// 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"
"golang.org/x/net/context"
)
// 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()
}()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
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(ctx, codec, reqs)
} else {
go s.exec(ctx, 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(ctx context.Context, 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 req.callb.hasCtx {
arguments = append(arguments, reflect.ValueOf(ctx))
}
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(ctx context.Context, codec ServerCodec, req *serverRequest) {
var response interface{}
if req.err != nil {
response = codec.CreateErrorResponse(&req.id, req.err)
} else {
response = s.handle(ctx, 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(ctx context.Context, 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(ctx, 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
}
