[8.x](backport #42412) otelconsumer: set document id attribute for elasticsearchexporter

libbeat/outputs/otelconsumer/otelconsumer.go

@@ -35,6 +35,11 @@ import (
 	"go.opentelemetry.io/collector/pdata/plog"
 )
 
+const (
+	// esDocumentIDAttribute is the attribute key used to store the document ID in the log record.
+	esDocumentIDAttribute = "elasticsearch.document_id"
+)
+
 func init() {
 	outputs.RegisterType("otelconsumer", makeOtelConsumer)
 }
@@ -84,9 +89,30 @@ func (out *otelConsumer) logsPublish(ctx context.Context, batch publisher.Batch)
 	sourceLogs := resourceLogs.ScopeLogs().AppendEmpty()
 	logRecords := sourceLogs.LogRecords()
 
+	// Convert the batch of events to Otel plog.Logs. The encoding we
+	// choose here is to set all fields in a Map in the Body of the log
+	// record. Each log record encodes a single beats event.
+	// This way we have full control over the final structure of the log in the
+	// destination, as long as the exporter allows it.
+	// For example, the elasticsearchexporter has an encoding specifically for this.
+	// See https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/35444.
 	events := batch.Events()
 	for _, event := range events {
 		logRecord := logRecords.AppendEmpty()
+
+		if id, ok := event.Content.Meta["_id"]; ok {
+			// Specify the id as an attribute used by the elasticsearchexporter
+			// to set the final document ID in Elasticsearch.
+			// When using the bodymap encoding in the exporter all attributes
+			// are stripped out of the final Elasticsearch document.
+			//
+			// See https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/36882.
+			switch id := id.(type) {
+			case string:
+				logRecord.Attributes().PutStr(esDocumentIDAttribute, id)
+			}
+		}
+
 		beatEvent := event.Content.Fields.Clone()
 		beatEvent["@timestamp"] = event.Content.Timestamp
 		logRecord.SetTimestamp(pcommon.NewTimestampFromTime(event.Content.Timestamp))

libbeat/outputs/otelconsumer/otelconsumer_test.go

@@ -43,6 +43,7 @@ func TestPublish(t *testing.T) {
 	event1 := beat.Event{Fields: mapstr.M{"field": 1}}
 	event2 := beat.Event{Fields: mapstr.M{"field": 2}}
 	event3 := beat.Event{Fields: mapstr.M{"field": 3}}
+	event4 := beat.Event{Meta: mapstr.M{"_id": "abc123"}}
 
 	makeOtelConsumer := func(t *testing.T, consumeFn func(ctx context.Context, ld plog.Logs) error) *otelConsumer {
 		t.Helper()
@@ -118,6 +119,26 @@ func TestPublish(t *testing.T) {
 		assert.Equal(t, outest.BatchRetry, batch.Signals[0].Tag)
 	})
 
+	t.Run("sets the elasticsearchexporter doc id attribute from metadata", func(t *testing.T) {
+		batch := outest.NewBatch(event4)
+
+		var docID string
+		otelConsumer := makeOtelConsumer(t, func(ctx context.Context, ld plog.Logs) error {
+			record := ld.ResourceLogs().At(0).ScopeLogs().At(0).LogRecords().At(0)
+			attr, ok := record.Attributes().Get(esDocumentIDAttribute)
+			assert.True(t, ok, "document ID attribute should be set")
+			docID = attr.AsString()
+
+			return nil
+		})
+
+		err := otelConsumer.Publish(ctx, batch)
+		assert.NoError(t, err)
+		assert.Len(t, batch.Signals, 1)
+		assert.Equal(t, outest.BatchACK, batch.Signals[0].Tag)
+		assert.Equal(t, event4.Meta["_id"], docID)
+	})
+
 	t.Run("sets the @timestamp field with the correct format", func(t *testing.T) {
 		batch := outest.NewBatch(event3)
 		batch.Events()[0].Content.Timestamp = time.Date(2025, time.January, 29, 9, 2, 39, 0, time.UTC)