Geth启动流程代码解析(完整解析）
init函数主要是做了一些初始化的工作，其中比较重要的有三个地方，app.Action=geth,app.Commands中consoleCommand。启动流程走的是consoleCommand命令语句：
func init() {
// Initialize the CLI app and start Geth
app.Action = geth
app.HideVersion = true // we have a command to print the version
app.Copyright = "Copyright 2013-2017 The go-ethereum Authors"
app.Commands = []cli.Command{
// See chaincmd.go:
initCommand,
importCommand,
exportCommand,
removedbCommand,
dumpCommand,
// See monitorcmd.go:
monitorCommand,
// See accountcmd.go:
accountCommand,
walletCommand,
// See consolecmd.go:
consoleCommand,
attachCommand,
javascriptCommand,
// See misccmd.go:
makedagCommand,
versionCommand,
bugCommand,
licenseCommand,
// See config.go
dumpConfigCommand,
}
app.Flags = append(app.Flags, nodeFlags...)
app.Flags = append(app.Flags, rpcFlags...)
app.Flags = append(app.Flags, consoleFlags...)
app.Flags = append(app.Flags, debug.Flags...)
app.Flags = append(app.Flags, whisperFlags...)
app.Before = func(ctx *cli.Context) error {
runtime.GOMAXPROCS(runtime.NumCPU())
if err := debug.Setup(ctx); err != nil {
return err
}
// Start system runtime metrics collection
go metrics.CollectProcessMetrics(3 * time.Second)
utils.SetupNetwork(ctx)
return nil
}
app.After = func(ctx *cli.Context) error {
debug.Exit()
console.Stdin.Close() // Resets terminal mode.
return nil
}
}
main函数的实现很简单，仅仅调用了app.Run函数，如果调用异常，则退出。
func main() {
if err := app.Run(os.Args); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
}
此处通过第三方包gopkg.in/urfave/cli.v1来衔接，app中的action的类型是「func(*Context) error」，此时将执行a(context)方法，那么此时调用那个Action呢，其实就是我们前面提到的App.init()初始化命令时的consoleCommand，接下来我们来看看cmd/geth/consolecmd中的consoleCommand：
consoleCommand = cli.Command{
Action: utils.MigrateFlags(localConsole),
Name: "console",
Usage: "Start an interactive JavaScript environment",
Flags: append(append(append(nodeFlags, rpcFlags...), consoleFlags...), whisperFlags...),
Category: "CONSOLE COMMANDS",
Description: `
The Geth console is an interactive shell for the JavaScript runtime environment
which exposes a node admin interface as well as the Ðapp JavaScript API.
See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Console.`,
}
其Action中的localConsole函数如下：
func localConsole(ctx *cli.Context) error {
// Create and start the node based on the CLI flags
node := makeFullNode(ctx)
startNode(ctx, node)
defer node.Stop()
// Attach to the newly started node and start the JavaScript console
client, err := node.Attach()
if err != nil {
utils.Fatalf("Failed to attach to the inproc geth: %v", err)
}
config := console.Config{
DataDir: utils.MakeDataDir(ctx),
DocRoot: ctx.GlobalString(utils.JSpathFlag.Name),
Client: client,
Preload: utils.MakeConsolePreloads(ctx),
}
console, err := console.New(config)
if err != nil {
utils.Fatalf("Failed to start the JavaScript console: %v", err)
}
defer console.Stop(false)
// If only a short execution was requested, evaluate and return
if script := ctx.GlobalString(utils.ExecFlag.Name); script != "" {
console.Evaluate(script)
return nil
}
// Otherwise print the welcome screen and enter interactive mode
console.Welcome()
console.Interactive()
return nil
}
该函数非常重要，主要完成以下几件事情
- 首先会创建一个节点、同时启动该节点
- 创建一个console的实例
- 显示Welcome信息
- 创建一个无限循环用于在控制台交互
首先我们来看该Node是如何创建的。makeFullNode函数的实现如下：
func makeFullNode(ctx *cli.Context) *node.Node {
stack, cfg := makeConfigNode(ctx)
utils.RegisterEthService(stack, &cfg.Eth)
// Whisper must be explicitly enabled by specifying at least 1 whisper flag or in dev mode
shhEnabled := enableWhisper(ctx)
shhAutoEnabled := !ctx.GlobalIsSet(utils.WhisperEnabledFlag.Name) && ctx.GlobalIsSet(utils.DevModeFlag.Name)
if shhEnabled || shhAutoEnabled {
if ctx.GlobalIsSet(utils.WhisperMaxMessageSizeFlag.Name) {
cfg.Shh.MaxMessageSize = uint32(ctx.Int(utils.WhisperMaxMessageSizeFlag.Name))
}
if ctx.GlobalIsSet(utils.WhisperMinPOWFlag.Name) {
cfg.Shh.MinimumAcceptedPOW = ctx.Float64(utils.WhisperMinPOWFlag.Name)
}
utils.RegisterShhService(stack, &cfg.Shh)
}
// Add the Ethereum Stats daemon if requested.
if cfg.Ethstats.URL != "" {
utils.RegisterEthStatsService(stack, cfg.Ethstats.URL)
}
// Add the release oracle service so it boots along with node.
if err := stack.Register(func(ctx *node.ServiceContext) (node.Service, error) {
config := release.Config{
Oracle: relOracle,
Major: uint32(params.VersionMajor),
Minor: uint32(params.VersionMinor),
Patch: uint32(params.VersionPatch),
}
commit, _ := hex.DecodeString(gitCommit)
copy(config.Commit[:], commit)
return release.NewReleaseService(ctx, config)
}); err != nil {
utils.Fatalf("Failed to register the Geth release oracle service: %v", err)
}
return stack
}
该函数首先创建一个Node，然后注册一个Ethereum Service，我们继续分析Node是如何创建的，makeConfigNode的函数实现逻辑如下：
func makeConfigNode(ctx *cli.Context) (*node.Node, gethConfig) {
// Load defaults.
cfg := gethConfig{
Eth: eth.DefaultConfig,
Shh: whisper.DefaultConfig,
Node: defaultNodeConfig(),
}
// Load config file.
if file := ctx.GlobalString(configFileFlag.Name); file != "" {
if err := loadConfig(file, &cfg); err != nil {
utils.Fatalf("%v", err)
}
}
// Apply flags.
utils.SetNodeConfig(ctx, &cfg.Node)
stack, err := node.New(&cfg.Node)
if err != nil {
utils.Fatalf("Failed to create the protocol stack: %v", err)
}
utils.SetEthConfig(ctx, stack, &cfg.Eth)
if ctx.GlobalIsSet(utils.EthStatsURLFlag.Name) {
cfg.Ethstats.URL = ctx.GlobalString(utils.EthStatsURLFlag.Name)
}
utils.SetShhConfig(ctx, stack, &cfg.Shh)
return stack, cfg
}
首先初始化gethConfig的变量，接下来调用node.New方法来创建一个Node，我们来看看New函数的实现：
func New(conf *Config) (*Node, error) {
// Copy config and resolve the datadir so future changes to the current
// working directory don't affect the node.
confCopy := *conf
conf = &confCopy
if conf.DataDir != "" {
absdatadir, err := filepath.Abs(conf.DataDir)
if err != nil {
return nil, err
}
conf.DataDir = absdatadir
}
// Ensure that the instance name doesn't cause weird conflicts with
// other files in the data directory.
if strings.ContainsAny(conf.Name, `/\`) {
return nil, errors.New(`Config.Name must not contain '/' or '\'`)
}
if conf.Name == datadirDefaultKeyStore {
return nil, errors.New(`Config.Name cannot be "` + datadirDefaultKeyStore + `"`)
}
if strings.HasSuffix(conf.Name, ".ipc") {
return nil, errors.New(`Config.Name cannot end in ".ipc"`)
}
// Ensure that the AccountManager method works before the node has started.
// We rely on this in cmd/geth.
am, ephemeralKeystore, err := makeAccountManager(conf)
if err != nil {
return nil, err
}
// Note: any interaction with Config that would create/touch files
// in the data directory or instance directory is delayed until Start.
return &Node{
accman: am,
ephemeralKeystore: ephemeralKeystore,
config: conf,
serviceFuncs: []ServiceConstructor{},
ipcEndpoint: conf.IPCEndpoint(),
httpEndpoint: conf.HTTPEndpoint(),
wsEndpoint: conf.WSEndpoint(),
eventmux: new(event.TypeMux),
}, nil
}
New函数首先将保存数据的目录转换成绝对路径，然后对配置进行相关的验证，确认是否合法，接下来创建一个AccountManager实例，然后创建一个Node节点，总体来说其内部的逻辑比较的简单。由于AccountManager负责Account的相关管理操作且后续经常使用，接下来我们看看是AccountManager的具体逻辑实现。AccountManager位于/node/config.go文件中，其实现如下：
func makeAccountManager(conf *Config) (*accounts.Manager, string, error) {
scryptN := keystore.StandardScryptN
scryptP := keystore.StandardScryptP
if conf.UseLightweightKDF {
scryptN = keystore.LightScryptN
scryptP = keystore.LightScryptP
}
var (
keydir string
ephemeral string
err error
)
switch {
case filepath.IsAbs(conf.KeyStoreDir):
keydir = conf.KeyStoreDir
case conf.DataDir != "":
if conf.KeyStoreDir == "" {
keydir = filepath.Join(conf.DataDir, datadirDefaultKeyStore)
} else {
keydir, err = filepath.Abs(conf.KeyStoreDir)
}
case conf.KeyStoreDir != "":
keydir, err = filepath.Abs(conf.KeyStoreDir)
default:
// There is no datadir.
keydir, err = ioutil.TempDir("", "go-ethereum-keystore")
ephemeral = keydir
}
if err != nil {
return nil, "", err
}
if err := os.MkdirAll(keydir, 0700); err != nil {
return nil, "", err
}
// Assemble the account manager and supported backends
backends := []accounts.Backend{
keystore.NewKeyStore(keydir, scryptN, scryptP),
}
if !conf.NoUSB {
if ledgerhub, err := usbwallet.NewLedgerHub(); err != nil {
log.Warn(fmt.Sprintf("Failed to start Ledger hub, disabling: %v", err))
} else {
backends = append(backends, ledgerhub)
}
}
return accounts.NewManager(backends...), ephemeral, nil
}
由于在上面，我们已经将保存数据的目录转换成了绝对路径（由于在命令行，我们已经指定了datadir且存在，如果不存在将创建一个默认的go-ethereum-keystore来保存相关信息），接下来我们来看keystore.NewKeyStore函数。该函数位于/accounts/keystore/keystore.go文件中，其实现如下：
func NewKeyStore(keydir string, scryptN, scryptP int) *KeyStore {
keydir, _ = filepath.Abs(keydir)
ks := &KeyStore{storage: &keyStorePassphrase{keydir, scryptN, scryptP}}
ks.init(keydir)
return ks
}
首先转换成绝对路径（前面已经转换，应该没有必要再次检测），接下来我们看看
ks.init(keydir)
方法的实现，其实现如下：
func (ks *KeyStore) init(keydir string) {
// Lock the mutex since the account cache might call back with events
ks.mu.Lock()
defer ks.mu.Unlock()
// Initialize the set of unlocked keys and the account cache
ks.unlocked = make(map[common.Address]*unlocked)
ks.cache, ks.changes = newAccountCache(keydir)
// TODO: In order for this finalizer to work, there must be no references
// to ks. addressCache doesn't keep a reference but unlocked keys do,
// so the finalizer will not trigger until all timed unlocks have expired.
runtime.SetFinalizer(ks, func(m *KeyStore) {
m.cache.close()
})
// Create the initial list of wallets from the cache
accs := ks.cache.accounts()
ks.wallets = make([]accounts.Wallet, len(accs))
for i := 0; i < len(accs); i++ {
ks.wallets[i] = &keystoreWallet{account: accs[i], keystore: ks}
}
}
该方法首先从缓存中（如果缓存存在则直接获取，否则从datadir中读取）获取Account，然后保存在keystore的钱包中，我们主要来看看ks.cache.accounts()函数，其实现逻辑如下：
func (ac *accountCache) accounts() []accounts.Account {
ac.maybeReload()
ac.mu.Lock()
defer ac.mu.Unlock()
cpy := make([]accounts.Account, len(ac.all))
copy(cpy, ac.all)
return cpy
}
如果账户数据未被加载到内存中，则首先加载进来，然后copy一份，防止外面对缓存的账户做修改，我们来看看ac.maybeReload是如何加载账户信息的。其实现如下：
func (ac *accountCache) maybeReload() {
ac.mu.Lock()
defer ac.mu.Unlock()
if ac.watcher.running {
return // A watcher is running and will keep the cache up-to-date.
}
if ac.throttle == nil {
ac.throttle = time.NewTimer(0)
} else {
select {
case <-ac.throttle.C:
default:
return // The cache was reloaded recently.
}
}
ac.watcher.start()
ac.reload()
ac.throttle.Reset(minReloadInterval)
}
首先使用goroutine启动一个watcher来监测keystore目录，防止其变化。接下来调用reload方法加载账户信息，reload方法的实现如下：
func (ac *accountCache) reload() {
accounts, err := ac.scan()
if err != nil {
log.Debug("Failed to reload keystore contents", "err", err)
}
ac.all = accounts
sort.Sort(ac.all)
for k := range ac.byAddr {
delete(ac.byAddr, k)
}
for _, a := range accounts {
ac.byAddr[a.Address] = append(ac.byAddr[a.Address], a)
}
select {
case ac.notify <- struct{}{}:
default:
}
log.Debug("Reloaded keystore contents", "accounts", len(ac.all))
}
reload方法首先加载Account信息，然后通过channel的方式通知加载结束。Scan方法就是最终从文件中加载账户信息的地方，其实现如下：
func (ac *accountCache) scan() ([]accounts.Account, error) {
files, err := ioutil.ReadDir(ac.keydir)
if err != nil {
return nil, err
}
var (
buf = new(bufio.Reader)
addrs []accounts.Account
keyJSON struct {
Address string `json:"address"`
}
)
for _, fi := range files {
path := filepath.Join(ac.keydir, fi.Name())
if skipKeyFile(fi) {
log.Trace("Ignoring file on account scan", "path", path)
continue
}
logger := log.New("path", path)
fd, err := os.Open(path)
if err != nil {
logger.Trace("Failed to open keystore file", "err", err)
continue
}
buf.Reset(fd)
// Parse the address.
keyJSON.Address = ""
err = json.NewDecoder(buf).Decode(&keyJSON)
addr := common.HexToAddress(keyJSON.Address)
switch {
case err != nil:
logger.Debug("Failed to decode keystore key", "err", err)
case (addr == common.Address{}):
logger.Debug("Failed to decode keystore key", "err", "missing or zero address")
default:
addrs = append(addrs, accounts.Account{Address: addr, URL: accounts.URL{Scheme: KeyStoreScheme, Path: path}})
}
fd.Close()
}
return addrs, err
}
该方法首先获取该目录下的文件，然后读取文件内容，JSON解析其address字段。下面是我的datadir/keystore中文件的内容,格式化后如下：
{
"address":"a8f8687d0da839cef651cc0d2dc41bb2dc796293",
"crypto":{
"cipher":"aes-128-ctr",
"ciphertext":"142da6b140f5f4ddd48205997cfc6257312dde63e227579bdc a427a24661b9f8",
"cipherparams":{
"iv":"8d45e1d8b9fbd72fa40799c3a2ca1d22"
},
"kdf":"scrypt",
"kdfparams":{
"dklen":32,
"n":262144,
"p":1,
"r":8,
"salt":"68d9776e818a5c1a92982752df1b3c66fc54a804d508a926519d33e046158959"
},
"mac":"898b1f94fda7731215e521ea7ca7eb7d9afd9b8255c6dccd244c78af88123e7e"
},
"id":"dfefe914-e328-4f7f-89a7-a85689b8e855",
"version":3
}
从json可以看出我这里只有一个账户的信息，因为以太坊对于每个用户都创建一个单独的文件来保存其信息。对于账户信息的加载，AccountManager的创建我们分析完了，同时整个Node也创建完成，此时我们来看以太坊是如何启动一个节点的。此时回到main函数，startNode函数的代码如下：
func startNode(ctx *cli.Context, stack *node.Node) {
// Start up the node itself
utils.StartNode(stack)
// Unlock any account specifically requested
ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
passwords := utils.MakePasswordList(ctx)
unlocks := strings.Split(ctx.GlobalString(utils.UnlockedAccountFlag.Name), ",")
for i, account := range unlocks {
if trimmed := strings.TrimSpace(account); trimmed != "" {
unlockAccount(ctx, ks, trimmed, i, passwords)
}
}
// Register wallet event handlers to open and auto-derive wallets
events := make(chan accounts.WalletEvent, 16)
stack.AccountManager().Subscribe(events)
go func() {
// Create an chain state reader for self-derivation
rpcClient, err := stack.Attach()
if err != nil {
utils.Fatalf("Failed to attach to self: %v", err)
}
stateReader := ethclient.NewClient(rpcClient)
// Open and self derive any wallets already attached
for _, wallet := range stack.AccountManager().Wallets() {
if err := wallet.Open(""); err != nil {
log.Warn("Failed to open wallet", "url", wallet.URL(), "err", err)
} else {
wallet.SelfDerive(accounts.DefaultBaseDerivationPath, stateReader)
}
}
// Listen for wallet event till termination
for event := range events {
if event.Arrive {
if err := event.Wallet.Open(""); err != nil {
log.Warn("New wallet appeared, failed to open", "url", event.Wallet.URL(), "err", err)
} else {
log.Info("New wallet appeared", "url", event.Wallet.URL(), "status", event.Wallet.Status())
event.Wallet.SelfDerive(accounts.DefaultBaseDerivationPath, stateReader)
}
} else {
log.Info("Old wallet dropped", "url", event.Wallet.URL())
event.Wallet.Close()
}
}
}()
// Start auxiliary services if enabled
if ctx.GlobalBool(utils.MiningEnabledFlag.Name) {
// Mining only makes sense if a full Ethereum node is running
var ethereum *eth.Ethereum
if err := stack.Service(ðereum); err != nil {
utils.Fatalf("ethereum service not running: %v", err)
}
// Use a reduced number of threads if requested
if threads := ctx.GlobalInt(utils.MinerThreadsFlag.Name); threads > 0 {
type threaded interface {
SetThreads(threads int)
}
if th, ok := ethereum.Engine().(threaded); ok {
th.SetThreads(threads)
}
}
// Set the gas price to the limits from the CLI and start mining
ethereum.TxPool().SetGasPrice(utils.GlobalBig(ctx, utils.GasPriceFlag.Name))
if err := ethereum.StartMining(true); err != nil {
utils.Fatalf("Failed to start mining: %v", err)
}
}
}
该函数内部首先将节点启动起来，然后建立跟RPC Server建立一个连接，用于RPC通信。我们来看看节点如何启动起来的。/cmd/utils/cmd.go文件如下：
func StartNode(stack *node.Node) {
if err := stack.Start(); err != nil {
Fatalf("Error starting protocol stack: %v", err)
}
go func() {
sigc := make(chan os.Signal, 1)
signal.Notify(sigc, os.Interrupt)
defer signal.Stop(sigc)
<-sigc
log.Info("Got interrupt, shutting down...")
go stack.Stop()
for i := 10; i > 0; i-- {
<-sigc
if i > 1 {
log.Warn("Already shutting down, interrupt more to panic.", "times", i-1)
}
}
debug.Exit() // ensure trace and CPU profile data is flushed.
debug.LoudPanic("boom")
}()
}
该函数调用了Node.go中的start方法，其实现如下：
func (n *Node) Start() error {
n.lock.Lock()
defer n.lock.Unlock()
// Short circuit if the node's already running
if n.server != nil {
return ErrNodeRunning
}
if err := n.openDataDir(); err != nil {
return err
}
// Initialize the p2p server. This creates the node key and
// discovery databases.
n.serverConfig = n.config.P2P
n.serverConfig.PrivateKey = n.config.NodeKey()
n.serverConfig.Name = n.config.NodeName()
if n.serverConfig.StaticNodes == nil {
n.serverConfig.StaticNodes = n.config.StaticNodes()
}
if n.serverConfig.TrustedNodes == nil {
n.serverConfig.TrustedNodes = n.config.TrustedNodes()
}
if n.serverConfig.NodeDatabase == "" {
n.serverConfig.NodeDatabase = n.config.NodeDB()
}
running := &p2p.Server{Config: n.serverConfig}
log.Info("Starting peer-to-peer node", "instance", n.serverConfig.Name)
// Otherwise copy and specialize the P2P configuration
services := make(map[reflect.Type]Service)
for _, constructor := range n.serviceFuncs {
// Create a new context for the particular service
ctx := &ServiceContext{
config: n.config,
services: make(map[reflect.Type]Service),
EventMux: n.eventmux,
AccountManager: n.accman,
}
for kind, s := range services { // copy needed for threaded access
ctx.services[kind] = s
}
// Construct and save the service
service, err := constructor(ctx)
if err != nil {
return err
}
kind := reflect.TypeOf(service)
if _, exists := services[kind]; exists {
return &DuplicateServiceError{Kind: kind}
}
services[kind] = service
}
// Gather the protocols and start the freshly assembled P2P server
for _, service := range services {
running.Protocols = append(running.Protocols, service.Protocols()...)
}
if err := running.Start(); err != nil {
if errno, ok := err.(syscall.Errno); ok && datadirInUseErrnos[uint(errno)] {
return ErrDatadirUsed
}
return err
}
// Start each of the services
started := []reflect.Type{}
for kind, service := range services {
// Start the next service, stopping all previous upon failure
if err := service.Start(running); err != nil {
for _, kind := range started {
services[kind].Stop()
}
running.Stop()
return err
}
// Mark the service started for potential cleanup
started = append(started, kind)
}
// Lastly start the configured RPC interfaces
if err := n.startRPC(services); err != nil {
for _, service := range services {
service.Stop()
}
running.Stop()
return err
}
// Finish initializing the startup
n.services = services
n.server = running
n.stop = make(chan struct{})
return nil
}
该方法首先打开datadir目录，接着初始化serverConfig的相关配置，接着创建一个p2p.server的一个变量，然后启动该节点，在接着把RPC的Service启动起来，我们先看看节点的启动。/p2p/server.go中Start方法如下：
func (srv *Server) Start() (err error) {
srv.lock.Lock()
defer srv.lock.Unlock()
if srv.running {
return errors.New("server already running")
}
srv.running = true
log.Info("Starting P2P networking")
// static fields
if srv.PrivateKey == nil {
return fmt.Errorf("Server.PrivateKey must be set to a non-nil key")
}
if srv.newTransport == nil {
srv.newTransport = newRLPX
}
if srv.Dialer == nil {
srv.Dialer = &net.Dialer{Timeout: defaultDialTimeout}
}
srv.quit = make(chan struct{})
srv.addpeer = make(chan *conn)
srv.delpeer = make(chan peerDrop)
srv.posthandshake = make(chan *conn)
srv.addstatic = make(chan *discover.Node)
srv.removestatic = make(chan *discover.Node)
srv.peerOp = make(chan peerOpFunc)
srv.peerOpDone = make(chan struct{})
// node table
if !srv.NoDiscovery {
ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT, srv.NodeDatabase, srv.NetRestrict)
if err != nil {
return err
}
if err := ntab.SetFallbackNodes(srv.BootstrapNodes); err != nil {
return err
}
srv.ntab = ntab
}
if srv.DiscoveryV5 {
ntab, err := discv5.ListenUDP(srv.PrivateKey, srv.DiscoveryV5Addr, srv.NAT, "", srv.NetRestrict) //srv.NodeDatabase)
if err != nil {
return err
}
if err := ntab.SetFallbackNodes(srv.BootstrapNodesV5); err != nil {
return err
}
srv.DiscV5 = ntab
}
dynPeers := (srv.MaxPeers + 1) / 2
if srv.NoDiscovery {
dynPeers = 0
}
dialer := newDialState(srv.StaticNodes, srv.BootstrapNodes, srv.ntab, dynPeers, srv.NetRestrict)
// handshake
srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: discover.PubkeyID(&srv.PrivateKey.PublicKey)}
for _, p := range srv.Protocols {
srv.ourHandshake.Caps = append(srv.ourHandshake.Caps, p.cap())
}
// listen/dial
if srv.ListenAddr != "" {
if err := srv.startListening(); err != nil {
return err
}
}
if srv.NoDial && srv.ListenAddr == "" {
log.Warn("P2P server will be useless, neither dialing nor listening")
}
srv.loopWG.Add(1)
go srv.run(dialer)
srv.running = true
return nil
}
该方法首先建立一个UDP连接，并且调用server.run启动起来，跟其它可用的节点建立连接等。关于如何建立连接，后续在讲P2P的时候，我们再来仔细的分析。到此，整个节点就启动起来了。接下来，我们来看前面4个步骤中的第二个–创建console实例。console.go中创建一个console的New方法实现如下：
func New(config Config) (*Console, error) {
// Handle unset config values gracefully
if config.Prompter == nil {
config.Prompter = Stdin
}
if config.Prompt == "" {
config.Prompt = DefaultPrompt
}
if config.Printer == nil {
config.Printer = colorable.NewColorableStdout()
}
// Initialize the console and return
console := &Console{
client: config.Client,
jsre: jsre.New(config.DocRoot, config.Printer),
prompt: config.Prompt,
prompter: config.Prompter,
printer: config.Printer,
histPath: filepath.Join(config.DataDir, HistoryFile),
}
if err := console.init(config.Preload); err != nil {
return nil, err
}
return console, nil
}
该函数首先对Config做一些默认设置，接着调用其jsre.New函数，在借这个调用init方法初始化相关RPC API。jsre.New方法的实现如下：
func New(assetPath string, output io.Writer) *JSRE {
re := &JSRE{
assetPath: assetPath,
output: output,
closed: make(chan struct{}),
evalQueue: make(chan *evalReq),
stopEventLoop: make(chan bool),
}
go re.runEventLoop()
re.Set("loadScript", re.loadScript)
re.Set("inspect", re.prettyPrintJS)
return re
}
该函数创建一个JSRE的变量然后使用goroutine的方式开启一个事件监听的循环，该事件为控制台输入后，经过一些处理通过channel的方式发送过来。具体接收到的命令后续处理，请读者自己跟踪其逻辑实现。总结下创建console的目的主要是监听控制台输入的命名。接下来我们来看看第三个步骤「显示Welcome信息 」，该信息在通过geth进入控制台的时候，会显示一些简单的信息，我们先来看看该函数的实现：
func (c *Console) Welcome() {
// Print some generic Geth metadata
fmt.Fprintf(c.printer, "Welcome to the Geth JavaScript console!\n\n")
c.jsre.Run(`
console.log("instance: " + web3.version.node);
console.log("coinbase: " + eth.coinbase);
console.log("at block: " + eth.blockNumber + " (" + new Date(1000 * eth.getBlock(eth.blockNumber).timestamp) + ")");
console.log(" datadir: " + admin.datadir);
`)
// List all the supported modules for the user to call
if apis, err := c.client.SupportedModules(); err == nil {
modules := make([]string, 0, len(apis))
for api, version := range apis {
modules = append(modules, fmt.Sprintf("%s:%s", api, version))
}
sort.Strings(modules)
fmt.Fprintln(c.printer, " modules:", strings.Join(modules, " "))
}
fmt.Fprintln(c.printer)
}
该方法首先打印「Welcome to the Geth JavaScript console!」信息，这个可以直接在控制台查看到，接着使用上面创建console的jsre执行四个控制台输出写版本、区块等信息。你可以直接复制出来在命令行执行，也能看到相同的结果。
接下来，我们来看最后的一个步骤「创建一个无限循环用于在控制台交互」，该函数的实现如下：
func (c *Console) Interactive() {
var (
prompt = c.prompt // Current prompt line (used for multi-line inputs)
indents = 0 // Current number of input indents (used for multi-line inputs)
input = "" // Current user input
scheduler = make(chan string) // Channel to send the next prompt on and receive the input
)
// Start a goroutine to listen for promt requests and send back inputs
go func() {
for {
// Read the next user input
line, err := c.prompter.PromptInput(<-scheduler)
if err != nil {
// In case of an error, either clear the prompt or fail
if err == liner.ErrPromptAborted { // ctrl-C
prompt, indents, input = c.prompt, 0, ""
scheduler <- ""
continue
}
close(scheduler)
return
}
// User input retrieved, send for interpretation and loop
scheduler <- line
}
}()
// Monitor Ctrl-C too in case the input is empty and we need to bail
abort := make(chan os.Signal, 1)
signal.Notify(abort, os.Interrupt)
// Start sending prompts to the user and reading back inputs
for {
// Send the next prompt, triggering an input read and process the result
scheduler <- prompt
select {
case <-abort:
// User forcefully quite the console
fmt.Fprintln(c.printer, "caught interrupt, exiting")
return
case line, ok := <-scheduler:
// User input was returned by the prompter, handle special cases
if !ok || (indents <= 0 && exit.MatchString(line)) {
return
}
if onlyWhitespace.MatchString(line) {
continue
}
// Append the line to the input and check for multi-line interpretation
input += line + "\n"
indents = countIndents(input)
if indents <= 0 {
prompt = c.prompt
} else {
prompt = strings.Repeat(".", indents*3) + " "
}
// If all the needed lines are present, save the command and run
if indents <= 0 {
if len(input) > 0 && input[0] != ' ' && !passwordRegexp.MatchString(input) {
if command := strings.TrimSpace(input); len(c.history) == 0 || command != c.history[len(c.history)-1] {
c.history = append(c.history, command)
if c.prompter != nil {
c.prompter.AppendHistory(command)
}
}
}
c.Evaluate(input)
input = ""
}
}
}
}