path: root/ethchain/transaction_pool.go

package ethchain

import (
    "bytes"
    "container/list"
    "errors"
    "fmt"
    "github.com/ethereum/eth-go/ethutil"
    "github.com/ethereum/eth-go/ethwire"
    "log"
    "math/big"
    "sync"
)

const (
    txPoolQueueSize = 50
)

type TxPoolHook chan *Transaction
type TxMsgTy byte

const (
    TxPre = iota
    TxPost
)

type TxMsg struct {
    Tx   *Transaction
    Type TxMsgTy
}

func FindTx(pool *list.List, finder func(*Transaction, *list.Element) bool) *Transaction {
    for e := pool.Front(); e != nil; e = e.Next() {
        if tx, ok := e.Value.(*Transaction); ok {
            if finder(tx, e) {
                return tx
            }
        }
    }

    return nil
}

type TxProcessor interface {
    ProcessTransaction(tx *Transaction)
}

// The tx pool a thread safe transaction pool handler. In order to
// guarantee a non blocking pool we use a queue channel which can be
// independently read without needing access to the actual pool. If the
// pool is being drained or synced for whatever reason the transactions
// will simple queue up and handled when the mutex is freed.
type TxPool struct {
    Ethereum EthManager
    // The mutex for accessing the Tx pool.
    mutex sync.Mutex
    // Queueing channel for reading and writing incoming
    // transactions to
    queueChan chan *Transaction
    // Quiting channel
    quit chan bool
    // The actual pool
    pool *list.List

    SecondaryProcessor TxProcessor

    subscribers []chan TxMsg
}

func NewTxPool(ethereum EthManager) *TxPool {
    return &TxPool{
        //server:    s,
        mutex:     sync.Mutex{},
        pool:      list.New(),
        queueChan: make(chan *Transaction, txPoolQueueSize),
        quit:      make(chan bool),
        Ethereum:  ethereum,
    }
}

// Blocking function. Don't use directly. Use QueueTransaction instead
func (pool *TxPool) addTransaction(tx *Transaction) {
    pool.mutex.Lock()
    pool.pool.PushBack(tx)
    pool.mutex.Unlock()

    // Broadcast the transaction to the rest of the peers
    pool.Ethereum.Broadcast(ethwire.MsgTxTy, []interface{}{tx.RlpData()})
}

// Process transaction validates the Tx and processes funds from the
// sender to the recipient.
func (pool *TxPool) ProcessTransaction(tx *Transaction, block *Block, toContract bool) (err error) {
    defer func() {
        if r := recover(); r != nil {
            log.Println(r)
            err = fmt.Errorf("%v", r)
        }
    }()
    // Get the sender
    sender := block.state.GetAccount(tx.Sender())

    if sender.Nonce != tx.Nonce {
        return fmt.Errorf("[TXPL] Invalid account nonce, state nonce is %d transaction nonce is %d instead", sender.Nonce, tx.Nonce)
    }

    // Make sure there's enough in the sender's account. Having insufficient
    // funds won't invalidate this transaction but simple ignores it.
    totAmount := new(big.Int).Add(tx.Value, new(big.Int).Mul(TxFee, TxFeeRat))
    if sender.Amount.Cmp(totAmount) < 0 {
        return fmt.Errorf("[TXPL] Insufficient amount in sender's (%x) account", tx.Sender())
    }

    // Get the receiver
    receiver := block.state.GetAccount(tx.Recipient)
    sender.Nonce += 1

    // Send Tx to self
    if bytes.Compare(tx.Recipient, tx.Sender()) == 0 {
        // Subtract the fee
        sender.SubAmount(new(big.Int).Mul(TxFee, TxFeeRat))
    } else {
        // Subtract the amount from the senders account
        sender.SubAmount(totAmount)

        // Add the amount to receivers account which should conclude this transaction
        receiver.AddAmount(tx.Value)

        block.state.UpdateStateObject(receiver)
    }

    block.state.UpdateStateObject(sender)

    log.Printf("[TXPL] Processed Tx %x\n", tx.Hash())

    pool.notifySubscribers(TxPost, tx)

    return
}

func (pool *TxPool) ValidateTransaction(tx *Transaction) error {
    // Get the last block so we can retrieve the sender and receiver from
    // the merkle trie
    block := pool.Ethereum.BlockChain().CurrentBlock
    // Something has gone horribly wrong if this happens
    if block == nil {
        return errors.New("[TXPL] No last block on the block chain")
    }

    // Get the sender
    accountState := pool.Ethereum.StateManager().GetAddrState(tx.Sender())
    sender := accountState.Object

    totAmount := new(big.Int).Add(tx.Value, new(big.Int).Mul(TxFee, TxFeeRat))
    // Make sure there's enough in the sender's account. Having insufficient
    // funds won't invalidate this transaction but simple ignores it.
    if sender.Amount.Cmp(totAmount) < 0 {
        return fmt.Errorf("[TXPL] Insufficient amount in sender's (%x) account", tx.Sender())
    }

    // Increment the nonce making each tx valid only once to prevent replay
    // attacks

    return nil
}

func (pool *TxPool) queueHandler() {
out:
    for {
        select {
        case tx := <-pool.queueChan:
            hash := tx.Hash()
            foundTx := FindTx(pool.pool, func(tx *Transaction, e *list.Element) bool {
                return bytes.Compare(tx.Hash(), hash) == 0
            })

            if foundTx != nil {
                break
            }

            // Validate the transaction
            err := pool.ValidateTransaction(tx)
            if err != nil {
                if ethutil.Config.Debug {
                    log.Println("Validating Tx failed", err)
                }
            } else {
                // Call blocking version.
                pool.addTransaction(tx)

                // Notify the subscribers
                pool.Ethereum.Reactor().Post("newTx", tx)

                // Notify the subscribers
                pool.notifySubscribers(TxPre, tx)
            }
        case <-pool.quit:
            break out
        }
    }
}

func (pool *TxPool) QueueTransaction(tx *Transaction) {
    pool.queueChan <- tx
}

func (pool *TxPool) CurrentTransactions() []*Transaction {
    pool.mutex.Lock()
    defer pool.mutex.Unlock()

    txList := make([]*Transaction, pool.pool.Len())
    i := 0
    for e := pool.pool.Front(); e != nil; e = e.Next() {
        if tx, ok := e.Value.(*Transaction); ok {
            txList[i] = tx
        }

        i++
    }

    return txList
}

func (pool *TxPool) Flush() []*Transaction {
    txList := pool.CurrentTransactions()

    // Recreate a new list all together
    // XXX Is this the fastest way?
    pool.pool = list.New()

    return txList
}

func (pool *TxPool) Start() {
    go pool.queueHandler()
}

func (pool *TxPool) Stop() {
    close(pool.quit)

    pool.Flush()

    log.Println("[TXP] Stopped")
}

func (pool *TxPool) Subscribe(channel chan TxMsg) {
    pool.subscribers = append(pool.subscribers, channel)
}

func (pool *TxPool) notifySubscribers(ty TxMsgTy, tx *Transaction) {
    msg := TxMsg{Type: ty, Tx: tx}
    for _, subscriber := range pool.subscribers {
        subscriber <- msg
    }
}