node: customizable protocol and service stacks

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
+}