src/pkg/rpc/server_test.go - go - Git at Google

 // Copyright 2009 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 rpc

 import (
 	"fmt"
 	"http/httptest"
 	"io"
 	"log"
 	"net"
 	"os"
 	"runtime"
 	"strings"
 	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
 )

 var (
 	newServer                 *Server
 	serverAddr, newServerAddr string
 	httpServerAddr            string
 	once, newOnce, httpOnce   sync.Once
 )

 const (
 	second      = 1e9
 	newHttpPath = "/foo"
 )

 type Args struct {
 	A, B int
 }

 type Reply struct {
 	C int
 }

 type Arith int

 // Some of Arith's methods have value args, some have pointer args. That's deliberate.

 func (t *Arith) Add(args Args, reply *Reply) os.Error {
 	reply.C = args.A + args.B
 	return nil
 }

 func (t *Arith) Mul(args *Args, reply *Reply) os.Error {
 	reply.C = args.A * args.B
 	return nil
 }

 func (t *Arith) Div(args Args, reply *Reply) os.Error {
 	if args.B == 0 {
 		return os.NewError("divide by zero")
 	}
 	reply.C = args.A / args.B
 	return nil
 }

 func (t *Arith) String(args *Args, reply *string) os.Error {
 	*reply = fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
 	return nil
 }

 func (t *Arith) Scan(args string, reply *Reply) (err os.Error) {
 	_, err = fmt.Sscan(args, &reply.C)
 	return
 }

 func (t *Arith) Error(args *Args, reply *Reply) os.Error {
 	panic("ERROR")
 }

 func listenTCP() (net.Listener, string) {
 	l, e := net.Listen("tcp", "127.0.0.1:0") // any available address
 	if e != nil {
 		log.Fatalf("net.Listen tcp :0: %v", e)
 	}
 	return l, l.Addr().String()
 }

 func startServer() {
 	Register(new(Arith))

 	var l net.Listener
 	l, serverAddr = listenTCP()
 	log.Println("Test RPC server listening on", serverAddr)
 	go Accept(l)

 	HandleHTTP()
 	httpOnce.Do(startHttpServer)
 }

 func startNewServer() {
 	newServer = NewServer()
 	newServer.Register(new(Arith))

 	var l net.Listener
 	l, newServerAddr = listenTCP()
 	log.Println("NewServer test RPC server listening on", newServerAddr)
 	go Accept(l)

 	newServer.HandleHTTP(newHttpPath, "/bar")
 	httpOnce.Do(startHttpServer)
 }

 func startHttpServer() {
 	server := httptest.NewServer(nil)
 	httpServerAddr = server.Listener.Addr().String()
 	log.Println("Test HTTP RPC server listening on", httpServerAddr)
 }

 func TestRPC(t *testing.T) {
 	once.Do(startServer)
 	testRPC(t, serverAddr)
 	newOnce.Do(startNewServer)
 	testRPC(t, newServerAddr)
 }

 func testRPC(t *testing.T, addr string) {
 	client, err := Dial("tcp", addr)
 	if err != nil {
 		t.Fatal("dialing", err)
 	}

 	// Synchronous calls
 	args := &Args{7, 8}
 	reply := new(Reply)
 	err = client.Call("Arith.Add", args, reply)
 	if err != nil {
 		t.Errorf("Add: expected no error but got string %q", err.String())
 	}
 	if reply.C != args.A+args.B {
 		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
 	}

 	// Nonexistent method
 	args = &Args{7, 0}
 	reply = new(Reply)
 	err = client.Call("Arith.BadOperation", args, reply)
 	// expect an error
 	if err == nil {
 		t.Error("BadOperation: expected error")
 	} else if !strings.HasPrefix(err.String(), "rpc: can't find method ") {
 		t.Errorf("BadOperation: expected can't find method error; got %q", err)
 	}

 	// Unknown service
 	args = &Args{7, 8}
 	reply = new(Reply)
 	err = client.Call("Arith.Unknown", args, reply)
 	if err == nil {
 		t.Error("expected error calling unknown service")
 	} else if strings.Index(err.String(), "method") < 0 {
 		t.Error("expected error about method; got", err)
 	}

 	// Out of order.
 	args = &Args{7, 8}
 	mulReply := new(Reply)
 	mulCall := client.Go("Arith.Mul", args, mulReply, nil)
 	addReply := new(Reply)
 	addCall := client.Go("Arith.Add", args, addReply, nil)

 	addCall = <-addCall.Done
 	if addCall.Error != nil {
 		t.Errorf("Add: expected no error but got string %q", addCall.Error.String())
 	}
 	if addReply.C != args.A+args.B {
 		t.Errorf("Add: expected %d got %d", addReply.C, args.A+args.B)
 	}

 	mulCall = <-mulCall.Done
 	if mulCall.Error != nil {
 		t.Errorf("Mul: expected no error but got string %q", mulCall.Error.String())
 	}
 	if mulReply.C != args.A*args.B {
 		t.Errorf("Mul: expected %d got %d", mulReply.C, args.A*args.B)
 	}

 	// Error test
 	args = &Args{7, 0}
 	reply = new(Reply)
 	err = client.Call("Arith.Div", args, reply)
 	// expect an error: zero divide
 	if err == nil {
 		t.Error("Div: expected error")
 	} else if err.String() != "divide by zero" {
 		t.Error("Div: expected divide by zero error; got", err)
 	}

 	// Bad type.
 	reply = new(Reply)
 	err = client.Call("Arith.Add", reply, reply) // args, reply would be the correct thing to use
 	if err == nil {
 		t.Error("expected error calling Arith.Add with wrong arg type")
 	} else if strings.Index(err.String(), "type") < 0 {
 		t.Error("expected error about type; got", err)
 	}

 	// Non-struct argument
 	const Val = 12345
 	str := fmt.Sprint(Val)
 	reply = new(Reply)
 	err = client.Call("Arith.Scan", &str, reply)
 	if err != nil {
 		t.Errorf("Scan: expected no error but got string %q", err.String())
 	} else if reply.C != Val {
 		t.Errorf("Scan: expected %d got %d", Val, reply.C)
 	}

 	// Non-struct reply
 	args = &Args{27, 35}
 	str = ""
 	err = client.Call("Arith.String", args, &str)
 	if err != nil {
 		t.Errorf("String: expected no error but got string %q", err.String())
 	}
 	expect := fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
 	if str != expect {
 		t.Errorf("String: expected %s got %s", expect, str)
 	}

 	args = &Args{7, 8}
 	reply = new(Reply)
 	err = client.Call("Arith.Mul", args, reply)
 	if err != nil {
 		t.Errorf("Mul: expected no error but got string %q", err.String())
 	}
 	if reply.C != args.A*args.B {
 		t.Errorf("Mul: expected %d got %d", reply.C, args.A*args.B)
 	}
 }

 func TestHTTP(t *testing.T) {
 	once.Do(startServer)
 	testHTTPRPC(t, "")
 	newOnce.Do(startNewServer)
 	testHTTPRPC(t, newHttpPath)
 }

 func testHTTPRPC(t *testing.T, path string) {
 	var client *Client
 	var err os.Error
 	if path == "" {
 		client, err = DialHTTP("tcp", httpServerAddr)
 	} else {
 		client, err = DialHTTPPath("tcp", httpServerAddr, path)
 	}
 	if err != nil {
 		t.Fatal("dialing", err)
 	}

 	// Synchronous calls
 	args := &Args{7, 8}
 	reply := new(Reply)
 	err = client.Call("Arith.Add", args, reply)
 	if err != nil {
 		t.Errorf("Add: expected no error but got string %q", err.String())
 	}
 	if reply.C != args.A+args.B {
 		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
 	}
 }

 // CodecEmulator provides a client-like api and a ServerCodec interface.
 // Can be used to test ServeRequest.
 type CodecEmulator struct {
 	server        *Server
 	serviceMethod string
 	args          *Args
 	reply         *Reply
 	err           os.Error
 }

 func (codec *CodecEmulator) Call(serviceMethod string, args *Args, reply *Reply) os.Error {
 	codec.serviceMethod = serviceMethod
 	codec.args = args
 	codec.reply = reply
 	codec.err = nil
 	var serverError os.Error
 	if codec.server == nil {
 		serverError = ServeRequest(codec)
 	} else {
 		serverError = codec.server.ServeRequest(codec)
 	}
 	if codec.err == nil && serverError != nil {
 		codec.err = serverError
 	}
 	return codec.err
 }

 func (codec *CodecEmulator) ReadRequestHeader(req *Request) os.Error {
 	req.ServiceMethod = codec.serviceMethod
 	req.Seq = 0
 	return nil
 }

 func (codec *CodecEmulator) ReadRequestBody(argv interface{}) os.Error {
 	if codec.args == nil {
 		return io.ErrUnexpectedEOF
 	}
 	*(argv.(*Args)) = *codec.args
 	return nil
 }

 func (codec *CodecEmulator) WriteResponse(resp *Response, reply interface{}) os.Error {
 	if resp.Error != "" {
 		codec.err = os.NewError(resp.Error)
 	} else {
 		*codec.reply = *(reply.(*Reply))
 	}
 	return nil
 }

 func (codec *CodecEmulator) Close() os.Error {
 	return nil
 }

 func TestServeRequest(t *testing.T) {
 	once.Do(startServer)
 	testServeRequest(t, nil)
 	newOnce.Do(startNewServer)
 	testServeRequest(t, newServer)
 }

 func testServeRequest(t *testing.T, server *Server) {
 	client := CodecEmulator{server: server}

 	args := &Args{7, 8}
 	reply := new(Reply)
 	err := client.Call("Arith.Add", args, reply)
 	if err != nil {
 		t.Errorf("Add: expected no error but got string %q", err.String())
 	}
 	if reply.C != args.A+args.B {
 		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
 	}

 	err = client.Call("Arith.Add", nil, reply)
 	if err == nil {
 		t.Errorf("expected error calling Arith.Add with nil arg")
 	}
 }

 type ReplyNotPointer int
 type ArgNotPublic int
 type ReplyNotPublic int
 type local struct{}

 func (t *ReplyNotPointer) ReplyNotPointer(args *Args, reply Reply) os.Error {
 	return nil
 }

 func (t *ArgNotPublic) ArgNotPublic(args *local, reply *Reply) os.Error {
 	return nil
 }

 func (t *ReplyNotPublic) ReplyNotPublic(args *Args, reply *local) os.Error {
 	return nil
 }

 // Check that registration handles lots of bad methods and a type with no suitable methods.
 func TestRegistrationError(t *testing.T) {
 	err := Register(new(ReplyNotPointer))
 	if err == nil {
 		t.Errorf("expected error registering ReplyNotPointer")
 	}
 	err = Register(new(ArgNotPublic))
 	if err == nil {
 		t.Errorf("expected error registering ArgNotPublic")
 	}
 	err = Register(new(ReplyNotPublic))
 	if err == nil {
 		t.Errorf("expected error registering ReplyNotPublic")
 	}
 }

 type WriteFailCodec int

 func (WriteFailCodec) WriteRequest(*Request, interface{}) os.Error {
 	// the panic caused by this error used to not unlock a lock.
 	return os.NewError("fail")
 }

 func (WriteFailCodec) ReadResponseHeader(*Response) os.Error {
 	time.Sleep(120e9)
 	panic("unreachable")
 }

 func (WriteFailCodec) ReadResponseBody(interface{}) os.Error {
 	time.Sleep(120e9)
 	panic("unreachable")
 }

 func (WriteFailCodec) Close() os.Error {
 	return nil
 }

 func TestSendDeadlock(t *testing.T) {
 	client := NewClientWithCodec(WriteFailCodec(0))

 	done := make(chan bool)
 	go func() {
 		testSendDeadlock(client)
 		testSendDeadlock(client)
 		done <- true
 	}()
 	select {
 	case <-done:
 		return
 	case <-time.After(5e9):
 		t.Fatal("deadlock")
 	}
 }

 func testSendDeadlock(client *Client) {
 	defer func() {
 		recover()
 	}()
 	args := &Args{7, 8}
 	reply := new(Reply)
 	client.Call("Arith.Add", args, reply)
 }

 func dialDirect() (*Client, os.Error) {
 	return Dial("tcp", serverAddr)
 }

 func dialHTTP() (*Client, os.Error) {
 	return DialHTTP("tcp", httpServerAddr)
 }

 func countMallocs(dial func() (*Client, os.Error), t *testing.T) uint64 {
 	once.Do(startServer)
 	client, err := dial()
 	if err != nil {
 		t.Fatal("error dialing", err)
 	}
 	args := &Args{7, 8}
 	reply := new(Reply)
 	runtime.UpdateMemStats()
 	mallocs := 0 - runtime.MemStats.Mallocs
 	const count = 100
 	for i := 0; i < count; i++ {
 		err := client.Call("Arith.Add", args, reply)
 		if err != nil {
 			t.Errorf("Add: expected no error but got string %q", err.String())
 		}
 		if reply.C != args.A+args.B {
 			t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
 		}
 	}
 	runtime.UpdateMemStats()
 	mallocs += runtime.MemStats.Mallocs
 	return mallocs / count
 }

 func TestCountMallocs(t *testing.T) {
 	fmt.Printf("mallocs per rpc round trip: %d\n", countMallocs(dialDirect, t))
 }

 func TestCountMallocsOverHTTP(t *testing.T) {
 	fmt.Printf("mallocs per HTTP rpc round trip: %d\n", countMallocs(dialHTTP, t))
 }

 type writeCrasher struct{}

 func (writeCrasher) Close() os.Error {
 	return nil
 }

 func (writeCrasher) Read(p []byte) (int, os.Error) {
 	return 0, os.EOF
 }

 func (writeCrasher) Write(p []byte) (int, os.Error) {
 	return 0, os.NewError("fake write failure")
 }

 func TestClientWriteError(t *testing.T) {
 	c := NewClient(writeCrasher{})
 	res := false
 	err := c.Call("foo", 1, &res)
 	if err == nil {
 		t.Fatal("expected error")
 	}
 	if err.String() != "fake write failure" {
 		t.Error("unexpected value of error:", err)
 	}
 }

 func benchmarkEndToEnd(dial func() (*Client, os.Error), b *testing.B) {
 	b.StopTimer()
 	once.Do(startServer)
 	client, err := dial()
 	if err != nil {
 		fmt.Println("error dialing", err)
 		return
 	}

 	// Synchronous calls
 	args := &Args{7, 8}
 	procs := runtime.GOMAXPROCS(-1)
 	N := int32(b.N)
 	var wg sync.WaitGroup
 	wg.Add(procs)
 	b.StartTimer()

 	for p := 0; p < procs; p++ {
 		go func() {
 			reply := new(Reply)
 			for atomic.AddInt32(&N, -1) >= 0 {
 				err = client.Call("Arith.Add", args, reply)
 				if err != nil {
 					fmt.Printf("Add: expected no error but got string %q", err.String())
 					panic("rpc error")
 				}
 				if reply.C != args.A+args.B {
 					fmt.Printf("Add: expected %d got %d", reply.C, args.A+args.B)
 					panic("rpc error")
 				}
 			}
 			wg.Done()
 		}()
 	}
 	wg.Wait()
 }

 func benchmarkEndToEndAsync(dial func() (*Client, os.Error), b *testing.B) {
 	const MaxConcurrentCalls = 100
 	b.StopTimer()
 	once.Do(startServer)
 	client, err := dial()
 	if err != nil {
 		fmt.Println("error dialing", err)
 		return
 	}

 	// Asynchronous calls
 	args := &Args{7, 8}
 	procs := 4 * runtime.GOMAXPROCS(-1)
 	send := int32(b.N)
 	recv := int32(b.N)
 	var wg sync.WaitGroup
 	wg.Add(procs)
 	gate := make(chan bool, MaxConcurrentCalls)
 	res := make(chan *Call, MaxConcurrentCalls)
 	b.StartTimer()

 	for p := 0; p < procs; p++ {
 		go func() {
 			for atomic.AddInt32(&send, -1) >= 0 {
 				gate <- true
 				reply := new(Reply)
 				client.Go("Arith.Add", args, reply, res)
 			}
 		}()
 		go func() {
 			for call := range res {
 				a := call.Args.(*Args).A
 				b := call.Args.(*Args).B
 				c := call.Reply.(*Reply).C
 				if a+b != c {
 					fmt.Printf("Add: expected %d got %d", a+b, c)
 					panic("incorrect reply")
 				}
 				<-gate
 				if atomic.AddInt32(&recv, -1) == 0 {
 					close(res)
 				}
 			}
 			wg.Done()
 		}()
 	}
 	wg.Wait()
 }

 func BenchmarkEndToEnd(b *testing.B) {
 	benchmarkEndToEnd(dialDirect, b)
 }

 func BenchmarkEndToEndHTTP(b *testing.B) {
 	benchmarkEndToEnd(dialHTTP, b)
 }

 func BenchmarkEndToEndAsync(b *testing.B) {
 	benchmarkEndToEndAsync(dialDirect, b)
 }

 func BenchmarkEndToEndAsyncHTTP(b *testing.B) {
 	benchmarkEndToEndAsync(dialHTTP, b)
 }
	// Copyright 2009 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 rpc

	import (
	"fmt"
	"http/httptest"
	"io"
	"log"
	"net"
	"os"
	"runtime"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"
	)

	var (
	newServer *Server
	serverAddr, newServerAddr string
	httpServerAddr string
	once, newOnce, httpOnce sync.Once
	)

	const (
	second = 1e9
	newHttpPath = "/foo"
	)

	type Args struct {
	A, B int
	}

	type Reply struct {
	C int
	}

	type Arith int

	// Some of Arith's methods have value args, some have pointer args. That's deliberate.

	func (t Arith) Add(args Args, reply Reply) os.Error {
	reply.C = args.A + args.B
	return nil
	}

	func (t Arith) Mul(args Args, reply *Reply) os.Error {
	reply.C = args.A * args.B
	return nil
	}

	func (t Arith) Div(args Args, reply Reply) os.Error {
	if args.B == 0 {
	return os.NewError("divide by zero")
	}
	reply.C = args.A / args.B
	return nil
	}

	func (t Arith) String(args Args, reply *string) os.Error {
	*reply = fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
	return nil
	}

	func (t Arith) Scan(args string, reply Reply) (err os.Error) {
	_, err = fmt.Sscan(args, &reply.C)
	return
	}

	func (t Arith) Error(args Args, reply *Reply) os.Error {
	panic("ERROR")
	}

	func listenTCP() (net.Listener, string) {
	l, e := net.Listen("tcp", "127.0.0.1:0") // any available address
	if e != nil {
	log.Fatalf("net.Listen tcp :0: %v", e)
	}
	return l, l.Addr().String()
	}

	func startServer() {
	Register(new(Arith))

	var l net.Listener
	l, serverAddr = listenTCP()
	log.Println("Test RPC server listening on", serverAddr)
	go Accept(l)

	HandleHTTP()
	httpOnce.Do(startHttpServer)
	}

	func startNewServer() {
	newServer = NewServer()
	newServer.Register(new(Arith))

	var l net.Listener
	l, newServerAddr = listenTCP()
	log.Println("NewServer test RPC server listening on", newServerAddr)
	go Accept(l)

	newServer.HandleHTTP(newHttpPath, "/bar")
	httpOnce.Do(startHttpServer)
	}

	func startHttpServer() {
	server := httptest.NewServer(nil)
	httpServerAddr = server.Listener.Addr().String()
	log.Println("Test HTTP RPC server listening on", httpServerAddr)
	}

	func TestRPC(t *testing.T) {
	once.Do(startServer)
	testRPC(t, serverAddr)
	newOnce.Do(startNewServer)
	testRPC(t, newServerAddr)
	}

	func testRPC(t *testing.T, addr string) {
	client, err := Dial("tcp", addr)
	if err != nil {
	t.Fatal("dialing", err)
	}

	// Synchronous calls
	args := &Args{7, 8}
	reply := new(Reply)
	err = client.Call("Arith.Add", args, reply)
	if err != nil {
	t.Errorf("Add: expected no error but got string %q", err.String())
	}
	if reply.C != args.A+args.B {
	t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
	}

	// Nonexistent method
	args = &Args{7, 0}
	reply = new(Reply)
	err = client.Call("Arith.BadOperation", args, reply)
	// expect an error
	if err == nil {
	t.Error("BadOperation: expected error")
	} else if !strings.HasPrefix(err.String(), "rpc: can't find method ") {
	t.Errorf("BadOperation: expected can't find method error; got %q", err)
	}

	// Unknown service
	args = &Args{7, 8}
	reply = new(Reply)
	err = client.Call("Arith.Unknown", args, reply)
	if err == nil {
	t.Error("expected error calling unknown service")
	} else if strings.Index(err.String(), "method") < 0 {
	t.Error("expected error about method; got", err)
	}

	// Out of order.
	args = &Args{7, 8}
	mulReply := new(Reply)
	mulCall := client.Go("Arith.Mul", args, mulReply, nil)
	addReply := new(Reply)
	addCall := client.Go("Arith.Add", args, addReply, nil)

	addCall = <-addCall.Done
	if addCall.Error != nil {
	t.Errorf("Add: expected no error but got string %q", addCall.Error.String())
	}
	if addReply.C != args.A+args.B {
	t.Errorf("Add: expected %d got %d", addReply.C, args.A+args.B)
	}

	mulCall = <-mulCall.Done
	if mulCall.Error != nil {
	t.Errorf("Mul: expected no error but got string %q", mulCall.Error.String())
	}
	if mulReply.C != args.A*args.B {
	t.Errorf("Mul: expected %d got %d", mulReply.C, args.A*args.B)
	}

	// Error test
	args = &Args{7, 0}
	reply = new(Reply)
	err = client.Call("Arith.Div", args, reply)
	// expect an error: zero divide
	if err == nil {
	t.Error("Div: expected error")
	} else if err.String() != "divide by zero" {
	t.Error("Div: expected divide by zero error; got", err)
	}

	// Bad type.
	reply = new(Reply)
	err = client.Call("Arith.Add", reply, reply) // args, reply would be the correct thing to use
	if err == nil {
	t.Error("expected error calling Arith.Add with wrong arg type")
	} else if strings.Index(err.String(), "type") < 0 {
	t.Error("expected error about type; got", err)
	}

	// Non-struct argument
	const Val = 12345
	str := fmt.Sprint(Val)
	reply = new(Reply)
	err = client.Call("Arith.Scan", &str, reply)
	if err != nil {
	t.Errorf("Scan: expected no error but got string %q", err.String())
	} else if reply.C != Val {
	t.Errorf("Scan: expected %d got %d", Val, reply.C)
	}

	// Non-struct reply
	args = &Args{27, 35}
	str = ""
	err = client.Call("Arith.String", args, &str)
	if err != nil {
	t.Errorf("String: expected no error but got string %q", err.String())
	}
	expect := fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
	if str != expect {
	t.Errorf("String: expected %s got %s", expect, str)
	}

	args = &Args{7, 8}
	reply = new(Reply)
	err = client.Call("Arith.Mul", args, reply)
	if err != nil {
	t.Errorf("Mul: expected no error but got string %q", err.String())
	}
	if reply.C != args.A*args.B {
	t.Errorf("Mul: expected %d got %d", reply.C, args.A*args.B)
	}
	}

	func TestHTTP(t *testing.T) {
	once.Do(startServer)
	testHTTPRPC(t, "")
	newOnce.Do(startNewServer)
	testHTTPRPC(t, newHttpPath)
	}

	func testHTTPRPC(t *testing.T, path string) {
	var client *Client
	var err os.Error
	if path == "" {
	client, err = DialHTTP("tcp", httpServerAddr)
	} else {
	client, err = DialHTTPPath("tcp", httpServerAddr, path)
	}
	if err != nil {
	t.Fatal("dialing", err)
	}

	// Synchronous calls
	args := &Args{7, 8}
	reply := new(Reply)
	err = client.Call("Arith.Add", args, reply)
	if err != nil {
	t.Errorf("Add: expected no error but got string %q", err.String())
	}
	if reply.C != args.A+args.B {
	t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
	}
	}

	// CodecEmulator provides a client-like api and a ServerCodec interface.
	// Can be used to test ServeRequest.
	type CodecEmulator struct {
	server *Server
	serviceMethod string
	args *Args
	reply *Reply
	err os.Error
	}

	func (codec CodecEmulator) Call(serviceMethod string, args Args, reply *Reply) os.Error {
	codec.serviceMethod = serviceMethod
	codec.args = args
	codec.reply = reply
	codec.err = nil
	var serverError os.Error
	if codec.server == nil {
	serverError = ServeRequest(codec)
	} else {
	serverError = codec.server.ServeRequest(codec)
	}
	if codec.err == nil && serverError != nil {
	codec.err = serverError
	}
	return codec.err
	}

	func (codec CodecEmulator) ReadRequestHeader(req Request) os.Error {
	req.ServiceMethod = codec.serviceMethod
	req.Seq = 0
	return nil
	}

	func (codec *CodecEmulator) ReadRequestBody(argv interface{}) os.Error {
	if codec.args == nil {
	return io.ErrUnexpectedEOF
	}
	(argv.(Args)) = *codec.args
	return nil
	}

	func (codec CodecEmulator) WriteResponse(resp Response, reply interface{}) os.Error {
	if resp.Error != "" {
	codec.err = os.NewError(resp.Error)
	} else {
	codec.reply = (reply.(*Reply))
	}
	return nil
	}

	func (codec *CodecEmulator) Close() os.Error {
	return nil
	}

	func TestServeRequest(t *testing.T) {
	once.Do(startServer)
	testServeRequest(t, nil)
	newOnce.Do(startNewServer)
	testServeRequest(t, newServer)
	}

	func testServeRequest(t testing.T, server Server) {
	client := CodecEmulator{server: server}

	args := &Args{7, 8}
	reply := new(Reply)
	err := client.Call("Arith.Add", args, reply)
	if err != nil {
	t.Errorf("Add: expected no error but got string %q", err.String())
	}
	if reply.C != args.A+args.B {
	t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
	}

	err = client.Call("Arith.Add", nil, reply)
	if err == nil {
	t.Errorf("expected error calling Arith.Add with nil arg")
	}
	}

	type ReplyNotPointer int
	type ArgNotPublic int
	type ReplyNotPublic int
	type local struct{}

	func (t ReplyNotPointer) ReplyNotPointer(args Args, reply Reply) os.Error {
	return nil
	}

	func (t ArgNotPublic) ArgNotPublic(args local, reply *Reply) os.Error {
	return nil
	}

	func (t ReplyNotPublic) ReplyNotPublic(args Args, reply *local) os.Error {
	return nil
	}

	// Check that registration handles lots of bad methods and a type with no suitable methods.
	func TestRegistrationError(t *testing.T) {
	err := Register(new(ReplyNotPointer))
	if err == nil {
	t.Errorf("expected error registering ReplyNotPointer")
	}
	err = Register(new(ArgNotPublic))
	if err == nil {
	t.Errorf("expected error registering ArgNotPublic")
	}
	err = Register(new(ReplyNotPublic))
	if err == nil {
	t.Errorf("expected error registering ReplyNotPublic")
	}
	}

	type WriteFailCodec int

	func (WriteFailCodec) WriteRequest(*Request, interface{}) os.Error {
	// the panic caused by this error used to not unlock a lock.
	return os.NewError("fail")
	}

	func (WriteFailCodec) ReadResponseHeader(*Response) os.Error {
	time.Sleep(120e9)
	panic("unreachable")
	}

	func (WriteFailCodec) ReadResponseBody(interface{}) os.Error {
	time.Sleep(120e9)
	panic("unreachable")
	}

	func (WriteFailCodec) Close() os.Error {
	return nil
	}

	func TestSendDeadlock(t *testing.T) {
	client := NewClientWithCodec(WriteFailCodec(0))

	done := make(chan bool)
	go func() {
	testSendDeadlock(client)
	testSendDeadlock(client)
	done <- true
	}()
	select {
	case <-done:
	return
	case <-time.After(5e9):
	t.Fatal("deadlock")
	}
	}

	func testSendDeadlock(client *Client) {
	defer func() {
	recover()
	}()
	args := &Args{7, 8}
	reply := new(Reply)
	client.Call("Arith.Add", args, reply)
	}

	func dialDirect() (*Client, os.Error) {
	return Dial("tcp", serverAddr)
	}

	func dialHTTP() (*Client, os.Error) {
	return DialHTTP("tcp", httpServerAddr)
	}

	func countMallocs(dial func() (Client, os.Error), t testing.T) uint64 {
	once.Do(startServer)
	client, err := dial()
	if err != nil {
	t.Fatal("error dialing", err)
	}
	args := &Args{7, 8}
	reply := new(Reply)
	runtime.UpdateMemStats()
	mallocs := 0 - runtime.MemStats.Mallocs
	const count = 100
	for i := 0; i < count; i++ {
	err := client.Call("Arith.Add", args, reply)
	if err != nil {
	t.Errorf("Add: expected no error but got string %q", err.String())
	}
	if reply.C != args.A+args.B {
	t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
	}
	}
	runtime.UpdateMemStats()
	mallocs += runtime.MemStats.Mallocs
	return mallocs / count
	}

	func TestCountMallocs(t *testing.T) {
	fmt.Printf("mallocs per rpc round trip: %d\n", countMallocs(dialDirect, t))
	}

	func TestCountMallocsOverHTTP(t *testing.T) {
	fmt.Printf("mallocs per HTTP rpc round trip: %d\n", countMallocs(dialHTTP, t))
	}

	type writeCrasher struct{}

	func (writeCrasher) Close() os.Error {
	return nil
	}

	func (writeCrasher) Read(p []byte) (int, os.Error) {
	return 0, os.EOF
	}

	func (writeCrasher) Write(p []byte) (int, os.Error) {
	return 0, os.NewError("fake write failure")
	}

	func TestClientWriteError(t *testing.T) {
	c := NewClient(writeCrasher{})
	res := false
	err := c.Call("foo", 1, &res)
	if err == nil {
	t.Fatal("expected error")
	}
	if err.String() != "fake write failure" {
	t.Error("unexpected value of error:", err)
	}
	}

	func benchmarkEndToEnd(dial func() (Client, os.Error), b testing.B) {
	b.StopTimer()
	once.Do(startServer)
	client, err := dial()
	if err != nil {
	fmt.Println("error dialing", err)
	return
	}

	// Synchronous calls
	args := &Args{7, 8}
	procs := runtime.GOMAXPROCS(-1)
	N := int32(b.N)
	var wg sync.WaitGroup
	wg.Add(procs)
	b.StartTimer()

	for p := 0; p < procs; p++ {
	go func() {
	reply := new(Reply)
	for atomic.AddInt32(&N, -1) >= 0 {
	err = client.Call("Arith.Add", args, reply)
	if err != nil {
	fmt.Printf("Add: expected no error but got string %q", err.String())
	panic("rpc error")
	}
	if reply.C != args.A+args.B {
	fmt.Printf("Add: expected %d got %d", reply.C, args.A+args.B)
	panic("rpc error")
	}
	}
	wg.Done()
	}()
	}
	wg.Wait()
	}

	func benchmarkEndToEndAsync(dial func() (Client, os.Error), b testing.B) {
	const MaxConcurrentCalls = 100
	b.StopTimer()
	once.Do(startServer)
	client, err := dial()
	if err != nil {
	fmt.Println("error dialing", err)
	return
	}

	// Asynchronous calls
	args := &Args{7, 8}
	procs := 4 * runtime.GOMAXPROCS(-1)
	send := int32(b.N)
	recv := int32(b.N)
	var wg sync.WaitGroup
	wg.Add(procs)
	gate := make(chan bool, MaxConcurrentCalls)
	res := make(chan *Call, MaxConcurrentCalls)
	b.StartTimer()

	for p := 0; p < procs; p++ {
	go func() {
	for atomic.AddInt32(&send, -1) >= 0 {
	gate <- true
	reply := new(Reply)
	client.Go("Arith.Add", args, reply, res)
	}
	}()
	go func() {
	for call := range res {
	a := call.Args.(*Args).A
	b := call.Args.(*Args).B
	c := call.Reply.(*Reply).C
	if a+b != c {
	fmt.Printf("Add: expected %d got %d", a+b, c)
	panic("incorrect reply")
	}
	<-gate
	if atomic.AddInt32(&recv, -1) == 0 {
	close(res)
	}
	}
	wg.Done()
	}()
	}
	wg.Wait()
	}

	func BenchmarkEndToEnd(b *testing.B) {
	benchmarkEndToEnd(dialDirect, b)
	}

	func BenchmarkEndToEndHTTP(b *testing.B) {
	benchmarkEndToEnd(dialHTTP, b)
	}

	func BenchmarkEndToEndAsync(b *testing.B) {
	benchmarkEndToEndAsync(dialDirect, b)
	}

	func BenchmarkEndToEndAsyncHTTP(b *testing.B) {
	benchmarkEndToEndAsync(dialHTTP, b)
	}