以太坊源码解读（16）miner模块和Worker模块

 最新的以太坊源码Miner模块有较大的改动，取消了原来的agent模块以及work对象，但是基本上的逻辑还是一样的。Miner模块的主要执行部分在worker中，Miner对象及其方法主要控制着模块的开关和外部接口。

一、Miner模块

type Miner struct {
	mux      *event.TypeMux
	worker   *worker
	coinbase common.Address
	eth      Backend
	engine   consensus.Engine
	exitCh   chan struct{}

	canStart    int32 // can start indicates whether we can start the mining operation
	shouldStart int32 // should start indicates whether we should start after sync
}

1）worker：worker模块，用于支持主要的挖矿流程； 2）coinbase：矿工地址； 3）eth：以太坊命令终端； 4）engine：共识引擎； 5）canStart、shouldStart：两个调控Miner模块是否运行的开关。

miner.update()方法监听downloader事件，控制着canStart和shouldStart这两个开关，用于抵挡DOS攻击。 1、当监听到downloader的StartEvent事件时，canStart设置为0，表示downloader同步时不可进行挖矿，如果正在挖矿（miner.mining == ture），停止挖矿，同时将shouldStart设置为1，以便下次直接开始挖矿； 2、当监听到downloader的DoneEvent事件或者FailedEvent事件，判断shouldStart是否打开。如果是打开的，则再打开canStart，将shouldStart关闭。此时，将挖矿的控制权完全交给miner.Start()方法。

func (self *Miner) update() {
	events := self.mux.Subscribe(downloader.StartEvent{}, downloader.DoneEvent{}, downloader.FailedEvent{})
	defer events.Unsubscribe()

	for {
		select {
		case ev := <-events.Chan():
			if ev == nil {
				return
			}
			switch ev.Data.(type) {
			case downloader.StartEvent:
				atomic.StoreInt32(&self.canStart, 0)
				if self.Mining() {
					self.Stop()
					atomic.StoreInt32(&self.shouldStart, 1)
					log.Info("Mining aborted due to sync")
				}
			case downloader.DoneEvent, downloader.FailedEvent:
				shouldStart := atomic.LoadInt32(&self.shouldStart) == 1

				atomic.StoreInt32(&self.canStart, 1)
				atomic.StoreInt32(&self.shouldStart, 0)
				if shouldStart {
					self.Start(self.coinbase)
				}
				// stop immediately and ignore all further pending events
				return
			}
		case <-self.exitCh:
			return
		}
	}
}

Miner的启动也很简单，打开shouldStart，设置coinbase，然后启动worker。

func (self *Miner) Start(coinbase common.Address) {
	atomic.StoreInt32(&self.shouldStart, 1)
	self.SetEtherbase(coinbase)

	if atomic.LoadInt32(&self.canStart) == 0 {
		log.Info("Network syncing, will start miner afterwards")
		return
	}
	self.worker.start()
}

二、Worker模块

先来看看Worker的数据结构比较重要的东西：

type worker struct {
	engine consensus.Engine   // 公式引擎
	eth    Backend            // 以太坊终端
	chain  *core.BlockChain   // 区块链对象

	gasFloor uint64     
	gasCeil  uint64

	// Subscriptions
	mux          *event.TypeMux
	txsCh        chan core.NewTxsEvent  // 交易池更新事件
	txsSub       event.Subscription
	chainHeadCh  chan core.ChainHeadEvent  // 区块头更新事件
	chainHeadSub event.Subscription
	chainSideCh  chan core.ChainSideEvent  // 区块链分叉事件
	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                 // 当前挖矿生命周期的执行环境
	localUncles  map[common.Hash]*types.Block // 本地分叉区块作为潜在叔块
	remoteUncles map[common.Hash]*types.Block // 分叉区块中潜在的叔块
	unconfirmed  *unconfirmedBlocks           // 本地产生但尚未被确认的区块

	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  // 挖矿任务map

	snapshotMu    sync.RWMutex
	snapshotBlock *types.Block  // 快照的区块
	snapshotState *state.StateDB  // 快照的状态

	// atomic status counters
	running int32 // 判断共识引擎是否启动
	newTxs  int32 // 记录上次递交任务后新来的区块数量

}

在初始化miner的时候就会新建worker，即调用newWorker()函数。该函数首先配置了worker对象，然后订阅交易池事件、规范链更新事件和分叉事件。最后启动了4个goroutine。

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{
		...
	}
	worker.txsSub = eth.TxPool().SubscribeNewTxsEvent(worker.txsCh)
	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
}

最后通过向startCh中传入一个struct{}{}，直接进入newWorkLoop的逻辑。

newWorkLoop

newWorkLoop主要监听两个重要的通道，一个是startCh通道，一个是chainHeadCh，这两个通道均用于清理特定父区块的pending tasks列表，然后递交基于父区块的挖矿task）。区别在于startCh通道启动是基于当前的currentBlock，而chainHeadCh是基于新传来的区块头。

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)
	}
	
        ...

	// 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)

清理残留挖矿任务后，就要构建新的挖矿任务，这时候调用commit函数，构建一个newWorkReq对象，传入newWorkCh通道，进入MainLoop协程。MainLoop()监听三个重要的通道，newWorkCh（新work请求通道）、txsCh（交易池更新事件通道）以及chainSideCh（区块链分叉事件通道）。

MainLoop：

for {
select {
// task1：直接启动commitNewWork，进一步递交挖矿task
case req := <-w.newWorkCh:
    w.commitNewWork(req.interrupt, req.noempty, req.timestamp)

// task2：出现分叉后，处理叔块
case ev := <-w.chainSideCh:
    // 检验该hash的区块是否已经被当做潜在叔块，如果是，则忽略
    if _, exist := w.localUncles[ev.Block.Hash()]; exist {
        continue
    }
    if _, exist := w.remoteUncles[ev.Block.Hash()]; exist {
        continue
    }
    // 将该区块作为潜在叔块加入叔块map，key为该区块的矿工地址
    if w.isLocalBlock != nil && w.isLocalBlock(ev.Block) {
        w.localUncles[ev.Block.Hash()] = ev.Block
    } else {
        w.remoteUncles[ev.Block.Hash()] = ev.Block
    }
    // 如果我们正在mining的区块少于两个uncles，则添加新的uncles并重新生成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)
        }
    }
// task3：交易池更新后
case ev := <-w.txsCh:
    // 待挖矿停止，执行该交易并更新世界状态
    // 如果该交易与正在mining的交易不连续，则直接忽略
    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)))

接着上面的的流程，newWorkCh通道传出req后，直接启动了commitNewWork()函数。

commitNewWork()函数的主要功能是递交一个新的task： 1）初始化一个新区块头给待挖矿的区块 2）为当前挖矿周期初始化一个工作环境work 3）获取交易池中每个账户地址的交易列表中的第一个交易后排序，然后应用这些交易 4）获取两个叔块 6）将区块递交给commit，用于生成task 7）更新状态快照，供前端查询

func (w *worker) commitNewWork(interrupt *int32, noempty bool, timestamp int64) {
	w.mu.RLock()
	defer w.mu.RUnlock()

	tstart := time.Now()
	parent := w.chain.CurrentBlock()
        // 如果父区块的时间比现在的时间还大，将当前时间设置为父区块时间+1
	if parent.Time().Cmp(new(big.Int).SetInt64(timestamp)) >= 0 {
		timestamp = parent.Time().Int64() + 1
	}
	// 如果父区块时间大于本地时间，就等一会
	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)
	}
        // task1:初始化区块头给待挖矿的区块，调用core.CalcGasLimit方法，计算gas限额
        // 如果父区块使用的gas大于父区块gasLimit的2/3，那么当前区块的gasLimit就会增加
	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:       big.NewInt(timestamp),
	}
	// 共识引擎启动后才能设置coinbase到区块头 (avoid spurious block rewards)
	if w.isRunning() {
		if w.coinbase == (common.Address{}) {
			log.Error("Refusing to mine without etherbase")
			return
		}
		header.Coinbase = w.coinbase
	}
        // 计算挖矿难度值
	if err := w.engine.Prepare(w.chain, header); err != nil {
		log.Error("Failed to prepare header for mining", "err", err)
		return
	}
	// 处理DAO事件分叉
	if daoBlock := w.config.DAOForkBlock; daoBlock != nil {
		...
	}
	// task2：设置当前任务的environment，其中获取了7个ancestors和与之直接相连的familily
	err := w.makeCurrent(parent, header)
	if err != nil {
		log.Error("Failed to create mining context", "err", err)
		return
	}
	// 创建当前work task
	env := w.current
	if w.config.DAOForkSupport && w.config.DAOForkBlock != nil && w.config.DAOForkBlock.Cmp(header.Number) == 0 {
		misc.ApplyDAOHardFork(env.state)
	}
	// task3：添加两个叔块到当前mining block中
	uncles := make([]*types.Header, 0, 2)
	commitUncles := func(blocks map[common.Hash]*types.Block) {
		// 先清除之前的uncle
		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())
			}
		}
	}
	// 优先选择本地叔块
	commitUncles(w.localUncles)
	commitUncles(w.remoteUncles)

	if !noempty {
		// 如果noempty参数为false，根据临时复制状态创建一个空块，以便在不等待块执行完成的情况下提前创建block
		w.commit(uncles, nil, false, tstart)
	}

	// task4：从交易池pending列表中向区块中添加可用的交易
	pending, err := w.eth.TxPool().Pending()
	if err != nil {
		log.Error("Failed to fetch pending transactions", "err", err)
		return
	}
	// 如果没有可用的交易，更新一下状态快照
	if len(pending) == 0 {
		w.updateSnapshot()
		return
	}
	// 将交易分为local和remote，分别执行commitTransaction，将交易执行并传入block
	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
		}
	}
        // task5：递交
	w.commit(uncles, w.fullTaskHook, true, tstart)
}

最后是commit方法计算挖矿奖励，更新block，将上面生成的block递交到一个挖矿task，最后将task传入taskCh通道。

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()
        // 计算挖矿奖励（包括叔块奖励）
	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 {
                // 生成task，传入taskCh通道
		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
}

taskLoop

task进入taskLoop后，被加入pendingTasks列表：

case task := <-w.taskCh:
    if w.newTaskHook != nil {
        w.newTaskHook(task)
    }
    // 计算header数据的RLP hash值，判断是否有相同的块已经在挖矿中了，如果是则放弃；如果不是，则终止之前的挖矿
    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()
    
    // 最后执行挖矿，结果会通过resultCh传入resultLoop
    if err := w.engine.Seal(w.chain, task.block, w.resultCh, stopCh); err != nil {
        log.Warn("Block sealing failed", "err", err)
    }

resultLoop

最后是resultLoop，挖矿结果传入resultLoop，先从pendingTasks列表中取出刚执行挖矿的task，更新收据日志中的blockHash。然后将区块存入数据库，最后将区块广播出去。

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
		}
	}
}

三、其他函数中一些值得注意的函数

1、commitTransaction

a）gasPool的设置

w.current.gasPool = new(core.GasPool).AddGas(w.current.header.GasLimit)

b）进入交易执行循环

交易执行的过程中有三种情况会被打断：（1）交易还在执行，但是新的区块已经经过广播到达本地，interrupt信号为1；（2）worker start或者restart，interrupt信号为1；（3）worker重新构造区块，包含了新到的交易，interrupt信号为2。

对于前两种，worker的本次执行就会终止，但对于第三种情况，本次执行依然会被递交到consensus engine。

c）如果区块工作环境剩余gas小于21000，则退出循环；否则从排好序的列表里取出交易；

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
}

d）执行交易并处理错误

// 首先准备当前世界状态
w.current.state.Prepare(tx.Hash(), common.Hash{}, w.current.tcount)

// 使用commitTransaction去调用交易执行的方法core.ApplyTransaction，得到收据并放入当前执行环境
logs, err := w.commitTransaction(tx, coinbase)
switch err {
case core.ErrGasLimitReached:
    // gasPool不够执行交易，则将当前交易从txs中移除
    log.Trace("Gas limit exceeded for current block", "sender", from)
    txs.Pop()

case core.ErrNonceTooLow:
    // 交易nonce太低，则取下一个交易替换处理列表中的第一个交易
    log.Trace("Skipping transaction with low nonce", "sender", from, "nonce", tx.Nonce())
    txs.Shift()

case core.ErrNonceTooHigh:
    // 交易Nonce太高，则将当前交易从txs列表中移除
    log.Trace("Skipping account with hight nonce", "sender", from, "nonce", tx.Nonce())
    txs.Pop()

case nil:
    // 一切正常，收集日志，统计执行成功的交易技术
    coalescedLogs = append(coalescedLogs, logs...)
    w.current.tcount++
    txs.Shift()

default:
    // Strange error, 如果当前交易发送者账户里还有交易，则取下一个交易替换列表中第一个交易，重新排序
    log.Debug("Transaction failed, account skipped", "hash", tx.Hash(), "err", err)
    txs.Shift()
}