add _total suffixes to prometheus counters

CHANGELOG.md

@@ -16,6 +16,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - `sdktrace.TraceProvider.Shutdown` and `sdktrace.TraceProvider.ForceFlush` to not return error when no processor register. (#3268)
 - The `"go.opentelemetry.io/otel/exporters/prometheus".New` now also returns an error indicating the failure to register the exporter with Prometheus. (#3239)
+- The `go.opentelemetry.io/otel/exporters/prometheus` exporter now correctly adds _total suffixes to counter metrics. (#TODO)
 
 ### Fixed
 

exporters/prometheus/exporter.go

@@ -43,6 +43,10 @@ type collector struct {
 	reader metric.Reader
 }
 
+// prometheus counters MUST have a _total suffix:
+// https://github.com/open-telemetry/opentelemetry-specification/blob/v1.14.0/specification/metrics/data-model.md#sums-1
+const counterSuffix = "_total"
+
 // New returns a Prometheus Exporter.
 func New(opts ...Option) (*Exporter, error) {
 	cfg := newConfig(opts...)
@@ -173,7 +177,7 @@ func getSumMetricData[N int64 | float64](sum metricdata.Sum[N], m metricdata.Met
 	dataPoints := make([]*metricData, 0, len(sum.DataPoints))
 	for _, dp := range sum.DataPoints {
 		keys, values := getAttrs(dp.Attributes)
-		desc := prometheus.NewDesc(sanitizeName(m.Name), m.Description, keys, nil)
+		desc := prometheus.NewDesc(sanitizeName(m.Name)+counterSuffix, m.Description, keys, nil)
 		md := &metricData{
 			name:            m.Name,
 			description:     desc,

exporters/prometheus/testdata/counter.txt

@@ -1,3 +1,3 @@
-# HELP foo a simple counter
-# TYPE foo counter
-foo{A="B",C="D",E="true",F="42"} 24.3
+# HELP foo_total a simple counter
+# TYPE foo_total counter
+foo_total{A="B",C="D",E="true",F="42"} 24.3

exporters/prometheus/testdata/gauge.txt

@@ -1,3 +1,3 @@
-# HELP bar a fun little gauge
-# TYPE bar counter
-bar{A="B",C="D"} 75
+# HELP bar_total a fun little gauge
+# TYPE bar_total counter
+bar_total{A="B",C="D"} 75

exporters/prometheus/testdata/sanitized_labels.txt

@@ -1,3 +1,3 @@
-# HELP foo a sanitary counter
-# TYPE foo counter
-foo{A_B="Q",C_D="Y;Z"} 24.3
+# HELP foo_total a sanitary counter
+# TYPE foo_total counter
+foo_total{A_B="Q",C_D="Y;Z"} 24.3

exporters/prometheus/testdata/sanitized_names.txt

@@ -1,12 +1,12 @@
-# HELP bar a fun little gauge
-# TYPE bar counter
-bar{A="B",C="D"} 75
-# HELP _0invalid_counter_name a counter with an invalid name
-# TYPE _0invalid_counter_name counter
-_0invalid_counter_name{A="B",C="D"} 100
-# HELP invalid_gauge_name a gauge with an invalid name
-# TYPE invalid_gauge_name counter
-invalid_gauge_name{A="B",C="D"} 100
+# HELP bar_total a fun little gauge
+# TYPE bar_total counter
+bar_total{A="B",C="D"} 75
+# HELP _0invalid_counter_name_total a counter with an invalid name
+# TYPE _0invalid_counter_name_total counter
+_0invalid_counter_name_total{A="B",C="D"} 100
+# HELP invalid_gauge_name_total a gauge with an invalid name
+# TYPE invalid_gauge_name_total counter
+invalid_gauge_name_total{A="B",C="D"} 100
 # HELP invalid_hist_name a histogram with an invalid name
 # TYPE invalid_hist_name histogram
 invalid_hist_name_bucket{A="B",C="D",le="0"} 0