以太坊交易基本流程：
完整流程分为以下几个步骤：
- 发起交易：指定目标地址和交易金额，以及需要的gas/gaslimit
- 交易签名：使用账户私钥对交易进行签名
- 提交交易：把交易加入到交易缓冲池txpool中（会先对交易签名进行验证）
- 广播交易：通知EVM执行，同时把交易信息广播给其他结点
发起交易
用户通过JSON RPC发起 eth_sendTransaction 请求，最终会调用 PublicTransactionPoolAPI 的 SendTransaction 实现，
首先根据from地址查找到对应的wallet，检查一下参数值，
- 通过SendTxArgs.toTransaction()创建交易
- 通过Wallet.SignTx()对交易进行签名
- 通过submitTransaction()提交交易
//代码位于 `internal/ethapi/api.go`
func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
if args.Nonce == nil {
// Hold the addresse's mutex around signing to prevent concurrent assignment of
// the same nonce to multiple accounts.
s.nonceLock.LockAddr(args.From)
defer s.nonceLock.UnlockAddr(args.From)
}
signed, err := s.signTransaction(ctx, args, passwd)
if err != nil {
return common.Hash{}, err
}
return submitTransaction(ctx, s.b, signed)
}交易签名主要实现在 signTransaction，主要功能：
toTransaction() ：创建交易wallet.SignTxWithPassphrase(account, passwd, tx, chainID)：对交易进行签名
func (s *PrivateAccountAPI) signTransaction(ctx context.Context, args SendTxArgs, passwd string) (*types.Transaction, error) {
// Look up the wallet containing the requested signer
account := accounts.Account{Address: args.From}
wallet, err := s.am.Find(account)
if err != nil {
return nil, err
}
// Set some sanity defaults and terminate on failure
if err := args.setDefaults(ctx, s.b); err != nil {
return nil, err
}
// Assemble the transaction and sign with the wallet
tx := args.toTransaction()
var chainID *big.Int
if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
chainID = config.ChainId
}
return wallet.SignTxWithPassphrase(account, passwd, tx, chainID)
}创建交易
tx := args.toTransaction() 创建交易
先看一下SendTxArgs类型的定义：
// 代码 internal/ethapi/api.go
// SendTxArgs represents the arguments to sumbit a new transaction into the transaction pool.
type SendTxArgs struct {
From common.Address `json:"from"`
To *common.Address `json:"to"`
Gas *hexutil.Uint64 `json:"gas"`
GasPrice *hexutil.Big `json:"gasPrice"`
Value *hexutil.Big `json:"value"`
Nonce *hexutil.Uint64 `json:"nonce"`
// We accept "data" and "input" for backwards-compatibility reasons. "input" is the
// newer name and should be preferred by clients.
Data *hexutil.Bytes `json:"data"`
Input *hexutil.Bytes `json:"input"`
}可以看到是和JSON字段相应的，包括了地址、gas、金额这些交易信息，nonce是一个随账户交易次数自增的数字，一般会自动填充。交易还可以携带一些额外数据，存放在data或者input字段中，推荐用input，data是为了向后兼容。
toTransaction()函数：
// 代码 internal/ethapi/api.go
func (args *SendTxArgs) toTransaction() *types.Transaction {
var input []byte
if args.Data != nil {
input = *args.Data
} else if args.Input != nil {
input = *args.Input
}
if args.To == nil {
return types.NewContractCreation(uint64(*args.Nonce), (*big.Int)(args.Value), uint64(*args.Gas), (*big.Int)(args.GasPrice), input)
}
return types.NewTransaction(uint64(*args.Nonce), *args.To, (*big.Int)(args.Value), uint64(*args.Gas), (*big.Int)(args.GasPrice), input)
}可以看到，如果目标地址为空的话，表示这是一个创建智能合约的交易，调用NewContractCreation()。否则说明这是一个普通交易，调用NewTransaction()。不管调用哪个，最终都会生成一个Transaction实例，我们看一下Transaction类型的定义：
// 代码位于core/types/transaction.go
type Transaction struct {
data txdata
// caches
hash atomic.Value
size atomic.Value
from atomic.Value
}
type txdata struct {
AccountNonce uint64 `json:"nonce" gencodec:"required"`
Price *big.Int `json:"gasPrice" gencodec:"required"`
GasLimit uint64 `json:"gas" gencodec:"required"`
Recipient *common.Address `json:"to" rlp:"nil"` // nil means contract creation
Amount *big.Int `json:"value" gencodec:"required"`
Payload []byte `json:"input" gencodec:"required"`
// Signature values
V *big.Int `json:"v" gencodec:"required"`
R *big.Int `json:"r" gencodec:"required"`
S *big.Int `json:"s" gencodec:"required"`
// This is only used when marshaling to JSON.
Hash *common.Hash `json:"hash" rlp:"-"`
}交易签名
wallet.SignTxWithPassphrase 代码
// accounts/keystore/keystore_wallet.go
// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
// transaction with the given account using passphrase as extra authentication.
func (w *keystoreWallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
// Make sure the requested account is contained within
if account.Address != w.account.Address {
return nil, accounts.ErrUnknownAccount
}
if account.URL != (accounts.URL{}) && account.URL != w.account.URL {
return nil, accounts.ErrUnknownAccount
}
// Account seems valid, request the keystore to sign
return w.keystore.SignTxWithPassphrase(account, passphrase, tx, chainID)
}w.keystore.SignTxWithPassphrase(account, passphrase, tx, chainID) 代码：
主要就是通过 SignTx 进行签名。
// 代码 accounts/keystore/keystore.go
func (ks *KeyStore) SignTxWithPassphrase(a accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
_, key, err := ks.getDecryptedKey(a, passphrase)
if err != nil {
return nil, err
}
defer zeroKey(key.PrivateKey)
// Depending on the presence of the chain ID, sign with EIP155 or homestead
if chainID != nil {
return types.SignTx(tx, types.NewEIP155Signer(chainID), key.PrivateKey)
}
return types.SignTx(tx, types.HomesteadSigner{}, key.PrivateKey)
}这里会首先判断账户是否已经解锁，如果已经解锁的话就可以获取它的私钥。
然后创建签名器，如果要符合EIP155规范的话，需要把chainID传进去，也就是我们的“–networkid”命令行参数。
最后调用一个全局函数SignTx()完成签名：
代码位于core/types/transaction_signing.go：
// SignTx signs the transaction using the given signer and private key
func SignTx(tx *Transaction, s Signer, prv *ecdsa.PrivateKey) (*Transaction, error) {
h := s.Hash(tx)
sig, err := crypto.Sign(h[:], prv)
if err != nil {
return nil, err
}
return tx.WithSignature(s, sig)
}主要分为3个步骤：
- 生成交易的hash值
- 根据hash值和私钥生成签名
- 把签名数据填充到Transaction实例中
生成交易的hash值
以EIP155Signer为例，代码如下：
func (s EIP155Signer) Hash(tx *Transaction) common.Hash {
return rlpHash([]interface{}{
tx.data.AccountNonce,
tx.data.Price,
tx.data.GasLimit,
tx.data.Recipient,
tx.data.Amount,
tx.data.Payload,
s.chainId, uint(0), uint(0),
})
}
func rlpHash(x interface{}) (h common.Hash) {
hw := sha3.NewKeccak256()
rlp.Encode(hw, x)
hw.Sum(h[:0])
return h
} 可以看到，先用SHA3-256生成hash值，然后再进行RLP编码。RLP是一种数据序列化方法。
根据hash值和私钥生成签名-crypto.Sign()
// 代码位于crypto/signature_cgo.go：
func Sign(hash []byte, prv *ecdsa.PrivateKey) (sig []byte, err error) {
if len(hash) != 32 {
return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
}
seckey := math.PaddedBigBytes(prv.D, prv.Params().BitSize/8)
defer zeroBytes(seckey)
return secp256k1.Sign(hash, seckey)
} 这里是通过ECDSA算法生成签名数据。最终会返回的签名是一个字节数组，按R / S / V的顺序排列。
填充签名数据 - WithSignature
//代码位于 core/types/transaction.go
func (tx *Transaction) WithSignature(signer Signer, sig []byte) (*Transaction, error) {
r, s, v, err := signer.SignatureValues(tx, sig)
if err != nil {
return nil, err
}
cpy := &Transaction{data: tx.data}
cpy.data.R, cpy.data.S, cpy.data.V = r, s, v
return cpy, nil
}生成的签名数据是字节数组类型，需要通过signer.SignatureValues()函数转换成3个big.Int类型的数据，然后填充到Transaction结构的R / S / V字段上
提交交易
签名完成以后，就需要调用 submitTransaction() 函数提交到交易缓冲池txpool中。
先看下TxPool中的几个重要字段：
// 代码 core/tx_pool.go
type TxPool struct {
config TxPoolConfig
chainconfig *params.ChainConfig
chain blockChain
gasPrice *big.Int
txFeed event.Feed
scope event.SubscriptionScope
chainHeadCh chan ChainHeadEvent
chainHeadSub event.Subscription
signer types.Signer
mu sync.RWMutex
currentState *state.StateDB // Current state in the blockchain head
pendingState *state.ManagedState // Pending state tracking virtual nonces
currentMaxGas uint64 // Current gas limit for transaction caps
locals *accountSet // Set of local transaction to exempt from eviction rules
journal *txJournal // Journal of local transaction to back up to disk
pending map[common.Address]*txList // All currently processable transactions
queue map[common.Address]*txList // Queued but non-processable transactions
beats map[common.Address]time.Time // Last heartbeat from each known account
all *txLookup // All transactions to allow lookups
priced *txPricedList // All transactions sorted by price
wg sync.WaitGroup // for shutdown sync
homestead bool
}pending字段中包含了当前所有可被处理的交易列表，而queue字段中包含了所有不可被处理、也就是新加入进来的交易。下面查看一下pending字段 的txList的结构：
type txList struct {
strict bool // Whether nonces are strictly continuous or not
txs *txSortedMap // Heap indexed sorted hash map of the transactions
costcap *big.Int // Price of the highest costing transaction (reset only if exceeds balance)
gascap uint64 // Gas limit of the highest spending transaction (reset only if exceeds block limit)
}
txList内部包含一个txSortedMap结构，实现按nonce排序，其内部维护了两张表：
- 一张是包含了所有Transaction的map，key是Transaction的nonce值。之前提到过，这个nonce是随着账户的交易次数自增的一个数字，所以越新的交易，nonce值越高。
- 还有一张表是一个数组，包含了所有nonce值，其内部是进行过堆排序的（小顶堆），nonce值按照从大到小排列。每次调用heap.Pop()时会取出最小的nonce值，也就是最老的交易。
all字段 中包含了所有的交易列表，以交易的hash作为key。
priced字段 则是把all中的交易列表按照gas price从大到小排列，如果gas price一样，则按照交易的nonce值从小到大排列。最终的目标是每次取出gas price最大、nonce最小的交易。
我们提交交易的目标是：先把交易放入queue中记录在案，然后再从queue中选一部分放入pending中进行处理。如果发现txpool满了，则依据priced中的排序，剔除低油价的交易。
txpool的默认配置：
var DefaultTxPoolConfig = TxPoolConfig{
Journal: "transactions.rlp",
Rejournal: time.Hour,
PriceLimit: 1,
PriceBump: 10,
AccountSlots: 16,
GlobalSlots: 4096,
AccountQueue: 64,
GlobalQueue: 1024,
Lifetime: 3 * time.Hour,
}- GlobalSlots：pending列表的最大长度，默认4096笔
- AccountSlots：pending中每个账户存储的交易数的阈值，超过这个数量可能会被认为是垃圾交易或者是攻击者，多余交易可能被丢弃
- GlobalQueue：queue列表的最大长度，默认1024笔
- AccountQueue：queue中每个账户允许存储的最大交易数，超过会被丢弃，默认64笔
- PriceLimit：允许进入txpool的最低gas price，默认1 Gwei
- PriceBump：如果出现两个nonce相同的交易，gas price的差值超过该阈值则用新交易替换老交易
现在我们分析submitTransaction()函数：
//代码位于 `internal/ethapi/api.go`
func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (common.Hash, error) {
if err := b.SendTx(ctx, tx); err != nil {
return common.Hash{}, err
}
if tx.To() == nil {
signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
from, err := types.Sender(signer, tx)
if err != nil {
return common.Hash{}, err
}
addr := crypto.CreateAddress(from, tx.Nonce())
log.Info("Submitted contract creation", "fullhash", tx.Hash().Hex(), "contract", addr.Hex())
} else {
log.Info("Submitted transaction", "fullhash", tx.Hash().Hex(), "recipient", tx.To())
}
return tx.Hash(), nil
}这里有一个Backend参数，是在eth Service初始化时创建的，具体实现在EthApiBackend中，代码位于eth/api_backend.go。可以看到，这里先调用了SendTx()函数提交交易，然后如果发现目标地址为空，表明这是一个创建智能合约的交易，会创建合约地址。
提交交易到txpool
//代码 eth/api_backend.go
func (b *EthAPIBackend) SendTx(ctx context.Context, signedTx *types.Transaction) error {
return b.eth.txPool.AddLocal(signedTx)
}继续跟踪TxPool的AddLocal()函数：
// 代码位于 core/tx_pool.go
func (pool *TxPool) AddLocal(tx *types.Transaction) error {
return pool.addTx(tx, !pool.config.NoLocals)
}
// addTx enqueues a single transaction into the pool if it is valid.
func (pool *TxPool) addTx(tx *types.Transaction, local bool) error {
pool.mu.Lock()
defer pool.mu.Unlock()
// Try to inject the transaction and update any state
replace, err := pool.add(tx, local)
if err != nil {
return err
}
// If we added a new transaction, run promotion checks and return
if !replace {
from, _ := types.Sender(pool.signer, tx) // already validated
pool.promoteExecutables([]common.Address{from})
}
return nil
}这里有两个主要函数：add()和promoteExecuteables()。
add()会判断是否应该把当前交易加入到queue列表中，promoteExecuteables()则会从queue中选取一些交易放入pending列表中等待执行。下面分别讨论这两个函数。
TxPool.add()
// 代码位于 core/tx_pool.go
func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
// If the transaction is already known, discard it
hash := tx.Hash()
if pool.all.Get(hash) != nil {
log.Trace("Discarding already known transaction", "hash", hash)
return false, fmt.Errorf("known transaction: %x", hash)
}
// If the transaction fails basic validation, discard it
if err := pool.validateTx(tx, local); err != nil {
log.Trace("Discarding invalid transaction", "hash", hash, "err", err)
invalidTxCounter.Inc(1)
return false, err
}
// If the transaction pool is full, discard underpriced transactions
if uint64(pool.all.Count()) >= pool.config.GlobalSlots+pool.config.GlobalQueue {
// If the new transaction is underpriced, don't accept it
if !local && pool.priced.Underpriced(tx, pool.locals) {
log.Trace("Discarding underpriced transaction", "hash", hash, "price", tx.GasPrice())
underpricedTxCounter.Inc(1)
return false, ErrUnderpriced
}
// New transaction is better than our worse ones, make room for it
drop := pool.priced.Discard(pool.all.Count()-int(pool.config.GlobalSlots+pool.config.GlobalQueue-1), pool.locals)
for _, tx := range drop {
log.Trace("Discarding freshly underpriced transaction", "hash", tx.Hash(), "price", tx.GasPrice())
underpricedTxCounter.Inc(1)
pool.removeTx(tx.Hash(), false)
}
}
// If the transaction is replacing an already pending one, do directly
from, _ := types.Sender(pool.signer, tx) // already validated
if list := pool.pending[from]; list != nil && list.Overlaps(tx) {
// Nonce already pending, check if required price bump is met
inserted, old := list.Add(tx, pool.config.PriceBump)
if !inserted {
pendingDiscardCounter.Inc(1)
return false, ErrReplaceUnderpriced
}
// New transaction is better, replace old one
if old != nil {
pool.all.Remove(old.Hash())
pool.priced.Removed()
pendingReplaceCounter.Inc(1)
}
pool.all.Add(tx)
pool.priced.Put(tx)
pool.journalTx(from, tx)
log.Trace("Pooled new executable transaction", "hash", hash, "from", from, "to", tx.To())
// We've directly injected a replacement transaction, notify subsystems
go pool.txFeed.Send(NewTxsEvent{types.Transactions{tx}})
return old != nil, nil
}
// New transaction isn't replacing a pending one, push into queue
replace, err := pool.enqueueTx(hash, tx)
if err != nil {
return false, err
}
// Mark local addresses and journal local transactions
if local {
pool.locals.add(from)
}
pool.journalTx(from, tx)
log.Trace("Pooled new future transaction", "hash", hash, "from", from, "to", tx.To())
return replace, nil
}我们分成一段一段的来分析：
hash := tx.Hash()
if pool.all.Get(hash) != nil {
log.Trace("Discarding already known transaction", "hash", hash)
return false, fmt.Errorf("known transaction: %x", hash)
}这一段是先计算交易的hash值，然后判断是不是已经在txpool 中，在的话就直接退出。
// If the transaction fails basic validation, discard it
if err := pool.validateTx(tx, local); err != nil {
log.Trace("Discarding invalid transaction", "hash", hash, "err", err)
invalidTxCounter.Inc(1)
return false, err
}查看 pool.validateTx(tx, local) 代码
// 代码位于 core/tx_pool.go
func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
// Heuristic limit, reject transactions over 32KB to prevent DOS attacks
if tx.Size() > 32*1024 {
return ErrOversizedData
}
// Transactions can't be negative. This may never happen using RLP decoded
// transactions but may occur if you create a transaction using the RPC.
if tx.Value().Sign() < 0 {
return ErrNegativeValue
}
// Ensure the transaction doesn't exceed the current block limit gas.
if pool.currentMaxGas < tx.Gas() {
return ErrGasLimit
}
// Make sure the transaction is signed properly
from, err := types.Sender(pool.signer, tx)
if err != nil {
return ErrInvalidSender
}
// Drop non-local transactions under our own minimal accepted gas price
local = local || pool.locals.contains(from) // account may be local even if the transaction arrived from the network
if !local && pool.gasPrice.Cmp(tx.GasPrice()) > 0 {
return ErrUnderpriced
}
// Ensure the transaction adheres to nonce ordering
if pool.currentState.GetNonce(from) > tx.Nonce() {
return ErrNonceTooLow
}
// Transactor should have enough funds to cover the costs
// cost == V + GP * GL
if pool.currentState.GetBalance(from).Cmp(tx.Cost()) < 0 {
return ErrInsufficientFunds
}
intrGas, err := IntrinsicGas(tx.Data(), tx.To() == nil, pool.homestead)
if err != nil {
return err
}
if tx.Gas() < intrGas {
return ErrIntrinsicGas
}
return nil
}这一段是验证交易的有效性，主要进行以下几个方面的检查：
- 数据量必须<32KB
- 交易金额必须非负（>=0）
- 交易的gas limit必须低于block的gas limit
- 签名数据必须有效，能够解析出发送者地址
- 交易的gas price必须高于pool设定的最低gas price（除非是本地交易）
- 交易的nonce值必须高于当前链上该账户的nonce值（低于则说明这笔交易已经被打包过了）
- 当前账户余额必须大于
“交易金额 + gasprice * gaslimit” - 交易的gas limit必须大于对应数据量所需的最低gas水平
if uint64(len(pool.all)) >= pool.config.GlobalSlots+pool.config.GlobalQueue {
// If the new transaction is underpriced, don't accept it
if !local && pool.priced.Underpriced(tx, pool.locals) {
log.Trace("Discarding underpriced transaction", "hash", hash, "price", tx.GasPrice())
underpricedTxCounter.Inc(1)
return false, ErrUnderpriced
}
// New transaction is better than our worse ones, make room for it
drop := pool.priced.Discard(len(pool.all)-int(pool.config.GlobalSlots+pool.config.GlobalQueue-1), pool.locals)
for _, tx := range drop {
log.Trace("Discarding freshly underpriced transaction", "hash", tx.Hash(), "price", tx.GasPrice())
underpricedTxCounter.Inc(1)
pool.removeTx(tx.Hash(), false)
}
} 这一段是在当前txpool已满的情况下，剔除掉低油价的交易。还记得之前有个priced字段存储了按gas price以及nonce排序的交易列表吗？这里会先把当前交易的gas price和当前池中的最低价进行比较：
- 如果低于最低价，直接丢弃该交易返回
- 如果高于最低价，则从txpool中剔除一些低价的交易
// New transaction isn't replacing a pending one, push into queue
replace, err := pool.enqueueTx(hash, tx)
if err != nil {
return false, err
} 如果之前的那些检查都没有问题，就真正调用enqueueTx()函数把交易加入到queue列表中了。
// Mark local addresses and journal local transactions
if local {
pool.locals.add(from)
}
pool.journalTx(from, tx)最后，如果发现这个账户是本地的，就把它加到一个白名单里，默认会保证本地交易优先被加到txpool中。
TxPool.promoteExecuteables()
主要目的是把交易从queue列表“提拔”到pending列表，代码逻辑比较清楚，具体可以参见下面这张图：
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-PUzBtCld-1656316462606)(http://olgjbx93m.bkt.clouddn.com/20180201-125715.png)]
根据不同的目的可以分为3块，分别以粉色、紫色、绿色标识。
粉色部分主要是为了把queue中的交易“提拔”到pending中。当然在这之前需要先要进行一番检查：
- 丢弃nonce < 账户当前nonce的交易，也就是已经被打包过的交易
- 丢弃转账金额 + gas消耗 > 账户余额的交易，也就是会out-of-gas的交易
- 丢弃gas limit > block gas limit的交易，这部分交易可能会导致区块生成失败
紫色部分主要是为了清理pending列表，使其满足GlobalSlots和AccountSlots的限制条件：
- 如果有些账户的交易数超过了AccountSlots，则先按交易数最少的账户进行均衡。举例来说，如果有10个账户交易数超过了AccountSlots（默认16），其中交易数最少的账户包含20笔交易，那么先把其他9个账户的交易数量削减到20。
- 如果经过上面的步骤，pending的长度还是超过了GlobalSlots，那就严格按照AccountSlots进行均衡，也就是把上面的10个账户的交易数进一步削减到16。
绿色部分主要是为了清理queue列表，使其满足GlobalQueue和AccountQueue的限制条件：
- 如果每个账户的交易数超过了AccountQueue，丢弃多余交易
- 如果queue的长度超过了GlobalQueue，则把账户按最后一次心跳时间排序，然后依次去除账户中的交易，直到满足限制条件位置。
// 代码位于 core/tx_pool.go
func (pool *TxPool) promoteExecutables(accounts []common.Address) {
// Track the promoted transactions to broadcast them at once
var promoted []*types.Transaction
// Gather all the accounts potentially needing updates
if accounts == nil {
accounts = make([]common.Address, 0, len(pool.queue))
for addr := range pool.queue {
accounts = append(accounts, addr)
}
}
// Iterate over all accounts and promote any executable transactions
for _, addr := range accounts {
list := pool.queue[addr]
if list == nil {
continue // Just in case someone calls with a non existing account
}
// Drop all transactions that are deemed too old (low nonce)
for _, tx := range list.Forward(pool.currentState.GetNonce(addr)) {
hash := tx.Hash()
log.Trace("Removed old queued transaction", "hash", hash)
pool.all.Remove(hash)
pool.priced.Removed()
}
// Drop all transactions that are too costly (low balance or out of gas)
drops, _ := list.Filter(pool.currentState.GetBalance(addr), pool.currentMaxGas)
for _, tx := range drops {
hash := tx.Hash()
log.Trace("Removed unpayable queued transaction", "hash", hash)
pool.all.Remove(hash)
pool.priced.Removed()
queuedNofundsCounter.Inc(1)
}
// Gather all executable transactions and promote them
for _, tx := range list.Ready(pool.pendingState.GetNonce(addr)) {
hash := tx.Hash()
if pool.promoteTx(addr, hash, tx) {
log.Trace("Promoting queued transaction", "hash", hash)
promoted = append(promoted, tx)
}
}
// Drop all transactions over the allowed limit
if !pool.locals.contains(addr) {
for _, tx := range list.Cap(int(pool.config.AccountQueue)) {
hash := tx.Hash()
pool.all.Remove(hash)
pool.priced.Removed()
queuedRateLimitCounter.Inc(1)
log.Trace("Removed cap-exceeding queued transaction", "hash", hash)
}
}
// Delete the entire queue entry if it became empty.
if list.Empty() {
delete(pool.queue, addr)
}
}
// Notify subsystem for new promoted transactions.
if len(promoted) > 0 {
pool.txFeed.Send(NewTxsEvent{promoted})
}
// If the pending limit is overflown, start equalizing allowances
pending := uint64(0)
for _, list := range pool.pending {
pending += uint64(list.Len())
}
if pending > pool.config.GlobalSlots {
pendingBeforeCap := pending
// Assemble a spam order to penalize large transactors first
spammers := prque.New()
for addr, list := range pool.pending {
// Only evict transactions from high rollers
if !pool.locals.contains(addr) && uint64(list.Len()) > pool.config.AccountSlots {
spammers.Push(addr, float32(list.Len()))
}
}
// Gradually drop transactions from offenders
offenders := []common.Address{}
for pending > pool.config.GlobalSlots && !spammers.Empty() {
// Retrieve the next offender if not local address
offender, _ := spammers.Pop()
offenders = append(offenders, offender.(common.Address))
// Equalize balances until all the same or below threshold
if len(offenders) > 1 {
// Calculate the equalization threshold for all current offenders
threshold := pool.pending[offender.(common.Address)].Len()
// Iteratively reduce all offenders until below limit or threshold reached
for pending > pool.config.GlobalSlots && pool.pending[offenders[len(offenders)-2]].Len() > threshold {
for i := 0; i < len(offenders)-1; i++ {
list := pool.pending[offenders[i]]
for _, tx := range list.Cap(list.Len() - 1) {
// Drop the transaction from the global pools too
hash := tx.Hash()
pool.all.Remove(hash)
pool.priced.Removed()
// Update the account nonce to the dropped transaction
if nonce := tx.Nonce(); pool.pendingState.GetNonce(offenders[i]) > nonce {
pool.pendingState.SetNonce(offenders[i], nonce)
}
log.Trace("Removed fairness-exceeding pending transaction", "hash", hash)
}
pending--
}
}
}
}
// If still above threshold, reduce to limit or min allowance
if pending > pool.config.GlobalSlots && len(offenders) > 0 {
for pending > pool.config.GlobalSlots && uint64(pool.pending[offenders[len(offenders)-1]].Len()) > pool.config.AccountSlots {
for _, addr := range offenders {
list := pool.pending[addr]
for _, tx := range list.Cap(list.Len() - 1) {
// Drop the transaction from the global pools too
hash := tx.Hash()
pool.all.Remove(hash)
pool.priced.Removed()
// Update the account nonce to the dropped transaction
if nonce := tx.Nonce(); pool.pendingState.GetNonce(addr) > nonce {
pool.pendingState.SetNonce(addr, nonce)
}
log.Trace("Removed fairness-exceeding pending transaction", "hash", hash)
}
pending--
}
}
}
pendingRateLimitCounter.Inc(int64(pendingBeforeCap - pending))
}
// If we've queued more transactions than the hard limit, drop oldest ones
queued := uint64(0)
for _, list := range pool.queue {
queued += uint64(list.Len())
}
if queued > pool.config.GlobalQueue {
// Sort all accounts with queued transactions by heartbeat
addresses := make(addresssByHeartbeat, 0, len(pool.queue))
for addr := range pool.queue {
if !pool.locals.contains(addr) { // don't drop locals
addresses = append(addresses, addressByHeartbeat{addr, pool.beats[addr]})
}
}
sort.Sort(addresses)
// Drop transactions until the total is below the limit or only locals remain
for drop := queued - pool.config.GlobalQueue; drop > 0 && len(addresses) > 0; {
addr := addresses[len(addresses)-1]
list := pool.queue[addr.address]
addresses = addresses[:len(addresses)-1]
// Drop all transactions if they are less than the overflow
if size := uint64(list.Len()); size <= drop {
for _, tx := range list.Flatten() {
pool.removeTx(tx.Hash(), true)
}
drop -= size
queuedRateLimitCounter.Inc(int64(size))
continue
}
// Otherwise drop only last few transactions
txs := list.Flatten()
for i := len(txs) - 1; i >= 0 && drop > 0; i-- {
pool.removeTx(txs[i].Hash(), true)
drop--
queuedRateLimitCounter.Inc(1)
}
}
}
}广播交易
交易提交到txpool中后，还需要广播出去，一方面通知EVM执行该交易，另一方面要把交易信息广播给其他结点。具体调用在 promoteExecutables 提到的promoteTx()函数中：
// 代码位于 core/tx_pool.go
func (pool *TxPool) promoteExecutables(accounts []common.Address) {
...
// Gather all executable transactions and promote them
for _, tx := range list.Ready(pool.pendingState.GetNonce(addr)) {
hash := tx.Hash()
if pool.promoteTx(addr, hash, tx) {
log.Trace("Promoting queued transaction", "hash", hash)
promoted = append(promoted, tx)
}
}
}
...
// Notify subsystem for new promoted transactions.
if len(promoted) > 0 {
pool.txFeed.Send(NewTxsEvent{promoted})
}promoteTx 详细代码：
// 代码 crypto/tx_pool.go
func (pool *TxPool) promoteTx(addr common.Address, hash common.Hash, tx *types.Transaction) bool {
// Try to insert the transaction into the pending queue
if pool.pending[addr] == nil {
pool.pending[addr] = newTxList(true)
}
list := pool.pending[addr]
inserted, old := list.Add(tx, pool.config.PriceBump)
if !inserted {
// An older transaction was better, discard this
pool.all.Remove(hash)
pool.priced.Removed()
pendingDiscardCounter.Inc(1)
return false
}
// Otherwise discard any previous transaction and mark this
if old != nil {
pool.all.Remove(old.Hash())
pool.priced.Removed()
pendingReplaceCounter.Inc(1)
}
// Failsafe to work around direct pending inserts (tests)
if pool.all.Get(hash) == nil {
pool.all.Add(tx)
pool.priced.Put(tx)
}
// Set the potentially new pending nonce and notify any subsystems of the new tx
pool.beats[addr] = time.Now()
pool.pendingState.SetNonce(addr, tx.Nonce()+1)
return true
}先更新了最后一次心跳时间，然后更新账户的nonce值。
pool.txFeed.Send 发送一个TxPreEvent事件，外部可以通过SubscribeNewTxsEvent()函数订阅该事件：
func (pool *TxPool) SubscribeNewTxsEvent(ch chan<- core.NewTxsEvent) event.Subscription {
return pool.scope.Track(pool.txFeed.Subscribe(ch))
}我们只要搜索一下这个函数，就可以知道哪些组件订阅了该事件了。
执行交易
第一个订阅的地方位于miner/worker.go：
func newWorker(config *params.ChainConfig, engine consensus.Engine, coinbase common.Address, eth Backend, mux *event.TypeMux) *worker {
....
// Subscribe NewTxsEvent for tx pool
worker.txsSub = eth.TxPool().SubscribeNewTxsEvent(worker.txsCh)
....
}
开启了一个goroutine来接收TxPreEvent，看一下update()函数：
func (self *worker) update() {
defer self.txsSub.Unsubscribe()
defer self.chainHeadSub.Unsubscribe()
defer self.chainSideSub.Unsubscribe()
for {
...
// Handle NewTxsEvent
case ev := <-self.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 atomic.LoadInt32(&self.mining) == 0 {
self.currentMu.Lock()
txs := make(map[common.Address]types.Transactions)
for _, tx := range ev.Txs {
acc, _ := types.Sender(self.current.signer, tx)
txs[acc] = append(txs[acc], tx)
}
txset := types.NewTransactionsByPriceAndNonce(self.current.signer, txs)
self.current.commitTransactions(self.mux, txset, self.chain, self.coinbase)
self.updateSnapshot()
self.currentMu.Unlock()
} else {
// If we're mining, but nothing is being processed, wake on new transactions
if self.config.Clique != nil && self.config.Clique.Period == 0 {
self.commitNewWork()
}
}
...
}
}
}可以看到，如果结点不挖矿的话，这里会立即调用commitTransactions()提交给EVM执行，获得本地回执。
如果结点挖矿的话，miner会调用commitNewWork()，内部也会调用commitTransactions()执行交易。
广播给其他结点
另一个订阅的地方位于eth/handler.go：
func (pm *ProtocolManager) Start(maxPeers int) {
...
// broadcast transactions
pm.txsCh = make(chan core.NewTxsEvent, txChanSize)
pm.txsSub = pm.txpool.SubscribeNewTxsEvent(pm.txsCh)
go pm.txBroadcastLoop()
...
}同样也是启动了一个goroutine来接收TxPreEvent事件，看一下txBroadcastLoop()函数：
func (pm *ProtocolManager) txBroadcastLoop() {
for {
select {
case event := <-pm.txCh:
pm.BroadcastTx(event.Tx.Hash(), event.Tx)
// Err() channel will be closed when unsubscribing.
case <-pm.txSub.Err():
return
}
}
}继续跟踪BroadcastTx()函数：
func (pm *ProtocolManager) BroadcastTxs(txs types.Transactions) {
var txset = make(map[*peer]types.Transactions)
// Broadcast transactions to a batch of peers not knowing about it
for _, tx := range txs {
peers := pm.peers.PeersWithoutTx(tx.Hash())
for _, peer := range peers {
txset[peer] = append(txset[peer], tx)
}
log.Trace("Broadcast transaction", "hash", tx.Hash(), "recipients", len(peers))
}
// FIXME include this again: peers = peers[:int(math.Sqrt(float64(len(peers))))]
for peer, txs := range txset {
peer.AsyncSendTransactions(txs)
}
}可以看到，这里会通过P2P向所有没有该交易的结点发送该交易。
