package mempool import ( "errors" "math/big" "sort" "sync" "time" "github.com/nspcc-dev/neo-go/pkg/core/transaction" "github.com/nspcc-dev/neo-go/pkg/util" ) var ( // ErrConflict is returned when transaction being added is incompatible // with the contents of the memory pool (Sender doesn't have enough GAS // to pay for all transactions in the pool). ErrConflict = errors.New("conflicts with the memory pool") // ErrDup is returned when transaction being added is already present // in the memory pool. ErrDup = errors.New("already in the memory pool") // ErrOOM is returned when transaction just doesn't fit in the memory // pool because of its capacity constraints. ErrOOM = errors.New("out of memory") ) // item represents a transaction in the the Memory pool. type item struct { txn *transaction.Transaction timeStamp time.Time } // items is a slice of item. type items []*item // utilityBalanceAndFees stores sender's balance and overall fees of // sender's transactions which are currently in mempool type utilityBalanceAndFees struct { balance *big.Int feeSum int64 } // Pool stores the unconfirms transactions. type Pool struct { lock sync.RWMutex verifiedMap map[util.Uint256]*item verifiedTxes items fees map[util.Uint160]utilityBalanceAndFees capacity int feePerByte int64 } func (p items) Len() int { return len(p) } func (p items) Swap(i, j int) { p[i], p[j] = p[j], p[i] } func (p items) Less(i, j int) bool { return p[i].CompareTo(p[j]) < 0 } // CompareTo returns the difference between two items. // difference < 0 implies p < otherP. // difference = 0 implies p = otherP. // difference > 0 implies p > otherP. func (p *item) CompareTo(otherP *item) int { if otherP == nil { return 1 } // Fees sorted ascending. if ret := int(p.txn.FeePerByte() - otherP.txn.FeePerByte()); ret != 0 { return ret } if ret := int(p.txn.NetworkFee - otherP.txn.NetworkFee); ret != 0 { return ret } // Transaction hash sorted descending. return otherP.txn.Hash().CompareTo(p.txn.Hash()) } // Count returns the total number of uncofirm transactions. func (mp *Pool) Count() int { mp.lock.RLock() defer mp.lock.RUnlock() return mp.count() } // count is an internal unlocked version of Count. func (mp *Pool) count() int { return len(mp.verifiedTxes) } // ContainsKey checks if a transactions hash is in the Pool. func (mp *Pool) ContainsKey(hash util.Uint256) bool { mp.lock.RLock() defer mp.lock.RUnlock() return mp.containsKey(hash) } // containsKey is an internal unlocked version of ContainsKey. func (mp *Pool) containsKey(hash util.Uint256) bool { if _, ok := mp.verifiedMap[hash]; ok { return true } return false } // tryAddSendersFee tries to add system fee and network fee to the total sender`s fee in mempool // and returns false if both balance check is required and sender has not enough GAS to pay func (mp *Pool) tryAddSendersFee(tx *transaction.Transaction, feer Feer, needCheck bool) bool { senderFee, ok := mp.fees[tx.Sender] if !ok { senderFee.balance = feer.GetUtilityTokenBalance(tx.Sender) mp.fees[tx.Sender] = senderFee } if needCheck && !checkBalance(tx, senderFee) { return false } senderFee.feeSum += tx.SystemFee + tx.NetworkFee mp.fees[tx.Sender] = senderFee return true } // checkBalance returns true in case when sender has enough GAS to pay for the // transaction func checkBalance(tx *transaction.Transaction, balance utilityBalanceAndFees) bool { needFee := balance.feeSum + tx.SystemFee + tx.NetworkFee return balance.balance.Cmp(big.NewInt(needFee)) >= 0 } // Add tries to add given transaction to the Pool. func (mp *Pool) Add(t *transaction.Transaction, fee Feer) error { var pItem = &item{ txn: t, timeStamp: time.Now().UTC(), } mp.lock.Lock() if !mp.checkTxConflicts(t, fee) { mp.lock.Unlock() return ErrConflict } if mp.containsKey(t.Hash()) { mp.lock.Unlock() return ErrDup } mp.verifiedMap[t.Hash()] = pItem // Insert into sorted array (from max to min, that could also be done // using sort.Sort(sort.Reverse()), but it incurs more overhead. Notice // also that we're searching for position that is strictly more // prioritized than our new item because we do expect a lot of // transactions with the same priority and appending to the end of the // slice is always more efficient. n := sort.Search(len(mp.verifiedTxes), func(n int) bool { return pItem.CompareTo(mp.verifiedTxes[n]) > 0 }) // We've reached our capacity already. if len(mp.verifiedTxes) == mp.capacity { // Less prioritized than the least prioritized we already have, won't fit. if n == len(mp.verifiedTxes) { mp.lock.Unlock() return ErrOOM } // Ditch the last one. unlucky := mp.verifiedTxes[len(mp.verifiedTxes)-1] delete(mp.verifiedMap, unlucky.txn.Hash()) mp.verifiedTxes[len(mp.verifiedTxes)-1] = pItem } else { mp.verifiedTxes = append(mp.verifiedTxes, pItem) } if n != len(mp.verifiedTxes)-1 { copy(mp.verifiedTxes[n+1:], mp.verifiedTxes[n:]) mp.verifiedTxes[n] = pItem } // we already checked balance in checkTxConflicts, so don't need to check again mp.tryAddSendersFee(pItem.txn, fee, false) updateMempoolMetrics(len(mp.verifiedTxes)) mp.lock.Unlock() return nil } // Remove removes an item from the mempool, if it exists there (and does // nothing if it doesn't). func (mp *Pool) Remove(hash util.Uint256) { mp.lock.Lock() if it, ok := mp.verifiedMap[hash]; ok { var num int delete(mp.verifiedMap, hash) for num = range mp.verifiedTxes { if hash.Equals(mp.verifiedTxes[num].txn.Hash()) { break } } if num < len(mp.verifiedTxes)-1 { mp.verifiedTxes = append(mp.verifiedTxes[:num], mp.verifiedTxes[num+1:]...) } else if num == len(mp.verifiedTxes)-1 { mp.verifiedTxes = mp.verifiedTxes[:num] } senderFee := mp.fees[it.txn.Sender] senderFee.feeSum -= it.txn.SystemFee + it.txn.NetworkFee mp.fees[it.txn.Sender] = senderFee } updateMempoolMetrics(len(mp.verifiedTxes)) mp.lock.Unlock() } // RemoveStale filters verified transactions through the given function keeping // only the transactions for which it returns a true result. It's used to quickly // drop part of the mempool that is now invalid after the block acceptance. func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool, feer Feer) { mp.lock.Lock() policyChanged := mp.loadPolicy(feer) // We can reuse already allocated slice // because items are iterated one-by-one in increasing order. newVerifiedTxes := mp.verifiedTxes[:0] mp.fees = make(map[util.Uint160]utilityBalanceAndFees) // it'd be nice to reuse existing map, but we can't easily clear it for _, itm := range mp.verifiedTxes { if isOK(itm.txn) && mp.checkPolicy(itm.txn, policyChanged) && mp.tryAddSendersFee(itm.txn, feer, true) { newVerifiedTxes = append(newVerifiedTxes, itm) } else { delete(mp.verifiedMap, itm.txn.Hash()) } } mp.verifiedTxes = newVerifiedTxes mp.lock.Unlock() } // loadPolicy updates feePerByte field and returns whether policy has been // changed. func (mp *Pool) loadPolicy(feer Feer) bool { newFeePerByte := feer.FeePerByte() if newFeePerByte > mp.feePerByte { mp.feePerByte = newFeePerByte return true } return false } // checkPolicy checks whether transaction fits policy. func (mp *Pool) checkPolicy(tx *transaction.Transaction, policyChanged bool) bool { if !policyChanged || tx.FeePerByte() >= mp.feePerByte { return true } return false } // NewMemPool returns a new Pool struct. func NewMemPool(capacity int) Pool { return Pool{ verifiedMap: make(map[util.Uint256]*item), verifiedTxes: make([]*item, 0, capacity), capacity: capacity, fees: make(map[util.Uint160]utilityBalanceAndFees), } } // TryGetValue returns a transaction and its fee if it exists in the memory pool. func (mp *Pool) TryGetValue(hash util.Uint256) (*transaction.Transaction, bool) { mp.lock.RLock() defer mp.lock.RUnlock() if pItem, ok := mp.verifiedMap[hash]; ok { return pItem.txn, ok } return nil, false } // GetVerifiedTransactions returns a slice of transactions with their fees. func (mp *Pool) GetVerifiedTransactions() []*transaction.Transaction { mp.lock.RLock() defer mp.lock.RUnlock() var t = make([]*transaction.Transaction, len(mp.verifiedTxes)) for i := range mp.verifiedTxes { t[i] = mp.verifiedTxes[i].txn } return t } // checkTxConflicts is an internal unprotected version of Verify. func (mp *Pool) checkTxConflicts(tx *transaction.Transaction, fee Feer) bool { senderFee, ok := mp.fees[tx.Sender] if !ok { senderFee.balance = fee.GetUtilityTokenBalance(tx.Sender) } return checkBalance(tx, senderFee) } // Verify checks if a Sender of tx is able to pay for it (and all the other // transactions in the pool). If yes, the transaction tx is a valid // transaction and the function returns true. If no, the transaction tx is // considered to be invalid the function returns false. func (mp *Pool) Verify(tx *transaction.Transaction, feer Feer) bool { mp.lock.RLock() defer mp.lock.RUnlock() return mp.checkTxConflicts(tx, feer) }