fix: truncated file size compare

filebeat/input/log/input.go

@@ -548,15 +548,28 @@ func (p *Input) harvestExistingFile(newState file.State, oldState file.State) {
 	}
 
 	// File size was reduced -> truncated file
-	if oldState.Finished && newState.Fileinfo.Size() < oldState.Offset {
-		logp.Debug("input", "Old file was truncated. Starting from the beginning: %s, offset: %d, new size: %d ", newState.Source, newState.Offset, newState.Fileinfo.Size())
-		err := p.startHarvester(newState, 0)
-		if err != nil {
-			logp.Err("Harvester could not be started on truncated file: %s, Err: %s", newState.Source, err)
-		}
+	if oldState.Finished {
+		if oldState.Fileinfo == nil && newState.Fileinfo.Size() < oldState.Offset {
+			logp.Err("Old file was truncated. Starting from the beginning: %s, old source: %s, offset: %d, new size: %d,"+
+				" old StateOS: %s, new StateOS: %s", newState.Source, oldState.Source, oldState.Offset, newState.Fileinfo.Size(), oldState.FileStateOS.String(), newState.FileStateOS.String())
+			err := p.startHarvester(newState, 0)
+			if err != nil {
+				logp.Err("Harvester could not be started on truncated file: %s, Err: %s", newState.Source, err)
+			}
 
-		filesTruncated.Add(1)
-		return
+			filesTruncated.Add(1)
+			return
+		} else if oldState.Fileinfo != nil && newState.Fileinfo.Size() < oldState.Fileinfo.Size() {
+			logp.Err("Old file was truncated. Starting from the beginning: %s, old source: %s, offset: %d, old size: %d, new size: %d,"+
+				" old StateOS: %s, new StateOS: %s", newState.Source, oldState.Source, oldState.Offset, oldState.Fileinfo.Size(), newState.Fileinfo.Size(), oldState.FileStateOS.String(), newState.FileStateOS.String())
+			err := p.startHarvester(newState, 0)
+			if err != nil {
+				logp.Err("Harvester could not be started on truncated file: %s, Err: %s", newState.Source, err)
+			}
+
+			filesTruncated.Add(1)
+			return
+		}
 	}
 
 	// Check if file was renamed