go实现函数递归栈(grpc拦截器)
2021/10/6 6:12:43
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package main import ( "context" "log" ) func main() { _Handler( "hello", context.Background(), multi([]Interceptor{A, B}...), ) } func A(ctx context.Context, req interface{}, handler Handler) (interface{}, error) { defer func() { log.Printf("call A() done") }() log.Printf("call A()") return handler(ctx, req) } func B(ctx context.Context, req interface{}, handler Handler) (interface{}, error) { defer func() { log.Printf("call B() done") }() log.Printf("call B()") return handler(ctx, req) } //------------------ type Handler = func(ctx context.Context, req interface{}) (interface{}, error) type Interceptor = func(ctx context.Context, req interface{}, handler Handler) (interface{}, error) func echo(ctx context.Context, req interface{}) (interface{}, error) { log.Println(req) return "ok", nil } func _Handler(req interface{}, ctx context.Context, inter Interceptor) (interface{}, error) { handler := func(ctx context.Context, req interface{}) (interface{}, error) { return echo(ctx, req) } return inter(ctx, req, handler) } func multi(interceptors ...Interceptor) Interceptor { n := len(interceptors) return func(ctx context.Context, req interface{}, handler Handler) (interface{}, error) { chainer := func(currentInter Interceptor, currentHandler Handler) Handler { return func(currentCtx context.Context, currentReq interface{}) (interface{}, error) { return currentInter(currentCtx, currentReq, currentHandler) } } chainedHandler := handler for i := n - 1; i >= 0; i-- { chainedHandler = chainer(interceptors[i], chainedHandler) } return chainedHandler(ctx, req) } }
grpc源码:
// 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 ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor { n := len(interceptors) return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) { chainer := func(currentInter grpc.UnaryServerInterceptor, currentHandler grpc.UnaryHandler) grpc.UnaryHandler { return func(currentCtx context.Context, currentReq interface{}) (interface{}, error) { return currentInter(currentCtx, currentReq, info, currentHandler) } } chainedHandler := handler for i := n - 1; i >= 0; i-- { chainedHandler = chainer(interceptors[i], chainedHandler) } return chainedHandler(ctx, req) } }
// 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) func _xx_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) { in := new(EchoReq) if err := dec(in); err != nil { return nil, err } if interceptor == nil { return srv.(xx).xx(ctx, in) } info := &grpc.UnaryServerInfo{ Server: srv, FullMethod: "/xx.xx/xx", } handler := func(ctx context.Context, req interface{}) (interface{}, error) { return srv.(xx).Echosvr(ctx, req.(*xx)) } return interceptor(ctx, in, info, handler) }
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