path: root/miner/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"
    "errors"
    "math/big"
    "sync"
    "sync/atomic"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/tangerine-network/go-tangerine/common"
    "github.com/tangerine-network/go-tangerine/consensus"
    "github.com/tangerine-network/go-tangerine/consensus/misc"
    "github.com/tangerine-network/go-tangerine/core"
    "github.com/tangerine-network/go-tangerine/core/state"
    "github.com/tangerine-network/go-tangerine/core/types"
    "github.com/tangerine-network/go-tangerine/event"
    "github.com/tangerine-network/go-tangerine/log"
    "github.com/tangerine-network/go-tangerine/params"
)

const (
    // resultQueueSize is the size of channel listening to sealing result.
    resultQueueSize = 10

    // txChanSize is the size of channel listening to NewTxsEvent.
    // 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

    // resubmitAdjustChanSize is the size of resubmitting interval adjustment channel.
    resubmitAdjustChanSize = 10

    // miningLogAtDepth is the number of confirmations before logging successful mining.
    miningLogAtDepth = 7

    // minRecommitInterval is the minimal time interval to recreate the mining block with
    // any newly arrived transactions.
    minRecommitInterval = 1 * time.Second

    // maxRecommitInterval is the maximum time interval to recreate the mining block with
    // any newly arrived transactions.
    maxRecommitInterval = 15 * time.Second

    // intervalAdjustRatio is the impact a single interval adjustment has on sealing work
    // resubmitting interval.
    intervalAdjustRatio = 0.1

    // intervalAdjustBias is applied during the new resubmit interval calculation in favor of
    // increasing upper limit or decreasing lower limit so that the limit can be reachable.
    intervalAdjustBias = 200 * 1000.0 * 1000.0

    // staleThreshold is the maximum depth of the acceptable stale block.
    staleThreshold = 7
)

// environment is the worker's current environment and holds all of the current state information.
type environment struct {
    signer types.Signer

    state     *state.StateDB // apply state changes here
    ancestors mapset.Set     // ancestor set (used for checking uncle parent validity)
    family    mapset.Set     // family set (used for checking uncle invalidity)
    uncles    mapset.Set     // uncle set
    tcount    int            // tx count in cycle
    gasPool   *core.GasPool  // available gas used to pack transactions

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

// task contains all information for consensus engine sealing and result submitting.
type task struct {
    receipts  []*types.Receipt
    state     *state.StateDB
    block     *types.Block
    createdAt time.Time
}

const (
    commitInterruptNone int32 = iota
    commitInterruptNewHead
    commitInterruptResubmit
)

// newWorkReq represents a request for new sealing work submitting with relative interrupt notifier.
type newWorkReq struct {
    interrupt *int32
    noempty   bool
    timestamp int64
}

// intervalAdjust represents a resubmitting interval adjustment.
type intervalAdjust struct {
    ratio float64
    inc   bool
}

// worker is the main object which takes care of submitting new work to consensus engine
// and gathering the sealing result.
type worker struct {
    config *params.ChainConfig
    engine consensus.Engine
    eth    Backend
    chain  *core.BlockChain

    gasFloor uint64
    gasCeil  uint64

    // Subscriptions
    mux          *event.TypeMux
    txsCh        chan core.NewTxsEvent
    txsSub       event.Subscription
    chainHeadCh  chan core.ChainHeadEvent
    chainHeadSub event.Subscription
    chainSideCh  chan core.ChainSideEvent
    chainSideSub event.Subscription

    // Channels
    newWorkCh          chan *newWorkReq
    taskCh             chan *task
    resultCh           chan *types.Block
    startCh            chan struct{}
    exitCh             chan struct{}
    resubmitIntervalCh chan time.Duration
    resubmitAdjustCh   chan *intervalAdjust

    current      *environment                 // An environment for current running cycle.
    localUncles  map[common.Hash]*types.Block // A set of side blocks generated locally as the possible uncle blocks.
    remoteUncles map[common.Hash]*types.Block // A set of side blocks as the possible uncle blocks.
    unconfirmed  *unconfirmedBlocks           // A set of locally mined blocks pending canonicalness confirmations.

    mu       sync.RWMutex // The lock used to protect the coinbase and extra fields
    coinbase common.Address
    extra    []byte

    pendingMu    sync.RWMutex
    pendingTasks map[common.Hash]*task

    snapshotMu    sync.RWMutex // The lock used to protect the block snapshot and state snapshot
    snapshotBlock *types.Block
    snapshotState *state.StateDB

    // atomic status counters
    running int32 // The indicator whether the consensus engine is running or not.
    newTxs  int32 // New arrival transaction count since last sealing work submitting.

    // External functions
    isLocalBlock func(block *types.Block) bool // Function used to determine whether the specified block is mined by local miner.

    // Test hooks
    newTaskHook  func(*task)                        // Method to call upon receiving a new sealing task.
    skipSealHook func(*task) bool                   // Method to decide whether skipping the sealing.
    fullTaskHook func()                             // Method to call before pushing the full sealing task.
    resubmitHook func(time.Duration, time.Duration) // Method to call upon updating resubmitting interval.
}

func newWorker(config *params.ChainConfig, engine consensus.Engine, eth Backend, mux *event.TypeMux, recommit time.Duration, gasFloor, gasCeil uint64, isLocalBlock func(*types.Block) bool) *worker {
    worker := &worker{
        config:             config,
        engine:             engine,
        eth:                eth,
        mux:                mux,
        chain:              eth.BlockChain(),
        gasFloor:           gasFloor,
        gasCeil:            gasCeil,
        isLocalBlock:       isLocalBlock,
        localUncles:        make(map[common.Hash]*types.Block),
        remoteUncles:       make(map[common.Hash]*types.Block),
        unconfirmed:        newUnconfirmedBlocks(eth.BlockChain(), miningLogAtDepth),
        pendingTasks:       make(map[common.Hash]*task),
        txsCh:              make(chan core.NewTxsEvent, txChanSize),
        chainHeadCh:        make(chan core.ChainHeadEvent, chainHeadChanSize),
        chainSideCh:        make(chan core.ChainSideEvent, chainSideChanSize),
        newWorkCh:          make(chan *newWorkReq),
        taskCh:             make(chan *task),
        resultCh:           make(chan *types.Block, resultQueueSize),
        exitCh:             make(chan struct{}),
        startCh:            make(chan struct{}, 1),
        resubmitIntervalCh: make(chan time.Duration),
        resubmitAdjustCh:   make(chan *intervalAdjust, resubmitAdjustChanSize),
    }
    // Subscribe NewTxsEvent for tx pool
    worker.txsSub = eth.TxPool().SubscribeNewTxsEvent(worker.txsCh)
    // Subscribe events for blockchain
    worker.chainHeadSub = eth.BlockChain().SubscribeChainHeadEvent(worker.chainHeadCh)
    worker.chainSideSub = eth.BlockChain().SubscribeChainSideEvent(worker.chainSideCh)

    // Sanitize recommit interval if the user-specified one is too short.
    if recommit < minRecommitInterval {
        log.Warn("Sanitizing miner recommit interval", "provided", recommit, "updated", minRecommitInterval)
        recommit = minRecommitInterval
    }

    go worker.mainLoop()
    go worker.newWorkLoop(recommit)
    go worker.resultLoop()
    go worker.taskLoop()

    // Submit first work to initialize pending state.
    worker.startCh <- struct{}{}

    return worker
}

// setEtherbase sets the etherbase used to initialize the block coinbase field.
func (w *worker) setEtherbase(addr common.Address) {
    w.mu.Lock()
    defer w.mu.Unlock()
    w.coinbase = addr
}

// setExtra sets the content used to initialize the block extra field.
func (w *worker) setExtra(extra []byte) {
    w.mu.Lock()
    defer w.mu.Unlock()
    w.extra = extra
}

// setRecommitInterval updates the interval for miner sealing work recommitting.
func (w *worker) setRecommitInterval(interval time.Duration) {
    w.resubmitIntervalCh <- interval
}

// pending returns the pending state and corresponding block.
func (w *worker) pending() (*types.Block, *state.StateDB) {
    // return a snapshot to avoid contention on currentMu mutex
    w.snapshotMu.RLock()
    defer w.snapshotMu.RUnlock()
    if w.snapshotState == nil {
        return nil, nil
    }
    return w.snapshotBlock, w.snapshotState.Copy()
}

// pendingBlock returns pending block.
func (w *worker) pendingBlock() *types.Block {
    // return a snapshot to avoid contention on currentMu mutex
    w.snapshotMu.RLock()
    defer w.snapshotMu.RUnlock()
    return w.snapshotBlock
}

// start sets the running status as 1 and triggers new work submitting.
func (w *worker) start() {
    atomic.StoreInt32(&w.running, 1)
    w.startCh <- struct{}{}
}

// stop sets the running status as 0.
func (w *worker) stop() {
    atomic.StoreInt32(&w.running, 0)
}

// isRunning returns an indicator whether worker is running or not.
func (w *worker) isRunning() bool {
    return atomic.LoadInt32(&w.running) == 1
}

// close terminates all background threads maintained by the worker.
// Note the worker does not support being closed multiple times.
func (w *worker) close() {
    close(w.exitCh)
}

// newWorkLoop is a standalone goroutine to submit new mining work upon received events.
func (w *worker) newWorkLoop(recommit time.Duration) {
    var (
        interrupt   *int32
        minRecommit = recommit // minimal resubmit interval specified by user.
        timestamp   int64      // timestamp for each round of mining.
    )

    timer := time.NewTimer(0)
    <-timer.C // discard the initial tick

    // commit aborts in-flight transaction execution with given signal and resubmits a new one.
    commit := func(noempty bool, s int32) {
        if interrupt != nil {
            atomic.StoreInt32(interrupt, s)
        }
        interrupt = new(int32)
        w.newWorkCh <- &newWorkReq{interrupt: interrupt, noempty: noempty, timestamp: timestamp}
        timer.Reset(recommit)
        atomic.StoreInt32(&w.newTxs, 0)
    }
    // recalcRecommit recalculates the resubmitting interval upon feedback.
    recalcRecommit := func(target float64, inc bool) {
        var (
            prev = float64(recommit.Nanoseconds())
            next float64
        )
        if inc {
            next = prev*(1-intervalAdjustRatio) + intervalAdjustRatio*(target+intervalAdjustBias)
            // Recap if interval is larger than the maximum time interval
            if next > float64(maxRecommitInterval.Nanoseconds()) {
                next = float64(maxRecommitInterval.Nanoseconds())
            }
        } else {
            next = prev*(1-intervalAdjustRatio) + intervalAdjustRatio*(target-intervalAdjustBias)
            // Recap if interval is less than the user specified minimum
            if next < float64(minRecommit.Nanoseconds()) {
                next = float64(minRecommit.Nanoseconds())
            }
        }
        recommit = time.Duration(int64(next))
    }
    // clearPending cleans the stale pending tasks.
    clearPending := func(number uint64) {
        w.pendingMu.Lock()
        for h, t := range w.pendingTasks {
            if t.block.NumberU64()+staleThreshold <= number {
                delete(w.pendingTasks, h)
            }
        }
        w.pendingMu.Unlock()
    }

    for {
        select {
        case <-w.startCh:
            clearPending(w.chain.CurrentBlock().NumberU64())
            timestamp = time.Now().Unix()
            commit(false, commitInterruptNewHead)

        case head := <-w.chainHeadCh:
            clearPending(head.Block.NumberU64())
            timestamp = time.Now().Unix()
            commit(false, commitInterruptNewHead)

        case <-timer.C:
            // If mining is running resubmit a new work cycle periodically to pull in
            // higher priced transactions. Disable this overhead for pending blocks.
            if w.isRunning() && (w.config.Clique == nil || w.config.Clique.Period > 0) {
                // Short circuit if no new transaction arrives.
                if atomic.LoadInt32(&w.newTxs) == 0 {
                    timer.Reset(recommit)
                    continue
                }
                commit(true, commitInterruptResubmit)
            }

        case interval := <-w.resubmitIntervalCh:
            // Adjust resubmit interval explicitly by user.
            if interval < minRecommitInterval {
                log.Warn("Sanitizing miner recommit interval", "provided", interval, "updated", minRecommitInterval)
                interval = minRecommitInterval
            }
            log.Info("Miner recommit interval update", "from", minRecommit, "to", interval)
            minRecommit, recommit = interval, interval

            if w.resubmitHook != nil {
                w.resubmitHook(minRecommit, recommit)
            }

        case adjust := <-w.resubmitAdjustCh:
            // Adjust resubmit interval by feedback.
            if adjust.inc {
                before := recommit
                recalcRecommit(float64(recommit.Nanoseconds())/adjust.ratio, true)
                log.Trace("Increase miner recommit interval", "from", before, "to", recommit)
            } else {
                before := recommit
                recalcRecommit(float64(minRecommit.Nanoseconds()), false)
                log.Trace("Decrease miner recommit interval", "from", before, "to", recommit)
            }

            if w.resubmitHook != nil {
                w.resubmitHook(minRecommit, recommit)
            }

        case <-w.exitCh:
            return
        }
    }
}

// mainLoop is a standalone goroutine to regenerate the sealing task based on the received event.
func (w *worker) mainLoop() {
    defer w.txsSub.Unsubscribe()
    defer w.chainHeadSub.Unsubscribe()
    defer w.chainSideSub.Unsubscribe()

    for {
        select {
        case req := <-w.newWorkCh:
            w.commitNewWork(req.interrupt, req.noempty, req.timestamp)

        case ev := <-w.chainSideCh:
            // Short circuit for duplicate side blocks
            if _, exist := w.localUncles[ev.Block.Hash()]; exist {
                continue
            }
            if _, exist := w.remoteUncles[ev.Block.Hash()]; exist {
                continue
            }
            // Add side block to possible uncle block set depending on the author.
            if w.isLocalBlock != nil && w.isLocalBlock(ev.Block) {
                w.localUncles[ev.Block.Hash()] = ev.Block
            } else {
                w.remoteUncles[ev.Block.Hash()] = ev.Block
            }
            // If our mining block contains less than 2 uncle blocks,
            // add the new uncle block if valid and regenerate a mining block.
            if w.isRunning() && w.current != nil && w.current.uncles.Cardinality() < 2 {
                start := time.Now()
                if err := w.commitUncle(w.current, ev.Block.Header()); err == nil {
                    var uncles []*types.Header
                    w.current.uncles.Each(func(item interface{}) bool {
                        hash, ok := item.(common.Hash)
                        if !ok {
                            return false
                        }
                        uncle, exist := w.localUncles[hash]
                        if !exist {
                            uncle, exist = w.remoteUncles[hash]
                        }
                        if !exist {
                            return false
                        }
                        uncles = append(uncles, uncle.Header())
                        return false
                    })
                    w.commit(uncles, nil, true, start)
                }
            }

        case ev := <-w.txsCh:
            // Apply transactions to the pending state if we're not mining.
            //
            // Note all transactions received may not be continuous with transactions
            // already included in the current mining block. These transactions will
            // be automatically eliminated.
            if !w.isRunning() && w.current != nil {
                w.mu.RLock()
                coinbase := w.coinbase
                w.mu.RUnlock()

                txs := make(map[common.Address]types.Transactions)
                for _, tx := range ev.Txs {
                    acc, _ := types.Sender(w.current.signer, tx)
                    txs[acc] = append(txs[acc], tx)
                }
                txset := types.NewTransactionsByPriceAndNonce(w.current.signer, txs)
                w.commitTransactions(txset, coinbase, nil)
                w.updateSnapshot()
            } else {
                // If we're mining, but nothing is being processed, wake on new transactions
                if w.config.Clique != nil && w.config.Clique.Period == 0 {
                    w.commitNewWork(nil, false, time.Now().Unix())
                }
            }
            atomic.AddInt32(&w.newTxs, int32(len(ev.Txs)))

        // System stopped
        case <-w.exitCh:
            return
        case <-w.txsSub.Err():
            return
        case <-w.chainHeadSub.Err():
            return
        case <-w.chainSideSub.Err():
            return
        }
    }
}

// taskLoop is a standalone goroutine to fetch sealing task from the generator and
// push them to consensus engine.
func (w *worker) taskLoop() {
    var (
        stopCh chan struct{}
        prev   common.Hash
    )

    // interrupt aborts the in-flight sealing task.
    interrupt := func() {
        if stopCh != nil {
            close(stopCh)
            stopCh = nil
        }
    }
    for {
        select {
        case task := <-w.taskCh:
            if w.newTaskHook != nil {
                w.newTaskHook(task)
            }
            // Reject duplicate sealing work due to resubmitting.
            sealHash := w.engine.SealHash(task.block.Header())
            if sealHash == prev {
                continue
            }
            // Interrupt previous sealing operation
            interrupt()
            stopCh, prev = make(chan struct{}), sealHash

            if w.skipSealHook != nil && w.skipSealHook(task) {
                continue
            }
            w.pendingMu.Lock()
            w.pendingTasks[w.engine.SealHash(task.block.Header())] = task
            w.pendingMu.Unlock()

            if err := w.engine.Seal(w.chain, task.block, w.resultCh, stopCh); err != nil {
                log.Warn("Block sealing failed", "err", err)
            }
        case <-w.exitCh:
            interrupt()
            return
        }
    }
}

// resultLoop is a standalone goroutine to handle sealing result submitting
// and flush relative data to the database.
func (w *worker) resultLoop() {
    for {
        select {
        case block := <-w.resultCh:
            // Short circuit when receiving empty result.
            if block == nil {
                continue
            }
            // Short circuit when receiving duplicate result caused by resubmitting.
            if w.chain.HasBlock(block.Hash(), block.NumberU64()) {
                continue
            }
            var (
                sealhash = w.engine.SealHash(block.Header())
                hash     = block.Hash()
            )
            w.pendingMu.RLock()
            task, exist := w.pendingTasks[sealhash]
            w.pendingMu.RUnlock()
            if !exist {
                log.Error("Block found but no relative pending task", "number", block.Number(), "sealhash", sealhash, "hash", hash)
                continue
            }
            // Different block could share same sealhash, deep copy here to prevent write-write conflict.
            var (
                receipts = make([]*types.Receipt, len(task.receipts))
                logs     []*types.Log
            )
            for i, receipt := range task.receipts {
                receipts[i] = new(types.Receipt)
                *receipts[i] = *receipt
                // Update the block hash in all logs since it is now available and not when the
                // receipt/log of individual transactions were created.
                for _, log := range receipt.Logs {
                    log.BlockHash = hash
                }
                logs = append(logs, receipt.Logs...)
            }
            // Commit block and state to database.
            stat, err := w.chain.WriteBlockWithState(block, receipts, task.state)
            if err != nil {
                log.Error("Failed writing block to chain", "err", err)
                continue
            }
            log.Info("Successfully sealed new block", "number", block.Number(), "sealhash", sealhash, "hash", hash,
                "elapsed", common.PrettyDuration(time.Since(task.createdAt)))

            // Broadcast the block and announce chain insertion event
            w.mux.Post(core.NewMinedBlockEvent{Block: block})

            var events []interface{}
            switch stat {
            case core.CanonStatTy:
                events = append(events, core.ChainEvent{Block: block, Hash: block.Hash(), Logs: logs})
                events = append(events, core.ChainHeadEvent{Block: block})
            case core.SideStatTy:
                events = append(events, core.ChainSideEvent{Block: block})
            }
            w.chain.PostChainEvents(events, logs)

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

        case <-w.exitCh:
            return
        }
    }
}

// makeCurrent creates a new environment for the current cycle.
func (w *worker) makeCurrent(parent *types.Block, header *types.Header) error {
    state, err := w.chain.StateAt(parent.Root())
    if err != nil {
        return err
    }
    env := &environment{
        signer:    types.NewEIP155Signer(w.config.ChainID),
        state:     state,
        ancestors: mapset.NewSet(),
        family:    mapset.NewSet(),
        uncles:    mapset.NewSet(),
        header:    header,
    }

    // when 08 is processed ancestors contain 07 (quick block)
    for _, ancestor := range w.chain.GetBlocksFromHash(parent.Hash(), 7) {
        for _, uncle := range ancestor.Uncles() {
            env.family.Add(uncle.Hash())
        }
        env.family.Add(ancestor.Hash())
        env.ancestors.Add(ancestor.Hash())
    }

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

// commitUncle adds the given block to uncle block set, returns error if failed to add.
func (w *worker) commitUncle(env *environment, uncle *types.Header) error {
    hash := uncle.Hash()
    if env.uncles.Contains(hash) {
        return errors.New("uncle not unique")
    }
    if env.header.ParentHash == uncle.ParentHash {
        return errors.New("uncle is sibling")
    }
    if !env.ancestors.Contains(uncle.ParentHash) {
        return errors.New("uncle's parent unknown")
    }
    if env.family.Contains(hash) {
        return errors.New("uncle already included")
    }
    env.uncles.Add(uncle.Hash())
    return nil
}

// updateSnapshot updates pending snapshot block and state.
// Note this function assumes the current variable is thread safe.
func (w *worker) updateSnapshot() {
    w.snapshotMu.Lock()
    defer w.snapshotMu.Unlock()

    var uncles []*types.Header
    w.current.uncles.Each(func(item interface{}) bool {
        hash, ok := item.(common.Hash)
        if !ok {
            return false
        }
        uncle, exist := w.localUncles[hash]
        if !exist {
            uncle, exist = w.remoteUncles[hash]
        }
        if !exist {
            return false
        }
        uncles = append(uncles, uncle.Header())
        return false
    })

    w.snapshotBlock = types.NewBlock(
        w.current.header,
        w.current.txs,
        uncles,
        w.current.receipts,
    )

    w.snapshotState = w.current.state.Copy()
}

func (w *worker) commitTransaction(tx *types.Transaction, coinbase common.Address) ([]*types.Log, error) {
    snap := w.current.state.Snapshot()

    receipt, _, err := core.ApplyTransaction(w.config, w.chain, &coinbase, w.current.gasPool, w.current.state, w.current.header, tx, &w.current.header.GasUsed, *w.chain.GetVMConfig())
    if err != nil {
        w.current.state.RevertToSnapshot(snap)
        return nil, err
    }
    w.current.txs = append(w.current.txs, tx)
    w.current.receipts = append(w.current.receipts, receipt)

    return receipt.Logs, nil
}

func (w *worker) commitTransactions(txs *types.TransactionsByPriceAndNonce, coinbase common.Address, interrupt *int32) bool {
    // Short circuit if current is nil
    if w.current == nil {
        return true
    }

    if w.current.gasPool == nil {
        w.current.gasPool = new(core.GasPool).AddGas(w.current.header.GasLimit)
    }

    var coalescedLogs []*types.Log

    for {
        // In the following three cases, we will interrupt the execution of the transaction.
        // (1) new head block event arrival, the interrupt signal is 1
        // (2) worker start or restart, the interrupt signal is 1
        // (3) worker recreate the mining block with any newly arrived transactions, the interrupt signal is 2.
        // For the first two cases, the semi-finished work will be discarded.
        // For the third case, the semi-finished work will be submitted to the consensus engine.
        if interrupt != nil && atomic.LoadInt32(interrupt) != commitInterruptNone {
            // Notify resubmit loop to increase resubmitting interval due to too frequent commits.
            if atomic.LoadInt32(interrupt) == commitInterruptResubmit {
                ratio := float64(w.current.header.GasLimit-w.current.gasPool.Gas()) / float64(w.current.header.GasLimit)
                if ratio < 0.1 {
                    ratio = 0.1
                }
                w.resubmitAdjustCh <- &intervalAdjust{
                    ratio: ratio,
                    inc:   true,
                }
            }
            return atomic.LoadInt32(interrupt) == commitInterruptNewHead
        }
        // If we don't have enough gas for any further transactions then we're done
        if w.current.gasPool.Gas() < params.TxGas {
            log.Trace("Not enough gas for further transactions", "have", w.current.gasPool, "want", params.TxGas)
            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(w.current.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() && !w.config.IsEIP155(w.current.header.Number) {
            log.Trace("Ignoring reply protected transaction", "hash", tx.Hash(), "eip155", w.config.EIP155Block)

            txs.Pop()
            continue
        }
        // Start executing the transaction
        w.current.state.Prepare(tx.Hash(), common.Hash{}, w.current.tcount)

        logs, err := w.commitTransaction(tx, coinbase)
        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 hight 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...)
            w.current.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 !w.isRunning() && len(coalescedLogs) > 0 {
        // We don't push the pendingLogsEvent while we are mining. The reason is that
        // when we are mining, the worker will regenerate a mining block every 3 seconds.
        // In order to avoid pushing the repeated pendingLog, we disable the pending log pushing.

        // 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 w.mux.Post(core.PendingLogsEvent{Logs: cpy})
    }
    // Notify resubmit loop to decrease resubmitting interval if current interval is larger
    // than the user-specified one.
    if interrupt != nil {
        w.resubmitAdjustCh <- &intervalAdjust{inc: false}
    }
    return false
}

// commitNewWork generates several new sealing tasks based on the parent block.
func (w *worker) commitNewWork(interrupt *int32, noempty bool, timestamp int64) {
    w.mu.RLock()
    defer w.mu.RUnlock()

    tstart := time.Now()
    parent := w.chain.CurrentBlock()

    if parent.Time() >= uint64(timestamp) {
        timestamp = int64(parent.Time() + 1)
    }
    // this will ensure we're not going off too far in the future
    if now := time.Now().Unix(); timestamp > now+1 {
        wait := time.Duration(timestamp-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:   core.CalcGasLimit(parent, w.gasFloor, w.gasCeil),
        Extra:      w.extra,
        Time:       uint64(timestamp),
    }
    // Only set the coinbase if our consensus engine is running (avoid spurious block rewards)
    if w.isRunning() {
        if w.coinbase == (common.Address{}) {
            log.Error("Refusing to mine without etherbase")
            return
        }
        header.Coinbase = w.coinbase
    }
    if err := w.engine.Prepare(w.chain, header); err != nil {
        log.Error("Failed to prepare header for mining", "err", err)
        return
    }
    // If we are care about TheDAO hard-fork check whether to override the extra-data or not
    if daoBlock := w.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 w.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 := w.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
    env := w.current
    if w.config.DAOForkSupport && w.config.DAOForkBlock != nil && w.config.DAOForkBlock.Cmp(header.Number) == 0 {
        misc.ApplyDAOHardFork(env.state)
    }
    // Accumulate the uncles for the current block
    uncles := make([]*types.Header, 0, 2)
    commitUncles := func(blocks map[common.Hash]*types.Block) {
        // Clean up stale uncle blocks first
        for hash, uncle := range blocks {
            if uncle.NumberU64()+staleThreshold <= header.Number.Uint64() {
                delete(blocks, hash)
            }
        }
        for hash, uncle := range blocks {
            if len(uncles) == 2 {
                break
            }
            if err := w.commitUncle(env, uncle.Header()); err != nil {
                log.Trace("Possible uncle rejected", "hash", hash, "reason", err)
            } else {
                log.Debug("Committing new uncle to block", "hash", hash)
                uncles = append(uncles, uncle.Header())
            }
        }
    }
    // Prefer to locally generated uncle
    commitUncles(w.localUncles)
    commitUncles(w.remoteUncles)

    if !noempty {
        // Create an empty block based on temporary copied state for sealing in advance without waiting block
        // execution finished.
        w.commit(uncles, nil, false, tstart)
    }

    // Fill the block with all available pending transactions.
    pending, err := w.eth.TxPool().Pending()
    if err != nil {
        log.Error("Failed to fetch pending transactions", "err", err)
        return
    }
    // Short circuit if there is no available pending transactions
    if len(pending) == 0 {
        w.updateSnapshot()
        return
    }
    // Split the pending transactions into locals and remotes
    localTxs, remoteTxs := make(map[common.Address]types.Transactions), pending
    for _, account := range w.eth.TxPool().Locals() {
        if txs := remoteTxs[account]; len(txs) > 0 {
            delete(remoteTxs, account)
            localTxs[account] = txs
        }
    }
    if len(localTxs) > 0 {
        txs := types.NewTransactionsByPriceAndNonce(w.current.signer, localTxs)
        if w.commitTransactions(txs, w.coinbase, interrupt) {
            return
        }
    }
    if len(remoteTxs) > 0 {
        txs := types.NewTransactionsByPriceAndNonce(w.current.signer, remoteTxs)
        if w.commitTransactions(txs, w.coinbase, interrupt) {
            return
        }
    }
    w.commit(uncles, w.fullTaskHook, true, tstart)
}

// commit runs any post-transaction state modifications, assembles the final block
// and commits new work if consensus engine is running.
func (w *worker) commit(uncles []*types.Header, interval func(), update bool, start time.Time) error {
    // Deep copy receipts here to avoid interaction between different tasks.
    receipts := make([]*types.Receipt, len(w.current.receipts))
    for i, l := range w.current.receipts {
        receipts[i] = new(types.Receipt)
        *receipts[i] = *l
    }
    s := w.current.state.Copy()
    block, err := w.engine.Finalize(w.chain, w.current.header, s, w.current.txs, uncles, w.current.receipts)
    if err != nil {
        return err
    }
    if w.isRunning() {
        if interval != nil {
            interval()
        }
        select {
        case w.taskCh <- &task{receipts: receipts, state: s, block: block, createdAt: time.Now()}:
            w.unconfirmed.Shift(block.NumberU64() - 1)

            feesWei := new(big.Int)
            for i, tx := range block.Transactions() {
                feesWei.Add(feesWei, new(big.Int).Mul(new(big.Int).SetUint64(receipts[i].GasUsed), tx.GasPrice()))
            }
            feesEth := new(big.Float).Quo(new(big.Float).SetInt(feesWei), new(big.Float).SetInt(big.NewInt(params.Ether)))

            log.Info("Commit new mining work", "number", block.Number(), "sealhash", w.engine.SealHash(block.Header()),
                "uncles", len(uncles), "txs", w.current.tcount, "gas", block.GasUsed(), "fees", feesEth, "elapsed", common.PrettyDuration(time.Since(start)))

        case <-w.exitCh:
            log.Info("Worker has exited")
        }
    }
    if update {
        w.updateSnapshot()
    }
    return nil
}