Merge pull request #1970 from karalabe/customizable-protocol-stacks

Customizable protocol stacks

1 files changed, 80 insertions, 0 deletions

diff --git a/node/service.go b/node/service.go
new file mode 100644
index 000000000..bfeeb7ab9
--- /dev/null
+++ b/node/service.go
@@ -0,0 +1,80 @@
+// 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"
+	"reflect"
+
+	"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
+	services map[reflect.Type]Service // Index of the already constructed services
+	EventMux *event.TypeMux           // Event multiplexer used for decoupled notifications
+}
+
+// OpenDatabase 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) OpenDatabase(name string, cache int) (ethdb.Database, error) {
+	if ctx.datadir == "" {
+		return ethdb.NewMemDatabase()
+	}
+	return ethdb.NewLDBDatabase(filepath.Join(ctx.datadir, name), cache)
+}
+
+// Service retrieves a currently running service registered of a specific type.
+func (ctx *ServiceContext) Service(service interface{}) error {
+	element := reflect.ValueOf(service).Elem()
+	if running, ok := ctx.services[element.Type()]; ok {
+		element.Set(reflect.ValueOf(running))
+		return nil
+	}
+	return ErrServiceUnknown
+}
+
+// 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 is called after all services have been constructed and the networking
+	// layer was also initialized to spawn any goroutines required by the service.
+	Start(server *p2p.Server) error
+
+	// Stop terminates all goroutines belonging to the service, blocking until they
+	// are all terminated.
+	Stop() error
+}