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"
    "fmt"
    "math/big"
    "sync"
    "sync/atomic"
    "time"

    mapset "github.com/deckarep/golang-set"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/consensus"
    "github.com/ethereum/go-ethereum/consensus/misc"
    "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/event"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/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
    miningLogAtDepth  = 5
)

// Env is the worker's current environment and holds all of the current state information.
type Env struct {
    config *params.ChainConfig
    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
}

func (env *Env) 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
}

func (env *Env) commitTransactions(mux *event.TypeMux, txs *types.TransactionsByPriceAndNonce, bc *core.BlockChain, coinbase common.Address) {
    if env.gasPool == nil {
        env.gasPool = new(core.GasPool).AddGas(env.header.GasLimit)
    }

    var coalescedLogs []*types.Log

    for {
        // If we don't have enough gas for any further transactions then we're done
        if env.gasPool.Gas() < params.TxGas {
            log.Trace("Not enough gas for further transactions", "have", env.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(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)

        err, logs := env.commitTransaction(tx, bc, coinbase, env.gasPool)
        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...)
            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)
    }
}

// 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
}

// 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

    // 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
    newWork  chan struct{}
    taskCh   chan *task
    resultCh chan *task
    exitCh   chan struct{}

    current        *Env                         // An environment for current running cycle.
    possibleUncles 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

    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.

    // Test hooks
    newTaskHook      func(*task) // Method to call upon receiving a new sealing task
    fullTaskInterval func()      // Method to call before pushing the full sealing task
}

func newWorker(config *params.ChainConfig, engine consensus.Engine, eth Backend, mux *event.TypeMux) *worker {
    worker := &worker{
        config:         config,
        engine:         engine,
        eth:            eth,
        mux:            mux,
        chain:          eth.BlockChain(),
        possibleUncles: make(map[common.Hash]*types.Block),
        unconfirmed:    newUnconfirmedBlocks(eth.BlockChain(), miningLogAtDepth),
        txsCh:          make(chan core.NewTxsEvent, txChanSize),
        chainHeadCh:    make(chan core.ChainHeadEvent, chainHeadChanSize),
        chainSideCh:    make(chan core.ChainSideEvent, chainSideChanSize),
        newWork:        make(chan struct{}, 1),
        taskCh:         make(chan *task),
        resultCh:       make(chan *task, resultQueueSize),
        exitCh:         make(chan struct{}),
    }
    // 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)

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

    // Submit first work to initialize pending state.
    worker.newWork <- 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
}

// 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.newWork <- 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 and cleans up buffered channels.
// Note the worker does not support being closed multiple times.
func (w *worker) close() {
    close(w.exitCh)
    // Clean up buffered channels
    for empty := false; !empty; {
        select {
        case <-w.resultCh:
        default:
            empty = true
        }
    }
}

// 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 <-w.newWork:
            // Submit a work when the worker is created or started.
            w.commitNewWork()

        case <-w.chainHeadCh:
            // Resubmit a work for new cycle once worker receives chain head event.
            w.commitNewWork()

        case ev := <-w.chainSideCh:
            // Add side block to possible uncle block set.
            w.possibleUncles[ev.Block.Hash()] = ev.Block

        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.Lock()
                coinbase := w.coinbase
                w.mu.Unlock()

                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.current.commitTransactions(w.mux, txset, w.chain, coinbase)
                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()
                }
            }

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

// seal pushes a sealing task to consensus engine and submits the result.
func (w *worker) seal(t *task, stop <-chan struct{}) {
    var (
        err error
        res *task
    )

    if t.block, err = w.engine.Seal(w.chain, t.block, stop); t.block != nil {
        log.Info("Successfully sealed new block", "number", t.block.Number(), "hash", t.block.Hash(),
            "elapsed", common.PrettyDuration(time.Since(t.createdAt)))
        res = t
    } else {
        if err != nil {
            log.Warn("Block sealing failed", "err", err)
        }
        res = nil
    }
    select {
    case w.resultCh <- res:
    case <-w.exitCh:
    }
}

// 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{}

    // 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)
            }
            interrupt()
            stopCh = make(chan struct{})
            go w.seal(task, stopCh)
        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 result := <-w.resultCh:
            if result == nil {
                continue
            }
            block := result.block

            // 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 result.receipts {
                for _, l := range r.Logs {
                    l.BlockHash = block.Hash()
                }
            }
            for _, log := range result.state.Logs() {
                log.BlockHash = block.Hash()
            }
            // Commit block and state to database.
            stat, err := w.chain.WriteBlockWithState(block, result.receipts, result.state)
            if err != nil {
                log.Error("Failed writing block to chain", "err", err)
                continue
            }
            // Broadcast the block and announce chain insertion event
            w.mux.Post(core.NewMinedBlockEvent{Block: block})
            var (
                events []interface{}
                logs   = result.state.Logs()
            )
            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 := &Env{
        config:    w.config,
        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 *Env, uncle *types.Header) error {
    hash := uncle.Hash()
    if env.uncles.Contains(hash) {
        return fmt.Errorf("uncle not unique")
    }
    if !env.ancestors.Contains(uncle.ParentHash) {
        return fmt.Errorf("uncle's parent unknown (%x)", uncle.ParentHash[0:4])
    }
    if env.family.Contains(hash) {
        return fmt.Errorf("uncle already in family (%x)", hash)
    }
    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.possibleUncles[hash]
        if !exist {
            return false
        }
        uncles = append(uncles, uncle.Header())
        return true
    })

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

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

// commitNewWork generates several new sealing tasks based on the parent block.
func (w *worker) commitNewWork() {
    w.mu.RLock()
    defer w.mu.RUnlock()

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

    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:   core.CalcGasLimit(parent),
        Extra:      w.extra,
        Time:       big.NewInt(tstamp),
    }
    // 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)
    }

    // compute uncles for the new block.
    var (
        uncles    []*types.Header
        badUncles []common.Hash
    )
    for hash, uncle := range w.possibleUncles {
        if len(uncles) == 2 {
            break
        }
        if err := w.commitUncle(env, 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(w.possibleUncles, hash)
    }

    var (
        emptyBlock, fullBlock *types.Block
        emptyState, fullState *state.StateDB
    )

    // Create an empty block based on temporary copied state for sealing in advance without waiting block
    // execution finished.
    emptyState = env.state.Copy()
    if emptyBlock, err = w.engine.Finalize(w.chain, header, emptyState, nil, uncles, nil); err != nil {
        log.Error("Failed to finalize block for temporary sealing", "err", err)
    } else {
        // Push empty work in advance without applying pending transaction.
        // The reason is transactions execution can cost a lot and sealer need to
        // take advantage of this part time.
        if w.isRunning() {
            select {
            case w.taskCh <- &task{receipts: nil, state: emptyState, block: emptyBlock, createdAt: time.Now()}:
                log.Info("Commit new empty mining work", "number", emptyBlock.Number(), "uncles", len(uncles))
            case <-w.exitCh:
                log.Info("Worker has exited")
                return
            }
        }
    }

    // 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
    }
    txs := types.NewTransactionsByPriceAndNonce(w.current.signer, pending)
    env.commitTransactions(w.mux, txs, w.chain, w.coinbase)

    // Create the full block to seal with the consensus engine
    fullState = env.state.Copy()
    if fullBlock, err = w.engine.Finalize(w.chain, header, fullState, env.txs, uncles, env.receipts); err != nil {
        log.Error("Failed to finalize block for sealing", "err", err)
        return
    }
    // Deep copy receipts here to avoid interaction between different tasks.
    cpy := make([]*types.Receipt, len(env.receipts))
    for i, l := range env.receipts {
        cpy[i] = new(types.Receipt)
        *cpy[i] = *l
    }
    // We only care about logging if we're actually mining.
    if w.isRunning() {
        if w.fullTaskInterval != nil {
            w.fullTaskInterval()
        }

        select {
        case w.taskCh <- &task{receipts: cpy, state: fullState, block: fullBlock, createdAt: time.Now()}:
            w.unconfirmed.Shift(fullBlock.NumberU64() - 1)
            log.Info("Commit new full mining work", "number", fullBlock.Number(), "txs", env.tcount, "uncles", len(uncles), "elapsed", common.PrettyDuration(time.Since(tstart)))
        case <-w.exitCh:
            log.Info("Worker has exited")
        }
    }
    w.updateSnapshot()
}