public void logFiles(List<TsFileResource> tsFiles, String flag) throws IOException {
    for (TsFileResource tsFileResource : tsFiles) {
      logFile(tsFileResource, flag);
    }
  }
MergeLogger records the progress of a merge in file "merge.log" as text lines.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/compaction/execute/utils/log/CompactionLogger.java