Interceptor

拦截器提供了在发送request之前和之后做一些事情的机会。

拦截器可以被设置给

  1. 所有URL
  2. 某个URL根路径 (也就是一组URL)
  3. 单个URL
  4. 单个URL,并且指定 HTTP 谓语

设置的粒度越精确,拦截器的优先级就越高

比如,拦截器 A 设置在 ‘GET /abc’,拦截器 B 设置给了所有URL,那么,当请求”GET /abc”时,拦截器A会被执行,B不会被执行,但请求”POST /abc”时,只有B会被执行。

下面,让我们来创建一个拦截器,设置给”/hello”,用来记录一些log。

编辑 “yourservice/interceptor/log.go”:

package interceptor

import (
       "github.com/vaporz/turbo"
       "fmt"
       "net/http"
)

type LogInterceptor struct {
       // optional, BaseInterceptor allows you to create an interceptor which implements
       // Before() or After() only, or none of them.
       // If you were to implement both, you can remove this line.
       turbo.BaseInterceptor
}

func (l *LogInterceptor) Before(resp http.ResponseWriter, req *http.Request) error {
       fmt.Println("[Before] Request URL:"+req.URL.Path)
       return nil
}

func (l *LogInterceptor) After(resp http.ResponseWriter, req *http.Request) error {
       fmt.Println("[After] Request URL:"+req.URL.Path)
       return nil
}

然后把它设置给 URL “/hello”。

编辑 “yourservice/grpcapi/component/components.go”:

package component

import (
       "github.com/vaporz/turbo-example/yourservice/gen/proto"
       "google.golang.org/grpc"
+      "github.com/vaporz/turbo-example/yourservice/interceptor"
)

func (i *ServiceInitializer) InitService(s turbo.Servable) error {
+       s.RegisterComponent("LogInterceptor", &interceptor.LogInterceptor{})
    return nil
}

编辑 “yourservice/service.yaml”:

+interceptor:
+  - GET /hello LogInterceptor

最后,重启服务并测试:

$ curl -w "\n" -X GET "http://localhost:8081/hello?your_name=Alice"
{"message":"[grpc server]Hello, Alice"}

查看HTTP server的控制台:

$ go run yourservice/yourserviceapi.go
[Before] Request URL:/hello
[After] Request URL:/hello

拦截器经常被用来做一些校验工作,当校验失败时,请求会被中止,并返回一个错误。

很简单,你只需要这样:

func (l *LogInterceptor) Before(resp http.ResponseWriter, req *http.Request) error {
       fmt.Println("[Before] Request URL:"+req.URL.Path)
+      resp.Write([]byte("Encounter an error from LogInterceptor!\n"))
-      return nil
+      return errors.New("error!")
}

测试:

$ curl -w "\n" "http://localhost:8081/hello"
Encounter an error from LogInterceptor!