app/vlinsert/opentelemetry: properly clean log attribute to the underlying byte slice after parsing the EventName field at the LogRecord

Previously the old log attributes at fs.Fields could continue pointing to the underlying byte slice
(the whole protobuf message received from the client) for long period of time
after parsing the LogRecord.EventName field. This could result in excess memory usage.

Fix this by properly cleaning all the references at fs.Fields after parsing the LogRecord.EventName field.

Updates #869

Author: valyala

app/vlinsert/opentelemetry/pb.go

@@ -175,13 +175,15 @@ func decodeScopeLogs(src []byte, fs *logstorage.Fields, fb *fmtBuffer, pushLogs
 				pushLogs(timestamp, fs.Fields, streamFieldsLen+1)
 
 				// Return back common fields to their places before the next iteration
+				fieldsLen := len(fs.Fields)
 				fs.Fields = append(fs.Fields[:streamFieldsLen], fs.Fields[streamFieldsLen+1:commonFieldsLen+1]...)
+				clear(fs.Fields[commonFieldsLen:fieldsLen])
 			} else {
 				pushLogs(timestamp, fs.Fields, streamFieldsLen)
-			}
 
-			clear(fs.Fields[commonFieldsLen:])
-			fs.Fields = fs.Fields[:commonFieldsLen]
+				clear(fs.Fields[commonFieldsLen:])
+				fs.Fields = fs.Fields[:commonFieldsLen]
+			}
 
 			fb.buf = fb.buf[:fbLen]
 		}

docs/victorialogs/CHANGELOG.md

@@ -25,6 +25,7 @@ according to the follosing docs:
 
 * BUGFIX: [OpenTelemetry data ingestion](https://docs.victoriametrics.com/victorialogs/data-ingestion/opentelemetry/): properly handle `null` values inside arrays. Previously, such arrays could cause a panic during ingestion. See [#869](https://github.com/VictoriaMetrics/VictoriaLogs/issues/869#issuecomment-3627177567). The issue has been introduced in [v1.40.0](https://github.com/VictoriaMetrics/VictoriaLogs/releases/tag/v1.40.0).
 * BUGFIX: [OpenTelemetry data ingestion](https://docs.victoriametrics.com/victorialogs/data-ingestion/opentelemetry/): properly skip attributes with missing key. See [this report](https://github.com/VictoriaMetrics/VictoriaLogs/issues/869#issuecomment-3631307996).
+* BUGFIX: [OpenTelemetry data ingestion](https://docs.victoriametrics.com/victorialogs/data-ingestion/opentelemetry/): reduce memory usage after [v1.40.0 release](https://github.com/VictoriaMetrics/VictoriaLogs/releases/tag/v1.40.0). See [#869](https://github.com/VictoriaMetrics/VictoriaLogs/issues/869).
 
 ## [v1.40.0](https://github.com/VictoriaMetrics/VictoriaLogs/releases/tag/v1.40.0)