rpc/v2: optionally passing context argument to rpc v2 api methods

Godeps/Godeps.json

@@ -101,6 +101,10 @@
 			"ImportPath": "golang.org/x/crypto/scrypt",
 			"Rev": "4ed45ec682102c643324fae5dff8dab085b6c300"
 		},
+		{
+			"ImportPath": "golang.org/x/net/context",
+			"Rev": "e0403b4e005737430c05a57aac078479844f919c"
+		},
 		{
 			"ImportPath": "golang.org/x/net/html",
 			"Rev": "e0403b4e005737430c05a57aac078479844f919c"

Godeps/_workspace/src/golang.org/x/net/context/withtimeout_test.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package context_test
+
+import (
+	"fmt"
+	"time"
+
+	"golang.org/x/net/context"
+)
+
+func ExampleWithTimeout() {
+	// Pass a context with a timeout to tell a blocking function that it
+	// should abandon its work after the timeout elapses.
+	ctx, _ := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	select {
+	case <-time.After(200 * time.Millisecond):
+		fmt.Println("overslept")
+	case <-ctx.Done():
+		fmt.Println(ctx.Err()) // prints "context deadline exceeded"
+	}
+	// Output:
+	// context deadline exceeded
+}

rpc/v2/server.go

@@ -25,6 +25,7 @@ import (
 	"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.
@@ -120,6 +121,9 @@ func (s *Server) ServeCodec(codec ServerCodec) {
 		codec.Close()
 	}()
 
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
 	for {
 		reqs, batch, err := s.readRequest(codec)
 		if err != nil {
@@ -129,9 +133,9 @@ func (s *Server) ServeCodec(codec ServerCodec) {
 		}
 
 		if batch {
-			go s.execBatch(codec, reqs)
+			go s.execBatch(ctx, codec, reqs)
 		} else {
-			go s.exec(codec, reqs[0])
+			go s.exec(ctx, codec, reqs[0])
 		}
 	}
 }
@@ -220,7 +224,7 @@ func (s *Server) unsubscribe(subid string) bool {
 }
 
 // handle executes a request and returns the response from the callback.
-func (s *Server) handle(codec ServerCodec, req *serverRequest) interface{} {
+func (s *Server) handle(ctx context.Context, codec ServerCodec, req *serverRequest) interface{} {
 	if req.err != nil {
 		return codec.CreateErrorResponse(&req.id, req.err)
 	}
@@ -255,6 +259,9 @@ func (s *Server) handle(codec ServerCodec, req *serverRequest) interface{} {
 	}
 
 	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...)
 	}
@@ -277,12 +284,12 @@ func (s *Server) handle(codec ServerCodec, req *serverRequest) interface{} {
 }
 
 // exec executes the given request and writes the result back using the codec.
-func (s *Server) exec(codec ServerCodec, req *serverRequest) {
+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(codec, req)
+		response = s.handle(ctx, codec, req)
 	}
 
 	if err := codec.Write(response); err != nil {
@@ -293,13 +300,13 @@ func (s *Server) exec(codec ServerCodec, req *serverRequest) {
 
 // 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) {
+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(codec, req)
+			responses[i] = s.handle(ctx, codec, req)
 		}
 	}
 

rpc/v2/server_test.go

@@ -6,6 +6,8 @@ import (
 	"reflect"
 	"testing"
 	"time"
+
+	"golang.org/x/net/context"
 )
 
 type Service struct{}
@@ -27,6 +29,10 @@ func (s *Service) Echo(str string, i int, args *Args) Result {
 	return Result{str, i, args}
 }
 
+func (s *Service) EchoWithCtx(ctx context.Context, str string, i int, args *Args) Result {
+	return Result{str, i, args}
+}
+
 func (s *Service) Rets() (string, error) {
 	return "", nil
 }
@@ -64,8 +70,8 @@ func TestServerRegisterName(t *testing.T) {
 		t.Fatalf("Expected service calc to be registered")
 	}
 
-	if len(svc.callbacks) != 3 {
-		t.Errorf("Expected 3 callbacks for service 'calc', got %d", len(svc.callbacks))
+	if len(svc.callbacks) != 4 {
+		t.Errorf("Expected 4 callbacks for service 'calc', got %d", len(svc.callbacks))
 	}
 
 	if len(svc.subscriptions) != 1 {
@@ -217,3 +223,33 @@ func TestServerMethodExecution(t *testing.T) {
 		t.Fatalf("expected %s, got %s\n", expected, codec.output)
 	}
 }
+
+func TestServerMethodWithCtx(t *testing.T) {
+	server := NewServer()
+	service := new(Service)
+
+	if err := server.RegisterName("test", service); err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	id := int64(12345)
+	req := jsonRequest{
+		Method:  "echoWithCtx",
+		Version: "2.0",
+		Id:      &id,
+	}
+	args := []interface{}{"string arg", 1122, &Args{"qwerty"}}
+	req.Payload, _ = json.Marshal(&args)
+
+	input, _ := json.Marshal(&req)
+	codec := &ServerTestCodec{input: input, closer: make(chan interface{})}
+	go server.ServeCodec(codec)
+
+	<-codec.closer
+
+	expected := `{"jsonrpc":"2.0","id":12345,"result":{"String":"string arg","Int":1122,"Args":{"S":"qwerty"}}}`
+
+	if expected != codec.output {
+		t.Fatalf("expected %s, got %s\n", expected, codec.output)
+	}
+}

rpc/v2/types.go

@@ -22,7 +22,6 @@ import (
 	"math/big"
 	"reflect"
 	"strings"
-
 	"sync"
 
 	"github.com/ethereum/go-ethereum/event"
@@ -41,6 +40,7 @@ type callback struct {
 	rcvr        reflect.Value  // receiver of method
 	method      reflect.Method // callback
 	argTypes    []reflect.Type // input argument types
+	hasCtx      bool           // method's first argument is a context (not included in argTypes)
 	errPos      int            // err return idx, of -1 when method cannot return error
 	isSubscribe bool           // indication if the callback is a subscription
 }

rpc/v2/utils.go

@@ -24,6 +24,8 @@ import (
 	"reflect"
 	"unicode"
 	"unicode/utf8"
+
+	"golang.org/x/net/context"
 )
 
 // Is this an exported - upper case - name?
@@ -107,6 +109,8 @@ func isBlockNumber(t reflect.Type) bool {
 	return t == blockNumberType
 }
 
+var contextType = reflect.TypeOf(new(context.Context)).Elem()
+
 // suitableCallbacks iterates over the methods of the given type. It will determine if a method satisfies the criteria
 // for a RPC callback or a subscription callback and adds it to the collection of callbacks or subscriptions. See server
 // documentation for a summary of these criteria.
@@ -129,12 +133,19 @@ METHODS:
 		h.method = method
 		h.errPos = -1
 
+		firstArg := 1
+		numIn := mtype.NumIn()
+		if numIn >= 2 && mtype.In(1) == contextType {
+			h.hasCtx = true
+			firstArg = 2
+		}
+
 		if h.isSubscribe {
-			h.argTypes = make([]reflect.Type, mtype.NumIn()-1) // skip rcvr type
-			for i := 1; i < mtype.NumIn(); i++ {
+			h.argTypes = make([]reflect.Type, numIn-firstArg) // skip rcvr type
+			for i := firstArg; i < numIn; i++ {
 				argType := mtype.In(i)
 				if isExportedOrBuiltinType(argType) {
-					h.argTypes[i-1] = argType
+					h.argTypes[i-firstArg] = argType
 				} else {
 					continue METHODS
 				}
@@ -144,17 +155,15 @@ METHODS:
 			continue METHODS
 		}
 
-		numIn := mtype.NumIn()
-
 		// determine method arguments, ignore first arg since it's the receiver type
 		// Arguments must be exported or builtin types
-		h.argTypes = make([]reflect.Type, numIn-1)
-		for i := 1; i < numIn; i++ {
+		h.argTypes = make([]reflect.Type, numIn-firstArg)
+		for i := firstArg; i < numIn; i++ {
 			argType := mtype.In(i)
 			if !isExportedOrBuiltinType(argType) {
 				continue METHODS
 			}
-			h.argTypes[i-1] = argType
+			h.argTypes[i-firstArg] = argType
 		}
 
 		// check that all returned values are exported or builtin types