@Override
      public int compare(BackupInfo o1, BackupInfo o2) {
        long ts1 = getTimestamp(o1.getBackupId());
        long ts2 = getTimestamp(o2.getBackupId());

        if (ts1 == ts2) {
          return 0;
        }

        return ts1 < ts2 ? 1 : -1;
      }
Given the backup root dir and the backup id, return the log file location for an incremental
backup.
@param backupRootDir backup root directory
@param backupId      backup id
@return logBackupDir: ".../user/biadmin/backup1/WALs/backup_1396650096738"
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/util/BackupUtils.java