ch4-05: 增加截取器内容

ch4-rpc/ch4-05-grpc-hack.md

@@ -266,15 +266,57 @@ func (a *Authentication) Auth(ctx context.Context) error {
 
 首先通过metadata.FromIncomingContext从ctx上下文中获取元信息，然后取出相应的认证信息进行认证。
 
-
-<!--
 ## 截取器
 
-流的截取器简单提下，重点是普通函数的截取
+GRPC中的grpc.UnaryInterceptor和grpc.StreamInterceptor分别对普通方法和流方法提供了截取器的支持。我们这里简单介绍普通方法的截取器用法。
 
-登陆，日志跟踪，panic捕获
+要实现普通方法的截取器，需要为grpc.UnaryInterceptor的参数实现一个函数：
 
-TODO
+```go
+func filter(ctx context.Context,
+	req interface{}, info *grpc.UnaryServerInfo,
+	handler grpc.UnaryHandler,
+) (resp interface{}, err error) {
+	log.Println("fileter:", info)
+	return handler(ctx, req)
+}
+```
+
+函数的ctx和req参数就是每个普通的RPC方法的前两个参数。第三个info参数表示当前是对应的那个GRPC方法，第四个handler参数对应当前的GRPC方法函数。上面的函数中首先是日志输出info参数，然后调用handler对应的GRPC方法函数。
+
+要使用filter截取器函数，只需要在启动GRPC服务时作为参数输入即可：
+
+```go
+server := grpc.NewServer(grpc.UnaryInterceptor(filter))
+```
+
+然后服务器在收到每个GRPC方法调用之前，会首先输出一行日志，然后再调用对方的方法。
+
+如果截取器函数返回了错误，那么该次GRPC方法调用将被视作失败处理。因此，我们可以在截取器中对输入的参数做一些简单的验证工作。同样，也可以对handler返回的结果做一些验证工作。截取器也非常适合前面对Token认证工作。
+
+下面是截取器增加了对GRPC方法异常对捕获：
+
+```go
+func filter(
+	ctx context.Context, req interface{},
+	info *grpc.UnaryServerInfo,
+	handler grpc.UnaryHandler,
+) (resp interface{}, err error) {
+	log.Println("fileter:", info)
+
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("panic: %v", r)
+		}
+	}()
+
+	return handler(ctx, req)
+}
+```
+
+不够GRPC框架中只能为每个服务设置一个截取器，因此所有对截取工作只能在一个函数中完成。不过开源的grpc-ecosystem项目中的go-grpc-middleware包已经基于GRPC对截取器实现了链式截取器的支持，感兴趣的同学可以参考。
+
+<!--
 
 ## 和Web服务共存
 

vendor/gobook.examples/ch4-05-grpc-hack/panic-and-log/Makefile

@@ -0,0 +1,10 @@
+
+run:
+	@go build -o a.out && ./a.out
+	-@rm ./a.out
+
+gen:
+	protoc -I . --go_out=plugins=grpc:. helloworld.proto
+
+clean:
+	-rm *.pb.go

vendor/gobook.examples/ch4-05-grpc-hack/panic-and-log/helloworld.pb.go

@@ -0,0 +1,192 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: helloworld.proto
+
+package main
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+import (
+	context "golang.org/x/net/context"
+	grpc "google.golang.org/grpc"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type HelloRequest struct {
+	Name                 string   `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *HelloRequest) Reset()         { *m = HelloRequest{} }
+func (m *HelloRequest) String() string { return proto.CompactTextString(m) }
+func (*HelloRequest) ProtoMessage()    {}
+func (*HelloRequest) Descriptor() ([]byte, []int) {
+	return fileDescriptor_helloworld_04dfe859c9b956ba, []int{0}
+}
+func (m *HelloRequest) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HelloRequest.Unmarshal(m, b)
+}
+func (m *HelloRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HelloRequest.Marshal(b, m, deterministic)
+}
+func (dst *HelloRequest) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HelloRequest.Merge(dst, src)
+}
+func (m *HelloRequest) XXX_Size() int {
+	return xxx_messageInfo_HelloRequest.Size(m)
+}
+func (m *HelloRequest) XXX_DiscardUnknown() {
+	xxx_messageInfo_HelloRequest.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HelloRequest proto.InternalMessageInfo
+
+func (m *HelloRequest) GetName() string {
+	if m != nil {
+		return m.Name
+	}
+	return ""
+}
+
+type HelloReply struct {
+	Message              string   `protobuf:"bytes,1,opt,name=message,proto3" json:"message,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *HelloReply) Reset()         { *m = HelloReply{} }
+func (m *HelloReply) String() string { return proto.CompactTextString(m) }
+func (*HelloReply) ProtoMessage()    {}
+func (*HelloReply) Descriptor() ([]byte, []int) {
+	return fileDescriptor_helloworld_04dfe859c9b956ba, []int{1}
+}
+func (m *HelloReply) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_HelloReply.Unmarshal(m, b)
+}
+func (m *HelloReply) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_HelloReply.Marshal(b, m, deterministic)
+}
+func (dst *HelloReply) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_HelloReply.Merge(dst, src)
+}
+func (m *HelloReply) XXX_Size() int {
+	return xxx_messageInfo_HelloReply.Size(m)
+}
+func (m *HelloReply) XXX_DiscardUnknown() {
+	xxx_messageInfo_HelloReply.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_HelloReply proto.InternalMessageInfo
+
+func (m *HelloReply) GetMessage() string {
+	if m != nil {
+		return m.Message
+	}
+	return ""
+}
+
+func init() {
+	proto.RegisterType((*HelloRequest)(nil), "main.HelloRequest")
+	proto.RegisterType((*HelloReply)(nil), "main.HelloReply")
+}
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ context.Context
+var _ grpc.ClientConn
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+const _ = grpc.SupportPackageIsVersion4
+
+// GreeterClient is the client API for Greeter service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
+type GreeterClient interface {
+	SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
+}
+
+type greeterClient struct {
+	cc *grpc.ClientConn
+}
+
+func NewGreeterClient(cc *grpc.ClientConn) GreeterClient {
+	return &greeterClient{cc}
+}
+
+func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
+	out := new(HelloReply)
+	err := c.cc.Invoke(ctx, "/main.Greeter/SayHello", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// GreeterServer is the server API for Greeter service.
+type GreeterServer interface {
+	SayHello(context.Context, *HelloRequest) (*HelloReply, error)
+}
+
+func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
+	s.RegisterService(&_Greeter_serviceDesc, srv)
+}
+
+func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(HelloRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(GreeterServer).SayHello(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/main.Greeter/SayHello",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+var _Greeter_serviceDesc = grpc.ServiceDesc{
+	ServiceName: "main.Greeter",
+	HandlerType: (*GreeterServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "SayHello",
+			Handler:    _Greeter_SayHello_Handler,
+		},
+	},
+	Streams:  []grpc.StreamDesc{},
+	Metadata: "helloworld.proto",
+}
+
+func init() { proto.RegisterFile("helloworld.proto", fileDescriptor_helloworld_04dfe859c9b956ba) }
+
+var fileDescriptor_helloworld_04dfe859c9b956ba = []byte{
+	// 142 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x12, 0xc8, 0x48, 0xcd, 0xc9,
+	0xc9, 0x2f, 0xcf, 0x2f, 0xca, 0x49, 0xd1, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0x62, 0xc9, 0x4d,
+	0xcc, 0xcc, 0x53, 0x52, 0xe2, 0xe2, 0xf1, 0x00, 0xc9, 0x04, 0xa5, 0x16, 0x96, 0xa6, 0x16, 0x97,
+	0x08, 0x09, 0x71, 0xb1, 0xe4, 0x25, 0xe6, 0xa6, 0x4a, 0x30, 0x2a, 0x30, 0x6a, 0x70, 0x06, 0x81,
+	0xd9, 0x4a, 0x6a, 0x5c, 0x5c, 0x50, 0x35, 0x05, 0x39, 0x95, 0x42, 0x12, 0x5c, 0xec, 0xb9, 0xa9,
+	0xc5, 0xc5, 0x89, 0xe9, 0x30, 0x45, 0x30, 0xae, 0x91, 0x35, 0x17, 0xbb, 0x7b, 0x51, 0x6a, 0x6a,
+	0x49, 0x6a, 0x91, 0x90, 0x01, 0x17, 0x47, 0x70, 0x62, 0x25, 0x58, 0x97, 0x90, 0x90, 0x1e, 0xc8,
+	0x26, 0x3d, 0x64, 0x6b, 0xa4, 0x04, 0x50, 0xc4, 0x0a, 0x72, 0x2a, 0x93, 0xd8, 0xc0, 0xae, 0x32,
+	0x06, 0x04, 0x00, 0x00, 0xff, 0xff, 0x18, 0x38, 0x13, 0xf1, 0xa9, 0x00, 0x00, 0x00,
+}

vendor/gobook.examples/ch4-05-grpc-hack/panic-and-log/helloworld.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+package main;
+
+service Greeter {
+	rpc SayHello (HelloRequest) returns (HelloReply);
+}
+
+message HelloRequest {
+	string name = 1;
+}
+
+message HelloReply {
+	string message = 1;
+}

vendor/gobook.examples/ch4-05-grpc-hack/panic-and-log/main.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	fmt "fmt"
+	"log"
+	"net"
+	"time"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+var port = ":5000"
+
+type myGrpcServer struct{}
+
+func (s *myGrpcServer) SayHello(ctx context.Context, in *HelloRequest) (*HelloReply, error) {
+	panic("debug")
+	return &HelloReply{Message: "Hello " + in.Name}, nil
+}
+
+func main() {
+	go startServer()
+	time.Sleep(time.Second)
+
+	doClientWork()
+}
+
+func filter(
+	ctx context.Context, req interface{},
+	info *grpc.UnaryServerInfo,
+	handler grpc.UnaryHandler,
+) (resp interface{}, err error) {
+	log.Println("fileter:", info)
+
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("panic: %v", r)
+		}
+	}()
+
+	// valiate req
+
+	return handler(ctx, req)
+}
+
+func startServer() {
+	server := grpc.NewServer(grpc.UnaryInterceptor(filter))
+	RegisterGreeterServer(server, new(myGrpcServer))
+
+	lis, err := net.Listen("tcp", port)
+	if err != nil {
+		log.Panicf("could not list on %s: %s", port, err)
+	}
+
+	if err := server.Serve(lis); err != nil {
+		log.Panicf("grpc serve error: %s", err)
+	}
+}
+
+func doClientWork() {
+	conn, err := grpc.Dial("localhost"+port, grpc.WithInsecure())
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close()
+
+	c := NewGreeterClient(conn)
+
+	r, err := c.SayHello(context.Background(), &HelloRequest{Name: "gopher"})
+	if err != nil {
+		log.Fatalf("could not greet: %v", err)
+	}
+	log.Printf("doClientWork: %s", r.Message)
+}