worker.go

// Copyright 2015 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 miner

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"math/big"
	"os"
	"sync"
	"sync/atomic"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/consensus"
	"github.com/ethereum/go-ethereum/consensus/misc"
	"github.com/ethereum/go-ethereum/consensus/posv"
	"github.com/ethereum/go-ethereum/contracts"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/params"
	"gopkg.in/fatih/set.v0"
)

const (
	resultQueueSize  = 10
	miningLogAtDepth = 5

	// txChanSize is the size of channel listening to TxPreEvent.
	// The number is referenced from the size of tx pool.
	txChanSize = 4096
	// chainHeadChanSize is the size of channel listening to ChainHeadEvent.
	chainHeadChanSize = 10
	// chainSideChanSize is the size of channel listening to ChainSideEvent.
	chainSideChanSize = 10
	// timeout waiting for M1
	waitPeriod = 10
	// timeout for checkpoint.
	waitPeriodCheckpoint = 20
)

// Agent can register themself with the worker
type Agent interface {
	Work() chan<- *Work
	SetReturnCh(chan<- *Result)
	Stop()
	Start()
	GetHashRate() int64
}

// Work is the workers current environment and holds
// all of the current state information
type Work struct {
	config *params.ChainConfig
	signer types.Signer

	state     *state.StateDB // apply state changes here
	ancestors *set.Set       // ancestor set (used for checking uncle parent validity)
	family    *set.Set       // family set (used for checking uncle invalidity)
	uncles    *set.Set       // uncle set
	tcount    int            // tx count in cycle

	Block *types.Block // the new block

	header   *types.Header
	txs      []*types.Transaction
	receipts []*types.Receipt

	createdAt time.Time
}

type Result struct {
	Work  *Work
	Block *types.Block
}

// worker is the main object which takes care of applying messages to the new state
type worker struct {
	config *params.ChainConfig
	engine consensus.Engine

	mu sync.Mutex

	// update loop
	mux          *event.TypeMux
	txCh         chan core.TxPreEvent
	txSub        event.Subscription
	chainHeadCh  chan core.ChainHeadEvent
	chainHeadSub event.Subscription
	chainSideCh  chan core.ChainSideEvent
	chainSideSub event.Subscription
	wg           sync.WaitGroup

	agents map[Agent]struct{}
	recv   chan *Result

	eth     Backend
	chain   *core.BlockChain
	proc    core.Validator
	chainDb ethdb.Database

	coinbase common.Address
	extra    []byte

	currentMu sync.Mutex
	current   *Work

	uncleMu        sync.Mutex
	possibleUncles map[common.Hash]*types.Block

	unconfirmed *unconfirmedBlocks // set of locally mined blocks pending canonicalness confirmations

	// atomic status counters
	mining                int32
	atWork                int32
	announceTxs           bool
	lastParentBlockCommit string
}

func newWorker(config *params.ChainConfig, engine consensus.Engine, coinbase common.Address, eth Backend, mux *event.TypeMux, announceTxs bool) *worker {
	worker := &worker{
		config:         config,
		engine:         engine,
		eth:            eth,
		mux:            mux,
		txCh:           make(chan core.TxPreEvent, txChanSize),
		chainHeadCh:    make(chan core.ChainHeadEvent, chainHeadChanSize),
		chainSideCh:    make(chan core.ChainSideEvent, chainSideChanSize),
		chainDb:        eth.ChainDb(),
		recv:           make(chan *Result, resultQueueSize),
		chain:          eth.BlockChain(),
		proc:           eth.BlockChain().Validator(),
		possibleUncles: make(map[common.Hash]*types.Block),
		coinbase:       coinbase,
		agents:         make(map[Agent]struct{}),
		unconfirmed:    newUnconfirmedBlocks(eth.BlockChain(), miningLogAtDepth),
		announceTxs:    announceTxs,
	}
	if worker.announceTxs {
		// Subscribe TxPreEvent for tx pool
		worker.txSub = eth.TxPool().SubscribeTxPreEvent(worker.txCh)
	}
	// Subscribe events for blockchain
	worker.chainHeadSub = eth.BlockChain().SubscribeChainHeadEvent(worker.chainHeadCh)
	worker.chainSideSub = eth.BlockChain().SubscribeChainSideEvent(worker.chainSideCh)
	go worker.update()

	go worker.wait()
	worker.commitNewWork()

	return worker
}

func (self *worker) setEtherbase(addr common.Address) {
	self.mu.Lock()
	defer self.mu.Unlock()
	self.coinbase = addr
}

func (self *worker) setExtra(extra []byte) {
	self.mu.Lock()
	defer self.mu.Unlock()
	self.extra = extra
}

func (self *worker) pending() (*types.Block, *state.StateDB) {
	self.currentMu.Lock()
	defer self.currentMu.Unlock()

	if atomic.LoadInt32(&self.mining) == 0 {
		return types.NewBlock(
			self.current.header,
			self.current.txs,
			nil,
			self.current.receipts,
		), self.current.state.Copy()
	}
	return self.current.Block, self.current.state.Copy()
}

func (self *worker) pendingBlock() *types.Block {
	self.currentMu.Lock()
	defer self.currentMu.Unlock()

	if atomic.LoadInt32(&self.mining) == 0 {
		return types.NewBlock(
			self.current.header,
			self.current.txs,
			nil,
			self.current.receipts,
		)
	}
	return self.current.Block
}

func (self *worker) start() {
	self.mu.Lock()
	defer self.mu.Unlock()

	atomic.StoreInt32(&self.mining, 1)

	// spin up agents
	for agent := range self.agents {
		agent.Start()
	}
}

func (self *worker) stop() {
	self.wg.Wait()

	self.mu.Lock()
	defer self.mu.Unlock()
	if atomic.LoadInt32(&self.mining) == 1 {
		for agent := range self.agents {
			agent.Stop()
		}
	}
	atomic.StoreInt32(&self.mining, 0)
	atomic.StoreInt32(&self.atWork, 0)
}

func (self *worker) register(agent Agent) {
	self.mu.Lock()
	defer self.mu.Unlock()
	self.agents[agent] = struct{}{}
	agent.SetReturnCh(self.recv)
}

func (self *worker) unregister(agent Agent) {
	self.mu.Lock()
	defer self.mu.Unlock()
	delete(self.agents, agent)
	agent.Stop()
}

func (self *worker) update() {
	if self.announceTxs {
		defer self.txSub.Unsubscribe()
	}
	defer self.chainHeadSub.Unsubscribe()
	defer self.chainSideSub.Unsubscribe()
	timeout := time.NewTimer(waitPeriod * time.Second)
	c := make(chan struct{})
	finish := make(chan struct{})
	defer close(finish)
	defer timeout.Stop()
	go func() {
		for {
			// A real event arrived, process interesting content
			select {
			case <-timeout.C:
				c <- struct{}{}
			case <-finish:
				return
			}
		}
	}()
	for {
		// A real event arrived, process interesting content
		select {
		case <-c:
			if atomic.LoadInt32(&self.mining) == 1 {
				self.commitNewWork()
			}
			timeout.Reset(waitPeriod * time.Second)
			// Handle ChainHeadEvent
		case <-self.chainHeadCh:
			self.commitNewWork()
			timeout.Reset(waitPeriod * time.Second)

			// Handle ChainSideEvent
		case ev := <-self.chainSideCh:
			if self.config.Posv == nil {
				self.uncleMu.Lock()
				self.possibleUncles[ev.Block.Hash()] = ev.Block
				self.uncleMu.Unlock()
			}
			// Handle TxPreEvent
		case ev := <-self.txCh:
			// Apply transaction to the pending state if we're not mining
			if atomic.LoadInt32(&self.mining) == 0 {
				self.currentMu.Lock()
				acc, _ := types.Sender(self.current.signer, ev.Tx)
				txs := map[common.Address]types.Transactions{acc: {ev.Tx}}
				txset, specialTxs := types.NewTransactionsByPriceAndNonce(self.current.signer, txs, nil)

				self.current.commitTransactions(self.mux, txset, specialTxs, self.chain, self.coinbase)
				self.currentMu.Unlock()
			} else {
				// If we're mining, but nothing is being processed, wake on new transactions
				if self.config.Posv != nil && self.config.Posv.Period == 0 {
					self.commitNewWork()
				}
			}
		case <-self.chainHeadSub.Err():
			return
		case <-self.chainSideSub.Err():
			return
		}
	}
}

func (self *worker) wait() {
	for {
		mustCommitNewWork := true
		for result := range self.recv {
			atomic.AddInt32(&self.atWork, -1)

			if result == nil {
				continue
			}
			block := result.Block
			if self.config.Posv != nil && block.NumberU64() >= self.config.Posv.Epoch && len(block.Validator()) == 0 {
				self.mux.Post(core.NewMinedBlockEvent{Block: block})
				continue
			}
			work := result.Work

			// Update the block hash in all logs since it is now available and not when the
			// receipt/log of individual transactions were created.
			for _, r := range work.receipts {
				for _, l := range r.Logs {
					l.BlockHash = block.Hash()
				}
			}
			for _, log := range work.state.Logs() {
				log.BlockHash = block.Hash()
			}
			stat, err := self.chain.WriteBlockWithState(block, work.receipts, work.state)
			if err != nil {
				log.Error("Failed writing block to chain", "err", err)
				continue
			}
			// check if canon block and write transactions
			if stat == core.CanonStatTy {
				// implicit by posting ChainHeadEvent
				mustCommitNewWork = false
			}
			// Broadcast the block and announce chain insertion event
			self.mux.Post(core.NewMinedBlockEvent{Block: block})
			var (
				events []interface{}
				logs   = work.state.Logs()
			)
			events = append(events, core.ChainEvent{Block: block, Hash: block.Hash(), Logs: logs})
			if stat == core.CanonStatTy {
				events = append(events, core.ChainHeadEvent{Block: block})
			}
			if work.config.Posv != nil {
				// epoch block
				if (block.NumberU64() % work.config.Posv.Epoch) == 0 {
					core.CheckpointCh <- 1
				}
				// prepare set of masternodes for the next epoch
				if (block.NumberU64() % work.config.Posv.Epoch) == (work.config.Posv.Epoch - work.config.Posv.Gap) {
					err := self.chain.UpdateM1()
					if err != nil {
						log.Error("Error when update masternodes set. Stopping node", "err", err)
						os.Exit(1)
					}
				}
			}
			self.chain.PostChainEvents(events, logs)

			// Insert the block into the set of pending ones to wait for confirmations
			self.unconfirmed.Insert(block.NumberU64(), block.Hash())

			if mustCommitNewWork {
				self.commitNewWork()
			}

			if self.config.Posv != nil {
				c := self.engine.(*posv.Posv)
				snap, err := c.GetSnapshot(self.chain, block.Header())
				if err != nil {
					log.Error("Fail to get snapshot for sign tx signer.")
					return
				}
				if _, authorized := snap.Signers[self.coinbase]; !authorized {
					valid := false
					masternodes := c.GetMasternodes(self.chain, block.Header())
					for _, m := range masternodes {
						if m == self.coinbase {
							valid = true
							break
						}
					}
					if !valid {
						log.Error("Coinbase address not in snapshot signers.")
						return
					}
				}
				// Send tx sign to smart contract blockSigners.
				if block.NumberU64()%common.MergeSignRange == 0 || !self.config.IsTIP2019(block.Number()) {
					if err := contracts.CreateTransactionSign(self.config, self.eth.TxPool(), self.eth.AccountManager(), block, self.chainDb); err != nil {
						log.Error("Fail to create tx sign for signer", "error", "err")
					}
				}
			}
		}
	}
}

// push sends a new work task to currently live miner agents.
func (self *worker) push(work *Work) {
	if atomic.LoadInt32(&self.mining) != 1 {
		return
	}
	for agent := range self.agents {
		atomic.AddInt32(&self.atWork, 1)
		if ch := agent.Work(); ch != nil {
			ch <- work
		}
	}
}

// makeCurrent creates a new environment for the current cycle.
func (self *worker) makeCurrent(parent *types.Block, header *types.Header) error {
	state, err := self.chain.StateAt(parent.Root())
	if err != nil {
		return err
	}
	work := &Work{
		config:    self.config,
		signer:    types.NewEIP155Signer(self.config.ChainId),
		state:     state,
		ancestors: set.New(),
		family:    set.New(),
		uncles:    set.New(),
		header:    header,
		createdAt: time.Now(),
	}

	if self.config.Posv == nil {
		// when 08 is processed ancestors contain 07 (quick block)
		for _, ancestor := range self.chain.GetBlocksFromHash(parent.Hash(), 7) {
			for _, uncle := range ancestor.Uncles() {
				work.family.Add(uncle.Hash())
			}
			work.family.Add(ancestor.Hash())
			work.ancestors.Add(ancestor.Hash())
		}
	}

	// Keep track of transactions which return errors so they can be removed
	work.tcount = 0
	self.current = work
	return nil
}

func abs(x int64) int64 {
	if x < 0 {
		return -x
	}
	return x
}

func (self *worker) commitNewWork() {
	self.mu.Lock()
	defer self.mu.Unlock()
	self.uncleMu.Lock()
	defer self.uncleMu.Unlock()
	self.currentMu.Lock()
	defer self.currentMu.Unlock()

	tstart := time.Now()
	parent := self.chain.CurrentBlock()
	var signers map[common.Address]struct{}
	if parent.Hash().Hex() == self.lastParentBlockCommit {
		return
	}
	if !self.announceTxs && atomic.LoadInt32(&self.mining) == 0 {
		return
	}

	// Only try to commit new work if we are mining
	if atomic.LoadInt32(&self.mining) == 1 {
		// check if we are right after parent's coinbase in the list
		// only go with Posv
		if self.config.Posv != nil {
			// get masternodes set from latest checkpoint
			c := self.engine.(*posv.Posv)
			len, preIndex, curIndex, ok, err := c.YourTurn(self.chain, parent.Header(), self.coinbase)
			if err != nil {
				log.Warn("Failed when trying to commit new work", "err", err)
				return
			}
			if !ok {
				log.Info("Not my turn to commit block. Waiting...")
				// in case some nodes are down
				if preIndex == -1 {
					// first block
					return
				}
				if curIndex == -1 {
					// you're not allowed to create this block
					return
				}
				h := posv.Hop(len, preIndex, curIndex)
				gap := waitPeriod * int64(h)
				// Check nearest checkpoint block in hop range.
				nearest := self.config.Posv.Epoch - (parent.Header().Number.Uint64() % self.config.Posv.Epoch)
				if uint64(h) >= nearest {
					gap = waitPeriodCheckpoint * int64(h)
				}
				log.Info("Distance from the parent block", "seconds", gap, "hops", h)
				waitedTime := time.Now().Unix() - parent.Header().Time.Int64()
				if gap > waitedTime {
					return
				}
				log.Info("Wait enough. It's my turn", "waited seconds", waitedTime)
			}
		}
	}
	tstamp := tstart.Unix()
	if parent.Time().Cmp(new(big.Int).SetInt64(tstamp)) >= 0 {
		tstamp = parent.Time().Int64() + 1
	}
	// this will ensure we're not going off too far in the future
	if now := time.Now().Unix(); tstamp > now+1 {
		wait := time.Duration(tstamp-now) * time.Second
		log.Info("Mining too far in the future", "wait", common.PrettyDuration(wait))
		time.Sleep(wait)
	}

	num := parent.Number()
	header := &types.Header{
		ParentHash: parent.Hash(),
		Number:     num.Add(num, common.Big1),
		GasLimit:   params.TargetGasLimit,
		Extra:      self.extra,
		Time:       big.NewInt(tstamp),
	}
	// Only set the coinbase if we are mining (avoid spurious block rewards)
	if atomic.LoadInt32(&self.mining) == 1 {
		header.Coinbase = self.coinbase
	}

	if err := self.engine.Prepare(self.chain, header); err != nil {
		log.Error("Failed to prepare header for new block", "err", err)
		return
	}
	// If we are care about TheDAO hard-fork check whether to override the extra-data or not
	if daoBlock := self.config.DAOForkBlock; daoBlock != nil {
		// Check whether the block is among the fork extra-override range
		limit := new(big.Int).Add(daoBlock, params.DAOForkExtraRange)
		if header.Number.Cmp(daoBlock) >= 0 && header.Number.Cmp(limit) < 0 {
			// Depending whether we support or oppose the fork, override differently
			if self.config.DAOForkSupport {
				header.Extra = common.CopyBytes(params.DAOForkBlockExtra)
			} else if bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
				header.Extra = []byte{} // If miner opposes, don't let it use the reserved extra-data
			}
		}
	}
	// Could potentially happen if starting to mine in an odd state.
	err := self.makeCurrent(parent, header)
	if err != nil {
		log.Error("Failed to create mining context", "err", err)
		return
	}
	// Create the current work task and check any fork transitions needed
	work := self.current
	if self.config.DAOForkSupport && self.config.DAOForkBlock != nil && self.config.DAOForkBlock.Cmp(header.Number) == 0 {
		misc.ApplyDAOHardFork(work.state)
	}
	if common.TIPSigning.Cmp(header.Number) == 0 {
		work.state.DeleteAddress(common.HexToAddress(common.BlockSigners))
	}
	// won't grasp txs at checkpoint
	var (
		txs        *types.TransactionsByPriceAndNonce
		specialTxs types.Transactions
	)
	if self.config.Posv != nil && header.Number.Uint64()%self.config.Posv.Epoch != 0 {
		pending, err := self.eth.TxPool().Pending()
		if err != nil {
			log.Error("Failed to fetch pending transactions", "err", err)
			return
		}
		txs, specialTxs = types.NewTransactionsByPriceAndNonce(self.current.signer, pending, signers)
	}
	work.commitTransactions(self.mux, txs, specialTxs, self.chain, self.coinbase)

	// compute uncles for the new block.
	var (
		uncles    []*types.Header
		badUncles []common.Hash
	)
	if self.config.Posv == nil {
		for hash, uncle := range self.possibleUncles {
			if len(uncles) == 2 {
				break
			}
			if err := self.commitUncle(work, uncle.Header()); err != nil {
				log.Trace("Bad uncle found and will be removed", "hash", hash)
				log.Trace(fmt.Sprint(uncle))

				badUncles = append(badUncles, hash)
			} else {
				log.Debug("Committing new uncle to block", "hash", hash)
				uncles = append(uncles, uncle.Header())
			}
		}
		for _, hash := range badUncles {
			delete(self.possibleUncles, hash)
		}
	}
	// Create the new block to seal with the consensus engine
	if work.Block, err = self.engine.Finalize(self.chain, header, work.state, work.txs, uncles, work.receipts); err != nil {
		log.Error("Failed to finalize block for sealing", "err", err)
		return
	}
	if atomic.LoadInt32(&self.mining) == 1 {
		log.Info("Committing new block", "number", work.Block.Number(), "txs", work.tcount, "special-txs", len(specialTxs), "uncles", len(uncles), "elapsed", common.PrettyDuration(time.Since(tstart)))
		self.unconfirmed.Shift(work.Block.NumberU64() - 1)
		self.lastParentBlockCommit = parent.Hash().Hex()
	}
	self.push(work)
}

func (self *worker) commitUncle(work *Work, uncle *types.Header) error {
	hash := uncle.Hash()
	if work.uncles.Has(hash) {
		return fmt.Errorf("uncle not unique")
	}
	if !work.ancestors.Has(uncle.ParentHash) {
		return fmt.Errorf("uncle's parent unknown (%x)", uncle.ParentHash[0:4])
	}
	if work.family.Has(hash) {
		return fmt.Errorf("uncle already in family (%x)", hash)
	}
	work.uncles.Add(uncle.Hash())
	return nil
}

func (env *Work) commitTransactions(mux *event.TypeMux, txs *types.TransactionsByPriceAndNonce, specialTxs types.Transactions, bc *core.BlockChain, coinbase common.Address) {
	gp := new(core.GasPool).AddGas(env.header.GasLimit)

	var coalescedLogs []*types.Log
	// first priority for special Txs
	for _, tx := range specialTxs {
		if gp.Gas() < params.TxGas && tx.Gas() > 0 {
			log.Trace("Not enough gas for further transactions", "gp", gp)
			break
		}
		// Error may be ignored here. The error has already been checked
		// during transaction acceptance is the transaction pool.
		//
		// We use the eip155 signer regardless of the current hf.
		from, _ := types.Sender(env.signer, tx)
		// Check whether the tx is replay protected. If we're not in the EIP155 hf
		// phase, start ignoring the sender until we do.
		if tx.Protected() && !env.config.IsEIP155(env.header.Number) {
			log.Trace("Ignoring reply protected special transaction", "hash", tx.Hash(), "eip155", env.config.EIP155Block)
			continue
		}
		if tx.To().Hex() == common.BlockSigners {
			if len(tx.Data()) < 68 {
				log.Trace("Data special transaction invalid length", "hash", tx.Hash(), "data", len(tx.Data()))
				continue
			}
			blkNumber := binary.BigEndian.Uint64(tx.Data()[8:40])
			if blkNumber >= env.header.Number.Uint64() || blkNumber <= env.header.Number.Uint64()-env.config.Posv.Epoch*2 {
				log.Trace("Data special transaction invalid number", "hash", tx.Hash(), "blkNumber", blkNumber, "miner", env.header.Number)
				continue
			}
		}
		// Start executing the transaction
		env.state.Prepare(tx.Hash(), common.Hash{}, env.tcount)
		nonce := env.state.GetNonce(from)
		if nonce != tx.Nonce() {
			log.Trace("Skipping account with special transaction invalide nonce", "sender", from, "nonce", nonce, "tx nonce ", tx.Nonce(), "to", tx.To())
			continue
		}
		err, logs := env.commitTransaction(tx, bc, coinbase, gp)
		switch err {
		case core.ErrNonceTooLow:
			// New head notification data race between the transaction pool and miner, shift
			log.Trace("Skipping special transaction with low nonce", "sender", from, "nonce", tx.Nonce(), "to", tx.To())

		case core.ErrNonceTooHigh:
			// Reorg notification data race between the transaction pool and miner, skip account =
			log.Trace("Skipping account with special transaction hight nonce", "sender", from, "nonce", tx.Nonce(), "to", tx.To())
		case nil:
			// Everything ok, collect the logs and shift in the next transaction from the same account
			coalescedLogs = append(coalescedLogs, logs...)
			env.tcount++

		default:
			// Strange error, discard the transaction and get the next in line (note, the
			// nonce-too-high clause will prevent us from executing in vain).
			log.Debug("Add Special Transaction failed, account skipped", "hash", tx.Hash(), "sender", from, "nonce", tx.Nonce(), "to", tx.To(), "err", err)
		}
	}
	for {
		// If we don't have enough gas for any further transactions then we're done
		if gp.Gas() < params.TxGas {
			log.Trace("Not enough gas for further transactions", "gp", gp)
			break
		}
		if txs == nil {
			log.Info("this block has no transaction")
			break
		}
		// Retrieve the next transaction and abort if all done
		tx := txs.Peek()
		if tx == nil {
			break
		}
		// Error may be ignored here. The error has already been checked
		// during transaction acceptance is the transaction pool.
		//
		// We use the eip155 signer regardless of the current hf.
		from, _ := types.Sender(env.signer, tx)
		// Check whether the tx is replay protected. If we're not in the EIP155 hf
		// phase, start ignoring the sender until we do.
		if tx.Protected() && !env.config.IsEIP155(env.header.Number) {
			log.Trace("Ignoring reply protected transaction", "hash", tx.Hash(), "eip155", env.config.EIP155Block)
			txs.Pop()
			continue
		}
		// Start executing the transaction
		env.state.Prepare(tx.Hash(), common.Hash{}, env.tcount)
		nonce := env.state.GetNonce(from)
		if nonce > tx.Nonce() {
			// New head notification data race between the transaction pool and miner, shift
			log.Trace("Skipping transaction with low nonce", "sender", from, "nonce", tx.Nonce())
			txs.Shift()
			continue
		}
		if nonce < tx.Nonce() {
			// Reorg notification data race between the transaction pool and miner, skip account =
			log.Trace("Skipping account with hight nonce", "sender", from, "nonce", tx.Nonce())
			txs.Pop()
			continue
		}
		err, logs := env.commitTransaction(tx, bc, coinbase, gp)
		switch err {
		case core.ErrGasLimitReached:
			// Pop the current out-of-gas transaction without shifting in the next from the account
			log.Trace("Gas limit exceeded for current block", "sender", from)
			txs.Pop()

		case core.ErrNonceTooLow:
			// New head notification data race between the transaction pool and miner, shift
			log.Trace("Skipping transaction with low nonce", "sender", from, "nonce", tx.Nonce())
			txs.Shift()

		case core.ErrNonceTooHigh:
			// Reorg notification data race between the transaction pool and miner, skip account =
			log.Trace("Skipping account with high nonce", "sender", from, "nonce", tx.Nonce())
			txs.Pop()

		case nil:
			// Everything ok, collect the logs and shift in the next transaction from the same account
			coalescedLogs = append(coalescedLogs, logs...)
			env.tcount++
			txs.Shift()

		default:
			// Strange error, discard the transaction and get the next in line (note, the
			// nonce-too-high clause will prevent us from executing in vain).
			log.Debug("Transaction failed, account skipped", "hash", tx.Hash(), "err", err)
			txs.Shift()
		}
	}
	if len(coalescedLogs) > 0 || env.tcount > 0 {
		// make a copy, the state caches the logs and these logs get "upgraded" from pending to mined
		// logs by filling in the block hash when the block was mined by the local miner. This can
		// cause a race condition if a log was "upgraded" before the PendingLogsEvent is processed.
		cpy := make([]*types.Log, len(coalescedLogs))
		for i, l := range coalescedLogs {
			cpy[i] = new(types.Log)
			*cpy[i] = *l
		}
		go func(logs []*types.Log, tcount int) {
			if len(logs) > 0 {
				mux.Post(core.PendingLogsEvent{Logs: logs})
			}
			if tcount > 0 {
				mux.Post(core.PendingStateEvent{})
			}
		}(cpy, env.tcount)
	}
}

func (env *Work) commitTransaction(tx *types.Transaction, bc *core.BlockChain, coinbase common.Address, gp *core.GasPool) (error, []*types.Log) {
	snap := env.state.Snapshot()

	receipt, _, err := core.ApplyTransaction(env.config, bc, &coinbase, gp, env.state, env.header, tx, &env.header.GasUsed, vm.Config{})
	if err != nil {
		env.state.RevertToSnapshot(snap)
		return err, nil
	}
	env.txs = append(env.txs, tx)
	env.receipts = append(env.receipts, receipt)

	return nil, receipt.Logs
}