Geth启动流程代码解析(完整解析）

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); e