github.com/murrekatt/go-ethereum@v1.5.8-0.20170123175102-fc52f2c007fb/node/service.go (about)

     1  // Copyright 2015 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package node
    18  
    19  import (
    20  	"reflect"
    21  
    22  	"github.com/ethereum/go-ethereum/accounts"
    23  	"github.com/ethereum/go-ethereum/ethdb"
    24  	"github.com/ethereum/go-ethereum/event"
    25  	"github.com/ethereum/go-ethereum/p2p"
    26  	"github.com/ethereum/go-ethereum/rpc"
    27  )
    28  
    29  // ServiceContext is a collection of service independent options inherited from
    30  // the protocol stack, that is passed to all constructors to be optionally used;
    31  // as well as utility methods to operate on the service environment.
    32  type ServiceContext struct {
    33  	config         *Config
    34  	services       map[reflect.Type]Service // Index of the already constructed services
    35  	EventMux       *event.TypeMux           // Event multiplexer used for decoupled notifications
    36  	AccountManager *accounts.Manager        // Account manager created by the node.
    37  }
    38  
    39  // OpenDatabase opens an existing database with the given name (or creates one
    40  // if no previous can be found) from within the node's data directory. If the
    41  // node is an ephemeral one, a memory database is returned.
    42  func (ctx *ServiceContext) OpenDatabase(name string, cache int, handles int) (ethdb.Database, error) {
    43  	if ctx.config.DataDir == "" {
    44  		return ethdb.NewMemDatabase()
    45  	}
    46  	return ethdb.NewLDBDatabase(ctx.config.resolvePath(name), cache, handles)
    47  }
    48  
    49  // Service retrieves a currently running service registered of a specific type.
    50  func (ctx *ServiceContext) Service(service interface{}) error {
    51  	element := reflect.ValueOf(service).Elem()
    52  	if running, ok := ctx.services[element.Type()]; ok {
    53  		element.Set(reflect.ValueOf(running))
    54  		return nil
    55  	}
    56  	return ErrServiceUnknown
    57  }
    58  
    59  // ServiceConstructor is the function signature of the constructors needed to be
    60  // registered for service instantiation.
    61  type ServiceConstructor func(ctx *ServiceContext) (Service, error)
    62  
    63  // Service is an individual protocol that can be registered into a node.
    64  //
    65  // Notes:
    66  //
    67  // • Service life-cycle management is delegated to the node. The service is allowed to
    68  // initialize itself upon creation, but no goroutines should be spun up outside of the
    69  // Start method.
    70  //
    71  // • Restart logic is not required as the node will create a fresh instance
    72  // every time a service is started.
    73  type Service interface {
    74  	// Protocols retrieves the P2P protocols the service wishes to start.
    75  	Protocols() []p2p.Protocol
    76  
    77  	// APIs retrieves the list of RPC descriptors the service provides
    78  	APIs() []rpc.API
    79  
    80  	// Start is called after all services have been constructed and the networking
    81  	// layer was also initialized to spawn any goroutines required by the service.
    82  	Start(server *p2p.Server) error
    83  
    84  	// Stop terminates all goroutines belonging to the service, blocking until they
    85  	// are all terminated.
    86  	Stop() error
    87  }