[exporter/splunkhec] Include trace and span id if set in log record

If the log record contains a span id or trace id include it as `span_id` and
`trace_id` respectively in the Splunk HEC output.

Resolves #3807

CHANGELOG.md

@@ -5,6 +5,7 @@
 ## 💡 Enhancements 💡
 
 - `tailsampling` processor: Add new policy `latency` (#3750)
+- `splunkhec` exporter: Include `trace_id` and `span_id` if set (#3850)
 
 ## v0.28.0
 

exporter/splunkhecexporter/logdata_to_splunk.go

@@ -24,6 +24,14 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/splunk"
 )
 
+const (
+	// Keys are taken from https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/overview.md#trace-context-in-legacy-formats.
+	// spanIDFieldKey is the key used in log event for the span id (if any).
+	spanIDFieldKey = "span_id"
+	// traceIDFieldKey is the key used in the log event for the trace id (if any).
+	traceIDFieldKey = "trace_id"
+)
+
 // Composite index of a log record in pdata.Logs.
 type logIndex struct {
 	// Index in orig list (i.e. root parent index).
@@ -47,6 +55,12 @@ func mapLogRecordToSplunkEvent(res pdata.Resource, lr pdata.LogRecord, config *C
 	if lr.Name() != "" {
 		fields[splunk.NameLabel] = lr.Name()
 	}
+	if spanID := lr.SpanID().HexString(); spanID != "" {
+		fields[spanIDFieldKey] = spanID
+	}
+	if traceID := lr.TraceID().HexString(); traceID != "" {
+		fields[traceIDFieldKey] = traceID
+	}
 	res.Attributes().Range(func(k string, v pdata.AttributeValue) bool {
 		switch k {
 		case conventions.AttributeHostName:

exporter/splunkhecexporter/logdata_to_splunk_test.go

@@ -145,6 +145,28 @@ func Test_mapLogRecordToSplunkEvent(t *testing.T) {
 				commonLogSplunkEvent(nil, 0, map[string]interface{}{}, "unknown", "source", "sourcetype"),
 			},
 		},
+		{
+			name: "with span and trace id",
+			logRecordFn: func() pdata.LogRecord {
+				logRecord := pdata.NewLogRecord()
+				logRecord.SetSpanID(pdata.NewSpanID([8]byte{0, 0, 0, 0, 0, 0, 0, 50}))
+				logRecord.SetTraceID(pdata.NewTraceID([16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 100}))
+				return logRecord
+			},
+			logResourceFn: pdata.NewResource,
+			configDataFn: func() *Config {
+				return &Config{
+					Source:     "source",
+					SourceType: "sourcetype",
+				}
+			},
+			wantSplunkEvents: func() []*splunk.Event {
+				event := commonLogSplunkEvent(nil, 0, map[string]interface{}{}, "unknown", "source", "sourcetype")
+				event.Fields["span_id"] = "0000000000000032"
+				event.Fields["trace_id"] = "00000000000000000000000000000064"
+				return []*splunk.Event{event}
+			}(),
+		},
 		{
 			name: "with double body",
 			logRecordFn: func() pdata.LogRecord {