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// 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(*p2p.Server) error { fmt.Println("Service starting..."); return nil }
func (s *SampleService) Stop() error { fmt.Println("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:
// Service starting...
// Service stopping...
// Service starting...
// Service stopping...
}
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