path: root/core/transaction_pool.go

package core

import (
    "errors"
    "fmt"
    "math/big"
    "sort"
    "sync"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/state"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
)

var (
    // Transaction Pool Errors
    ErrInvalidSender      = errors.New("Invalid sender")
    ErrNonce              = errors.New("Nonce too low")
    ErrCheap              = errors.New("Gas price too low for acceptance")
    ErrBalance            = errors.New("Insufficient balance")
    ErrNonExistentAccount = errors.New("Account does not exist or account balance too low")
    ErrInsufficientFunds  = errors.New("Insufficient funds for gas * price + value")
    ErrIntrinsicGas       = errors.New("Intrinsic gas too low")
    ErrGasLimit           = errors.New("Exceeds block gas limit")
    ErrNegativeValue      = errors.New("Negative value")
)

const (
    maxQueued = 200 // max limit of queued txs per address
)

type stateFn func() *state.StateDB

// TxPool contains all currently known transactions. Transactions
// enter the pool when they are received from the network or submitted
// locally. They exit the pool when they are included in the blockchain.
//
// The pool separates processable transactions (which can be applied to the
// current state) and future transactions. Transactions move between those
// two states over time as they are received and processed.
type TxPool struct {
    quit         chan bool // Quiting channel
    currentState stateFn   // The state function which will allow us to do some pre checkes
    pendingState *state.ManagedState
    gasLimit     func() *big.Int // The current gas limit function callback
    minGasPrice  *big.Int
    eventMux     *event.TypeMux
    events       event.Subscription

    mu      sync.RWMutex
    pending map[common.Hash]*types.Transaction // processable transactions
    queue   map[common.Address]map[common.Hash]*types.Transaction
}

func NewTxPool(eventMux *event.TypeMux, currentStateFn stateFn, gasLimitFn func() *big.Int) *TxPool {
    pool := &TxPool{
        pending:      make(map[common.Hash]*types.Transaction),
        queue:        make(map[common.Address]map[common.Hash]*types.Transaction),
        quit:         make(chan bool),
        eventMux:     eventMux,
        currentState: currentStateFn,
        gasLimit:     gasLimitFn,
        minGasPrice:  new(big.Int),
        pendingState: state.ManageState(currentStateFn()),
        events:       eventMux.Subscribe(ChainEvent{}, GasPriceChanged{}),
    }
    go pool.eventLoop()

    return pool
}

func (pool *TxPool) eventLoop() {
    // Track chain events. When a chain events occurs (new chain canon block)
    // we need to know the new state. The new state will help us determine
    // the nonces in the managed state
    for ev := range pool.events.Chan() {
        pool.mu.Lock()

        switch ev := ev.(type) {
        case ChainEvent:
            pool.resetState()
        case GasPriceChanged:
            pool.minGasPrice = ev.Price
        }

        pool.mu.Unlock()
    }
}

func (pool *TxPool) resetState() {
    pool.pendingState = state.ManageState(pool.currentState())

    // validate the pool of pending transactions, this will remove
    // any transactions that have been included in the block or
    // have been invalidated because of another transaction (e.g.
    // higher gas price)
    pool.validatePool()

    // Loop over the pending transactions and base the nonce of the new
    // pending transaction set.
    for _, tx := range pool.pending {
        if addr, err := tx.From(); err == nil {
            // Set the nonce. Transaction nonce can never be lower
            // than the state nonce; validatePool took care of that.
            if pool.pendingState.GetNonce(addr) < tx.Nonce() {
                pool.pendingState.SetNonce(addr, tx.Nonce())
            }
        }
    }

    // Check the queue and move transactions over to the pending if possible
    // or remove those that have become invalid
    pool.checkQueue()
}

func (pool *TxPool) Stop() {
    close(pool.quit)
    pool.events.Unsubscribe()
    glog.V(logger.Info).Infoln("TX Pool stopped")
}

func (pool *TxPool) State() *state.ManagedState {
    pool.mu.RLock()
    defer pool.mu.RUnlock()

    return pool.pendingState
}

// validateTx checks whether a transaction is valid according
// to the consensus rules.
func (pool *TxPool) validateTx(tx *types.Transaction) error {
    // Validate sender
    var (
        from common.Address
        err  error
    )

    // Drop transactions under our own minimal accepted gas price
    if pool.minGasPrice.Cmp(tx.GasPrice()) > 0 {
        return ErrCheap
    }

    // Validate the transaction sender and it's sig. Throw
    // if the from fields is invalid.
    if from, err = tx.From(); err != nil {
        return ErrInvalidSender
    }

    // Make sure the account exist. Non existant accounts
    // haven't got funds and well therefor never pass.
    if !pool.currentState().HasAccount(from) {
        return ErrNonExistentAccount
    }

    // Last but not least check for nonce errors
    if pool.currentState().GetNonce(from) > tx.Nonce() {
        return ErrNonce
    }

    // Check the transaction doesn't exceed the current
    // block limit gas.
    if pool.gasLimit().Cmp(tx.GasLimit) < 0 {
        return ErrGasLimit
    }

    // Transactions can't be negative. This may never happen
    // using RLP decoded transactions but may occur if you create
    // a transaction using the RPC for example.
    if tx.Amount.Cmp(common.Big0) < 0 {
        return ErrNegativeValue
    }

    // Transactor should have enough funds to cover the costs
    // cost == V + GP * GL
    total := new(big.Int).Mul(tx.Price, tx.GasLimit)
    total.Add(total, tx.Value())
    if pool.currentState().GetBalance(from).Cmp(total) < 0 {
        return ErrInsufficientFunds
    }

    // Should supply enough intrinsic gas
    if tx.GasLimit.Cmp(IntrinsicGas(tx)) < 0 {
        return ErrIntrinsicGas
    }

    return nil
}

// validate and queue transactions.
func (self *TxPool) add(tx *types.Transaction) error {
    hash := tx.Hash()

    if self.pending[hash] != nil {
        return fmt.Errorf("Known transaction (%x)", hash[:4])
    }
    err := self.validateTx(tx)
    if err != nil {
        return err
    }
    self.queueTx(hash, tx)

    if glog.V(logger.Debug) {
        var toname string
        if to := tx.To(); to != nil {
            toname = common.Bytes2Hex(to[:4])
        } else {
            toname = "[NEW_CONTRACT]"
        }
        // we can ignore the error here because From is
        // verified in ValidateTransaction.
        f, _ := tx.From()
        from := common.Bytes2Hex(f[:4])
        glog.Infof("(t) %x => %s (%v) %x\n", from, toname, tx.Value, hash)
    }

    // check and validate the queueue
    self.checkQueue()

    return nil
}

// queueTx will queue an unknown transaction
func (self *TxPool) queueTx(hash common.Hash, tx *types.Transaction) {
    from, _ := tx.From() // already validated
    if self.queue[from] == nil {
        self.queue[from] = make(map[common.Hash]*types.Transaction)
    }
    self.queue[from][hash] = tx
}

// addTx will add a transaction to the pending (processable queue) list of transactions
func (pool *TxPool) addTx(hash common.Hash, addr common.Address, tx *types.Transaction) {
    if _, ok := pool.pending[hash]; !ok {
        pool.pending[hash] = tx

        // Increment the nonce on the pending state. This can only happen if
        // the nonce is +1 to the previous one.
        pool.pendingState.SetNonce(addr, tx.AccountNonce+1)
        // Notify the subscribers. This event is posted in a goroutine
        // because it's possible that somewhere during the post "Remove transaction"
        // gets called which will then wait for the global tx pool lock and deadlock.
        go pool.eventMux.Post(TxPreEvent{tx})
    }
}

// Add queues a single transaction in the pool if it is valid.
func (self *TxPool) Add(tx *types.Transaction) error {
    self.mu.Lock()
    defer self.mu.Unlock()

    return self.add(tx)
}

// AddTransactions attempts to queue all valid transactions in txs.
func (self *TxPool) AddTransactions(txs []*types.Transaction) {
    self.mu.Lock()
    defer self.mu.Unlock()

    for _, tx := range txs {
        if err := self.add(tx); err != nil {
            glog.V(logger.Debug).Infoln("tx error:", err)
        } else {
            h := tx.Hash()
            glog.V(logger.Debug).Infof("tx %x\n", h[:4])
        }
    }
}

// GetTransaction returns a transaction if it is contained in the pool
// and nil otherwise.
func (tp *TxPool) GetTransaction(hash common.Hash) *types.Transaction {
    // check the txs first
    if tx, ok := tp.pending[hash]; ok {
        return tx
    }
    // check queue
    for _, txs := range tp.queue {
        if tx, ok := txs[hash]; ok {
            return tx
        }
    }
    return nil
}

// GetTransactions returns all currently processable transactions.
// The returned slice may be modified by the caller.
func (self *TxPool) GetTransactions() (txs types.Transactions) {
    self.mu.Lock()
    defer self.mu.Unlock()

    // check queue first
    self.checkQueue()
    // invalidate any txs
    self.validatePool()

    txs = make(types.Transactions, len(self.pending))
    i := 0
    for _, tx := range self.pending {
        txs[i] = tx
        i++
    }
    return txs
}

// GetQueuedTransactions returns all non-processable transactions.
func (self *TxPool) GetQueuedTransactions() types.Transactions {
    self.mu.RLock()
    defer self.mu.RUnlock()

    var ret types.Transactions
    for _, txs := range self.queue {
        for _, tx := range txs {
            ret = append(ret, tx)
        }
    }
    sort.Sort(types.TxByNonce{ret})
    return ret
}

// RemoveTransactions removes all given transactions from the pool.
func (self *TxPool) RemoveTransactions(txs types.Transactions) {
    self.mu.Lock()
    defer self.mu.Unlock()
    for _, tx := range txs {
        self.removeTx(tx.Hash())
    }
}

// checkQueue moves transactions that have become processable to main pool.
func (pool *TxPool) checkQueue() {
    state := pool.pendingState

    var addq txQueue
    for address, txs := range pool.queue {
        // guessed nonce is the nonce currently kept by the tx pool (pending state)
        guessedNonce := state.GetNonce(address)
        // true nonce is the nonce known by the last state
        trueNonce := pool.currentState().GetNonce(address)
        addq := addq[:0]
        for hash, tx := range txs {
            if tx.AccountNonce < trueNonce {
                // Drop queued transactions whose nonce is lower than
                // the account nonce because they have been processed.
                delete(txs, hash)
            } else {
                // Collect the remaining transactions for the next pass.
                addq = append(addq, txQueueEntry{hash, address, tx})
            }
        }
        // Find the next consecutive nonce range starting at the
        // current account nonce.
        sort.Sort(addq)
        for i, e := range addq {
            // start deleting the transactions from the queue if they exceed the limit
            if i > maxQueued {
                if glog.V(logger.Debug) {
                    glog.Infof("Queued tx limit exceeded for %s. Tx %s removed\n", common.PP(address[:]), common.PP(e.hash[:]))
                }
                delete(pool.queue[address], e.hash)
                continue
            }

            if e.AccountNonce > guessedNonce {
                break
            }
            delete(txs, e.hash)
            pool.addTx(e.hash, address, e.Transaction)
        }
        // Delete the entire queue entry if it became empty.
        if len(txs) == 0 {
            delete(pool.queue, address)
        }
    }
}

func (pool *TxPool) removeTx(hash common.Hash) {
    // delete from pending pool
    delete(pool.pending, hash)
    // delete from queue
    for address, txs := range pool.queue {
        if _, ok := txs[hash]; ok {
            if len(txs) == 1 {
                // if only one tx, remove entire address entry.
                delete(pool.queue, address)
            } else {
                delete(txs, hash)
            }
            break
        }
    }
}

// validatePool removes invalid and processed transactions from the main pool.
func (pool *TxPool) validatePool() {
    state := pool.currentState()
    for hash, tx := range pool.pending {
        from, _ := tx.From() // err already checked
        // perform light nonce validation
        if state.GetNonce(from) > tx.Nonce() {
            if glog.V(logger.Core) {
                glog.Infof("removed tx (%x) from pool: low tx nonce\n", hash[:4])
            }
            delete(pool.pending, hash)
        }
    }
}

type txQueue []txQueueEntry

type txQueueEntry struct {
    hash common.Hash
    addr common.Address
    *types.Transaction
}

func (q txQueue) Len() int           { return len(q) }
func (q txQueue) Swap(i, j int)      { q[i], q[j] = q[j], q[i] }
func (q txQueue) Less(i, j int) bool { return q[i].AccountNonce < q[j].AccountNonce }