rpc: new RPC implementation with pub/sub support

1 files changed, 378 insertions, 0 deletions

diff --git a/rpc/v2/server.go b/rpc/v2/server.go
new file mode 100644
index 000000000..ff6b69015
--- /dev/null
+++ b/rpc/v2/server.go
@@ -0,0 +1,378 @@
+// 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 v2
+
+import (
+	"fmt"
+	"reflect"
+
+	"runtime"
+
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+)
+
+// NewServer will create a new server instance with no registered handlers.
+func NewServer() *Server {
+	server := &Server{services: make(serviceRegistry), subscriptions: make(subscriptionRegistry)}
+
+	// register a default service which will provide meta information about the RPC service such as the services and
+	// methods it offers.
+	rpcService := &RPCService{server}
+	server.RegisterName("rpc", rpcService)
+
+	return server
+}
+
+// RPCService gives meta information about the server.
+// e.g. gives information about the loaded modules.
+type RPCService struct {
+	server *Server
+}
+
+// Modules returns the list of RPC services with their version number
+func (s *RPCService) Modules() map[string]string {
+	modules := make(map[string]string)
+	for name, _ := range s.server.services {
+		modules[name] = "1.0"
+	}
+	return modules
+}
+
+// RegisterName will create an service for the given rcvr type under the given name. When no methods on the given rcvr
+// match the criteria to be either a RPC method or a subscription an error is returned. Otherwise a new service is
+// created and added to the service collection this server instance serves.
+func (s *Server) RegisterName(name string, rcvr interface{}) error {
+	if s.services == nil {
+		s.services = make(serviceRegistry)
+	}
+
+	svc := new(service)
+	svc.typ = reflect.TypeOf(rcvr)
+	rcvrVal := reflect.ValueOf(rcvr)
+
+	if name == "" {
+		return fmt.Errorf("no service name for type %s", svc.typ.String())
+	}
+	if !isExported(reflect.Indirect(rcvrVal).Type().Name()) {
+		return fmt.Errorf("%s is not exported", reflect.Indirect(rcvrVal).Type().Name())
+	}
+
+	// already a previous service register under given sname, merge methods/subscriptions
+	if regsvc, present := s.services[name]; present {
+		methods, subscriptions := suitableCallbacks(rcvrVal, svc.typ)
+		if len(methods) == 0 && len(subscriptions) == 0 {
+			return fmt.Errorf("Service doesn't have any suitable methods/subscriptions to expose")
+		}
+
+		for _, m := range methods {
+			regsvc.callbacks[formatName(m.method.Name)] = m
+		}
+		for _, s := range subscriptions {
+			regsvc.subscriptions[formatName(s.method.Name)] = s
+		}
+
+		return nil
+	}
+
+	svc.name = name
+	svc.callbacks, svc.subscriptions = suitableCallbacks(rcvrVal, svc.typ)
+
+	if len(svc.callbacks) == 0 && len(svc.subscriptions) == 0 {
+		return fmt.Errorf("Service doesn't have any suitable methods/subscriptions to expose")
+	}
+
+	s.services[svc.name] = svc
+
+	return nil
+}
+
+// ServeCodec reads incoming requests from codec, calls the appropriate callback and writes the
+// response back using the given codec. It will block until the codec is closed.
+//
+// This server will:
+// 1. allow for asynchronous and parallel request execution
+// 2. supports notifications (pub/sub)
+// 3. supports request batches
+func (s *Server) ServeCodec(codec ServerCodec) {
+	defer func() {
+		if err := recover(); err != nil {
+			const size = 64 << 10
+			buf := make([]byte, size)
+			buf = buf[:runtime.Stack(buf, false)]
+			glog.Errorln(string(buf))
+		}
+		codec.Close()
+	}()
+
+	for {
+		reqs, batch, err := s.readRequest(codec)
+		if err != nil {
+			glog.V(logger.Debug).Infof("%v\n", err)
+			codec.Write(codec.CreateErrorResponse(nil, err))
+			break
+		}
+
+		if batch {
+			go s.execBatch(codec, reqs)
+		} else {
+			go s.exec(codec, reqs[0])
+		}
+	}
+}
+
+// sendNotification will create a notification from the given event by serializing member fields of the event.
+// It will then send the notification to the client, when it fails the codec is closed. When the event has multiple
+// fields an array of values is returned.
+func sendNotification(codec ServerCodec, subid string, event interface{}) {
+	notification := codec.CreateNotification(subid, event)
+
+	if err := codec.Write(notification); err != nil {
+		codec.Close()
+	}
+}
+
+// createSubscription will register a new subscription and waits for raised events. When an event is raised it will:
+// 1. test if the event is raised matches the criteria the user has (optionally) specified
+// 2. create a notification of the event and send it the client when it matches the criteria
+// It will unsubscribe the subscription when the socket is closed or the subscription is unsubscribed by the user.
+func (s *Server) createSubscription(c ServerCodec, req *serverRequest) (string, error) {
+	args := []reflect.Value{req.callb.rcvr}
+	if len(req.args) > 0 {
+		args = append(args, req.args...)
+	}
+
+	subid, err := newSubscriptionId()
+	if err != nil {
+		return "", err
+	}
+
+	reply := req.callb.method.Func.Call(args)
+
+	if reply[1].IsNil() { // no error
+		if subscription, ok := reply[0].Interface().(Subscription); ok {
+			s.muSubcriptions.Lock()
+			s.subscriptions[subid] = subscription
+			s.muSubcriptions.Unlock()
+			go func() {
+				cases := []reflect.SelectCase{
+					reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(subscription.Chan())}, // new event
+					reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(c.Closed())},          // connection closed
+				}
+
+				for {
+					idx, notification, recvOk := reflect.Select(cases)
+					switch idx {
+					case 0: // new event, or channel closed
+						if recvOk { // send notification
+							if event, ok := notification.Interface().(*event.Event); ok {
+								if subscription.match == nil || subscription.match(event.Data) {
+									sendNotification(c, subid, subscription.format(event.Data))
+								}
+							}
+						} else { // user send an eth_unsubscribe request
+							return
+						}
+					case 1: // connection closed
+						s.unsubscribe(subid)
+						return
+					}
+				}
+			}()
+		} else { // unable to create subscription
+			s.muSubcriptions.Lock()
+			delete(s.subscriptions, subid)
+			s.muSubcriptions.Unlock()
+		}
+	} else {
+		return "", fmt.Errorf("Unable to create subscription")
+	}
+
+	return subid, nil
+}
+
+// unsubscribe calls the Unsubscribe method on the subscription and removes a subscription from the subscription
+// registry.
+func (s *Server) unsubscribe(subid string) bool {
+	s.muSubcriptions.Lock()
+	defer s.muSubcriptions.Unlock()
+	if sub, ok := s.subscriptions[subid]; ok {
+		sub.Unsubscribe()
+		delete(s.subscriptions, subid)
+		return true
+	}
+	return false
+}
+
+// handle executes a request and returns the response from the callback.
+func (s *Server) handle(codec ServerCodec, req *serverRequest) interface{} {
+	if req.err != nil {
+		return codec.CreateErrorResponse(&req.id, req.err)
+	}
+
+	if req.isUnsubscribe { // first param must be the subscription id
+		if len(req.args) >= 1 && req.args[0].Kind() == reflect.String {
+			subid := req.args[0].String()
+			if s.unsubscribe(subid) {
+				return codec.CreateResponse(req.id, true)
+			} else {
+				return codec.CreateErrorResponse(&req.id,
+					&callbackError{fmt.Sprintf("subscription '%s' not found", subid)})
+			}
+		}
+		return codec.CreateErrorResponse(&req.id, &invalidParamsError{"Expected subscription id as argument"})
+	}
+
+	if req.callb.isSubscribe {
+		subid, err := s.createSubscription(codec, req)
+		if err != nil {
+			return codec.CreateErrorResponse(&req.id, &callbackError{err.Error()})
+		}
+		return codec.CreateResponse(req.id, subid)
+	}
+
+	// regular RPC call
+	if len(req.args) != len(req.callb.argTypes) {
+		rpcErr := &invalidParamsError{fmt.Sprintf("%s%s%s expects %d parameters, got %d",
+			req.svcname, serviceMethodSeparator, req.callb.method.Name,
+			len(req.callb.argTypes), len(req.args))}
+		return codec.CreateErrorResponse(&req.id, rpcErr)
+	}
+
+	arguments := []reflect.Value{req.callb.rcvr}
+	if len(req.args) > 0 {
+		arguments = append(arguments, req.args...)
+	}
+
+	reply := req.callb.method.Func.Call(arguments)
+
+	if len(reply) == 0 {
+		return codec.CreateResponse(req.id, nil)
+	}
+
+	if req.callb.errPos >= 0 { // test if method returned an error
+		if !reply[req.callb.errPos].IsNil() {
+			e := reply[req.callb.errPos].Interface().(error)
+			res := codec.CreateErrorResponse(&req.id, &callbackError{e.Error()})
+			return res
+		}
+	}
+
+	return codec.CreateResponse(req.id, reply[0].Interface())
+}
+
+// exec executes the given request and writes the result back using the codec.
+func (s *Server) exec(codec ServerCodec, req *serverRequest) {
+	var response interface{}
+	if req.err != nil {
+		response = codec.CreateErrorResponse(&req.id, req.err)
+	} else {
+		response = s.handle(codec, req)
+	}
+
+	if err := codec.Write(response); err != nil {
+		glog.V(logger.Error).Infof("%v\n", err)
+		codec.Close()
+	}
+}
+
+// execBatch executes the given requests and writes the result back using the codec. It will only write the response
+// back when the last request is processed.
+func (s *Server) execBatch(codec ServerCodec, requests []*serverRequest) {
+	responses := make([]interface{}, len(requests))
+	for i, req := range requests {
+		if req.err != nil {
+			responses[i] = codec.CreateErrorResponse(&req.id, req.err)
+		} else {
+			responses[i] = s.handle(codec, req)
+		}
+	}
+
+	if err := codec.Write(responses); err != nil {
+		glog.V(logger.Error).Infof("%v\n", err)
+		codec.Close()
+	}
+}
+
+// readRequest requests the next (batch) request from the codec. It will return the collection of requests, an
+// indication if the request was a batch, the invalid request identifier and an error when the request could not be
+// read/parsed.
+func (s *Server) readRequest(codec ServerCodec) ([]*serverRequest, bool, RPCError) {
+	reqs, batch, err := codec.ReadRequestHeaders()
+	if err != nil {
+		return nil, batch, err
+	}
+
+	requests := make([]*serverRequest, len(reqs))
+
+	// verify requests
+	for i, r := range reqs {
+		var ok bool
+		var svc *service
+
+		if r.isPubSub && r.method == unsubscribeMethod {
+			requests[i] = &serverRequest{id: r.id, isUnsubscribe: true}
+			argTypes := []reflect.Type{reflect.TypeOf("")}
+			if args, err := codec.ParseRequestArguments(argTypes, r.params); err == nil {
+				requests[i].args = args
+			} else {
+				requests[i].err = &invalidParamsError{err.Error()}
+			}
+			continue
+		}
+
+		if svc, ok = s.services[r.service]; !ok {
+			requests[i] = &serverRequest{id: r.id, err: &methodNotFoundError{r.service, r.method}}
+			continue
+		}
+
+		if r.isPubSub { // eth_subscribe
+			if callb, ok := svc.subscriptions[r.method]; ok {
+				requests[i] = &serverRequest{id: r.id, svcname: svc.name, callb: callb}
+				if r.params != nil && len(callb.argTypes) > 0 {
+					argTypes := []reflect.Type{reflect.TypeOf("")}
+					argTypes = append(argTypes, callb.argTypes...)
+					if args, err := codec.ParseRequestArguments(argTypes, r.params); err == nil {
+						requests[i].args = args[1:] // first one is service.method name which isn't an actual argument
+					} else {
+						requests[i].err = &invalidParamsError{err.Error()}
+					}
+				}
+			} else {
+				requests[i] = &serverRequest{id: r.id, err: &methodNotFoundError{subscribeMethod, r.method}}
+			}
+			continue
+		}
+
+		if callb, ok := svc.callbacks[r.method]; ok {
+			requests[i] = &serverRequest{id: r.id, svcname: svc.name, callb: callb}
+			if r.params != nil && len(callb.argTypes) > 0 {
+				if args, err := codec.ParseRequestArguments(callb.argTypes, r.params); err == nil {
+					requests[i].args = args
+				} else {
+					requests[i].err = &invalidParamsError{err.Error()}
+				}
+			}
+			continue
+		}
+
+		requests[i] = &serverRequest{id: r.id, err: &methodNotFoundError{r.service, r.method}}
+	}
+
+	return requests, batch, nil
+}