neo-go/pkg/core/mempool/mem_pool.go
2020-09-10 15:35:19 +03:00

319 lines
9.6 KiB
Go

package mempool
import (
"errors"
"math/big"
"sort"
"sync"
"github.com/nspcc-dev/neo-go/pkg/core/transaction"
"github.com/nspcc-dev/neo-go/pkg/util"
)
var (
// ErrInsufficientFunds is returned when Sender is not able to pay for
// transaction being added irrespective of the other contents of the
// pool.
ErrInsufficientFunds = errors.New("insufficient funds")
// 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
blockStamp uint32
}
// 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 *big.Int
}
// Pool stores the unconfirms transactions.
type Pool struct {
lock sync.RWMutex
verifiedMap map[util.Uint256]*transaction.Transaction
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 {
pHigh := p.txn.HasAttribute(transaction.HighPriority)
otherHigh := otherP.txn.HasAttribute(transaction.HighPriority)
if pHigh && !otherHigh {
return 1
} else if !pHigh && otherHigh {
return -1
}
// Fees sorted ascending.
if ret := int(p.txn.FeePerByte() - otherP.txn.FeePerByte()); ret != 0 {
return ret
}
return int(p.txn.NetworkFee - otherP.txn.NetworkFee)
}
// 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())
senderFee.feeSum = big.NewInt(0)
mp.fees[tx.Sender()] = senderFee
}
if needCheck {
newFeeSum, err := checkBalance(tx, senderFee)
if err != nil {
return false
}
senderFee.feeSum.Set(newFeeSum)
} else {
senderFee.feeSum.Add(senderFee.feeSum, big.NewInt(tx.SystemFee+tx.NetworkFee))
}
return true
}
// checkBalance returns new cumulative fee balance for account or an error in
// case sender doesn't have enough GAS to pay for the transaction.
func checkBalance(tx *transaction.Transaction, balance utilityBalanceAndFees) (*big.Int, error) {
txFee := big.NewInt(tx.SystemFee + tx.NetworkFee)
if balance.balance.Cmp(txFee) < 0 {
return nil, ErrInsufficientFunds
}
txFee.Add(txFee, balance.feeSum)
if balance.balance.Cmp(txFee) < 0 {
return nil, ErrConflict
}
return txFee, nil
}
// Add tries to add given transaction to the Pool.
func (mp *Pool) Add(t *transaction.Transaction, fee Feer) error {
var pItem = item{
txn: t,
blockStamp: fee.BlockHeight(),
}
mp.lock.Lock()
if mp.containsKey(t.Hash()) {
mp.lock.Unlock()
return ErrDup
}
err := mp.checkTxConflicts(t, fee)
if err != nil {
mp.lock.Unlock()
return err
}
mp.verifiedMap[t.Hash()] = t
// 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 tx, 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[tx.Sender()]
senderFee.feeSum.Sub(senderFee.feeSum, big.NewInt(tx.SystemFee+tx.NetworkFee))
mp.fees[tx.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
}
// New returns a new Pool struct.
func New(capacity int) *Pool {
return &Pool{
verifiedMap: make(map[util.Uint256]*transaction.Transaction),
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 tx, ok := mp.verifiedMap[hash]; ok {
return tx, 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) error {
senderFee, ok := mp.fees[tx.Sender()]
if !ok {
senderFee.balance = fee.GetUtilityTokenBalance(tx.Sender())
senderFee.feeSum = big.NewInt(0)
}
_, err := checkBalance(tx, senderFee)
return err
}
// 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) == nil
}