node: customizable protocol and service stacks

9 files changed, 1313 insertions, 0 deletions

diff --git a/node/config.go b/node/config.go
new file mode 100644
index 000000000..93f0ba79d
--- /dev/null
+++ b/node/config.go
@@ -0,0 +1,171 @@
+// 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
+
+import (
+	"crypto/ecdsa"
+	"encoding/json"
+	"io/ioutil"
+	"net"
+	"os"
+	"path/filepath"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/p2p/nat"
+)
+
+var (
+	datadirPrivateKey   = "nodekey"            // Path within the datadir to the node's private key
+	datadirStaticNodes  = "static-nodes.json"  // Path within the datadir to the static node list
+	datadirTrustedNodes = "trusted-nodes.json" // Path within the datadir to the trusted node list
+	datadirNodeDatabase = "nodes"              // Path within the datadir to store the node infos
+)
+
+// Config represents a small collection of configuration values to fine tune the
+// P2P network layer of a protocol stack. These values can be further extended by
+// all registered services.
+type Config struct {
+	// DataDir is the file system folder the node should use for any data storage
+	// requirements. The configured data directory will not be directly shared with
+	// registered services, instead those can use utility methods to create/access
+	// databases or flat files. This enables ephemeral nodes which can fully reside
+	// in memory.
+	DataDir string
+
+	// This field should be a valid secp256k1 private key that will be used for both
+	// remote peer identification as well as network traffic encryption. If no key
+	// is configured, the preset one is loaded from the data dir, generating it if
+	// needed.
+	PrivateKey *ecdsa.PrivateKey
+
+	// Name sets the node name of this server. Use common.MakeName to create a name
+	// that follows existing conventions.
+	Name string
+
+	// NoDiscovery specifies whether the peer discovery mechanism should be started
+	// or not. Disabling is usually useful for protocol debugging (manual topology).
+	NoDiscovery bool
+
+	// Bootstrap nodes used to establish connectivity with the rest of the network.
+	BootstrapNodes []*discover.Node
+
+	// Network interface address on which the node should listen for inbound peers.
+	ListenAddr string
+
+	// If set to a non-nil value, the given NAT port mapper is used to make the
+	// listening port available to the Internet.
+	NAT nat.Interface
+
+	// If Dialer is set to a non-nil value, the given Dialer is used to dial outbound
+	// peer connections.
+	Dialer *net.Dialer
+
+	// If NoDial is true, the node will not dial any peers.
+	NoDial bool
+
+	// MaxPeers is the maximum number of peers that can be connected. If this is
+	// set to zero, then only the configured static and trusted peers can connect.
+	MaxPeers int
+
+	// MaxPendingPeers is the maximum number of peers that can be pending in the
+	// handshake phase, counted separately for inbound and outbound connections.
+	// Zero defaults to preset values.
+	MaxPendingPeers int
+}
+
+// NodeKey retrieves the currently configured private key of the node, checking
+// first any manually set key, falling back to the one found in the configured
+// data folder. If no key can be found, a new one is generated.
+func (c *Config) NodeKey() *ecdsa.PrivateKey {
+	// Use any specifically configured key
+	if c.PrivateKey != nil {
+		return c.PrivateKey
+	}
+	// Generate ephemeral key if no datadir is being used
+	if c.DataDir == "" {
+		key, err := crypto.GenerateKey()
+		if err != nil {
+			glog.Fatalf("Failed to generate ephemeral node key: %v", err)
+		}
+		return key
+	}
+	// Fall back to persistent key from the data directory
+	keyfile := filepath.Join(c.DataDir, datadirPrivateKey)
+	if key, err := crypto.LoadECDSA(keyfile); err == nil {
+		return key
+	}
+	// No persistent key found, generate and store a new one
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		glog.Fatalf("Failed to generate node key: %v", err)
+	}
+	if err := crypto.SaveECDSA(keyfile, key); err != nil {
+		glog.V(logger.Error).Infof("Failed to persist node key: %v", err)
+	}
+	return key
+}
+
+// StaticNodes returns a list of node enode URLs configured as static nodes.
+func (c *Config) StaticNodes() []*discover.Node {
+	return c.parsePersistentNodes(datadirStaticNodes)
+}
+
+// TrusterNodes returns a list of node enode URLs configured as trusted nodes.
+func (c *Config) TrusterNodes() []*discover.Node {
+	return c.parsePersistentNodes(datadirTrustedNodes)
+}
+
+// parsePersistentNodes parses a list of discovery node URLs loaded from a .json
+// file from within the data directory.
+func (c *Config) parsePersistentNodes(file string) []*discover.Node {
+	// Short circuit if no node config is present
+	if c.DataDir == "" {
+		return nil
+	}
+	path := filepath.Join(c.DataDir, file)
+	if _, err := os.Stat(path); err != nil {
+		return nil
+	}
+	// Load the nodes from the config file
+	blob, err := ioutil.ReadFile(path)
+	if err != nil {
+		glog.V(logger.Error).Infof("Failed to access nodes: %v", err)
+		return nil
+	}
+	nodelist := []string{}
+	if err := json.Unmarshal(blob, &nodelist); err != nil {
+		glog.V(logger.Error).Infof("Failed to load nodes: %v", err)
+		return nil
+	}
+	// Interpret the list as a discovery node array
+	var nodes []*discover.Node
+	for _, url := range nodelist {
+		if url == "" {
+			continue
+		}
+		node, err := discover.ParseNode(url)
+		if err != nil {
+			glog.V(logger.Error).Infof("Node URL %s: %v\n", url, err)
+			continue
+		}
+		nodes = append(nodes, node)
+	}
+	return nodes
+}
diff --git a/node/config_test.go b/node/config_test.go
new file mode 100644
index 000000000..f59f3c0fe
--- /dev/null
+++ b/node/config_test.go
@@ -0,0 +1,120 @@
+// 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
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// Tests that datadirs can be successfully created, be them manually configured
+// ones or automatically generated temporary ones.
+func TestDatadirCreation(t *testing.T) {
+	// Create a temporary data dir and check that it can be used by a node
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create manual data dir: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	if _, err := New(&Config{DataDir: dir}); err != nil {
+		t.Fatalf("failed to create stack with existing datadir: %v", err)
+	}
+	// Generate a long non-existing datadir path and check that it gets created by a node
+	dir = filepath.Join(dir, "a", "b", "c", "d", "e", "f")
+	if _, err := New(&Config{DataDir: dir}); err != nil {
+		t.Fatalf("failed to create stack with creatable datadir: %v", err)
+	}
+	if _, err := os.Stat(dir); err != nil {
+		t.Fatalf("freshly created datadir not accessible: %v", err)
+	}
+	// Verify that an impossible datadir fails creation
+	file, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatalf("failed to create temporary file: %v", err)
+	}
+	defer os.Remove(file.Name())
+
+	dir = filepath.Join(file.Name(), "invalid/path")
+	if _, err := New(&Config{DataDir: dir}); err == nil {
+		t.Fatalf("protocol stack created with an invalid datadir")
+	}
+}
+
+// Tests that node keys can be correctly created, persisted, loaded and/or made
+// ephemeral.
+func TestNodeKeyPersistency(t *testing.T) {
+	// Create a temporary folder and make sure no key is present
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temporary data directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	if _, err := os.Stat(filepath.Join(dir, datadirPrivateKey)); err == nil {
+		t.Fatalf("non-created node key already exists")
+	}
+	// Configure a node with a preset key and ensure it's not persisted
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		t.Fatalf("failed to generate one-shot node key: %v", err)
+	}
+	if _, err := New(&Config{DataDir: dir, PrivateKey: key}); err != nil {
+		t.Fatalf("failed to create empty stack: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, datadirPrivateKey)); err == nil {
+		t.Fatalf("one-shot node key persisted to data directory")
+	}
+	// Configure a node with no preset key and ensure it is persisted this time
+	if _, err := New(&Config{DataDir: dir}); err != nil {
+		t.Fatalf("failed to create newly keyed stack: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, datadirPrivateKey)); err != nil {
+		t.Fatalf("node key not persisted to data directory: %v", err)
+	}
+	key, err = crypto.LoadECDSA(filepath.Join(dir, datadirPrivateKey))
+	if err != nil {
+		t.Fatalf("failed to load freshly persisted node key: %v", err)
+	}
+	blob1, err := ioutil.ReadFile(filepath.Join(dir, datadirPrivateKey))
+	if err != nil {
+		t.Fatalf("failed to read freshly persisted node key: %v", err)
+	}
+	// Configure a new node and ensure the previously persisted key is loaded
+	if _, err := New(&Config{DataDir: dir}); err != nil {
+		t.Fatalf("failed to create previously keyed stack: %v", err)
+	}
+	blob2, err := ioutil.ReadFile(filepath.Join(dir, datadirPrivateKey))
+	if err != nil {
+		t.Fatalf("failed to read previously persisted node key: %v", err)
+	}
+	if bytes.Compare(blob1, blob2) != 0 {
+		t.Fatalf("persisted node key mismatch: have %x, want %x", blob2, blob1)
+	}
+	// Configure ephemeral node and ensure no key is dumped locally
+	if _, err := New(&Config{DataDir: ""}); err != nil {
+		t.Fatalf("failed to create ephemeral stack: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(".", datadirPrivateKey)); err == nil {
+		t.Fatalf("ephemeral node key persisted to disk")
+	}
+}
diff --git a/node/errors.go b/node/errors.go
new file mode 100644
index 000000000..f8eece06d
--- /dev/null
+++ b/node/errors.go
@@ -0,0 +1,31 @@
+// 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
+
+import "fmt"
+
+// StopError is returned if a node fails to stop either any of its registered
+// services or itself.
+type StopError struct {
+	Server   error
+	Services map[string]error
+}
+
+// Error generates a textual representation of the stop error.
+func (e *StopError) Error() string {
+	return fmt.Sprintf("server: %v, services: %v", e.Server, e.Services)
+}
diff --git a/node/node.go b/node/node.go
new file mode 100644
index 000000000..ad4e69414
--- /dev/null
+++ b/node/node.go
@@ -0,0 +1,252 @@
+// 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"
+	"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("service not registered")
+	ErrServiceRegistered = errors.New("service already registered")
+
+	datadirInUseErrnos = map[uint]bool{11: true, 32: true, 35: true}
+)
+
+// Node represents a P2P node into which arbitrary services might be registered.
+type Node struct {
+	datadir string                        // Path to the currently used data directory
+	config  *p2p.Server                   // Configuration of the underlying P2P networking layer
+	stack   map[string]ServiceConstructor // Protocol stack registered into this node
+	emux    *event.TypeMux                // Event multiplexer used between the services of a stack
+
+	running  *p2p.Server        // Currently running P2P networking layer
+	services map[string]Service // Currently running services
+
+	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,
+		config: &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,
+		},
+		stack: make(map[string]ServiceConstructor),
+		emux:  new(event.TypeMux),
+	}, nil
+}
+
+// Register injects a new service into the node's stack.
+func (n *Node) Register(id string, constructor ServiceConstructor) error {
+	n.lock.Lock()
+	defer n.lock.Unlock()
+
+	// Short circuit if the node is running or if the id is taken
+	if n.running != nil {
+		return ErrNodeRunning
+	}
+	if _, ok := n.stack[id]; ok {
+		return ErrServiceRegistered
+	}
+	// Otherwise register the service and return
+	n.stack[id] = constructor
+
+	return nil
+}
+
+// Unregister removes a service from a node's stack. If the node is currently
+// running, an error will be returned.
+func (n *Node) Unregister(id string) error {
+	n.lock.Lock()
+	defer n.lock.Unlock()
+
+	// Short circuit if the node is running, or if the service is unknown
+	if n.running != nil {
+		return ErrNodeRunning
+	}
+	if _, ok := n.stack[id]; !ok {
+		return ErrServiceUnknown
+	}
+	// Otherwise drop the service and return
+	delete(n.stack, id)
+	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.running != nil {
+		return ErrNodeRunning
+	}
+	// Otherwise copy and specialize the P2P configuration
+	running := new(p2p.Server)
+	*running = *n.config
+
+	ctx := &ServiceContext{
+		dataDir:  n.datadir,
+		EventMux: n.emux,
+	}
+	services := make(map[string]Service)
+	for id, constructor := range n.stack {
+		service, err := constructor(ctx)
+		if err != nil {
+			return err
+		}
+		services[id] = 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 := []string{}
+	for id, service := range services {
+		// Start the next service, stopping all previous upon failure
+		if err := service.Start(); err != nil {
+			for _, id := range started {
+				services[id].Stop()
+			}
+			return err
+		}
+		// Mark the service started for potential cleanup
+		started = append(started, id)
+	}
+	// Finish initializing the startup
+	n.services = services
+	n.running = running
+
+	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.running == nil {
+		return ErrNodeStopped
+	}
+	// Otherwise terminate all the services and the P2P server too
+	failure := &StopError{
+		Services: make(map[string]error),
+	}
+	for id, service := range n.services {
+		if err := service.Stop(); err != nil {
+			failure.Services[id] = err
+		}
+	}
+	n.running.Stop()
+
+	n.services = nil
+	n.running = nil
+
+	if len(failure.Services) > 0 {
+		return failure
+	}
+	return nil
+}
+
+// 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.running
+}
+
+// Service retrieves a currently running services registered under a given id.
+func (n *Node) Service(id string) Service {
+	n.lock.RLock()
+	defer n.lock.RUnlock()
+
+	if n.services == nil {
+		return nil
+	}
+	return n.services[id]
+}
+
+// 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.emux
+}
diff --git a/node/node_example_test.go b/node/node_example_test.go
new file mode 100644
index 000000000..f2bd014b0
--- /dev/null
+++ b/node/node_example_test.go
@@ -0,0 +1,87 @@
+// 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_test
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/ethereum/go-ethereum/node"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+)
+
+// SampleService is a trivial network service that can be attached to a node for
+// life cycle management.
+//
+// The following methods are needed to implement a node.Service:
+//  - Protocols() []p2p.Protocol - devp2p protocols the service can communicate on
+//  - Start() error              - method invoked when the node is ready to start the service
+//  - Stop() error               - method invoked when the node terminates the service
+type SampleService struct{}
+
+func (s *SampleService) Protocols() []p2p.Protocol { return nil }
+func (s *SampleService) Start() error              { fmt.Println("Sample service starting..."); return nil }
+func (s *SampleService) Stop() error               { fmt.Println("Sample service stopping..."); return nil }
+
+func ExampleUsage() {
+	// Create a network node to run protocols with the default values. The below list
+	// is only used to display each of the configuration options. All of these could
+	// have been ommited if the default behavior is desired.
+	nodeConfig := &node.Config{
+		DataDir:         "",                 // Empty uses ephemeral storage
+		PrivateKey:      nil,                // Nil generates a node key on the fly
+		Name:            "",                 // Any textual node name is allowed
+		NoDiscovery:     false,              // Can disable discovering remote nodes
+		BootstrapNodes:  []*discover.Node{}, // List of bootstrap nodes to use
+		ListenAddr:      ":0",               // Network interface to listen on
+		NAT:             nil,                // UPnP port mapper to use for crossing firewalls
+		Dialer:          nil,                // Custom dialer to use for establishing peer connections
+		NoDial:          false,              // Can prevent this node from dialing out
+		MaxPeers:        0,                  // Number of peers to allow
+		MaxPendingPeers: 0,                  // Number of peers allowed to handshake concurrently
+	}
+	stack, err := node.New(nodeConfig)
+	if err != nil {
+		log.Fatalf("Failed to create network node: %v", err)
+	}
+	// Create and register a simple network service. This is done through the definition
+	// of a node.ServiceConstructor that will instantiate a node.Service. The reason for
+	// the factory method approach is to support service restarts without relying on the
+	// individual implementations' support for such operations.
+	constructor := func(context *node.ServiceContext) (node.Service, error) {
+		return new(SampleService), nil
+	}
+	if err := stack.Register("my sample service", constructor); err != nil {
+		log.Fatalf("Failed to register service: %v", err)
+	}
+	// Boot up the entire protocol stack, do a restart and terminate
+	if err := stack.Start(); err != nil {
+		log.Fatalf("Failed to start the protocol stack: %v", err)
+	}
+	if err := stack.Restart(); err != nil {
+		log.Fatalf("Failed to restart the protocol stack: %v", err)
+	}
+	if err := stack.Stop(); err != nil {
+		log.Fatalf("Failed to stop the protocol stack: %v", err)
+	}
+	// Output:
+	// Sample service starting...
+	// Sample service stopping...
+	// Sample service starting...
+	// Sample service stopping...
+}
diff --git a/node/node_test.go b/node/node_test.go
new file mode 100644
index 000000000..7201276b5
--- /dev/null
+++ b/node/node_test.go
@@ -0,0 +1,492 @@
+// 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
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p"
+)
+
+var (
+	testNodeKey, _ = crypto.GenerateKey()
+
+	testNodeConfig = &Config{
+		PrivateKey: testNodeKey,
+		Name:       "test node",
+	}
+)
+
+// Tests that an empty protocol stack can be started, restarted and stopped.
+func TestNodeLifeCycle(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Ensure that a stopped node can be stopped again
+	for i := 0; i < 3; i++ {
+		if err := stack.Stop(); err != ErrNodeStopped {
+			t.Fatalf("iter %d: stop failure mismatch: have %v, want %v", i, err, ErrNodeStopped)
+		}
+	}
+	// Ensure that a node can be successfully started, but only once
+	if err := stack.Start(); err != nil {
+		t.Fatalf("failed to start node: %v", err)
+	}
+	if err := stack.Start(); err != ErrNodeRunning {
+		t.Fatalf("start failure mismatch: have %v, want %v ", err, ErrNodeRunning)
+	}
+	// Ensure that a node can be restarted arbitrarily many times
+	for i := 0; i < 3; i++ {
+		if err := stack.Restart(); err != nil {
+			t.Fatalf("iter %d: failed to restart node: %v", i, err)
+		}
+	}
+	// Ensure that a node can be stopped, but only once
+	if err := stack.Stop(); err != nil {
+		t.Fatalf("failed to stop node: %v", err)
+	}
+	if err := stack.Stop(); err != ErrNodeStopped {
+		t.Fatalf("stop failure mismatch: have %v, want %v ", err, ErrNodeStopped)
+	}
+}
+
+// Tests that if the data dir is already in use, an appropriate error is returned.
+func TestNodeUsedDataDir(t *testing.T) {
+	// Create a temporary folder to use as the data directory
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temporary data directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	// Create a new node based on the data directory
+	original, err := New(&Config{DataDir: dir})
+	if err != nil {
+		t.Fatalf("failed to create original protocol stack: %v", err)
+	}
+	if err := original.Start(); err != nil {
+		t.Fatalf("failed to start original protocol stack: %v", err)
+	}
+	defer original.Stop()
+
+	// Create a second node based on the same data directory and ensure failure
+	duplicate, err := New(&Config{DataDir: dir})
+	if err != nil {
+		t.Fatalf("failed to create duplicate protocol stack: %v", err)
+	}
+	if err := duplicate.Start(); err != ErrDatadirUsed {
+		t.Fatalf("duplicate datadir failure mismatch: have %v, want %v", err, ErrDatadirUsed)
+	}
+}
+
+// NoopService is a trivial implementation of the Service interface.
+type NoopService struct{}
+
+func (s *NoopService) Protocols() []p2p.Protocol { return nil }
+func (s *NoopService) Start() error              { return nil }
+func (s *NoopService) Stop() error               { return nil }
+
+func NewNoopService(*ServiceContext) (Service, error) { return new(NoopService), nil }
+
+// Tests whether services can be registered and unregistered.
+func TestServiceRegistry(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Create a batch of dummy services and ensure they don't exist
+	ids := []string{"A", "B", "C"}
+	for i, id := range ids {
+		if err := stack.Unregister(id); err != ErrServiceUnknown {
+			t.Fatalf("service %d: pre-unregistration failure mismatch: have %v, want %v", i, err, ErrServiceUnknown)
+		}
+	}
+	// Register the services, checking that the operation succeeds only once
+	for i, id := range ids {
+		if err := stack.Register(id, NewNoopService); err != nil {
+			t.Fatalf("service %d: registration failed: %v", i, err)
+		}
+		if err := stack.Register(id, NewNoopService); err != ErrServiceRegistered {
+			t.Fatalf("service %d: registration failure mismatch: have %v, want %v", i, err, ErrServiceRegistered)
+		}
+	}
+	// Unregister the services, checking that the operation succeeds only once
+	for i, id := range ids {
+		if err := stack.Unregister(id); err != nil {
+			t.Fatalf("service %d: unregistration failed: %v", i, err)
+		}
+		if err := stack.Unregister(id); err != ErrServiceUnknown {
+			t.Fatalf("service %d: unregistration failure mismatch: have %v, want %v", i, err, ErrServiceUnknown)
+		}
+	}
+}
+
+// InstrumentedService is an implementation of Service for which all interface
+// methods can be instrumented both return value as well as event hook wise.
+type InstrumentedService struct {
+	protocols []p2p.Protocol
+	start     error
+	stop      error
+
+	protocolsHook func()
+	startHook     func()
+	stopHook      func()
+}
+
+func (s *InstrumentedService) Protocols() []p2p.Protocol {
+	if s.protocolsHook != nil {
+		s.protocolsHook()
+	}
+	return s.protocols
+}
+
+func (s *InstrumentedService) Start() error {
+	if s.startHook != nil {
+		s.startHook()
+	}
+	return s.start
+}
+
+func (s *InstrumentedService) Stop() error {
+	if s.stopHook != nil {
+		s.stopHook()
+	}
+	return s.stop
+}
+
+// Tests that registered services get started and stopped correctly.
+func TestServiceLifeCycle(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Register a batch of life-cycle instrumented services
+	ids := []string{"A", "B", "C"}
+
+	started := make(map[string]bool)
+	stopped := make(map[string]bool)
+
+	for i, id := range ids {
+		id := id // Closure for the constructor
+		constructor := func(*ServiceContext) (Service, error) {
+			return &InstrumentedService{
+				startHook: func() { started[id] = true },
+				stopHook:  func() { stopped[id] = true },
+			}, nil
+		}
+		if err := stack.Register(id, constructor); err != nil {
+			t.Fatalf("service %d: registration failed: %v", i, err)
+		}
+	}
+	// Start the node and check that all services are running
+	if err := stack.Start(); err != nil {
+		t.Fatalf("failed to start protocol stack: %v", err)
+	}
+	for i, id := range ids {
+		if !started[id] {
+			t.Fatalf("service %d: freshly started service not running", i)
+		}
+		if stopped[id] {
+			t.Fatalf("service %d: freshly started service already stopped", i)
+		}
+		if stack.Service(id) == nil {
+			t.Fatalf("service %d: freshly started service unaccessible", i)
+		}
+	}
+	// Stop the node and check that all services have been stopped
+	if err := stack.Stop(); err != nil {
+		t.Fatalf("failed to stop protocol stack: %v", err)
+	}
+	for i, id := range ids {
+		if !stopped[id] {
+			t.Fatalf("service %d: freshly terminated service still running", i)
+		}
+		if service := stack.Service(id); service != nil {
+			t.Fatalf("service %d: freshly terminated service still accessible: %v", i, service)
+		}
+	}
+}
+
+// Tests that services are restarted cleanly as new instances.
+func TestServiceRestarts(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Define a service that does not support restarts
+	var (
+		running bool
+		started int
+	)
+	constructor := func(*ServiceContext) (Service, error) {
+		running = false
+
+		return &InstrumentedService{
+			startHook: func() {
+				if running {
+					panic("already running")
+				}
+				running = true
+				started++
+			},
+		}, nil
+	}
+	// Register the service and start the protocol stack
+	if err := stack.Register("service", constructor); err != nil {
+		t.Fatalf("failed to register the service: %v", err)
+	}
+	if err := stack.Start(); err != nil {
+		t.Fatalf("failed to start protocol stack: %v", err)
+	}
+	defer stack.Stop()
+
+	if running != true || started != 1 {
+		t.Fatalf("running/started mismatch: have %v/%d, want true/1", running, started)
+	}
+	// Restart the stack a few times and check successful service restarts
+	for i := 0; i < 3; i++ {
+		if err := stack.Restart(); err != nil {
+			t.Fatalf("iter %d: failed to restart stack: %v", i, err)
+		}
+	}
+	if running != true || started != 4 {
+		t.Fatalf("running/started mismatch: have %v/%d, want true/4", running, started)
+	}
+}
+
+// Tests that if a service fails to initialize itself, none of the other services
+// will be allowed to even start.
+func TestServiceConstructionAbortion(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Define a batch of good services
+	ids := []string{"A", "B", "C", "D", "E", "F"}
+
+	started := make(map[string]bool)
+	for i, id := range ids {
+		id := id // Closure for the constructor
+		constructor := func(*ServiceContext) (Service, error) {
+			return &InstrumentedService{
+				startHook: func() { started[id] = true },
+			}, nil
+		}
+		if err := stack.Register(id, constructor); err != nil {
+			t.Fatalf("service %d: registration failed: %v", i, err)
+		}
+	}
+	// Register a service that fails to construct itself
+	failure := errors.New("fail")
+	failer := func(*ServiceContext) (Service, error) {
+		return nil, failure
+	}
+	if err := stack.Register("failer", failer); err != nil {
+		t.Fatalf("failer registration failed: %v", err)
+	}
+	// Start the protocol stack and ensure none of the services get started
+	for i := 0; i < 100; i++ {
+		if err := stack.Start(); err != failure {
+			t.Fatalf("iter %d: stack startup failure mismatch: have %v, want %v", i, err, failure)
+		}
+		for i, id := range ids {
+			if started[id] {
+				t.Fatalf("service %d: started should not have", i)
+			}
+			delete(started, id)
+		}
+	}
+}
+
+// Tests that if a service fails to start, all others started before it will be
+// shut down.
+func TestServiceStartupAbortion(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Register a batch of good services
+	ids := []string{"A", "B", "C", "D", "E", "F"}
+
+	started := make(map[string]bool)
+	stopped := make(map[string]bool)
+
+	for i, id := range ids {
+		id := id // Closure for the constructor
+		constructor := func(*ServiceContext) (Service, error) {
+			return &InstrumentedService{
+				startHook: func() { started[id] = true },
+				stopHook:  func() { stopped[id] = true },
+			}, nil
+		}
+		if err := stack.Register(id, constructor); err != nil {
+			t.Fatalf("service %d: registration failed: %v", i, err)
+		}
+	}
+	// Register a service that fails to start
+	failure := errors.New("fail")
+	failer := func(*ServiceContext) (Service, error) {
+		return &InstrumentedService{
+			start: failure,
+		}, nil
+	}
+	if err := stack.Register("failer", failer); err != nil {
+		t.Fatalf("failer registration failed: %v", err)
+	}
+	// Start the protocol stack and ensure all started services stop
+	for i := 0; i < 100; i++ {
+		if err := stack.Start(); err != failure {
+			t.Fatalf("iter %d: stack startup failure mismatch: have %v, want %v", i, err, failure)
+		}
+		for i, id := range ids {
+			if started[id] && !stopped[id] {
+				t.Fatalf("service %d: started but not stopped", i)
+			}
+			delete(started, id)
+			delete(stopped, id)
+		}
+	}
+}
+
+// Tests that even if a registered service fails to shut down cleanly, it does
+// not influece the rest of the shutdown invocations.
+func TestServiceTerminationGuarantee(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Register a batch of good services
+	ids := []string{"A", "B", "C", "D", "E", "F"}
+
+	started := make(map[string]bool)
+	stopped := make(map[string]bool)
+
+	for i, id := range ids {
+		id := id // Closure for the constructor
+		constructor := func(*ServiceContext) (Service, error) {
+			return &InstrumentedService{
+				startHook: func() { started[id] = true },
+				stopHook:  func() { stopped[id] = true },
+			}, nil
+		}
+		if err := stack.Register(id, constructor); err != nil {
+			t.Fatalf("service %d: registration failed: %v", i, err)
+		}
+	}
+	// Register a service that fails to shot down cleanly
+	failure := errors.New("fail")
+	failer := func(*ServiceContext) (Service, error) {
+		return &InstrumentedService{
+			stop: failure,
+		}, nil
+	}
+	if err := stack.Register("failer", failer); err != nil {
+		t.Fatalf("failer registration failed: %v", err)
+	}
+	// Start the protocol stack, and ensure that a failing shut down terminates all
+	for i := 0; i < 100; i++ {
+		// Start the stack and make sure all is online
+		if err := stack.Start(); err != nil {
+			t.Fatalf("iter %d: failed to start protocol stack: %v", i, err)
+		}
+		for j, id := range ids {
+			if !started[id] {
+				t.Fatalf("iter %d, service %d: service not running", i, j)
+			}
+			if stopped[id] {
+				t.Fatalf("iter %d, service %d: service already stopped", i, j)
+			}
+		}
+		// Stop the stack, verify failure and check all terminations
+		err := stack.Stop()
+		if err, ok := err.(*StopError); !ok {
+			t.Fatalf("iter %d: termination failure mismatch: have %v, want StopError", i, err)
+		} else {
+			if err.Services["failer"] != failure {
+				t.Fatalf("iter %d: failer termination failure mismatch: have %v, want %v", i, err.Services["failer"], failure)
+			}
+			if len(err.Services) != 1 {
+				t.Fatalf("iter %d: failure count mismatch: have %d, want %d", i, len(err.Services), 1)
+			}
+		}
+		for j, id := range ids {
+			if !stopped[id] {
+				t.Fatalf("iter %d, service %d: service not terminated", i, j)
+			}
+			delete(started, id)
+			delete(stopped, id)
+		}
+	}
+}
+
+// Tests that all protocols defined by individual services get launched.
+func TestProtocolGather(t *testing.T) {
+	stack, err := New(testNodeConfig)
+	if err != nil {
+		t.Fatalf("failed to create protocol stack: %v", err)
+	}
+	// Register a batch of services with some configured number of protocols
+	services := map[string]int{
+		"Zero Protocols":  0,
+		"Single Protocol": 1,
+		"Many Protocols":  25,
+	}
+	for id, count := range services {
+		protocols := make([]p2p.Protocol, count)
+		for i := 0; i < len(protocols); i++ {
+			protocols[i].Name = id
+			protocols[i].Version = uint(i)
+		}
+		constructor := func(*ServiceContext) (Service, error) {
+			return &InstrumentedService{
+				protocols: protocols,
+			}, nil
+		}
+		if err := stack.Register(id, constructor); err != nil {
+			t.Fatalf("service %s: registration failed: %v", id, err)
+		}
+	}
+	// Start the services and ensure all protocols start successfully
+	if err := stack.Start(); err != nil {
+		t.Fatalf("failed to start protocol stack: %v", err)
+	}
+	defer stack.Stop()
+
+	protocols := stack.Server().Protocols
+	if len(protocols) != 26 {
+		t.Fatalf("mismatching number of protocols launched: have %d, want %d", len(protocols), 26)
+	}
+	for id, count := range services {
+		for ver := 0; ver < count; ver++ {
+			launched := false
+			for i := 0; i < len(protocols); i++ {
+				if protocols[i].Name == id && protocols[i].Version == uint(ver) {
+					launched = true
+					break
+				}
+			}
+			if !launched {
+				t.Errorf("configured protocol not launched: %s v%d", id, ver)
+			}
+		}
+	}
+}
diff --git a/node/service.go b/node/service.go
new file mode 100644
index 000000000..ec838dbe8
--- /dev/null
+++ b/node/service.go
@@ -0,0 +1,67 @@
+// 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
+
+import (
+	"path/filepath"
+
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/p2p"
+)
+
+// ServiceContext is a collection of service independent options inherited from
+// the protocol stack, that is passed to all constructors to be optionally used;
+// as well as utility methods to operate on the service environment.
+type ServiceContext struct {
+	dataDir  string         // Data directory for protocol persistence
+	EventMux *event.TypeMux // Event multiplexer used for decoupled notifications
+}
+
+// Database opens an existing database with the given name (or creates one if no
+// previous can be found) from within the node's data directory. If the node is
+// an ephemeral one, a memory database is returned.
+func (ctx *ServiceContext) Database(name string, cache int) (ethdb.Database, error) {
+	if ctx.dataDir == "" {
+		return ethdb.NewMemDatabase()
+	}
+	return ethdb.NewLDBDatabase(filepath.Join(ctx.dataDir, name), cache)
+}
+
+// ServiceConstructor is the function signature of the constructors needed to be
+// registered for service instantiation.
+type ServiceConstructor func(ctx *ServiceContext) (Service, error)
+
+// Service is an individual protocol that can be registered into a node.
+//
+// Notes:
+//  - Service life-cycle management is delegated to the node. The service is
+//    allowed to initialize itself upon creation, but no goroutines should be
+//    spun up outside of the Start method.
+//  - Restart logic is not required as the node will create a fresh instance
+//    every time a service is started.
+type Service interface {
+	// Protocol retrieves the P2P protocols the service wishes to start.
+	Protocols() []p2p.Protocol
+
+	// Start spawns any goroutines required by the service.
+	Start() error
+
+	// Stop terminates all goroutines belonging to the service, blocking until they
+	// are all terminated.
+	Stop() error
+}
diff --git a/node/service_test.go b/node/service_test.go
new file mode 100644
index 000000000..50a4f9715
--- /dev/null
+++ b/node/service_test.go
@@ -0,0 +1,60 @@
+// 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
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// Tests that service context methods work properly.
+func TestServiceContext(t *testing.T) {
+	// Create a temporary folder and ensure no database is contained within
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("failed to create temporary data directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	if _, err := os.Stat(filepath.Join(dir, "database")); err == nil {
+		t.Fatalf("non-created database already exists")
+	}
+	// Request the opening/creation of a database and ensure it persists to disk
+	ctx := &ServiceContext{dataDir: dir}
+	db, err := ctx.Database("persistent", 0)
+	if err != nil {
+		t.Fatalf("failed to open persistent database: %v", err)
+	}
+	db.Close()
+
+	if _, err := os.Stat(filepath.Join(dir, "persistent")); err != nil {
+		t.Fatalf("persistent database doesn't exists: %v", err)
+	}
+	// Request th opening/creation of an ephemeral database and ensure it's not persisted
+	ctx = &ServiceContext{dataDir: ""}
+	db, err = ctx.Database("ephemeral", 0)
+	if err != nil {
+		t.Fatalf("failed to open ephemeral database: %v", err)
+	}
+	db.Close()
+
+	if _, err := os.Stat(filepath.Join(dir, "ephemeral")); err == nil {
+		t.Fatalf("ephemeral database exists")
+	}
+}
diff --git a/node/utils.go b/node/utils.go
new file mode 100644
index 000000000..deaa6c5fb
--- /dev/null
+++ b/node/utils.go
@@ -0,0 +1,33 @@
+// 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
+
+import (
+	"path/filepath"
+
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+// openDatabase opens an existing database with the given name from within the
+// specified data directory, creating one if none exists. If the data directory
+// is empty, an ephemeral memory database is returned.
+func openDatabase(dataDir string, name string, cache int) (ethdb.Database, error) {
+	if dataDir == "" {
+		return ethdb.NewMemDatabase()
+	}
+	return ethdb.NewLDBDatabase(filepath.Join(dataDir, name), cache)
+}