chore: add constants for prometheus translation (#32830)

**Description:**

This is a cleanup to consolidate the constants used for prometheus
translation in a single place.

---------

Co-authored-by: Curtis Robert <[email protected]>

Author: dashpole

exporter/prometheusexporter/collector.go

@@ -18,10 +18,6 @@ import (
 	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
-const (
-	targetMetricName = "target_info"
-)
-
 var (
 	separatorString = string([]byte{model.SeparatorByte})
 )
@@ -56,11 +52,11 @@ func convertExemplars(exemplars pmetric.ExemplarSlice) []prometheus.Exemplar {
 		exemplarLabels := make(prometheus.Labels, 0)
 
 		if traceID := e.TraceID(); !traceID.IsEmpty() {
-			exemplarLabels["trace_id"] = hex.EncodeToString(traceID[:])
+			exemplarLabels[prometheustranslator.ExemplarTraceIDKey] = hex.EncodeToString(traceID[:])
 		}
 
 		if spanID := e.SpanID(); !spanID.IsEmpty() {
-			exemplarLabels["span_id"] = hex.EncodeToString(spanID[:])
+			exemplarLabels[prometheustranslator.ExemplarSpanIDKey] = hex.EncodeToString(spanID[:])
 		}
 
 		var value float64
@@ -332,7 +328,7 @@ func (c *collector) createTargetInfoMetrics(resourceAttrs []pcommon.Map) ([]prom
 			labels[model.InstanceLabel] = instance
 		}
 
-		name := targetMetricName
+		name := prometheustranslator.TargetInfoMetricName
 		if len(c.namespace) > 0 {
 			name = c.namespace + "_" + name
 		}
@@ -370,7 +366,7 @@ func (c *collector) Collect(ch chan<- prometheus.Metric) {
 
 	targetMetrics, err := c.createTargetInfoMetrics(resourceAttrs)
 	if err != nil {
-		c.logger.Error(fmt.Sprintf("failed to convert metric %s: %s", targetMetricName, err.Error()))
+		c.logger.Error(fmt.Sprintf("failed to convert metric %s: %s", prometheustranslator.TargetInfoMetricName, err.Error()))
 	}
 	for _, m := range targetMetrics {
 		ch <- m

pkg/translator/prometheus/constants.go

@@ -8,4 +8,30 @@ const (
 	// type in metric metadata:
 	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#metric-metadata
 	MetricMetadataTypeKey = "prometheus.type"
+	// ExemplarTraceIDKey is the key used to store the trace ID in Prometheus
+	// exemplars:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#exemplars
+	ExemplarTraceIDKey = "trace_id"
+	// ExemplarSpanIDKey is the key used to store the Span ID in Prometheus
+	// exemplars:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#exemplars
+	ExemplarSpanIDKey = "span_id"
+	// ScopeInfoMetricName is the name of the metric used to preserve scope
+	// attributes in Prometheus format:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#instrumentation-scope
+	ScopeInfoMetricName = "otel_scope_info"
+	// ScopeNameLabelKey is the name of the label key used to identify the name
+	// of the OpenTelemetry scope which produced the metric:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#instrumentation-scope
+	ScopeNameLabelKey = "otel_scope_name"
+	// ScopeVersionLabelKey is the name of the label key used to identify the
+	// version of the OpenTelemetry scope which produced the metric:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#instrumentation-scope
+	ScopeVersionLabelKey = "otel_scope_version"
+	// TargetInfoMetricName is the name of the metric used to preserve resource
+	// attributes in Prometheus format:
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/e6eccba97ebaffbbfad6d4358408a2cead0ec2df/specification/compatibility/prometheus_and_openmetrics.md#resource-attributes-1
+	// It originates from OpenMetrics:
+	// https://github.com/OpenObservability/OpenMetrics/blob/1386544931307dff279688f332890c31b6c5de36/specification/OpenMetrics.md#supporting-target-metadata-in-both-push-based-and-pull-based-systems
+	TargetInfoMetricName = "target_info"
 )

pkg/translator/prometheusremotewrite/helper.go

@@ -38,12 +38,7 @@ const (
 	// according to the prometheus specification
 	// https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#exemplars
 	maxExemplarRunes = 128
-	// Trace and Span id keys are defined as part of the spec:
-	// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification%2Fmetrics%2Fdatamodel.md#exemplars-2
-	traceIDKey       = "trace_id"
-	spanIDKey        = "span_id"
 	infoType         = "info"
-	targetMetricName = "target_info"
 )
 
 type bucketBoundsData struct {
@@ -303,18 +298,18 @@ func getPromExemplars[T exemplarType](pt T) []prompb.Exemplar {
 		}
 		if traceID := exemplar.TraceID(); !traceID.IsEmpty() {
 			val := hex.EncodeToString(traceID[:])
-			exemplarRunes += utf8.RuneCountInString(traceIDKey) + utf8.RuneCountInString(val)
+			exemplarRunes += utf8.RuneCountInString(prometheustranslator.ExemplarTraceIDKey) + utf8.RuneCountInString(val)
 			promLabel := prompb.Label{
-				Name:  traceIDKey,
+				Name:  prometheustranslator.ExemplarTraceIDKey,
 				Value: val,
 			}
 			promExemplar.Labels = append(promExemplar.Labels, promLabel)
 		}
 		if spanID := exemplar.SpanID(); !spanID.IsEmpty() {
 			val := hex.EncodeToString(spanID[:])
-			exemplarRunes += utf8.RuneCountInString(spanIDKey) + utf8.RuneCountInString(val)
+			exemplarRunes += utf8.RuneCountInString(prometheustranslator.ExemplarSpanIDKey) + utf8.RuneCountInString(val)
 			promLabel := prompb.Label{
-				Name:  spanIDKey,
+				Name:  prometheustranslator.ExemplarSpanIDKey,
 				Value: val,
 			}
 			promExemplar.Labels = append(promExemplar.Labels, promLabel)
@@ -534,7 +529,7 @@ func addResourceTargetInfo(resource pcommon.Resource, settings Settings, timesta
 		return
 	}
 
-	name := targetMetricName
+	name := prometheustranslator.TargetInfoMetricName
 	if len(settings.Namespace) > 0 {
 		name = settings.Namespace + "_" + name
 	}

pkg/translator/prometheusremotewrite/helper_test.go

@@ -20,6 +20,7 @@ import (
 	conventions "go.opentelemetry.io/collector/semconv/v1.6.1"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/testdata"
+	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
 func Test_isValidAggregationTemporality(t *testing.T) {
@@ -462,7 +463,7 @@ func Test_getPromExemplars(t *testing.T) {
 				{
 					Value:     floatVal1,
 					Timestamp: timestamp.FromTime(tnow),
-					Labels:    []prompb.Label{getLabel(traceIDKey, traceIDValue1), getLabel(spanIDKey, spanIDValue1), getLabel(label11, value11)},
+					Labels:    []prompb.Label{getLabel(prometheustranslator.ExemplarTraceIDKey, traceIDValue1), getLabel(prometheustranslator.ExemplarSpanIDKey, spanIDValue1), getLabel(label11, value11)},
 				},
 			},
 		},
@@ -505,7 +506,7 @@ func Test_getPromExemplars(t *testing.T) {
 				{
 					Value:     floatVal1,
 					Timestamp: timestamp.FromTime(tnow),
-					Labels:    []prompb.Label{getLabel(traceIDKey, traceIDValue1), getLabel(spanIDKey, spanIDValue1)},
+					Labels:    []prompb.Label{getLabel(prometheustranslator.ExemplarTraceIDKey, traceIDValue1), getLabel(prometheustranslator.ExemplarSpanIDKey, spanIDValue1)},
 				},
 			},
 		},

pkg/translator/prometheusremotewrite/testutils_test.go

@@ -14,6 +14,8 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
+
+	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
 var (
@@ -170,7 +172,7 @@ func getExemplar(v float64, t int64) prompb.Exemplar {
 	return prompb.Exemplar{
 		Value:     v,
 		Timestamp: t,
-		Labels:    []prompb.Label{getLabel(traceIDKey, traceIDValue1)},
+		Labels:    []prompb.Label{getLabel(prometheustranslator.ExemplarTraceIDKey, traceIDValue1)},
 	}
 }
 

receiver/prometheusreceiver/internal/metricfamily.go

@@ -22,11 +22,6 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
-const (
-	traceIDKey = "trace_id"
-	spanIDKey  = "span_id"
-)
-
 type metricFamily struct {
 	mtype pmetric.MetricType
 	// isMonotonic only applies to sums
@@ -545,15 +540,15 @@ func convertExemplar(pe exemplar.Exemplar, e pmetric.Exemplar) {
 	e.FilteredAttributes().EnsureCapacity(pe.Labels.Len())
 	pe.Labels.Range(func(lb labels.Label) {
 		switch strings.ToLower(lb.Name) {
-		case traceIDKey:
+		case prometheus.ExemplarTraceIDKey:
 			var tid [16]byte
 			err := decodeAndCopyToLowerBytes(tid[:], []byte(lb.Value))
 			if err == nil {
 				e.SetTraceID(tid)
 			} else {
 				e.FilteredAttributes().PutStr(lb.Name, lb.Value)
 			}
-		case spanIDKey:
+		case prometheus.ExemplarSpanIDKey:
 			var sid [8]byte
 			err := decodeAndCopyToLowerBytes(sid[:], []byte(lb.Value))
 			if err == nil {

receiver/prometheusreceiver/internal/transaction.go

@@ -24,16 +24,12 @@ import (
 	"go.opentelemetry.io/collector/receiver"
 	"go.opentelemetry.io/collector/receiver/receiverhelper"
 	"go.uber.org/zap"
-)
 
-const (
-	targetMetricName  = "target_info"
-	scopeMetricName   = "otel_scope_info"
-	scopeNameLabel    = "otel_scope_name"
-	scopeVersionLabel = "otel_scope_version"
-	receiverName      = "otelcol/prometheusreceiver"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 )
 
+const receiverName = "otelcol/prometheusreceiver"
+
 type transaction struct {
 	isNew                  bool
 	trimSuffixes           bool
@@ -138,13 +134,13 @@ func (t *transaction) Append(_ storage.SeriesRef, ls labels.Labels, atMs int64,
 	}
 
 	// For the `target_info` metric we need to convert it to resource attributes.
-	if metricName == targetMetricName {
+	if metricName == prometheus.TargetInfoMetricName {
 		t.AddTargetInfo(ls)
 		return 0, nil
 	}
 
 	// For the `otel_scope_info` metric we need to convert it to scope attributes.
-	if metricName == scopeMetricName {
+	if metricName == prometheus.ScopeInfoMetricName {
 		t.addScopeInfo(ls)
 		return 0, nil
 	}
@@ -349,10 +345,10 @@ func (t *transaction) getMetrics(resource pcommon.Resource) (pmetric.Metrics, er
 func getScopeID(ls labels.Labels) scopeID {
 	var scope scopeID
 	ls.Range(func(lbl labels.Label) {
-		if lbl.Name == scopeNameLabel {
+		if lbl.Name == prometheus.ScopeNameLabelKey {
 			scope.name = lbl.Value
 		}
-		if lbl.Name == scopeVersionLabel {
+		if lbl.Name == prometheus.ScopeVersionLabelKey {
 			scope.version = lbl.Value
 		}
 	})
@@ -431,11 +427,11 @@ func (t *transaction) addScopeInfo(ls labels.Labels) {
 		if lbl.Name == model.JobLabel || lbl.Name == model.InstanceLabel || lbl.Name == model.MetricNameLabel {
 			return
 		}
-		if lbl.Name == scopeNameLabel {
+		if lbl.Name == prometheus.ScopeNameLabelKey {
 			scope.name = lbl.Value
 			return
 		}
-		if lbl.Name == scopeVersionLabel {
+		if lbl.Name == prometheus.ScopeVersionLabelKey {
 			scope.version = lbl.Value
 			return
 		}