path: root/light/txpool.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package light

import (
    "context"
    "fmt"
    "sync"
    "time"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/core"
    "github.com/dexon-foundation/dexon/core/rawdb"
    "github.com/dexon-foundation/dexon/core/state"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/ethdb"
    "github.com/dexon-foundation/dexon/event"
    "github.com/dexon-foundation/dexon/log"
    "github.com/dexon-foundation/dexon/params"
    "github.com/dexon-foundation/dexon/rlp"
)

const (
    // chainHeadChanSize is the size of channel listening to ChainHeadEvent.
    chainHeadChanSize = 10
)

// txPermanent is the number of mined blocks after a mined transaction is
// considered permanent and no rollback is expected
var txPermanent = uint64(500)

// TxPool implements the transaction pool for light clients, which keeps track
// of the status of locally created transactions, detecting if they are included
// in a block (mined) or rolled back. There are no queued transactions since we
// always receive all locally signed transactions in the same order as they are
// created.
type TxPool struct {
    config       *params.ChainConfig
    signer       types.Signer
    quit         chan bool
    txFeed       event.Feed
    scope        event.SubscriptionScope
    chainHeadCh  chan core.ChainHeadEvent
    chainHeadSub event.Subscription
    mu           sync.RWMutex
    chain        *LightChain
    odr          OdrBackend
    chainDb      ethdb.Database
    relay        TxRelayBackend
    head         common.Hash
    nonce        map[common.Address]uint64            // "pending" nonce
    pending      map[common.Hash]*types.Transaction   // pending transactions by tx hash
    mined        map[common.Hash][]*types.Transaction // mined transactions by block hash
    clearIdx     uint64                               // earliest block nr that can contain mined tx info

    homestead bool
}

// TxRelayBackend provides an interface to the mechanism that forwards transacions
// to the ETH network. The implementations of the functions should be non-blocking.
//
// Send instructs backend to forward new transactions
// NewHead notifies backend about a new head after processed by the tx pool,
//  including  mined and rolled back transactions since the last event
// Discard notifies backend about transactions that should be discarded either
//  because they have been replaced by a re-send or because they have been mined
//  long ago and no rollback is expected
type TxRelayBackend interface {
    Send(txs types.Transactions)
    NewHead(head common.Hash, mined []common.Hash, rollback []common.Hash)
    Discard(hashes []common.Hash)
}

// NewTxPool creates a new light transaction pool
func NewTxPool(config *params.ChainConfig, chain *LightChain, relay TxRelayBackend) *TxPool {
    pool := &TxPool{
        config:      config,
        signer:      types.NewEIP155Signer(config.ChainID),
        nonce:       make(map[common.Address]uint64),
        pending:     make(map[common.Hash]*types.Transaction),
        mined:       make(map[common.Hash][]*types.Transaction),
        quit:        make(chan bool),
        chainHeadCh: make(chan core.ChainHeadEvent, chainHeadChanSize),
        chain:       chain,
        relay:       relay,
        odr:         chain.Odr(),
        chainDb:     chain.Odr().Database(),
        head:        chain.CurrentHeader().Hash(),
        clearIdx:    chain.CurrentHeader().Number.Uint64(),
    }
    // Subscribe events from blockchain
    pool.chainHeadSub = pool.chain.SubscribeChainHeadEvent(pool.chainHeadCh)
    go pool.eventLoop()

    return pool
}

// currentState returns the light state of the current head header
func (pool *TxPool) currentState(ctx context.Context) *state.StateDB {
    return NewState(ctx, pool.chain.CurrentHeader(), pool.odr)
}

// GetNonce returns the "pending" nonce of a given address. It always queries
// the nonce belonging to the latest header too in order to detect if another
// client using the same key sent a transaction.
func (pool *TxPool) GetNonce(ctx context.Context, addr common.Address) (uint64, error) {
    state := pool.currentState(ctx)
    nonce := state.GetNonce(addr)
    if state.Error() != nil {
        return 0, state.Error()
    }
    sn, ok := pool.nonce[addr]
    if ok && sn > nonce {
        nonce = sn
    }
    if !ok || sn < nonce {
        pool.nonce[addr] = nonce
    }
    return nonce, nil
}

// txStateChanges stores the recent changes between pending/mined states of
// transactions. True means mined, false means rolled back, no entry means no change
type txStateChanges map[common.Hash]bool

// setState sets the status of a tx to either recently mined or recently rolled back
func (txc txStateChanges) setState(txHash common.Hash, mined bool) {
    val, ent := txc[txHash]
    if ent && (val != mined) {
        delete(txc, txHash)
    } else {
        txc[txHash] = mined
    }
}

// getLists creates lists of mined and rolled back tx hashes
func (txc txStateChanges) getLists() (mined []common.Hash, rollback []common.Hash) {
    for hash, val := range txc {
        if val {
            mined = append(mined, hash)
        } else {
            rollback = append(rollback, hash)
        }
    }
    return
}

// checkMinedTxs checks newly added blocks for the currently pending transactions
// and marks them as mined if necessary. It also stores block position in the db
// and adds them to the received txStateChanges map.
func (pool *TxPool) checkMinedTxs(ctx context.Context, hash common.Hash, number uint64, txc txStateChanges) error {
    // If no transactions are pending, we don't care about anything
    if len(pool.pending) == 0 {
        return nil
    }
    block, err := GetBlock(ctx, pool.odr, hash, number)
    if err != nil {
        return err
    }
    // Gather all the local transaction mined in this block
    list := pool.mined[hash]
    for _, tx := range block.Transactions() {
        if _, ok := pool.pending[tx.Hash()]; ok {
            list = append(list, tx)
        }
    }
    // If some transactions have been mined, write the needed data to disk and update
    if list != nil {
        // Retrieve all the receipts belonging to this block and write the loopup table
        if _, err := GetBlockReceipts(ctx, pool.odr, hash, number); err != nil { // ODR caches, ignore results
            return err
        }
        rawdb.WriteTxLookupEntries(pool.chainDb, block)

        // Update the transaction pool's state
        for _, tx := range list {
            delete(pool.pending, tx.Hash())
            txc.setState(tx.Hash(), true)
        }
        pool.mined[hash] = list
    }
    return nil
}

// rollbackTxs marks the transactions contained in recently rolled back blocks
// as rolled back. It also removes any positional lookup entries.
func (pool *TxPool) rollbackTxs(hash common.Hash, txc txStateChanges) {
    batch := pool.chainDb.NewBatch()
    if list, ok := pool.mined[hash]; ok {
        for _, tx := range list {
            txHash := tx.Hash()
            rawdb.DeleteTxLookupEntry(batch, txHash)
            pool.pending[txHash] = tx
            txc.setState(txHash, false)
        }
        delete(pool.mined, hash)
    }
    batch.Write()
}

// reorgOnNewHead sets a new head header, processing (and rolling back if necessary)
// the blocks since the last known head and returns a txStateChanges map containing
// the recently mined and rolled back transaction hashes. If an error (context
// timeout) occurs during checking new blocks, it leaves the locally known head
// at the latest checked block and still returns a valid txStateChanges, making it
// possible to continue checking the missing blocks at the next chain head event
func (pool *TxPool) reorgOnNewHead(ctx context.Context, newHeader *types.Header) (txStateChanges, error) {
    txc := make(txStateChanges)
    oldh := pool.chain.GetHeaderByHash(pool.head)
    newh := newHeader
    // find common ancestor, create list of rolled back and new block hashes
    var oldHashes, newHashes []common.Hash
    for oldh.Hash() != newh.Hash() {
        if oldh.Number.Uint64() >= newh.Number.Uint64() {
            oldHashes = append(oldHashes, oldh.Hash())
            oldh = pool.chain.GetHeader(oldh.ParentHash, oldh.Number.Uint64()-1)
        }
        if oldh.Number.Uint64() < newh.Number.Uint64() {
            newHashes = append(newHashes, newh.Hash())
            newh = pool.chain.GetHeader(newh.ParentHash, newh.Number.Uint64()-1)
            if newh == nil {
                // happens when CHT syncing, nothing to do
                newh = oldh
            }
        }
    }
    if oldh.Number.Uint64() < pool.clearIdx {
        pool.clearIdx = oldh.Number.Uint64()
    }
    // roll back old blocks
    for _, hash := range oldHashes {
        pool.rollbackTxs(hash, txc)
    }
    pool.head = oldh.Hash()
    // check mined txs of new blocks (array is in reversed order)
    for i := len(newHashes) - 1; i >= 0; i-- {
        hash := newHashes[i]
        if err := pool.checkMinedTxs(ctx, hash, newHeader.Number.Uint64()-uint64(i), txc); err != nil {
            return txc, err
        }
        pool.head = hash
    }

    // clear old mined tx entries of old blocks
    if idx := newHeader.Number.Uint64(); idx > pool.clearIdx+txPermanent {
        idx2 := idx - txPermanent
        if len(pool.mined) > 0 {
            for i := pool.clearIdx; i < idx2; i++ {
                hash := rawdb.ReadCanonicalHash(pool.chainDb, i)
                if list, ok := pool.mined[hash]; ok {
                    hashes := make([]common.Hash, len(list))
                    for i, tx := range list {
                        hashes[i] = tx.Hash()
                    }
                    pool.relay.Discard(hashes)
                    delete(pool.mined, hash)
                }
            }
        }
        pool.clearIdx = idx2
    }

    return txc, nil
}

// blockCheckTimeout is the time limit for checking new blocks for mined
// transactions. Checking resumes at the next chain head event if timed out.
const blockCheckTimeout = time.Second * 3

// eventLoop processes chain head events and also notifies the tx relay backend
// about the new head hash and tx state changes
func (pool *TxPool) eventLoop() {
    for {
        select {
        case ev := <-pool.chainHeadCh:
            pool.setNewHead(ev.Block.Header())
            // hack in order to avoid hogging the lock; this part will
            // be replaced by a subsequent PR.
            time.Sleep(time.Millisecond)

        // System stopped
        case <-pool.chainHeadSub.Err():
            return
        }
    }
}

func (pool *TxPool) setNewHead(head *types.Header) {
    pool.mu.Lock()
    defer pool.mu.Unlock()

    ctx, cancel := context.WithTimeout(context.Background(), blockCheckTimeout)
    defer cancel()

    txc, _ := pool.reorgOnNewHead(ctx, head)
    m, r := txc.getLists()
    pool.relay.NewHead(pool.head, m, r)
    pool.homestead = pool.config.IsHomestead(head.Number)
    pool.signer = types.MakeSigner(pool.config, head.Number)
}

// Stop stops the light transaction pool
func (pool *TxPool) Stop() {
    // Unsubscribe all subscriptions registered from txpool
    pool.scope.Close()
    // Unsubscribe subscriptions registered from blockchain
    pool.chainHeadSub.Unsubscribe()
    close(pool.quit)
    log.Info("Transaction pool stopped")
}

// SubscribeNewTxsEvent registers a subscription of core.NewTxsEvent and
// starts sending event to the given channel.
func (pool *TxPool) SubscribeNewTxsEvent(ch chan<- core.NewTxsEvent) event.Subscription {
    return pool.scope.Track(pool.txFeed.Subscribe(ch))
}

// Stats returns the number of currently pending (locally created) transactions
func (pool *TxPool) Stats() (pending int) {
    pool.mu.RLock()
    defer pool.mu.RUnlock()

    pending = len(pool.pending)
    return
}

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

    // Validate the transaction sender and it's sig. Throw
    // if the from fields is invalid.
    if from, err = types.Sender(pool.signer, tx); err != nil {
        return core.ErrInvalidSender
    }
    // Last but not least check for nonce errors
    currentState := pool.currentState(ctx)
    if n := currentState.GetNonce(from); n > tx.Nonce() {
        return core.ErrNonceTooLow
    }

    // Check the transaction doesn't exceed the current
    // block limit gas.
    header := pool.chain.GetHeaderByHash(pool.head)
    if header.GasLimit < tx.Gas() {
        return core.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.Value().Sign() < 0 {
        return core.ErrNegativeValue
    }

    // Transactor should have enough funds to cover the costs
    // cost == V + GP * GL
    if b := currentState.GetBalance(from); b.Cmp(tx.Cost()) < 0 {
        return core.ErrInsufficientFunds
    }

    // Should supply enough intrinsic gas
    gas, err := core.IntrinsicGas(tx.Data(), tx.To() == nil, pool.homestead)
    if err != nil {
        return err
    }
    if tx.Gas() < gas {
        return core.ErrIntrinsicGas
    }
    return currentState.Error()
}

// add validates a new transaction and sets its state pending if processable.
// It also updates the locally stored nonce if necessary.
func (self *TxPool) add(ctx context.Context, tx *types.Transaction) error {
    hash := tx.Hash()

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

    if _, ok := self.pending[hash]; !ok {
        self.pending[hash] = tx

        nonce := tx.Nonce() + 1

        addr, _ := types.Sender(self.signer, tx)
        if nonce > self.nonce[addr] {
            self.nonce[addr] = nonce
        }

        // 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 self.txFeed.Send(core.NewTxsEvent{Txs: types.Transactions{tx}})
    }

    // Print a log message if low enough level is set
    log.Debug("Pooled new transaction", "hash", hash, "from", log.Lazy{Fn: func() common.Address { from, _ := types.Sender(self.signer, tx); return from }}, "to", tx.To())
    return nil
}

// Add adds a transaction to the pool if valid and passes it to the tx relay
// backend
func (self *TxPool) Add(ctx context.Context, tx *types.Transaction) error {
    self.mu.Lock()
    defer self.mu.Unlock()

    data, err := rlp.EncodeToBytes(tx)
    if err != nil {
        return err
    }

    if err := self.add(ctx, tx); err != nil {
        return err
    }
    //fmt.Println("Send", tx.Hash())
    self.relay.Send(types.Transactions{tx})

    self.chainDb.Put(tx.Hash().Bytes(), data)
    return nil
}

// AddTransactions adds all valid transactions to the pool and passes them to
// the tx relay backend
func (self *TxPool) AddBatch(ctx context.Context, txs []*types.Transaction) {
    self.mu.Lock()
    defer self.mu.Unlock()
    var sendTx types.Transactions

    for _, tx := range txs {
        if err := self.add(ctx, tx); err == nil {
            sendTx = append(sendTx, tx)
        }
    }
    if len(sendTx) > 0 {
        self.relay.Send(sendTx)
    }
}

// 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
    }
    return nil
}

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

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

// Content retrieves the data content of the transaction pool, returning all the
// pending as well as queued transactions, grouped by account and nonce.
func (self *TxPool) Content() (map[common.Address]types.Transactions, map[common.Address]types.Transactions) {
    self.mu.RLock()
    defer self.mu.RUnlock()

    // Retrieve all the pending transactions and sort by account and by nonce
    pending := make(map[common.Address]types.Transactions)
    for _, tx := range self.pending {
        account, _ := types.Sender(self.signer, tx)
        pending[account] = append(pending[account], tx)
    }
    // There are no queued transactions in a light pool, just return an empty map
    queued := make(map[common.Address]types.Transactions)
    return pending, queued
}

// RemoveTransactions removes all given transactions from the pool.
func (self *TxPool) RemoveTransactions(txs types.Transactions) {
    self.mu.Lock()
    defer self.mu.Unlock()

    var hashes []common.Hash
    batch := self.chainDb.NewBatch()
    for _, tx := range txs {
        hash := tx.Hash()
        delete(self.pending, hash)
        batch.Delete(hash.Bytes())
        hashes = append(hashes, hash)
    }
    batch.Write()
    self.relay.Discard(hashes)
}

// RemoveTx removes the transaction with the given hash from the pool.
func (pool *TxPool) RemoveTx(hash common.Hash) {
    pool.mu.Lock()
    defer pool.mu.Unlock()
    // delete from pending pool
    delete(pool.pending, hash)
    pool.chainDb.Delete(hash[:])
    pool.relay.Discard([]common.Hash{hash})
}