path: root/p2p/simulations/adapters/exec.go

// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package adapters

import (
    "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 is a NodeAdapter which runs simulation nodes by executing the
// current binary as a child process.
//
// An init hook is used so that the child process executes the node services
// (rather than whataver the main() function would normally do), see the
// execP2PNode function for more information.
type ExecAdapter struct {
    // BaseDir is the directory under which the data directories for each
    // simulation node are created.
    BaseDir string

    nodes map[discover.NodeID]*ExecNode
}

// NewExecAdapter returns an ExecAdapter which stores node data in
// subdirectories of the given base directory
func NewExecAdapter(baseDir string) *ExecAdapter {
    return &ExecAdapter{
        BaseDir: baseDir,
        nodes:   make(map[discover.NodeID]*ExecNode),
    }
}

// Name returns the name of the adapter for logging purposes
func (e *ExecAdapter) Name() string {
    return "exec-adapter"
}

// NewNode returns a new ExecNode using the given config
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)
        }
    }

    // create the node directory using the first 12 characters of the ID
    // as Unix socket paths cannot be longer than 256 characters
    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)
    }

    // generate the config
    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

    // listen on a random localhost port (we'll get the actual port after
    // starting the node through the RPC admin.nodeInfo method)
    conf.Stack.P2P.ListenAddr = "127.0.0.1:0"

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

// ExecNode starts a simulation node by exec'ing the current binary and
// running the configured services
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 returns the node's enode URL
func (n *ExecNode) Addr() []byte {
    if n.Info == nil {
        return nil
    }
    return []byte(n.Info.Enode)
}

// Client returns an rpc.Client which can be used to communicate with the
// underlying services (it is set once the node has started)
func (n *ExecNode) Client() (*rpc.Client, error) {
    return n.client, nil
}

// Start exec's the node passing the ID and service as command line arguments
// and the node config encoded as JSON in the _P2P_NODE_CONFIG environment
// variable
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()
        }
    }()

    // encode a copy of the config containing the snapshot
    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)
    }

    // use a pipe for stderr so we can both copy the node's stderr to
    // os.Stderr and read the WebSocket address from the logs
    stderrR, stderrW := io.Pipe()
    stderr := io.MultiWriter(os.Stderr, stderrW)

    // start the node
    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

    // read the WebSocket address from the stderr logs
    wsAddr, err := findWSAddr(stderrR, 10*time.Second)
    if err != nil {
        return fmt.Errorf("error getting WebSocket address: %s", err)
    }

    // create the RPC client and load the node info
    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
}

// execCommand returns a command which runs the node locally by exec'ing
// the current binary but setting argv[0] to "p2p-node" so that the child
// runs 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 stops the node by first sending SIGTERM and then SIGKILL if the node
// doesn't stop within 5s
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 returns information about the node
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 serves RPC requests over the given connection by dialling the
// node's WebSocket address and joining the two connections
func (n *ExecNode) ServeRPC(clientConn net.Conn) error {
    conn, err := websocket.Dial(n.wsAddr, "", "http://localhost")
    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)
        // close the write end of the destination connection
        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
}

// Snapshots creates snapshots of the services by calling the
// simulation_snapshot RPC method
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() {
    // register a reexec function to start a devp2p node when the current
    // binary is executed as "p2p-node"
    reexec.Register("p2p-node", execP2PNode)
}

// execNodeConfig is used to serialize the node configuration so it can be
// passed to the child process as a JSON encoded environment variable
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"`
}

// execP2PNode starts a devp2p node when the current binary is executed with
// argv[0] being "p2p-node", reading the service / ID from argv[1] / argv[2]
// and the node config from the _P2P_NODE_CONFIG environment variable
func execP2PNode() {
    glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.LogfmtFormat()))
    glogger.Verbosity(log.LvlInfo)
    log.Root().SetHandler(glogger)

    // read the services from argv
    serviceNames := strings.Split(os.Args[1], ",")

    // decode the config
    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())

    // use explicit IP address in ListenAddr so that Enode URL is usable
    externalIP := func() string {
        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() {
                return ip.IP.String()
            }
        }
        log.Crit("unable to determine explicit IP address")
        return ""
    }
    if strings.HasPrefix(conf.Stack.P2P.ListenAddr, ":") {
        conf.Stack.P2P.ListenAddr = externalIP() + conf.Stack.P2P.ListenAddr
    }
    if conf.Stack.WSHost == "0.0.0.0" {
        conf.Stack.WSHost = externalIP()
    }

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

    // register the services, collecting them into a map so we can wrap
    // them in a snapshot service
    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)
        }
    }

    // register the snapshot service
    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)
    }

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

    // stop the stack if we get a SIGTERM signal
    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()
    }()

    // wait for the stack to exit
    stack.Wait()
}

// snapshotService is a node.Service which wraps a list of services and
// exposes an API to generate a snapshot of those services
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 provides an RPC method to create snapshots of services
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 implements the RPCDialer interface by creating a WebSocket RPC
// client of the given node
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://localhost")
}