在“以太坊源码深入分析（2）”一文中，我们提到Ethereum作为一个service，被Node 注册进去。Node start的时候会启动其注册的所有服务，Ethereum service也是一样。
一，ethereum service的初始化和启动
初始化方法
func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
if config.SyncMode == downloader.LightSync {
return nil, errors.New("can't run eth.Ethereum in light sync mode, use les.LightEthereum")
}
if !config.SyncMode.IsValid() {
return nil, fmt.Errorf("invalid sync mode %d", config.SyncMode)
}
chainDb, err := CreateDB(ctx, config, "chaindata")
if err != nil {
return nil, err
}
stopDbUpgrade := upgradeDeduplicateData(chainDb)
chainConfig, genesisHash, genesisErr := core.SetupGenesisBlock(chainDb, config.Genesis)
if _, ok := genesisErr.(*params.ConfigCompatError); genesisErr != nil && !ok {
return nil, genesisErr
}
log.Info("Initialised chain configuration", "config", chainConfig)
eth := &Ethereum{
config: config,
chainDb: chainDb,
chainConfig: chainConfig,
eventMux: ctx.EventMux,
accountManager: ctx.AccountManager,
engine: CreateConsensusEngine(ctx, &config.Ethash, chainConfig, chainDb),
shutdownChan: make(chan bool),
stopDbUpgrade: stopDbUpgrade,
networkId: config.NetworkId,
gasPrice: config.GasPrice,
etherbase: config.Etherbase,
bloomRequests: make(chan chan *bloombits.Retrieval),
bloomIndexer: NewBloomIndexer(chainDb, params.BloomBitsBlocks),
}
log.Info("Initialising Ethereum protocol", "versions", ProtocolVersions, "network", config.NetworkId)
if !config.SkipBcVersionCheck {
bcVersion := core.GetBlockChainVersion(chainDb)
if bcVersion != core.BlockChainVersion && bcVersion != 0 {
return nil, fmt.Errorf("Blockchain DB version mismatch (%d / %d). Run geth upgradedb.\n", bcVersion, core.BlockChainVersion)
}
core.WriteBlockChainVersion(chainDb, core.BlockChainVersion)
}
var (
vmConfig = vm.Config{EnablePreimageRecording: config.EnablePreimageRecording}
cacheConfig = &core.CacheConfig{Disabled: config.NoPruning, TrieNodeLimit: config.TrieCache, TrieTimeLimit: config.TrieTimeout}
)
eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, eth.chainConfig, eth.engine, vmConfig)
if err != nil {
return nil, err
}
// Rewind the chain in case of an incompatible config upgrade.
if compat, ok := genesisErr.(*params.ConfigCompatError); ok {
log.Warn("Rewinding chain to upgrade configuration", "err", compat)
eth.blockchain.SetHead(compat.RewindTo)
core.WriteChainConfig(chainDb, genesisHash, chainConfig)
}
eth.bloomIndexer.Start(eth.blockchain)
if config.TxPool.Journal != "" {
config.TxPool.Journal = ctx.ResolvePath(config.TxPool.Journal)
}
eth.txPool = core.NewTxPool(config.TxPool, eth.chainConfig, eth.blockchain)
if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.SyncMode, config.NetworkId, eth.eventMux, eth.txPool, eth.engine, eth.blockchain, chainDb); err != nil {
return nil, err
}
eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine)
eth.miner.SetExtra(makeExtraData(config.ExtraData))
eth.ApiBackend = &EthApiBackend{eth, nil}
gpoParams := config.GPO
if gpoParams.Default == nil {
gpoParams.Default = config.GasPrice
}
eth.ApiBackend.gpo = gasprice.NewOracle(eth.ApiBackend, gpoParams)
return eth, nil
}
1，如果config.SyncMode 是 downloader.LightSync，走的是les/backend.go的初始化方法。
2，chainDb, err := CreateDB(ctx, config, "chaindata")打开leveldb，leveldb是eth存储数据库。
3，stopDbUpgrade := upgradeDeduplicateData(chainDb) 检查chainDb版本，如果需要的话，启动后台进程进行升级。
4，chainConfig, genesisHash, genesisErr := core.SetupGenesisBlock(chainDb, config.Genesis)装载创世区块。 根据节点条件判断是从数据库里面读取，还是从默认配置文件读取，还是从自定义配置文件读取，或者是从代码里面获取默认值。并返回区块链的config和创世块的hash。
5，装载Etherum struct的各个成员。eventMux和accountManager 是Node 启动 eth service的时候传入的。eventMux可以认为是一个全局的事件多路复用器，accountManager认为是一个全局的账户管理器。engine创建共识引擎。etherbase 配置此Etherum的主账号地址。初始化bloomRequests 通道和bloom过滤器。
6，判断客户端版本号和数据库版本号是否一致
7，eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, eth.chainConfig, eth.engine, vmConfig) 初始化eth的blockchain，也就是eth的区块链
8，eth.blockchain.SetHead(compat.RewindTo) 根据创始区块设置区块头
9，eth.bloomIndexer.Start(eth.blockchain)启动bloomIndexer
10，eth.txPool = core.NewTxPool(config.TxPool, eth.chainConfig, eth.blockchain) 初始化eth 区块链的交易池，存储本地生产的和P2P网络同步过来的交易。
11，eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.SyncMode, config.NetworkId, eth.eventMux, eth.txPool, eth.engine, eth.blockchain, chainDb)初始化以太坊协议管理器，用于区块链P2P通讯
12， miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine) 初始化矿工
13，eth.ApiBackend.gpo = gasprice.NewOracle(eth.ApiBackend, gpoParams) 创建预言最新gasprice的预言机。
ethereum service的初始化配置了不少东西，基本上涉及到了以太坊区块链系统的所有内容，后续一一分解各个模块。
启动方法
func (s *Ethereum) Start(srvr *p2p.Server) error {
// Start the bloom bits servicing goroutines
s.startBloomHandlers()
// Start the RPC service
s.netRPCService = ethapi.NewPublicNetAPI(srvr, s.NetVersion())
// Figure out a max peers count based on the server limits
maxPeers := srvr.MaxPeers
if s.config.LightServ > 0 {
if s.config.LightPeers >= srvr.MaxPeers {
return fmt.Errorf("invalid peer config: light peer count (%d) >= total peer count (%d)", s.config.LightPeers, srvr.MaxPeers)
}
maxPeers -= s.config.LightPeers
}
// Start the networking layer and the light server if requested
s.protocolManager.Start(maxPeers)
if s.lesServer != nil {
s.lesServer.Start(srvr)
}
return nil
}
首先启动bloom过滤器
eth 的net 相关Api 加入RPC 服务。
s.protocolManager.Start(maxPeers) 设置最大同步节点数，并启动eth P2P通讯。
如果ethereum service 出问题了才会启动lesServer。
二，ProtocolManager 以太坊P2P通讯协议管理
首先分析一下同在eth目录下的eth/handler.go。
ProtocolManager 的初始化方法
func NewProtocolManager(config *params.ChainConfig, mode downloader.SyncMode, networkId uint64, mux *event.TypeMux, txpool txPool, engine consensus.Engine, blockchain *core.BlockChain, chaindb ethdb.Database) (*ProtocolManager, error) {
// Create the protocol manager with the base fields
manager := &ProtocolManager{
networkId: networkId,
eventMux: mux,
txpool: txpool,
blockchain: blockchain,
chainconfig: config,
peers: newPeerSet(),
newPeerCh: make(chan *peer),
noMorePeers: make(chan struct{}),
txsyncCh: make(chan *txsync),
quitSync: make(chan struct{}),
}
// Figure out whether to allow fast sync or not
if mode == downloader.FastSync && blockchain.CurrentBlock().NumberU64() > 0 {
log.Warn("Blockchain not empty, fast sync disabled")
mode = downloader.FullSync
}
if mode == downloader.FastSync {
manager.fastSync = uint32(1)
}
// Initiate a sub-protocol for every implemented version we can handle
manager.SubProtocols = make([]p2p.Protocol, 0, len(ProtocolVersions))
for i, version := range ProtocolVersions {
// Skip protocol version if incompatible with the mode of operation
if mode == downloader.FastSync && version < eth63 {
continue
}
// Compatible; initialise the sub-protocol
version := version // Closure for the run
manager.SubProtocols = append(manager.SubProtocols, p2p.Protocol{
Name: ProtocolName,
Version: version,
Length: ProtocolLengths[i],
Run: func(p *p2p.Peer, rw p2p.MsgReadWriter) error {
peer := manager.newPeer(int(version), p, rw)
select {
case manager.newPeerCh <- peer:
manager.wg.Add(1)
defer manager.wg.Done()
return manager.handle(peer)
case <-manager.quitSync:
return p2p.DiscQuitting
}
},
NodeInfo: func() interface{} {
return manager.NodeInfo()
},
PeerInfo: func(id discover.NodeID) interface{} {
if p := manager.peers.Peer(fmt.Sprintf("%x", id[:8])); p != nil {
return p.Info()
}
return nil
},
})
}
if len(manager.SubProtocols) == 0 {
return nil, errIncompatibleConfig
}
// Construct the different synchronisation mechanisms
manager.downloader = downloader.New(mode, chaindb, manager.eventMux, blockchain, nil, manager.removePeer)
validator := func(header *types.Header) error {
return engine.VerifyHeader(blockchain, header, true)
}
heighter := func() uint64 {
return blockchain.CurrentBlock().NumberU64()
}
inserter := func(blocks types.Blocks) (int, error) {
// If fast sync is running, deny importing weird blocks
if atomic.LoadUint32(&manager.fastSync) == 1 {
log.Warn("Discarded bad propagated block", "number", blocks[0].Number(), "hash", blocks[0].Hash())
return 0, nil
}
atomic.StoreUint32(&manager.acceptTxs, 1) // Mark initial sync done on any fetcher import
return manager.blockchain.InsertChain(blocks)
}
manager.fetcher = fetcher.New(blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, inserter, manager.removePeer)
return manager, nil
}
1，peers 为以太坊临近的同步网络节点，newPeerCh、noMorePeers、txsyncCh、quitSync对应同步的通知
2，manager.SubProtocols 创建以太坊 P2P server 的 通讯协议，通常只有一个值。manager.SubProtocols，在Node start的时候传给以太坊 P2P server并同时start P2P server。协议里面三个函数指针（Run、NodeInfo、PeerInfo）非常重要，后面会用到。
3，manager.downloader = downloader.New(mode, chaindb, manager.eventMux, blockchain, nil, manager.removePeer)
创建了一个下载器，从远程网络节点中获取hashes和blocks。
4，manager.fetcher = fetcher.New(blockchain.GetBlockByHash, validator, manager.BroadcastBlock, heighter, inserter, manager.removePeer)收集网络其他以太坊节点发过来的同步通知，进行验证，并做出相应的处理。初始化传入的几个参数 都是用于处理同步区块链数据的函数指针
Ethereum service 启动的时候会同时启动ProtocolManager，ProtocolManager的start()方法：
func (pm *ProtocolManager) Start(maxPeers int) {
pm.maxPeers = maxPeers
// broadcast transactions
pm.txCh = make(chan core.TxPreEvent, txChanSize)
pm.txSub = pm.txpool.SubscribeTxPreEvent(pm.txCh)
go pm.txBroadcastLoop()
// broadcast mined blocks
pm.minedBlockSub = pm.eventMux.Subscribe(core.NewMinedBlockEvent{})
go pm.minedBroadcastLoop()
// start sync handlers
go pm.syncer()
go pm.txsyncLoop()
}
1，创建一个新交易的订阅通道，并启动交易广播的goroutine
2，创建一个挖坑的订阅通道，并启动挖坑广播的goroutine
注：同为订阅通道为什么pm.txSub和pm.minedBlockSub的实现不一样？深入代码会发现pm.txSub用的是event/feed通知方式，pm.minedBlockSub用的是event/TypeMuxEvent通知方式，event/TypeMuxEvent方式将要被Deprecated。
3，pm.syncer() 启动同步goroutine，定时的和网络其他节点同步，并处理网络节点的相关通知
4，pm.txsyncLoop() 启动交易同步goroutine，把新的交易均匀的同步给网路节点
三，ProtocolManager主动向网络节点广播
ProtocolManager Start()方法里面的4个goroutine都是处理ProtocolManager向以太坊网络节点进行广播的。
1，pm.txBroadcastLoop()方法
func (self *ProtocolManager) txBroadcastLoop() {
for {
select {
case event := <-self.txCh:
self.BroadcastTx(event.Tx.Hash(), event.Tx)
// Err() channel will be closed when unsubscribing.
case <-self.txSub.Err():
return
}
}
}
core/tx_pool.go 产生新的交易的时候会send self.txCh，这时候会激活
self.BroadcastTx(event.Tx.Hash(), event.Tx)
func (pm *ProtocolManager) BroadcastTx(hash common.Hash, tx *types.Transaction) {
// Broadcast transaction to a batch of peers not knowing about it
peers := pm.peers.PeersWithoutTx(hash)
//FIXME include this again: peers = peers[:int(math.Sqrt(float64(len(peers))))]
for _, peer := range peers {
peer.SendTransactions(types.Transactions{tx})
}
log.Trace("Broadcast transaction", "hash", hash, "recipients", len(peers))
}
向缓存的没有这个交易hash的网络节点广播此次交易。
2，pm.minedBroadcastLoop()方法
// Mined broadcast loop
func (self *ProtocolManager) minedBroadcastLoop() {
// automatically stops if unsubscribe
for obj := range self.minedBlockSub.Chan() {
switch ev := obj.Data.(type) {
case core.NewMinedBlockEvent:
self.BroadcastBlock(ev.Block, true) // First propagate block to peers
self.BroadcastBlock(ev.Block, false) // Only then announce to the rest
}
}
}
收到miner.go 里面NewMinedBlockEvent 挖到新区块的事件通知，激活self.BroadcastBlock(ev.Block, true)
func (pm *ProtocolManager) BroadcastBlock(block *types.Block, propagate bool) {
hash := block.Hash()
peers := pm.peers.PeersWithoutBlock(hash)
// If propagation is requested, send to a subset of the peer
if propagate {
// Calculate the TD of the block (it's not imported yet, so block.Td is not valid)
var td *big.Int
if parent := pm.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1); parent != nil {
td = new(big.Int).Add(block.Difficulty(), pm.blockchain.GetTd(block.ParentHash(), block.NumberU64()-1))
} else {
log.Error("Propagating dangling block", "number", block.Number(), "hash", hash)
return
}
// Send the block to a subset of our peers
transfer := peers[:int(math.Sqrt(float64(len(peers))))]
for _, peer := range transfer {
peer.SendNewBlock(block, td)
}
log.Trace("Propagated block", "hash", hash, "recipients", len(transfer), "duration", common.PrettyDuration(time.Since(block.ReceivedAt)))
return
}
// Otherwise if the block is indeed in out own chain, announce it
if pm.blockchain.HasBlock(hash, block.NumberU64()) {
for _, peer := range peers {
peer.SendNewBlockHashes([]common.Hash{hash}, []uint64{block.NumberU64()})
}
log.Trace("Announced block", "hash", hash, "recipients", len(peers), "duration", common.PrettyDuration(time.Since(block.ReceivedAt)))
}
}
如果propagate为true 向网络节点广播整个挖到的block，为false 只广播挖到的区块的hash值和number值。广播的区块还包括这个区块打包的所有交易。
3，pm.syncer() 方法
func (pm *ProtocolManager) syncer() {
// Start and ensure cleanup of sync mechanisms
pm.fetcher.Start()
defer pm.fetcher.Stop()
defer pm.downloader.Terminate()
// Wait for different events to fire synchronisation operations
forceSync := time.NewTicker(forceSyncCycle)
defer forceSync.Stop()
for {
select {
case <-pm.newPeerCh:
// Make sure we have peers to select from, then sync
if pm.peers.Len() < minDesiredPeerCount {
break
}
go pm.synchronise(pm.peers.BestPeer())
case <-forceSync.C:
// Force a sync even if not enough peers are present
go pm.synchronise(pm.peers.BestPeer())
case <-pm.noMorePeers:
return
}
}
}
pm.fetcher.Start()启动 fetcher，辅助同步区块数据
当P2P server执行 ProtocolManager 的p2p.Protocol 的Run指针的时候会send pm.newPeerCh，这时候选择最优的网络节点（TD 总难度最大的）启动pm.synchronise(pm.peers.BestPeer()) goroutine。
// synchronise tries to sync up our local block chain with a remote peer.
func (pm *ProtocolManager) synchronise(peer *peer) {
// Short circuit if no peers are available
if peer == nil {
return
}
// Make sure the peer's TD is higher than our own
currentBlock := pm.blockchain.CurrentBlock()
td := pm.blockchain.GetTd(currentBlock.Hash(), currentBlock.NumberU64())
pHead, pTd := peer.Head()
if pTd.Cmp(td) <= 0 {
return
}
// Otherwise try to sync with the downloader
mode := downloader.FullSync
if atomic.LoadUint32(&pm.fastSync) == 1 {
// Fast sync was explicitly requested, and explicitly granted
mode = downloader.FastSync
} else if currentBlock.NumberU64() == 0 && pm.blockchain.CurrentFastBlock().NumberU64() > 0 {
// The database seems empty as the current block is the genesis. Yet the fast
// block is ahead, so fast sync was enabled for this node at a certain point.
// The only scenario where this can happen is if the user manually (or via a
// bad block) rolled back a fast sync node below the sync point. In this case
// however it's safe to reenable fast sync.
atomic.StoreUint32(&pm.fastSync, 1)
mode = downloader.FastSync
}
// Run the sync cycle, and disable fast sync if we've went past the pivot block
if err := pm.downloader.Synchronise(peer.id, pHead, pTd, mode); err != nil {
return
}
if atomic.LoadUint32(&pm.fastSync) == 1 {
log.Info("Fast sync complete, auto disabling")
atomic.StoreUint32(&pm.fastSync, 0)
}
atomic.StoreUint32(&pm.acceptTxs, 1) // Mark initial sync done
if head := pm.blockchain.CurrentBlock(); head.NumberU64() > 0 {
// We've completed a sync cycle, notify all peers of new state. This path is
// essential in star-topology networks where a gateway node needs to notify
// all its out-of-date peers of the availability of a new block. This failure
// scenario will most often crop up in private and hackathon networks with
// degenerate connectivity, but it should be healthy for the mainnet too to
// more reliably update peers or the local TD state.
go pm.BroadcastBlock(head, false)
}
}
如果最优的网络节点的TD值大于本地最新区块的TD值，调用pm.downloader.Synchronise(peer.id, pHead, pTd, mode)进行同步。同步完成后再屌用go pm.BroadcastBlock(head, false)，把自己最新的区块状态广播出去。
4，pm.txsyncLoop()方法
func (pm *ProtocolManager) txsyncLoop() {
var (
pending = make(map[discover.NodeID]*txsync)
sending = false // whether a send is active
pack = new(txsync) // the pack that is being sent
done = make(chan error, 1) // result of the send
)
// send starts a sending a pack of transactions from the sync.
send := func(s *txsync) {
// Fill pack with transactions up to the target size.
size := common.StorageSize(0)
pack.p = s.p
pack.txs = pack.txs[:0]
for i := 0; i < len(s.txs) && size < txsyncPackSize; i++ {
pack.txs = append(pack.txs, s.txs[i])
size += s.txs[i].Size()
}
// Remove the transactions that will be sent.
s.txs = s.txs[:copy(s.txs, s.txs[len(pack.txs):])]
if len(s.txs) == 0 {
delete(pending, s.p.ID())
}
// Send the pack in the background.
s.p.Log().Trace("Sending batch of transactions", "count", len(pack.txs), "bytes", size)
sending = true
go func() { done <- pack.p.SendTransactions(pack.txs) }()
}
// pick chooses the next pending sync.
pick := func() *txsync {
if len(pending) == 0 {
return nil
}
n := rand.Intn(len(pending)) + 1
for _, s := range pending {
if n--; n == 0 {
return s
}
}
return nil
}
for {
select {
case s := <-pm.txsyncCh:
pending[s.p.ID()] = s
if !sending {
send(s)
}
case err := <-done:
sending = false
// Stop tracking peers that cause send failures.
if err != nil {
pack.p.Log().Debug("Transaction send failed", "err", err)
delete(pending, pack.p.ID())
}
// Schedule the next send.
if s := pick(); s != nil {
send(s)
}
case <-pm.quitSync:
return
}
}
}
当从网络节点同步过来最新的交易数据后，本地也会把新同步下来的交易数据广播给网络中的其他节点。
总结一下
这四个goroutine 基本上就在不停的做广播区块、广播交易，同步到区块、同步到交易，再广播区块、广播交易。
