code: File syncLog(RequestInfo reqInfo, final SegmentStateProto segment,
        final URL url) throws IOException {
      long startTxId = segment.getStartTxId();
      long epoch = reqInfo.getEpoch();
      return syncLog(epoch, segment.getStartTxId(), url, segment.toString(),
          journalStorage.getSyncLogTemporaryFile(startTxId, epoch));
    }
docs: Synchronize a log segment from another JournalNode. The log is
  downloaded from the provided URL into a temporary location on disk,
  which is named based on the current request's epoch.
  
  @return the temporary location of the downloaded file