内容简介:RoundTripper is an interface representing the ability to execute a single HTTP transaction, obtaining the Response for a given Request.对于http客户端,可以使用不同的实现了
RoundTripper is an interface representing the ability to execute a single HTTP transaction, obtaining the Response for a given Request.
对于http客户端,可以使用不同的实现了 RoundTripper
接口的 Transport
实现来配置它的行为
RoundTripper
有点像 http.Client
的中间件
接口定义
type RoundTripper interface { RoundTrip(*Request) (*Response, error) }
需要实现RoundTrip函数
type SomeClient struct {} func (s *SomeClient) RoundTrip(r *http.Request)(*Response, error) { //Something comes here...Maybe }
场景
原文: https://lanre.wtf/blog/2017/0...
-
缓存 responses,比如 app需要访问 Github api,获取 trending repos,这个数据变动不频繁,假设30分钟变动一次,你显然不希望每次都要点击api都要来请求Github api,解决这个问题的方法是实现这样的
http.RoundTripper
- 有缓存时从缓存取出response数据
- 过期,数据通过重新请求api获取
- 根据需要设置http header, 一个容易想到的例子 go-github 一个Github的 api的 go 客户端。某些github api不需要认证,有些需要认证则需要提供自己的http client,比如 ghinstallation ,下面是ghinstallation 的 RoundTrip 函数实现 ,设置 Authorization 头
- 限速(Rate limiting) 控制请求速率
实际的例子
实现 http.RoundTripper
缓存 http response的逻辑。
一个http server的实现
import ( "fmt" "net/http" ) func main() { // server/main.go mux := http.NewServeMux() mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { // This is here so we can actually see that the responses that have been cached don't get here fmt.Println("The request actually got here") w.Write([]byte("You got here")) }) http.ListenAndServe(":8000", mux) }
http client中创建新的 http.Transport
实现 http.RoundTripper
接口
主程序main实现
https://github.com/adelowo/ro...func main() { cachedTransport := newTransport() // cachedTransport 是自定义实现http.RoundTripper接口的 Transport client := &http.Client{ Transport: cachedTransport, Timeout: time.Second * 5, } // 每5秒清除缓存 cacheClearTicker := time.NewTicker(time.Second * 5) //每秒请求一次,可以看出response是从缓存获取还是从服务器请求 reqTicker := time.NewTicker(time.Second * 1) terminateChannel := make(chan os.Signal, 1) signal.Notify(terminateChannel, syscall.SIGTERM, syscall.SIGHUP) req, err := http.NewRequest(http.MethodGet, "http://localhost:8000", strings.NewReader("")) if err != nil { panic("Whoops") } for { select { case <-cacheClearTicker.C: // Clear the cache so we can hit the original server cachedTransport.Clear() case <-terminateChannel: cacheClearTicker.Stop() reqTicker.Stop() return case <-reqTicker.C: resp, err := client.Do(req) if err != nil { log.Printf("An error occurred.... %v", err) continue } buf, err := ioutil.ReadAll(resp.Body) if err != nil { log.Printf("An error occurred.... %v", err) continue } fmt.Printf("The body of the response is \"%s\" \n\n", string(buf)) } } }
cacheTransport 中 RoundTrip 函数实现读取缓存中的reponse
func (c *cacheTransport) RoundTrip(r *http.Request) (*http.Response, error) { // Check if we have the response cached.. // If yes, we don't have to hit the server // We just return it as is from the cache store. if val, err := c.Get(r); err == nil { fmt.Println("Fetching the response from the cache") return cachedResponse([]byte(val), r) } // Ok, we don't have the response cached, the store was probably cleared. // Make the request to the server. resp, err := c.originalTransport.RoundTrip(r) if err != nil { return nil, err } // Get the body of the response so we can save it in the cache for the next request. buf, err := httputil.DumpResponse(resp, true) if err != nil { return nil, err } // Saving it to the cache store c.Set(r, string(buf)) fmt.Println("Fetching the data from the real source") return resp, nil }
运行结果
links:
以上所述就是小编给大家介绍的《Golang http.RoundTripper 笔记》,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持!
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