felixhao
6 years ago
parent
afb16a0f56
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1c83b7cade
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# 说明 |
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gRPC暴露了两个拦截器接口，分别是： |
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* `grpc.UnaryServerInterceptor`服务端拦截器 |
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* `grpc.UnaryClientInterceptor`客户端拦截器 |
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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。 |
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# 分析 |
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## 服务端拦截器 |
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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)： |
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```go |
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// UnaryServerInfo consists of various information about a unary RPC on |
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// server side. All per-rpc information may be mutated by the interceptor. |
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type UnaryServerInfo struct { |
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// Server is the service implementation the user provides. This is read-only. |
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Server interface{} |
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// FullMethod is the full RPC method string, i.e., /package.service/method. |
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FullMethod string |
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} |
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// UnaryHandler defines the handler invoked by UnaryServerInterceptor to complete the normal |
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// execution of a unary RPC. If a UnaryHandler returns an error, it should be produced by the |
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// status package, or else gRPC will use codes.Unknown as the status code and err.Error() as |
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// the status message of the RPC. |
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type UnaryHandler func(ctx context.Context, req interface{}) (interface{}, error) |
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// UnaryServerInterceptor provides a hook to intercept the execution of a unary RPC on the server. info |
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// contains all the information of this RPC the interceptor can operate on. And handler is the wrapper |
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// of the service method implementation. It is the responsibility of the interceptor to invoke handler |
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// to complete the RPC. |
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type UnaryServerInterceptor func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (resp interface{}, err error) |
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``` |
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看起来很简单包括： |
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* 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 |
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* 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 |
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* 一个`UnaryServerInterceptor`用于拦截`Handler`方法，可在`Handler`执行前后插入拦截代码 |
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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)： |
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```go |
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func _Demo_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) { |
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in := new(HelloReq) |
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if err := dec(in); err != nil { |
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return nil, err |
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} |
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if interceptor == nil { |
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return srv.(DemoServer).SayHello(ctx, in) |
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} |
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info := &grpc.UnaryServerInfo{ |
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Server: srv, |
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FullMethod: "/demo.service.v1.Demo/SayHello", |
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} |
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handler := func(ctx context.Context, req interface{}) (interface{}, error) { |
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return srv.(DemoServer).SayHello(ctx, req.(*HelloReq)) |
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} |
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return interceptor(ctx, in, info, handler) |
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} |
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``` |
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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)`。 |
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* 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 |
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* `_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` |
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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)： |
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```go |
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// UnaryInterceptor returns a ServerOption that sets the UnaryServerInterceptor for the |
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// server. Only one unary interceptor can be installed. The construction of multiple |
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// interceptors (e.g., chaining) can be implemented at the caller. |
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func UnaryInterceptor(i UnaryServerInterceptor) ServerOption { |
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return func(o *options) { |
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if o.unaryInt != nil { |
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panic("The unary server interceptor was already set and may not be reset.") |
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} |
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o.unaryInt = i |
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} |
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} |
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``` |
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请一定注意这方法的注释！！！ |
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> Only one unary interceptor can be installed. The construction of multiple interceptors (e.g., chaining) can be implemented at the caller. |
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`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)： |
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```go |
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// Use attachs a global inteceptor to the server. |
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// For example, this is the right place for a rate limiter or error management inteceptor. |
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func (s *Server) Use(handlers ...grpc.UnaryServerInterceptor) *Server { |
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finalSize := len(s.handlers) + len(handlers) |
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if finalSize >= int(_abortIndex) { |
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panic("warden: server use too many handlers") |
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} |
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mergedHandlers := make([]grpc.UnaryServerInterceptor, finalSize) |
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copy(mergedHandlers, s.handlers) |
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copy(mergedHandlers[len(s.handlers):], handlers) |
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s.handlers = mergedHandlers |
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return s |
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} |
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// interceptor is a single interceptor out of a chain of many interceptors. |
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// Execution is done in left-to-right order, including passing of context. |
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// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three |
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// will see context changes of one and two. |
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func (s *Server) interceptor(ctx context.Context, req interface{}, args *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) { |
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var ( |
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i int |
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chain grpc.UnaryHandler |
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) |
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n := len(s.handlers) |
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if n == 0 { |
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return handler(ctx, req) |
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} |
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chain = func(ic context.Context, ir interface{}) (interface{}, error) { |
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if i == n-1 { |
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return handler(ic, ir) |
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} |
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i++ |
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return s.handlers[i](ic, ir, args, chain) |
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} |
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return s.handlers[0](ctx, req, args, chain) |
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} |
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``` |
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很简单的逻辑： |
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* `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` |
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* `func (s *Server) interceptor`可以根据注册的`grpc.UnaryServerInterceptor`顺序从前到后依次执行 |
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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： |
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```go |
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opt = append(opt, keepParam, grpc.UnaryInterceptor(s.interceptor)) |
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s.server = grpc.NewServer(opt...) |
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``` |
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如此完整的服务端拦截器逻辑就串联完成。 |
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## 客户端拦截器 |
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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)： |
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```go |
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// UnaryInvoker is called by UnaryClientInterceptor to complete RPCs. |
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type UnaryInvoker func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, opts ...CallOption) error |
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// UnaryClientInterceptor intercepts the execution of a unary RPC on the client. invoker is the handler to complete the RPC |
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// and it is the responsibility of the interceptor to call it. |
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// This is an EXPERIMENTAL API. |
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type UnaryClientInterceptor func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, invoker UnaryInvoker, opts ...CallOption) error |
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``` |
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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： |
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* 一个`UnaryInvoker`表示客户端具体要发出的执行方法 |
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* 一个`UnaryClientInterceptor`用于拦截`Invoker`方法，可在`Invoker`执行前后插入拦截代码 |
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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)： |
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```go |
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func (c *demoClient) SayHello(ctx context.Context, in *HelloReq, opts ...grpc.CallOption) (*google_protobuf1.Empty, error) { |
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out := new(google_protobuf1.Empty) |
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err := grpc.Invoke(ctx, "/demo.service.v1.Demo/SayHello", in, out, c.cc, opts...) |
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if err != nil { |
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return nil, err |
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} |
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return out, nil |
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} |
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``` |
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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)： |
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```go |
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// Invoke sends the RPC request on the wire and returns after response is |
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// received. This is typically called by generated code. |
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// |
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// All errors returned by Invoke are compatible with the status package. |
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func (cc *ClientConn) Invoke(ctx context.Context, method string, args, reply interface{}, opts ...CallOption) error { |
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// allow interceptor to see all applicable call options, which means those |
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// configured as defaults from dial option as well as per-call options |
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opts = combine(cc.dopts.callOptions, opts) |
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if cc.dopts.unaryInt != nil { |
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return cc.dopts.unaryInt(ctx, method, args, reply, cc, invoke, opts...) |
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} |
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return invoke(ctx, method, args, reply, cc, opts...) |
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} |
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``` |
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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)： |
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```go |
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// WithUnaryInterceptor returns a DialOption that specifies the interceptor for |
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// unary RPCs. |
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func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption { |
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return newFuncDialOption(func(o *dialOptions) { |
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o.unaryInt = f |
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}) |
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} |
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``` |
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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)： |
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```go |
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// Use attachs a global inteceptor to the Client. |
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// For example, this is the right place for a circuit breaker or error management inteceptor. |
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func (c *Client) Use(handlers ...grpc.UnaryClientInterceptor) *Client { |
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finalSize := len(c.handlers) + len(handlers) |
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if finalSize >= int(_abortIndex) { |
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panic("warden: client use too many handlers") |
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} |
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mergedHandlers := make([]grpc.UnaryClientInterceptor, finalSize) |
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copy(mergedHandlers, c.handlers) |
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copy(mergedHandlers[len(c.handlers):], handlers) |
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c.handlers = mergedHandlers |
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return c |
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} |
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// chainUnaryClient creates a single interceptor out of a chain of many interceptors. |
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// |
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// Execution is done in left-to-right order, including passing of context. |
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// For example ChainUnaryClient(one, two, three) will execute one before two before three. |
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func (c *Client) chainUnaryClient() grpc.UnaryClientInterceptor { |
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n := len(c.handlers) |
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if n == 0 { |
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return func(ctx context.Context, method string, req, reply interface{}, |
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cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error { |
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return invoker(ctx, method, req, reply, cc, opts...) |
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} |
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} |
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return func(ctx context.Context, method string, req, reply interface{}, |
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cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error { |
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var ( |
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i int |
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chainHandler grpc.UnaryInvoker |
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) |
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chainHandler = func(ictx context.Context, imethod string, ireq, ireply interface{}, ic *grpc.ClientConn, iopts ...grpc.CallOption) error { |
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if i == n-1 { |
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return invoker(ictx, imethod, ireq, ireply, ic, iopts...) |
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} |
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i++ |
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return c.handlers[i](ictx, imethod, ireq, ireply, ic, chainHandler, iopts...) |
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} |
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return c.handlers[0](ctx, method, req, reply, cc, chainHandler, opts...) |
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} |
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} |
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``` |
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如此完整的客户端拦截器逻辑就串联完成。 |
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# 实现自己的拦截器 |
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以服务端拦截器`logging`为例： |
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```go |
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// serverLogging warden grpc logging |
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func serverLogging() grpc.UnaryServerInterceptor { |
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return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) { |
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// 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 |
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// 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 |
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startTime := time.Now() |
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caller := metadata.String(ctx, metadata.Caller) |
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if caller == "" { |
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caller = "no_user" |
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} |
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var remoteIP string |
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if peerInfo, ok := peer.FromContext(ctx); ok { |
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remoteIP = peerInfo.Addr.String() |
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} |
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var quota float64 |
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if deadline, ok := ctx.Deadline(); ok { |
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quota = time.Until(deadline).Seconds() |
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} |
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// call server handler |
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resp, err := handler(ctx, req) // NOTE: 以具体执行的handler为分界线！！！ |
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// NOTE: handler执行之后的拦截代码：主要进行耗时计算、日志记录 |
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// 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 |
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// after server response |
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code := ecode.Cause(err).Code() |
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duration := time.Since(startTime) |
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// monitor |
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statsServer.Timing(caller, int64(duration/time.Millisecond), info.FullMethod) |
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statsServer.Incr(caller, info.FullMethod, strconv.Itoa(code)) |
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logFields := []log.D{ |
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log.KVString("user", caller), |
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log.KVString("ip", remoteIP), |
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log.KVString("path", info.FullMethod), |
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log.KVInt("ret", code), |
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// TODO: it will panic if someone remove String method from protobuf message struct that auto generate from protoc. |
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log.KVString("args", req.(fmt.Stringer).String()), |
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log.KVFloat64("ts", duration.Seconds()), |
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log.KVFloat64("timeout_quota", quota), |
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log.KVString("source", "grpc-access-log"), |
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} |
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if err != nil { |
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logFields = append(logFields, log.KV("error", err.Error()), log.KV("stack", fmt.Sprintf("%+v", err))) |
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} |
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logFn(code, duration)(ctx, logFields...) |
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return resp, err |
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} |
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} |
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``` |
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# 扩展阅读 |
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[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) |
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------------- |
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[文档目录树](summary.md) |
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@ -0,0 +1,47 @@ |
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# 介绍 |
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基于proto文件可以快速生成`warden`框架对应的代码，提前需要准备以下工作： |
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* 安装`kratos tool protoc`工具，请看[kratos工具](kratos-tool.md) |
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* 编写`proto`文件，示例可参考[kratos-demo内proto文件](https://github.com/bilibili/kratos-demo/blob/master/api/api.proto) |
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### kratos工具说明 |
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`kratos tool protoc`工具可以生成`warden` `bm` `swagger`对应的代码和文档，想要单独生成`warden`代码只需加上`--grpc`如： |
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```shell |
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# generate gRPC |
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kratos tool protoc --grpc api.proto |
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``` |
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# 使用 |
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建议在项目`api`目录下编写`proto`文件及生成对应的代码，可参考[kratos-demo内的api目录](https://github.com/bilibili/kratos-demo/tree/master/api)。 |
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执行命令后生成的`api.pb.go`代码，注意其中的`DemoClient`和`DemoServer`，其中： |
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* `DemoClient`接口为客户端调用接口，相对应的有`demoClient`结构体为其实现 |
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* `DemoServer`接口为服务端接口声明，需要业务自己实现该接口的所有方法，`kratos`建议在`internal/service`目录下使用`Service`结构体实现 |
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`internal/service`内的`Service`结构实现了`DemoServer`接口可参考[kratos-demo内的service](https://github.com/bilibili/kratos-demo/blob/master/internal/service/service.go)内的如下代码： |
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```go |
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// SayHelloURL bm demo func. |
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func (s *Service) SayHelloURL(ctx context.Context, req *pb.HelloReq) (reply *pb.HelloResp, err error) { |
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reply = &pb.HelloResp{ |
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Content: "hello " + req.Name, |
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} |
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fmt.Printf("hello url %s", req.Name) |
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return |
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} |
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``` |
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更详细的客户端和服务端使用请看[warden快速开始](warden-quickstart.md) |
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# 扩展阅读 |
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[warden快速开始](warden-quickstart.md) [warden拦截器](warden-mid.md) [warden负载均衡](warden-balancer.md) [warden服务发现](warden-resolver.md) |
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------------- |
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|
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[文档目录树](summary.md) |
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