Preserve unknown, info, and stateset metric types from prometheus rec…

…eivers to exporters (#32605)

.chloggen/prometheus-additional-types.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: prometheusreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Prometheus receivers and exporters now preserve 'unknown', 'info', and 'stateset' types.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [16768]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: It uses the metric.metadata field with the 'prometheus.type' key to store the original type.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

exporter/prometheusexporter/collector.go

@@ -147,7 +147,12 @@ func (c *collector) convertGauge(metric pmetric.Metric, resourceAttrs pcommon.Ma
 	case pmetric.NumberDataPointValueTypeDouble:
 		value = ip.DoubleValue()
 	}
-	m, err := prometheus.NewConstMetric(desc, prometheus.GaugeValue, value, attributes...)
+	metricType := prometheus.GaugeValue
+	originalType, ok := metric.Metadata().Get(prometheustranslator.MetricMetadataTypeKey)
+	if ok && originalType.Str() == string(model.MetricTypeUnknown) {
+		metricType = prometheus.UntypedValue
+	}
+	m, err := prometheus.NewConstMetric(desc, metricType, value, attributes...)
 	if err != nil {
 		return nil, err
 	}

exporter/prometheusexporter/collector_test.go

@@ -17,6 +17,8 @@ import (
 	conventions "go.opentelemetry.io/collector/semconv/v1.6.1"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
+
+	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
 type mockAccumulator struct {
@@ -396,6 +398,24 @@ func TestCollectMetrics(t *testing.T) {
 				dp.Attributes().PutStr("label_2", "2")
 				dp.SetTimestamp(pcommon.NewTimestampFromTime(ts))
 
+				return
+			},
+		},
+		{
+			name:       "Unknown",
+			metricType: prometheus.UntypedValue,
+			value:      42.42,
+			metric: func(ts time.Time) (metric pmetric.Metric) {
+				metric = pmetric.NewMetric()
+				metric.SetName("test_metric")
+				metric.SetDescription("test description")
+				metric.Metadata().PutStr(prometheustranslator.MetricMetadataTypeKey, "unknown")
+				dp := metric.SetEmptyGauge().DataPoints().AppendEmpty()
+				dp.SetDoubleValue(42.42)
+				dp.Attributes().PutStr("label_1", "1")
+				dp.Attributes().PutStr("label_2", "2")
+				dp.SetTimestamp(pcommon.NewTimestampFromTime(ts))
+
 				return
 			},
 		},

pkg/translator/prometheus/constants.go

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package prometheus // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
+
+const (
+	// MetricMetadataTypeKey is the key used to store the original Prometheus
+	// type in metric metadata:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#metric-metadata
+	MetricMetadataTypeKey = "prometheus.type"
+)

pkg/translator/prometheusremotewrite/otlp_to_openmetrics_metadata.go

@@ -4,22 +4,34 @@
 package prometheusremotewrite // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheusremotewrite"
 
 import (
+	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/prompb"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 
 	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
 func otelMetricTypeToPromMetricType(otelMetric pmetric.Metric) prompb.MetricMetadata_MetricType {
+	// metric metadata can be used to support Prometheus types that don't exist
+	// in OpenTelemetry.
+	typeFromMetadata, hasTypeFromMetadata := otelMetric.Metadata().Get(prometheustranslator.MetricMetadataTypeKey)
 	switch otelMetric.Type() {
 	case pmetric.MetricTypeGauge:
+		if hasTypeFromMetadata && typeFromMetadata.Str() == string(model.MetricTypeUnknown) {
+			return prompb.MetricMetadata_UNKNOWN
+		}
 		return prompb.MetricMetadata_GAUGE
 	case pmetric.MetricTypeSum:
-		metricType := prompb.MetricMetadata_GAUGE
 		if otelMetric.Sum().IsMonotonic() {
-			metricType = prompb.MetricMetadata_COUNTER
+			return prompb.MetricMetadata_COUNTER
+		}
+		if hasTypeFromMetadata && typeFromMetadata.Str() == string(model.MetricTypeInfo) {
+			return prompb.MetricMetadata_INFO
 		}
-		return metricType
+		if hasTypeFromMetadata && typeFromMetadata.Str() == string(model.MetricTypeStateset) {
+			return prompb.MetricMetadata_STATESET
+		}
+		return prompb.MetricMetadata_GAUGE
 	case pmetric.MetricTypeHistogram:
 		return prompb.MetricMetadata_HISTOGRAM
 	case pmetric.MetricTypeSummary:

pkg/translator/prometheusremotewrite/otlp_to_openmetrics_metadata_test.go

@@ -93,6 +93,50 @@ func TestOtelMetricTypeToPromMetricType(t *testing.T) {
 			},
 			want: prompb.MetricMetadata_SUMMARY,
 		},
+		{
+			name: "unknown from metadata",
+			metric: func() pmetric.Metric {
+				metric := pmetric.NewMetric()
+				metric.SetName("test_sum")
+				metric.Metadata().PutStr(prometheustranslator.MetricMetadataTypeKey, "unknown")
+
+				dp := metric.SetEmptyGauge().DataPoints().AppendEmpty()
+				dp.SetDoubleValue(1)
+
+				return metric
+			},
+			want: prompb.MetricMetadata_UNKNOWN,
+		},
+		{
+			name: "info from metadata",
+			metric: func() pmetric.Metric {
+				metric := pmetric.NewMetric()
+				metric.SetName("test_sum")
+				metric.Metadata().PutStr(prometheustranslator.MetricMetadataTypeKey, "info")
+				metric.SetEmptySum().SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
+				metric.SetEmptySum().SetIsMonotonic(false)
+				dp := metric.Sum().DataPoints().AppendEmpty()
+				dp.SetDoubleValue(1)
+
+				return metric
+			},
+			want: prompb.MetricMetadata_INFO,
+		},
+		{
+			name: "stateset from metadata",
+			metric: func() pmetric.Metric {
+				metric := pmetric.NewMetric()
+				metric.SetName("test_sum")
+				metric.Metadata().PutStr(prometheustranslator.MetricMetadataTypeKey, "stateset")
+				metric.SetEmptySum().SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
+				metric.SetEmptySum().SetIsMonotonic(false)
+				dp := metric.Sum().DataPoints().AppendEmpty()
+				dp.SetDoubleValue(1)
+
+				return metric
+			},
+			want: prompb.MetricMetadata_STATESET,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

receiver/prometheusreceiver/internal/metricfamily.go

@@ -471,6 +471,7 @@ func (mf *metricFamily) appendMetric(metrics pmetric.MetricSlice, trimSuffixes b
 	metric.SetName(name)
 	metric.SetDescription(mf.metadata.Help)
 	metric.SetUnit(prometheus.UnitWordToUCUM(mf.metadata.Unit))
+	metric.Metadata().PutStr(prometheus.MetricMetadataTypeKey, string(mf.metadata.Type))
 
 	var pointCount int
 

receiver/prometheusreceiver/internal/metricsutil_test.go

@@ -65,6 +65,7 @@ func histogramPointNoValue(attributes []*kv, startTimestamp, timestamp pcommon.T
 func histogramMetric(name string, points ...pmetric.HistogramDataPoint) pmetric.Metric {
 	metric := pmetric.NewMetric()
 	metric.SetName(name)
+	metric.Metadata().PutStr("prometheus.type", "histogram")
 	histogram := metric.SetEmptyHistogram()
 	histogram.SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
 
@@ -81,6 +82,7 @@ func histogramMetric(name string, points ...pmetric.HistogramDataPoint) pmetric.
 func exponentialHistogramMetric(name string, points ...pmetric.ExponentialHistogramDataPoint) pmetric.Metric {
 	metric := pmetric.NewMetric()
 	metric.SetName(name)
+	metric.Metadata().PutStr("prometheus.type", "histogram")
 	histogram := metric.SetEmptyExponentialHistogram()
 	histogram.SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
 
@@ -198,6 +200,7 @@ func doublePointNoValue(attributes []*kv, startTimestamp, timestamp pcommon.Time
 func gaugeMetric(name string, points ...pmetric.NumberDataPoint) pmetric.Metric {
 	metric := pmetric.NewMetric()
 	metric.SetName(name)
+	metric.Metadata().PutStr("prometheus.type", "gauge")
 	destPointL := metric.SetEmptyGauge().DataPoints()
 	for _, point := range points {
 		destPoint := destPointL.AppendEmpty()
@@ -210,6 +213,7 @@ func gaugeMetric(name string, points ...pmetric.NumberDataPoint) pmetric.Metric
 func sumMetric(name string, points ...pmetric.NumberDataPoint) pmetric.Metric {
 	metric := pmetric.NewMetric()
 	metric.SetName(name)
+	metric.Metadata().PutStr("prometheus.type", "counter")
 	sum := metric.SetEmptySum()
 	sum.SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
 	sum.SetIsMonotonic(true)
@@ -260,6 +264,7 @@ func summaryPointNoValue(attributes []*kv, startTimestamp, timestamp pcommon.Tim
 func summaryMetric(name string, points ...pmetric.SummaryDataPoint) pmetric.Metric {
 	metric := pmetric.NewMetric()
 	metric.SetName(name)
+	metric.Metadata().PutStr("prometheus.type", "summary")
 	destPointL := metric.SetEmptySummary().DataPoints()
 	for _, point := range points {
 		destPoint := destPointL.AppendEmpty()