presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/ShardCleaner.java/ShardCleaner/startTransactionCleanup
class ShardCleaner:    private void startTransactionCleanup()
    {
        scheduler.scheduleWithFixedDelay(() -> {
            try {
                abortOldTransactions();
                deleteOldCompletedTransactions();
                deleteOldShards();
            }
            catch (Throwable t) {
                log.error(t, "Error cleaning transactions");
                transactionJobErrors.update(1);
            }
        }, 0, transactionCleanerInterval.toMillis(), MILLISECONDS);
    }