector) scopeInfo(scope instrumentation.Scope) (prometheus.Metric, error) {
diff --git a/exporters/prometheus/exporter_test.go b/exporters/prometheus/exporter_test.go
index fb234aa1f26b..80eab25d7003 100644
--- a/exporters/prometheus/exporter_test.go
+++ b/exporters/prometheus/exporter_test.go
@@ -71,6 +71,35 @@ func TestPrometheusExporter(t *testing.T) {
 				counter.Add(ctx, 5, otelmetric.WithAttributeSet(attrs2))
 			},
 		},
+		{
+			name:         "counter that already has a total suffix",
+			expectedFile: "testdata/counter.txt",
+			recordMetrics: func(ctx context.Context, meter otelmetric.Meter) {
+				opt := otelmetric.WithAttributes(
+					attribute.Key("A").String("B"),
+					attribute.Key("C").String("D"),
+					attribute.Key("E").Bool(true),
+					attribute.Key("F").Int(42),
+				)
+				counter, err := meter.Float64Counter(
+					"foo.total",
+					otelmetric.WithDescription("a simple counter"),
+					otelmetric.WithUnit("ms"),
+				)
+				require.NoError(t, err)
+				counter.Add(ctx, 5, opt)
+				counter.Add(ctx, 10.3, opt)
+				counter.Add(ctx, 9, opt)
+
+				attrs2 := attribute.NewSet(
+					attribute.Key("A").String("D"),
+					attribute.Key("C").String("B"),
+					attribute.Key("E").Bool(true),
+					attribute.Key("F").Int(42),
+				)
+				counter.Add(ctx, 5, otelmetric.WithAttributeSet(attrs2))
+			},
+		},
 		{
 			name:         "counter with suffixes disabled",
 			expectedFile: "testdata/counter_disabled_suffix.txt",