presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/ShardCleaner.java/ShardCleaner/runBackupCleanup
class ShardCleaner:    private synchronized void runBackupCleanup()
    {
        try {
            cleanBackupShards();
        }
        catch (Throwable t) {
            log.error(t, "Error cleaning backup shards");
            backupJobErrors.update(1);
        }
    }