91 lines
3.7 KiB
Go
91 lines
3.7 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package node
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import (
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"path/filepath"
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"reflect"
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"github.com/ethereum/go-ethereum/ethdb"
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"github.com/ethereum/go-ethereum/event"
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"github.com/ethereum/go-ethereum/p2p"
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)
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// ServiceContext is a collection of service independent options inherited from
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// the protocol stack, that is passed to all constructors to be optionally used;
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// as well as utility methods to operate on the service environment.
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type ServiceContext struct {
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datadir string // Data directory for protocol persistence
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services map[string]Service // Index of the already constructed services
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EventMux *event.TypeMux // Event multiplexer used for decoupled notifications
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}
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// Database opens an existing database with the given name (or creates one if no
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// previous can be found) from within the node's data directory. If the node is
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// an ephemeral one, a memory database is returned.
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func (ctx *ServiceContext) Database(name string, cache int) (ethdb.Database, error) {
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if ctx.datadir == "" {
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return ethdb.NewMemDatabase()
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}
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return ethdb.NewLDBDatabase(filepath.Join(ctx.datadir, name), cache)
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}
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// Service retrieves an already constructed service registered under a given id.
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func (ctx *ServiceContext) Service(id string) Service {
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return ctx.services[id]
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}
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// SingletonService retrieves an already constructed service using a specific type
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// implementing the Service interface. This is a utility function for scenarios
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// where it is known that only one instance of a given service type is running,
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// allowing to access services without needing to know their specific id with
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// which they were registered.
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func (ctx *ServiceContext) SingletonService(service interface{}) (string, error) {
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for id, running := range ctx.services {
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if reflect.TypeOf(running) == reflect.ValueOf(service).Elem().Type() {
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reflect.ValueOf(service).Elem().Set(reflect.ValueOf(running))
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return id, nil
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}
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}
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return "", ErrServiceUnknown
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}
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// ServiceConstructor is the function signature of the constructors needed to be
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// registered for service instantiation.
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type ServiceConstructor func(ctx *ServiceContext) (Service, error)
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// Service is an individual protocol that can be registered into a node.
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//
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// Notes:
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// - Service life-cycle management is delegated to the node. The service is
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// allowed to initialize itself upon creation, but no goroutines should be
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// spun up outside of the Start method.
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// - Restart logic is not required as the node will create a fresh instance
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// every time a service is started.
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type Service interface {
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// Protocol retrieves the P2P protocols the service wishes to start.
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Protocols() []p2p.Protocol
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// Start is called after all services have been constructed and the networking
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// layer was also initialized to spawn any goroutines required by the service.
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Start(server *p2p.Server) error
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// Stop terminates all goroutines belonging to the service, blocking until they
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// are all terminated.
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Stop() error
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}
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