path: root/node/node.go

// Copyright 2015 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 node represents the Ethereum protocol stack container.
package node

import (
    "errors"
    "os"
    "path/filepath"
    "reflect"
    "sync"
    "syscall"

    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/p2p"
)

var (
    ErrDatadirUsed    = errors.New("datadir already used")
    ErrNodeStopped    = errors.New("node not started")
    ErrNodeRunning    = errors.New("node already running")
    ErrServiceUnknown = errors.New("unknown service")

    datadirInUseErrnos = map[uint]bool{11: true, 32: true, 35: true}
)

// Node represents a P2P node into which arbitrary (uniquely typed) services might
// be registered.
type Node struct {
    datadir  string         // Path to the currently used data directory
    eventmux *event.TypeMux // Event multiplexer used between the services of a stack

    serverConfig *p2p.Server // Configuration of the underlying P2P networking layer
    server       *p2p.Server // Currently running P2P networking layer

    serviceFuncs []ServiceConstructor     // Service constructors (in dependency order)
    services     map[reflect.Type]Service // Currently running services

    stop chan struct{} // Channel to wait for termination notifications
    lock sync.RWMutex
}

// New creates a new P2P node, ready for protocol registration.
func New(conf *Config) (*Node, error) {
    // Ensure the data directory exists, failing if it cannot be created
    if conf.DataDir != "" {
        if err := os.MkdirAll(conf.DataDir, 0700); err != nil {
            return nil, err
        }
    }
    // Assemble the networking layer and the node itself
    nodeDbPath := ""
    if conf.DataDir != "" {
        nodeDbPath = filepath.Join(conf.DataDir, datadirNodeDatabase)
    }
    return &Node{
        datadir: conf.DataDir,
        serverConfig: &p2p.Server{
            PrivateKey:      conf.NodeKey(),
            Name:            conf.Name,
            Discovery:       !conf.NoDiscovery,
            BootstrapNodes:  conf.BootstrapNodes,
            StaticNodes:     conf.StaticNodes(),
            TrustedNodes:    conf.TrusterNodes(),
            NodeDatabase:    nodeDbPath,
            ListenAddr:      conf.ListenAddr,
            NAT:             conf.NAT,
            Dialer:          conf.Dialer,
            NoDial:          conf.NoDial,
            MaxPeers:        conf.MaxPeers,
            MaxPendingPeers: conf.MaxPendingPeers,
        },
        serviceFuncs: []ServiceConstructor{},
        eventmux:     new(event.TypeMux),
    }, nil
}

// Register injects a new service into the node's stack. The service created by
// the passed constructor must be unique in its type with regard to sibling ones.
func (n *Node) Register(constructor ServiceConstructor) error {
    n.lock.Lock()
    defer n.lock.Unlock()

    if n.server != nil {
        return ErrNodeRunning
    }
    n.serviceFuncs = append(n.serviceFuncs, constructor)
    return nil
}

// Start create a live P2P node and starts running it.
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
    }
    // Otherwise copy and specialize the P2P configuration
    running := new(p2p.Server)
    *running = *n.serverConfig

    services := make(map[reflect.Type]Service)
    for _, constructor := range n.serviceFuncs {
        // Create a new context for the particular service
        ctx := &ServiceContext{
            datadir:  n.datadir,
            services: make(map[reflect.Type]Service),
            EventMux: n.eventmux,
        }
        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)
    }
    // Finish initializing the startup
    n.services = services
    n.server = running
    n.stop = make(chan struct{})

    return nil
}

// Stop terminates a running node along with all it's services. In the node was
// not started, an error is returned.
func (n *Node) Stop() error {
    n.lock.Lock()
    defer n.lock.Unlock()

    // Short circuit if the node's not running
    if n.server == nil {
        return ErrNodeStopped
    }
    // Otherwise terminate all the services and the P2P server too
    failure := &StopError{
        Services: make(map[reflect.Type]error),
    }
    for kind, service := range n.services {
        if err := service.Stop(); err != nil {
            failure.Services[kind] = err
        }
    }
    n.server.Stop()

    n.services = nil
    n.server = nil
    close(n.stop)

    if len(failure.Services) > 0 {
        return failure
    }
    return nil
}

// Wait blocks the thread until the node is stopped. If the node is not running
// at the time of invocation, the method immediately returns.
func (n *Node) Wait() {
    n.lock.RLock()
    if n.server == nil {
        return
    }
    stop := n.stop
    n.lock.RUnlock()

    <-stop
}

// Restart terminates a running node and boots up a new one in its place. If the
// node isn't running, an error is returned.
func (n *Node) Restart() error {
    if err := n.Stop(); err != nil {
        return err
    }
    if err := n.Start(); err != nil {
        return err
    }
    return nil
}

// Server retrieves the currently running P2P network layer. This method is meant
// only to inspect fields of the currently running server, life cycle management
// should be left to this Node entity.
func (n *Node) Server() *p2p.Server {
    n.lock.RLock()
    defer n.lock.RUnlock()

    return n.server
}

// Service retrieves a currently running service registered of a specific type.
func (n *Node) Service(service interface{}) error {
    n.lock.RLock()
    defer n.lock.RUnlock()

    // Short circuit if the node's not running
    if n.server == nil {
        return ErrNodeStopped
    }
    // Otherwise try to find the service to return
    element := reflect.ValueOf(service).Elem()
    if running, ok := n.services[element.Type()]; ok {
        element.Set(reflect.ValueOf(running))
        return nil
    }
    return ErrServiceUnknown
}

// DataDir retrieves the current datadir used by the protocol stack.
func (n *Node) DataDir() string {
    return n.datadir
}

// EventMux retrieves the event multiplexer used by all the network services in
// the current protocol stack.
func (n *Node) EventMux() *event.TypeMux {
    return n.eventmux
}