Use of grpc interceptor

gRPC As a universal RPC frame , Built in interceptor function . Including server-side interceptors and client-side interceptors , It's the same in use . The main function is to rpc Additional processing before and after the call .

Interceptors are used in many scenarios , For example, verify whether the user logs in before calling the interface , For example, judge the user in the interface useragent Do some anti climbing strategies and so on , In a large number of cases, the request is intercepted , Do the interface preprocessing , We can't write it in every interface , We need to build a unified interceptor .

Implement simple interceptors

1） Server side ：grpc.UnaryInterceptor(interceptor)

interceptor Is a custom interceptor function , The parameters of the tracking function are known ,interceptor It's a :

type UnaryServerInterceptor func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (resp interface{}, err error)

Parameter meaning ： 

• ctx context.Context： Request context
• req interface{}：RPC Method
• info *UnaryServerInfo：RPC All information about the method
• handler UnaryHandler：RPC The logic that the method really executes

  Case study ：

// Interceptor 
interceptor :=  func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error){
	fmt.Println(" Received a new request ")
	res,err := handler(ctx, req)
	fmt.Println(" Request completed ")
	return res, err
}
opt := grpc.UnaryInterceptor(interceptor)
g := grpc.NewServer(opt)
//...

2） client ：grpc.WithUnaryInterceptor(interceptor)

interceptor Is a custom interceptor function , The parameters of the tracking function are known ,interceptor It's a :

type UnaryClientInterceptor func(ctx context.Context, method string, req, reply interface{}, cc *ClientConn, invoker UnaryInvoker, opts ...CallOption) error

Case study ：

interceptor := func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error{
	start := time.Now()
	err := invoker(ctx, method, req, reply, cc, opts...)
	fmt.Printf(" Time consuming ：%s\n", time.Since(start))
	return err
}
opt := grpc.WithUnaryInterceptor(interceptor)
conn, err := grpc.Dial(":8083", grpc.WithInsecure(), opt)
//...

3） Some open source interceptors

https://github.com/grpc-ecosystem/go-grpc-middleware