path: root/rpc/v2/server.go

// 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
}