You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
330 lines
14 KiB
330 lines
14 KiB
# 说明
|
|
|
|
gRPC暴露了两个拦截器接口，分别是：
|
|
|
|
* `grpc.UnaryServerInterceptor`服务端拦截器
|
|
* `grpc.UnaryClientInterceptor`客户端拦截器
|
|
|
|
基于两个拦截器可以针对性的定制公共模块的封装代码，比如`warden/logging.go`是通用日志逻辑。
|
|
|
|
# 分析
|
|
|
|
## 服务端拦截器
|
|
|
|
让我们先看一下`grpc.UnaryServerInterceptor`的声明，[官方代码位置](https://github.com/grpc/grpc-go/blob/master/interceptor.go)：
|
|
|
|
```go
|
|
// UnaryServerInfo consists of various information about a unary RPC on
|
|
// server side. All per-rpc information may be mutated by the interceptor.
|
|
type UnaryServerInfo struct {
|
|
// Server is the service implementation the user provides. This is read-only.
|
|
Server interface{}
|
|
// FullMethod is the full RPC method string, i.e., /package.service/method.
|
|
FullMethod string
|
|
}
|
|
|
|
// UnaryHandler defines the handler invoked by UnaryServerInterceptor to complete the normal
|
|
// execution of a unary RPC. If a UnaryHandler returns an error, it should be produced by the
|
|
// status package, or else gRPC will use codes.Unknown as the status code and err.Error() as
|
|
// the status message of the RPC.
|
|
type UnaryHandler func(ctx context.Context, req interface{}) (interface{}, error)
|
|
|
|
// UnaryServerInterceptor provides a hook to intercept the execution of a unary RPC on the server. info
|
|
// contains all the information of this RPC the interceptor can operate on. And handler is the wrapper
|
|
// of the service method implementation. It is the responsibility of the interceptor to invoke handler
|
|
// to complete the RPC.
|
|
type UnaryServerInterceptor func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (resp interface{}, err error)
|
|
```
|
|
|
|
看起来很简单包括：
|
|
|
|
* 一个`UnaryServerInfo`结构体用于`Server`和`FullMethod`字段传递，`Server`为`gRPC server`的对象实例，`FullMethod`为请求方法的全名
|
|
* 一个`UnaryHandler`方法用于传递`Handler`，就是基于`proto`文件`service`内声明而生成的方法
|
|
* 一个`UnaryServerInterceptor`用于拦截`Handler`方法，可在`Handler`执行前后插入拦截代码
|
|
|
|
为了更形象的说明拦截器的执行过程，请看基于`proto`生成的以下代码[代码位置](https://github.com/bilibili/kratos-demo/blob/master/api/api.pb.go)：
|
|
|
|
```go
|
|
func _Demo_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
|
|
in := new(HelloReq)
|
|
if err := dec(in); err != nil {
|
|
return nil, err
|
|
}
|
|
if interceptor == nil {
|
|
return srv.(DemoServer).SayHello(ctx, in)
|
|
}
|
|
info := &grpc.UnaryServerInfo{
|
|
Server: srv,
|
|
FullMethod: "/demo.service.v1.Demo/SayHello",
|
|
}
|
|
handler := func(ctx context.Context, req interface{}) (interface{}, error) {
|
|
return srv.(DemoServer).SayHello(ctx, req.(*HelloReq))
|
|
}
|
|
return interceptor(ctx, in, info, handler)
|
|
}
|
|
```
|
|
|
|
这个`_Demo_SayHello_Handler`方法是关键，该方法会被包装为`grpc.ServiceDesc`结构，被注册到gRPC内部，具体可在生成的`pb.go`代码内查找`s.RegisterService(&_Demo_serviceDesc, srv)`。
|
|
|
|
* 当`gRPC server`收到一次请求时，首先根据请求方法从注册到`server`内的`grpc.ServiceDesc`找到该方法对应的`Handler`如：`_Demo_SayHello_Handler`并执行
|
|
* `_Demo_SayHello_Handler`执行过程请看上面具体代码，当`interceptor`不为`nil`时，会将`SayHello`包装为`grpc.UnaryHandler`结构传递给`interceptor`
|
|
|
|
这样就完成了`UnaryServerInterceptor`的执行过程。那么`_Demo_SayHello_Handler`内的`interceptor`是如何注入到`gRPC server`内，则看下面这段代码[官方代码位置](https://github.com/grpc/grpc-go/blob/master/server.go)：
|
|
|
|
```go
|
|
// UnaryInterceptor returns a ServerOption that sets the UnaryServerInterceptor for the
|
|
// server. Only one unary interceptor can be installed. The construction of multiple
|
|
// interceptors (e.g., chaining) can be implemented at the caller.
|
|
func UnaryInterceptor(i UnaryServerInterceptor) ServerOption {
|
|
return func(o *options) {
|
|
if o.unaryInt != nil {
|
|
panic("The unary server interceptor was already set and may not be reset.")
|
|
}
|
|
o.unaryInt = i
|
|
}
|
|
}
|
|
```
|
|
|
|
请一定注意这方法的注释！！！
|
|
|
|
> Only one unary interceptor can be installed. The construction of multiple interceptors (e.g., chaining) can be implemented at the caller.
|
|
|
|
`gRPC`本身只支持一个`interceptor`，想要多`interceptors`需要自己实现~~所以`warden`基于`grpc.UnaryClientInterceptor`实现了`interceptor chain`，请看下面代码[代码位置](https://github.com/bilibili/kratos/blob/master/pkg/net/rpc/warden/server.go)：
|
|
|
|
```go
|
|
// Use attachs a global inteceptor to the server.
|
|
// For example, this is the right place for a rate limiter or error management inteceptor.
|
|
func (s *Server) Use(handlers ...grpc.UnaryServerInterceptor) *Server {
|
|
finalSize := len(s.handlers) + len(handlers)
|
|
if finalSize >= int(_abortIndex) {
|
|
panic("warden: server use too many handlers")
|
|
}
|
|
mergedHandlers := make([]grpc.UnaryServerInterceptor, finalSize)
|
|
copy(mergedHandlers, s.handlers)
|
|
copy(mergedHandlers[len(s.handlers):], handlers)
|
|
s.handlers = mergedHandlers
|
|
return s
|
|
}
|
|
|
|
// interceptor is a single interceptor out of a chain of many interceptors.
|
|
// Execution is done in left-to-right order, including passing of context.
|
|
// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
|
|
// will see context changes of one and two.
|
|
func (s *Server) interceptor(ctx context.Context, req interface{}, args *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
|
|
var (
|
|
i int
|
|
chain grpc.UnaryHandler
|
|
)
|
|
|
|
n := len(s.handlers)
|
|
if n == 0 {
|
|
return handler(ctx, req)
|
|
}
|
|
|
|
chain = func(ic context.Context, ir interface{}) (interface{}, error) {
|
|
if i == n-1 {
|
|
return handler(ic, ir)
|
|
}
|
|
i++
|
|
return s.handlers[i](ic, ir, args, chain)
|
|
}
|
|
|
|
return s.handlers[0](ctx, req, args, chain)
|
|
}
|
|
```
|
|
|
|
很简单的逻辑：
|
|
|
|
* `warden server`使用`Use`方法进行`grpc.UnaryServerInterceptor`的注入，而`func (s *Server) interceptor`本身就实现了`grpc.UnaryServerInterceptor`
|
|
* `func (s *Server) interceptor`可以根据注册的`grpc.UnaryServerInterceptor`顺序从前到后依次执行
|
|
|
|
而`warden`在初始化的时候将该方法本身注册到了`gRPC server`，在`NewServer`方法内可以看到下面代码：
|
|
|
|
```go
|
|
opt = append(opt, keepParam, grpc.UnaryInterceptor(s.interceptor))
|
|
s.server = grpc.NewServer(opt...)
|
|
```
|
|
|
|
如此完整的服务端拦截器逻辑就串联完成。
|
|
|
|
## 客户端拦截器
|
|
|
|
|
|
让我们先看一下`grpc.UnaryClientInterceptor`的声明，[官方代码位置](https://github.com/grpc/grpc-go/blob/master/interceptor.go)：
|
|
|
|
```go
|
|
// UnaryInvoker is called by UnaryClientInterceptor to complete RPCs.
|
|
type UnaryInvoker func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error
|
|
|
|
// UnaryClientInterceptor intercepts the execution of a unary RPC on the client. invoker is the handler to complete the RPC
|
|
// and it is the responsibility of the interceptor to call it.
|
|
// This is an EXPERIMENTAL API.
|
|
type UnaryClientInterceptor func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, invoker UnaryInvoker, opts ...CallOption) error
|
|
```
|
|
|
|
看起来和服务端拦截器并没有什么太大的区别，比较简单包括：
|
|
|
|
* 一个`UnaryInvoker`表示客户端具体要发出的执行方法
|
|
* 一个`UnaryClientInterceptor`用于拦截`Invoker`方法，可在`Invoker`执行前后插入拦截代码
|
|
|
|
具体执行过程，请看基于`proto`生成的下面代码[代码位置](https://github.com/bilibili/kratos-demo/blob/master/api/api.pb.go)：
|
|
|
|
```go
|
|
func (c *demoClient) SayHello(ctx context.Context, in *HelloReq, opts ...grpc.CallOption) (*google_protobuf1.Empty, error) {
|
|
out := new(google_protobuf1.Empty)
|
|
err := grpc.Invoke(ctx, "/demo.service.v1.Demo/SayHello", in, out, c.cc, opts...)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return out, nil
|
|
}
|
|
```
|
|
|
|
当客户端调用`SayHello`时可以看到执行了`grpc.Invoke`方法，并且将`fullMethod`和其他参数传入，最终会执行下面代码[官方代码位置](https://github.com/grpc/grpc-go/blob/master/call.go)：
|
|
|
|
```go
|
|
// Invoke sends the RPC request on the wire and returns after response is
|
|
// received. This is typically called by generated code.
|
|
//
|
|
// All errors returned by Invoke are compatible with the status package.
|
|
func (cc *ClientConn) Invoke(ctx context.Context, method string, args, reply interface{}, opts ...CallOption) error {
|
|
// allow interceptor to see all applicable call options, which means those
|
|
// configured as defaults from dial option as well as per-call options
|
|
opts = combine(cc.dopts.callOptions, opts)
|
|
|
|
if cc.dopts.unaryInt != nil {
|
|
return cc.dopts.unaryInt(ctx, method, args, reply, cc, invoke, opts...)
|
|
}
|
|
return invoke(ctx, method, args, reply, cc, opts...)
|
|
}
|
|
```
|
|
|
|
其中的`unaryInt`即为客户端连接创建时注册的拦截器，使用下面代码注册[官方代码位置](https://github.com/grpc/grpc-go/blob/master/dialoptions.go)：
|
|
|
|
```go
|
|
// WithUnaryInterceptor returns a DialOption that specifies the interceptor for
|
|
// unary RPCs.
|
|
func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption {
|
|
return newFuncDialOption(func(o *dialOptions) {
|
|
o.unaryInt = f
|
|
})
|
|
}
|
|
```
|
|
|
|
需要注意的是客户端的拦截器在官方`gRPC`内也只能支持注册一个，与服务端拦截器`interceptor chain`逻辑类似`warden`在客户端拦截器也做了相同处理，并且在客户端连接时进行注册，请看下面代码[代码位置](https://github.com/bilibili/kratos/blob/master/pkg/net/rpc/warden/client.go)：
|
|
|
|
```go
|
|
// Use attachs a global inteceptor to the Client.
|
|
// For example, this is the right place for a circuit breaker or error management inteceptor.
|
|
func (c *Client) Use(handlers ...grpc.UnaryClientInterceptor) *Client {
|
|
finalSize := len(c.handlers) + len(handlers)
|
|
if finalSize >= int(_abortIndex) {
|
|
panic("warden: client use too many handlers")
|
|
}
|
|
mergedHandlers := make([]grpc.UnaryClientInterceptor, finalSize)
|
|
copy(mergedHandlers, c.handlers)
|
|
copy(mergedHandlers[len(c.handlers):], handlers)
|
|
c.handlers = mergedHandlers
|
|
return c
|
|
}
|
|
|
|
// chainUnaryClient creates a single interceptor out of a chain of many interceptors.
|
|
//
|
|
// Execution is done in left-to-right order, including passing of context.
|
|
// For example ChainUnaryClient(one, two, three) will execute one before two before three.
|
|
func (c *Client) chainUnaryClient() grpc.UnaryClientInterceptor {
|
|
n := len(c.handlers)
|
|
if n == 0 {
|
|
return func(ctx context.Context, method string, req, reply interface{},
|
|
cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
|
|
return invoker(ctx, method, req, reply, cc, opts...)
|
|
}
|
|
}
|
|
|
|
return func(ctx context.Context, method string, req, reply interface{},
|
|
cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
|
|
var (
|
|
i int
|
|
chainHandler grpc.UnaryInvoker
|
|
)
|
|
chainHandler = func(ictx context.Context, imethod string, ireq, ireply interface{}, ic *grpc.ClientConn, iopts ...grpc.CallOption) error {
|
|
if i == n-1 {
|
|
return invoker(ictx, imethod, ireq, ireply, ic, iopts...)
|
|
}
|
|
i++
|
|
return c.handlers[i](ictx, imethod, ireq, ireply, ic, chainHandler, iopts...)
|
|
}
|
|
|
|
return c.handlers[0](ctx, method, req, reply, cc, chainHandler, opts...)
|
|
}
|
|
}
|
|
```
|
|
|
|
如此完整的客户端拦截器逻辑就串联完成。
|
|
|
|
# 实现自己的拦截器
|
|
|
|
以服务端拦截器`logging`为例：
|
|
|
|
```go
|
|
// serverLogging warden grpc logging
|
|
func serverLogging() grpc.UnaryServerInterceptor {
|
|
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
|
|
// NOTE: handler执行之前的拦截代码：主要获取一些关键参数，如耗时计时、ip等
|
|
// 如果自定义的拦截器只需要在handler执行后，那么可以直接执行handler
|
|
|
|
startTime := time.Now()
|
|
caller := metadata.String(ctx, metadata.Caller)
|
|
if caller == "" {
|
|
caller = "no_user"
|
|
}
|
|
var remoteIP string
|
|
if peerInfo, ok := peer.FromContext(ctx); ok {
|
|
remoteIP = peerInfo.Addr.String()
|
|
}
|
|
var quota float64
|
|
if deadline, ok := ctx.Deadline(); ok {
|
|
quota = time.Until(deadline).Seconds()
|
|
}
|
|
|
|
// call server handler
|
|
resp, err := handler(ctx, req) // NOTE: 以具体执行的handler为分界线！！！
|
|
|
|
// NOTE: handler执行之后的拦截代码：主要进行耗时计算、日志记录
|
|
// 如果自定义的拦截器在handler执行后不需要逻辑，这可直接返回
|
|
|
|
// after server response
|
|
code := ecode.Cause(err).Code()
|
|
duration := time.Since(startTime)
|
|
|
|
// monitor
|
|
statsServer.Timing(caller, int64(duration/time.Millisecond), info.FullMethod)
|
|
statsServer.Incr(caller, info.FullMethod, strconv.Itoa(code))
|
|
logFields := []log.D{
|
|
log.KVString("user", caller),
|
|
log.KVString("ip", remoteIP),
|
|
log.KVString("path", info.FullMethod),
|
|
log.KVInt("ret", code),
|
|
// TODO: it will panic if someone remove String method from protobuf message struct that auto generate from protoc.
|
|
log.KVString("args", req.(fmt.Stringer).String()),
|
|
log.KVFloat64("ts", duration.Seconds()),
|
|
log.KVFloat64("timeout_quota", quota),
|
|
log.KVString("source", "grpc-access-log"),
|
|
}
|
|
if err != nil {
|
|
logFields = append(logFields, log.KV("error", err.Error()), log.KV("stack", fmt.Sprintf("%+v", err)))
|
|
}
|
|
logFn(code, duration)(ctx, logFields...)
|
|
return resp, err
|
|
}
|
|
}
|
|
```
|
|
|
|
# 扩展阅读
|
|
|
|
[warden快速开始](warden-quickstart.md) [warden基于pb生成](warden-pb.md) [warden负载均衡](warden-balancer.md) [warden服务发现](warden-resolver.md)
|
|
|
|
-------------
|
|
|
|
[文档目录树](summary.md)
|
|
|
|
|