github.com/linapex/ethereum-dpos-chinese@v0.0.0-20190316121959-b78b3a4a1ece/p2p/simulations/adapters/exec.go

//<developer>
//    <name>linapex 曹一峰</name>
//    <email>linapex@163.com</email>
//    <wx>superexc</wx>
//    <qqgroup>128148617</qqgroup>
//    <url>https://jsq.ink</url>
//    <role>pku engineer</role>
//    <date>2019-03-16 12:09:44</date>
//</624342660601090048>


package adapters

import (
	"bufio"
	"context"
	"crypto/ecdsa"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"os/exec"
	"os/signal"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/docker/docker/pkg/reexec"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/node"
	"github.com/ethereum/go-ethereum/p2p"
	"github.com/ethereum/go-ethereum/p2p/discover"
	"github.com/ethereum/go-ethereum/rpc"
	"golang.org/x/net/websocket"
)

//Execadapter是一个节点适配器，通过执行
//当前二进制文件作为子进程。
//
//使用init钩子以便子进程执行节点服务
//（而不是main（）函数通常执行的操作），请参见
//有关详细信息，请参阅execp2pnode函数。
type ExecAdapter struct {
//basedir是每个目录下的数据目录
//创建模拟节点。
	BaseDir string

	nodes map[discover.NodeID]*ExecNode
}

//newexecadapter返回一个execadapter，该execadapter将节点数据存储在
//给定基目录的子目录
func NewExecAdapter(baseDir string) *ExecAdapter {
	return &ExecAdapter{
		BaseDir: baseDir,
		nodes:   make(map[discover.NodeID]*ExecNode),
	}
}

//name返回用于日志记录的适配器的名称
func (e *ExecAdapter) Name() string {
	return "exec-adapter"
}

//newnode使用给定的配置返回新的execnode
func (e *ExecAdapter) NewNode(config *NodeConfig) (Node, error) {
	if len(config.Services) == 0 {
		return nil, errors.New("node must have at least one service")
	}
	for _, service := range config.Services {
		if _, exists := serviceFuncs[service]; !exists {
			return nil, fmt.Errorf("unknown node service %q", service)
		}
	}

//使用ID的前12个字符创建节点目录
//因为unix套接字路径不能超过256个字符
	dir := filepath.Join(e.BaseDir, config.ID.String()[:12])
	if err := os.Mkdir(dir, 0755); err != nil {
		return nil, fmt.Errorf("error creating node directory: %s", err)
	}

//生成配置
	conf := &execNodeConfig{
		Stack: node.DefaultConfig,
		Node:  config,
	}
	conf.Stack.DataDir = filepath.Join(dir, "data")
	conf.Stack.WSHost = "127.0.0.1"
	conf.Stack.WSPort = 0
	conf.Stack.WSOrigins = []string{"*"}
	conf.Stack.WSExposeAll = true
	conf.Stack.P2P.EnableMsgEvents = false
	conf.Stack.P2P.NoDiscovery = true
	conf.Stack.P2P.NAT = nil
	conf.Stack.NoUSB = true

//监听本地主机端口，当我们
//初始化nodeconfig（通常是随机端口）
	conf.Stack.P2P.ListenAddr = fmt.Sprintf(":%d", config.Port)

	node := &ExecNode{
		ID:      config.ID,
		Dir:     dir,
		Config:  conf,
		adapter: e,
	}
	node.newCmd = node.execCommand
	e.nodes[node.ID] = node
	return node, nil
}

//exec node通过执行当前二进制文件和
//运行配置的服务
type ExecNode struct {
	ID     discover.NodeID
	Dir    string
	Config *execNodeConfig
	Cmd    *exec.Cmd
	Info   *p2p.NodeInfo

	adapter *ExecAdapter
	client  *rpc.Client
	wsAddr  string
	newCmd  func() *exec.Cmd
	key     *ecdsa.PrivateKey
}

//addr返回节点的enode url
func (n *ExecNode) Addr() []byte {
	if n.Info == nil {
		return nil
	}
	return []byte(n.Info.Enode)
}

//客户端返回一个rpc.client，可用于与
//基础服务（节点启动后设置）
func (n *ExecNode) Client() (*rpc.Client, error) {
	return n.client, nil
}

//start exec是将ID和服务作为命令行参数传递的节点
//节点配置在节点配置环境中编码为json
//变量
func (n *ExecNode) Start(snapshots map[string][]byte) (err error) {
	if n.Cmd != nil {
		return errors.New("already started")
	}
	defer func() {
		if err != nil {
			log.Error("node failed to start", "err", err)
			n.Stop()
		}
	}()

//对包含快照的配置副本进行编码
	confCopy := *n.Config
	confCopy.Snapshots = snapshots
	confCopy.PeerAddrs = make(map[string]string)
	for id, node := range n.adapter.nodes {
		confCopy.PeerAddrs[id.String()] = node.wsAddr
	}
	confData, err := json.Marshal(confCopy)
	if err != nil {
		return fmt.Errorf("error generating node config: %s", err)
	}

//为stderr使用管道，这样我们都可以将节点的stderr复制到
//os.stderr并从日志中读取websocket地址
	stderrR, stderrW := io.Pipe()
	stderr := io.MultiWriter(os.Stderr, stderrW)

//启动节点
	cmd := n.newCmd()
	cmd.Stdout = os.Stdout
	cmd.Stderr = stderr
	cmd.Env = append(os.Environ(), fmt.Sprintf("_P2P_NODE_CONFIG=%s", confData))
	if err := cmd.Start(); err != nil {
		return fmt.Errorf("error starting node: %s", err)
	}
	n.Cmd = cmd

//从stderr日志中读取websocket地址
	var wsAddr string
	wsAddrC := make(chan string)
	go func() {
		s := bufio.NewScanner(stderrR)
		for s.Scan() {
			if strings.Contains(s.Text(), "WebSocket endpoint opened") {
				wsAddrC <- wsAddrPattern.FindString(s.Text())
			}
		}
	}()
	select {
	case wsAddr = <-wsAddrC:
		if wsAddr == "" {
			return errors.New("failed to read WebSocket address from stderr")
		}
	case <-time.After(10 * time.Second):
		return errors.New("timed out waiting for WebSocket address on stderr")
	}

//创建RPC客户端并加载节点信息
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	client, err := rpc.DialWebsocket(ctx, wsAddr, "")
	if err != nil {
		return fmt.Errorf("error dialing rpc websocket: %s", err)
	}
	var info p2p.NodeInfo
	if err := client.CallContext(ctx, &info, "admin_nodeInfo"); err != nil {
		return fmt.Errorf("error getting node info: %s", err)
	}
	n.client = client
	n.wsAddr = wsAddr
	n.Info = &info

	return nil
}

//exec command返回一个命令，该命令通过exeng在本地运行节点
//当前二进制文件，但将argv[0]设置为“p2p node”，以便子级
//运行execp2pnode
func (n *ExecNode) execCommand() *exec.Cmd {
	return &exec.Cmd{
		Path: reexec.Self(),
		Args: []string{"p2p-node", strings.Join(n.Config.Node.Services, ","), n.ID.String()},
	}
}

//stop首先发送sigterm，然后在节点
//在5秒内没有停止
func (n *ExecNode) Stop() error {
	if n.Cmd == nil {
		return nil
	}
	defer func() {
		n.Cmd = nil
	}()

	if n.client != nil {
		n.client.Close()
		n.client = nil
		n.wsAddr = ""
		n.Info = nil
	}

	if err := n.Cmd.Process.Signal(syscall.SIGTERM); err != nil {
		return n.Cmd.Process.Kill()
	}
	waitErr := make(chan error)
	go func() {
		waitErr <- n.Cmd.Wait()
	}()
	select {
	case err := <-waitErr:
		return err
	case <-time.After(5 * time.Second):
		return n.Cmd.Process.Kill()
	}
}

//nodeinfo返回有关节点的信息
func (n *ExecNode) NodeInfo() *p2p.NodeInfo {
	info := &p2p.NodeInfo{
		ID: n.ID.String(),
	}
	if n.client != nil {
		n.client.Call(&info, "admin_nodeInfo")
	}
	return info
}

//serverpc通过拨
//节点的WebSocket地址和连接两个连接
func (n *ExecNode) ServeRPC(clientConn net.Conn) error {
conn, err := websocket.Dial(n.wsAddr, "", "http://“本地主机”
	if err != nil {
		return err
	}
	var wg sync.WaitGroup
	wg.Add(2)
	join := func(src, dst net.Conn) {
		defer wg.Done()
		io.Copy(dst, src)
//关闭目标连接的写入端
		if cw, ok := dst.(interface {
			CloseWrite() error
		}); ok {
			cw.CloseWrite()
		} else {
			dst.Close()
		}
	}
	go join(conn, clientConn)
	go join(clientConn, conn)
	wg.Wait()
	return nil
}

//快照通过调用
//模拟快照RPC方法
func (n *ExecNode) Snapshots() (map[string][]byte, error) {
	if n.client == nil {
		return nil, errors.New("RPC not started")
	}
	var snapshots map[string][]byte
	return snapshots, n.client.Call(&snapshots, "simulation_snapshot")
}

func init() {
//注册reexec函数以在当前
//二进制作为“p2p节点”执行
	reexec.Register("p2p-node", execP2PNode)
}

//ExecOnDeconfig用于序列化节点配置，以便
//作为JSON编码的环境变量传递给子进程
type execNodeConfig struct {
	Stack     node.Config       `json:"stack"`
	Node      *NodeConfig       `json:"node"`
	Snapshots map[string][]byte `json:"snapshots,omitempty"`
	PeerAddrs map[string]string `json:"peer_addrs,omitempty"`
}

//ExternalIP获取外部IP地址，以便enode url可用
func ExternalIP() net.IP {
	addrs, err := net.InterfaceAddrs()
	if err != nil {
		log.Crit("error getting IP address", "err", err)
	}
	for _, addr := range addrs {
		if ip, ok := addr.(*net.IPNet); ok && !ip.IP.IsLoopback() && !ip.IP.IsLinkLocalUnicast() {
			return ip.IP
		}
	}
	log.Warn("unable to determine explicit IP address, falling back to loopback")
	return net.IP{127, 0, 0, 1}
}

//执行当前二进制文件时，execp2pnode启动devp2p节点
//argv[0]为“p2p节点”，从argv[1]/argv[2]读取服务/id
//以及_p2p_node_config环境变量中的节点配置
func execP2PNode() {
	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.LogfmtFormat()))
	glogger.Verbosity(log.LvlInfo)
	log.Root().SetHandler(glogger)

//从argv读取服务
	serviceNames := strings.Split(os.Args[1], ",")

//解码配置
	confEnv := os.Getenv("_P2P_NODE_CONFIG")
	if confEnv == "" {
		log.Crit("missing _P2P_NODE_CONFIG")
	}
	var conf execNodeConfig
	if err := json.Unmarshal([]byte(confEnv), &conf); err != nil {
		log.Crit("error decoding _P2P_NODE_CONFIG", "err", err)
	}
	conf.Stack.P2P.PrivateKey = conf.Node.PrivateKey
	conf.Stack.Logger = log.New("node.id", conf.Node.ID.String())

	if strings.HasPrefix(conf.Stack.P2P.ListenAddr, ":") {
		conf.Stack.P2P.ListenAddr = ExternalIP().String() + conf.Stack.P2P.ListenAddr
	}
	if conf.Stack.WSHost == "0.0.0.0" {
		conf.Stack.WSHost = ExternalIP().String()
	}

//初始化devp2p堆栈
	stack, err := node.New(&conf.Stack)
	if err != nil {
		log.Crit("error creating node stack", "err", err)
	}

//注册服务，将它们收集到地图中，以便我们可以包装
//它们在快照服务中
	services := make(map[string]node.Service, len(serviceNames))
	for _, name := range serviceNames {
		serviceFunc, exists := serviceFuncs[name]
		if !exists {
			log.Crit("unknown node service", "name", name)
		}
		constructor := func(nodeCtx *node.ServiceContext) (node.Service, error) {
			ctx := &ServiceContext{
				RPCDialer:   &wsRPCDialer{addrs: conf.PeerAddrs},
				NodeContext: nodeCtx,
				Config:      conf.Node,
			}
			if conf.Snapshots != nil {
				ctx.Snapshot = conf.Snapshots[name]
			}
			service, err := serviceFunc(ctx)
			if err != nil {
				return nil, err
			}
			services[name] = service
			return service, nil
		}
		if err := stack.Register(constructor); err != nil {
			log.Crit("error starting service", "name", name, "err", err)
		}
	}

//注册快照服务
	if err := stack.Register(func(ctx *node.ServiceContext) (node.Service, error) {
		return &snapshotService{services}, nil
	}); err != nil {
		log.Crit("error starting snapshot service", "err", err)
	}

//启动堆栈
	if err := stack.Start(); err != nil {
		log.Crit("error stating node stack", "err", err)
	}

//如果我们得到一个sigterm信号，就停止堆栈
	go func() {
		sigc := make(chan os.Signal, 1)
		signal.Notify(sigc, syscall.SIGTERM)
		defer signal.Stop(sigc)
		<-sigc
		log.Info("Received SIGTERM, shutting down...")
		stack.Stop()
	}()

//等待堆栈退出
	stack.Wait()
}

//SnapshotService是一个node.service，它包装了服务列表和
//公开API以生成这些服务的快照
type snapshotService struct {
	services map[string]node.Service
}

func (s *snapshotService) APIs() []rpc.API {
	return []rpc.API{{
		Namespace: "simulation",
		Version:   "1.0",
		Service:   SnapshotAPI{s.services},
	}}
}

func (s *snapshotService) Protocols() []p2p.Protocol {
	return nil
}

func (s *snapshotService) Start(*p2p.Server) error {
	return nil
}

func (s *snapshotService) Stop() error {
	return nil
}

//Snapshotapi提供了一个RPC方法来创建服务的快照
type SnapshotAPI struct {
	services map[string]node.Service
}

func (api SnapshotAPI) Snapshot() (map[string][]byte, error) {
	snapshots := make(map[string][]byte)
	for name, service := range api.services {
		if s, ok := service.(interface {
			Snapshot() ([]byte, error)
		}); ok {
			snap, err := s.Snapshot()
			if err != nil {
				return nil, err
			}
			snapshots[name] = snap
		}
	}
	return snapshots, nil
}

type wsRPCDialer struct {
	addrs map[string]string
}

//DialRPC通过创建WebSocket RPC来实现RpcDialer接口
//给定节点的客户端
func (w *wsRPCDialer) DialRPC(id discover.NodeID) (*rpc.Client, error) {
	addr, ok := w.addrs[id.String()]
	if !ok {
		return nil, fmt.Errorf("unknown node: %s", id)
	}
return rpc.DialWebsocket(context.Background(), addr, "http://“本地主机”
}