@Override
  public void setConf(Configuration config) {
    // If backup is disabled, keep all members null
    super.setConf(config);
    if (
      !config.getBoolean(BackupRestoreConstants.BACKUP_ENABLE_KEY,
        BackupRestoreConstants.BACKUP_ENABLE_DEFAULT)
    ) {
      LOG.warn("Backup is disabled - allowing all wals to be deleted");
    }
  }
Calculates the timestamp boundary up to which all backup roots have already included the WAL.
I.e. WALs with a lower (= older) or equal timestamp are no longer needed for future incremental
backups.
hbase-backup/src/main/java/org/apache/hadoop/hbase/backup/master/BackupLogCleaner.java