enrichments: implement t-value representative count

enrichments/internal/elastic/span.go

@@ -28,10 +28,10 @@ import (
 	"net/http"
 	"net/url"
 	"strconv"
-	"strings"
 
 	"github.com/elastic/opentelemetry-lib/elasticattr"
 	"github.com/elastic/opentelemetry-lib/enrichments/config"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/sampling"
 	"github.com/ua-parser/uap-go/uaparser"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/ptrace"
@@ -41,6 +41,11 @@ import (
 	"google.golang.org/grpc/codes"
 )
 
+// defaultRepresentativeCount is the representative count to use for adjusting
+// sampled spans when a value could not be found from tracestate. Our default is
+// to assume sampling all spans.
+const defaultRepresentativeCount = 1.0
+
 // EnrichSpan adds Elastic specific attributes to the OTel span.
 // These attributes are derived from the base attributes and appended to
 // the span attributes. The enrichment logic is performed by categorizing
@@ -658,20 +663,39 @@ func (s *spanEventEnrichmentContext) enrich(
 // with a difference that representative count can also include
 // dynamically calculated representivity for non-probabilistic sampling.
 // In addition, the representative count defaults to 1 if the adjusted
-// count is UNKNOWN or the p-value is invalid.
+// count is UNKNOWN or the t-value is invalid.
+//
+// Def: https://opentelemetry.io/docs/specs/otel/trace/tracestate-probability-sampling/#converting-threshold-to-an-adjusted-count-sampling-rate
+//
+// The count is calculated by using t-value:
+// https://opentelemetry.io/docs/specs/otel/trace/tracestate-probability-sampling/#rejection-threshold-t
+//
+// For compatibility, older calculation is also supported.
 //
 // Def: https://opentelemetry.io/docs/specs/otel/trace/tracestate-probability-sampling/#adjusted-count)
 //
 // The count is calculated by using p-value:
 // https://opentelemetry.io/docs/reference/specification/trace/tracestate-probability-sampling/#p-value
 func getRepresentativeCount(tracestate string) float64 {
-	var p uint64
-	otValue := getValueForKeyInString(tracestate, "ot", ',', '=')
-	if otValue != "" {
-		pValue := getValueForKeyInString(otValue, "p", ';', ':')
+	w3cts, err := sampling.NewW3CTraceState(tracestate)
+	if err != nil || w3cts.OTelValue() == nil {
+		return defaultRepresentativeCount
+	}
+
+	otts := w3cts.OTelValue()
+	// Use t-value if provided.
+	if th, ok := otts.TValueThreshold(); ok {
+		// Small optimization for always-sampled case since it's commonly used.
+		if th.Unsigned() == 0 {
+			return defaultRepresentativeCount
+		}
+		return th.AdjustedCount()
+	}
 
-		if pValue != "" {
-			p, _ = strconv.ParseUint(pValue, 10, 6)
+	var p uint64
+	for _, kv := range otts.ExtraValues() {
+		if kv.Key == "p" && kv.Value != "" {
+			p, _ = strconv.ParseUint(kv.Value, 10, 6)
 		}
 	}
 
@@ -705,29 +729,6 @@ func isElasticTransaction(span ptrace.Span) bool {
 	return false
 }
 
-// parses string format `<key>=val<seperator>`
-func getValueForKeyInString(str string, key string, separator rune, assignChar rune) string {
-	for {
-		str = strings.TrimSpace(str)
-		if str == "" {
-			break
-		}
-		kv := str
-		if sepIdx := strings.IndexRune(str, separator); sepIdx != -1 {
-			kv = strings.TrimSpace(str[:sepIdx])
-			str = str[sepIdx+1:]
-		} else {
-			str = ""
-		}
-		equal := strings.IndexRune(kv, assignChar)
-		if equal != -1 && kv[:equal] == key {
-			return kv[equal+1:]
-		}
-	}
-
-	return ""
-}
-
 func getHostPort(
 	urlFull *url.URL, urlDomain string, urlPort int64,
 	fallbackServerAddress string, fallbackServerPort int64,

enrichments/internal/elastic/span_test.go

@@ -92,7 +92,7 @@ func TestElasticTransactionEnrich(t *testing.T) {
 			name: "with_pvalue",
 			input: func() ptrace.Span {
 				span := ptrace.NewSpan()
-				span.TraceState().FromRaw("ot=p:8;")
+				span.TraceState().FromRaw("ot=p:8")
 				return span
 			}(),
 			config: config.Enabled().Transaction,
@@ -111,6 +111,98 @@ func TestElasticTransactionEnrich(t *testing.T) {
 				elasticattr.TransactionType:                "unknown",
 			},
 		},
+		{
+			name: "with_tvalue (ratio 1.0)",
+			input: func() ptrace.Span {
+				span := ptrace.NewSpan()
+				span.TraceState().FromRaw("ot=th:0")
+				return span
+			}(),
+			config: config.Enabled().Transaction,
+			enrichedAttrs: map[string]any{
+				elasticattr.TimestampUs:                    int64(0),
+				elasticattr.TransactionSampled:             true,
+				elasticattr.TransactionRoot:                true,
+				elasticattr.TransactionID:                  "",
+				elasticattr.TransactionName:                "",
+				elasticattr.ProcessorEvent:                 "transaction",
+				elasticattr.TransactionRepresentativeCount: float64(1),
+				elasticattr.TransactionDurationUs:          int64(0),
+				elasticattr.EventOutcome:                   "success",
+				elasticattr.SuccessCount:                   int64(1),
+				elasticattr.TransactionResult:              "Success",
+				elasticattr.TransactionType:                "unknown",
+			},
+		},
+		{
+			name: "with_tvalue (ratio 0.5)",
+			input: func() ptrace.Span {
+				span := ptrace.NewSpan()
+				span.TraceState().FromRaw("ot=th:8")
+				return span
+			}(),
+			config: config.Enabled().Transaction,
+			enrichedAttrs: map[string]any{
+				elasticattr.TimestampUs:                    int64(0),
+				elasticattr.TransactionSampled:             true,
+				elasticattr.TransactionRoot:                true,
+				elasticattr.TransactionID:                  "",
+				elasticattr.TransactionName:                "",
+				elasticattr.ProcessorEvent:                 "transaction",
+				elasticattr.TransactionRepresentativeCount: float64(2),
+				elasticattr.TransactionDurationUs:          int64(0),
+				elasticattr.EventOutcome:                   "success",
+				elasticattr.SuccessCount:                   int64(2),
+				elasticattr.TransactionResult:              "Success",
+				elasticattr.TransactionType:                "unknown",
+			},
+		},
+		{
+			name: "with_tvalue (ratio 0.25)",
+			input: func() ptrace.Span {
+				span := ptrace.NewSpan()
+				span.TraceState().FromRaw("ot=th:c")
+				return span
+			}(),
+			config: config.Enabled().Transaction,
+			enrichedAttrs: map[string]any{
+				elasticattr.TimestampUs:                    int64(0),
+				elasticattr.TransactionSampled:             true,
+				elasticattr.TransactionRoot:                true,
+				elasticattr.TransactionID:                  "",
+				elasticattr.TransactionName:                "",
+				elasticattr.ProcessorEvent:                 "transaction",
+				elasticattr.TransactionRepresentativeCount: float64(4),
+				elasticattr.TransactionDurationUs:          int64(0),
+				elasticattr.EventOutcome:                   "success",
+				elasticattr.SuccessCount:                   int64(4),
+				elasticattr.TransactionResult:              "Success",
+				elasticattr.TransactionType:                "unknown",
+			},
+		},
+		{
+			name: "with_tvalue and p",
+			input: func() ptrace.Span {
+				span := ptrace.NewSpan()
+				span.TraceState().FromRaw("ot=th:c;p:8")
+				return span
+			}(),
+			config: config.Enabled().Transaction,
+			enrichedAttrs: map[string]any{
+				elasticattr.TimestampUs:                    int64(0),
+				elasticattr.TransactionSampled:             true,
+				elasticattr.TransactionRoot:                true,
+				elasticattr.TransactionID:                  "",
+				elasticattr.TransactionName:                "",
+				elasticattr.ProcessorEvent:                 "transaction",
+				elasticattr.TransactionRepresentativeCount: float64(4),
+				elasticattr.TransactionDurationUs:          int64(0),
+				elasticattr.EventOutcome:                   "success",
+				elasticattr.SuccessCount:                   int64(4),
+				elasticattr.TransactionResult:              "Success",
+				elasticattr.TransactionType:                "unknown",
+			},
+		},
 		{
 			name: "http_status_ok",
 			input: func() ptrace.Span {

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/google/go-cmp v0.7.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden v0.131.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.131.0
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/sampling v0.131.0
 	github.com/stretchr/testify v1.10.0
 	github.com/ua-parser/uap-go v0.0.0-20250213224047-9c035f085b90
 	go.opentelemetry.io/collector/component v1.37.0

go.sum

@@ -77,6 +77,8 @@ github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.131.0
 github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.131.0/go.mod h1:29C3uJZWtRu6wM4xqm023BcN6SpYge2eJs/5bAq2dGU=
 github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.131.0 h1:lb0PuWuVEQPafzYBhrS8AX0sugKjG7RDi9+DRStjJhE=
 github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.131.0/go.mod h1:PmUOI9ZjJpUXFp8V6NE/r0mnmJAmHU/x9A+N7YYMJ1o=
+github.com/open-telemetry/opentelemetry-collector-contrib/pkg/sampling v0.131.0 h1:5sPZErUo231/wBoKp/HiEieW8uhiQXHIHnII3HXIcYM=
+github.com/open-telemetry/opentelemetry-collector-contrib/pkg/sampling v0.131.0/go.mod h1:0eTDOk4+HDSo+3oA2N+2Q41ypGZDTvZpzODQsOHQ4cw=
 github.com/pierrec/lz4/v4 v4.1.22 h1:cKFw6uJDK+/gfw5BcDL0JL5aBsAFdsIT18eRtLj7VIU=
 github.com/pierrec/lz4/v4 v4.1.22/go.mod h1:gZWDp/Ze/IJXGXf23ltt2EXimqmTUXEy0GFuRQyBid4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=