class TransactionStore implements ReadWriterStore<Sha3Hash, Transaction> {

    @Override
    public void put(Sha3Hash key, Transaction tx) {
        lock.lock();
        try {
            if (!containsUnlock(key)) {
                pendingPool.put(key, tx);
                if (pendingPool.containsKey(key)) {
                    pendingKeys.add(key);
                } else {
                    log.debug("unconfirmedTxs size={}, ignore key={}", pendingKeys.size(), key);
                }
            }
        } catch (Exception e) {
            log.warn("put() is failed. {} {}", e.getMessage(), key.toString());
        } finally {
            lock.unlock();
        }
    }

    public  TransactionStore(DbSource<byte[], byte[]> db);
      TransactionStore(DbSource<byte[], byte[]> db, int cacheSize);

}