如何在 Go 中使用 httptrace 跟踪 http.Client

Question

根据这个文档，我们可以http.Client用httptrace这种方式追踪 t := &transport{}    req, _ := http.NewRequest("GET", "https://google.com", nil)    trace := &httptrace.ClientTrace{        GotConn: t.GotConn,    }    req = req.WithContext(httptrace.WithClientTrace(req.Context(), trace))    client := &http.Client{Transport: t}对于google API 客户端，这里是一个包装代码func NewWithClient(jsonKey []byte, cli *http.Client) (*Client, error) {    if cli == nil {        return nil, fmt.Errorf("client is nil")    }    ctx := context.WithValue(context.Background(), oauth2.HTTPClient, cli)    conf, err := google.JWTConfigFromJSON(jsonKey, androidpublisher.AndroidpublisherScope)    if err != nil {        return nil, err    }    service, err := androidpublisher.NewService(ctx, option.WithHTTPClient(conf.Client(ctx)))    if err != nil {        return nil, err    }    return &Client{service}, err}我们要应用到做 HTTP 跟踪httptrace的http.Client参数。NewWithClient我们尝试过的type TraceTransport struct {}var traceTransport = &TraceTransport{}var trace = &httptrace.ClientTrace{    GotConn: traceTransport.GotConn,}func (t *TraceTransport) RoundTrip(req *http.Request) (*http.Response, error) {    return http.DefaultTransport.RoundTrip(req)}func (t *TraceTransport) GotConn(info httptrace.GotConnInfo) {    fmt.Printf("Connection reused for %v \n", info.Reused)}type ClientWrapper struct {    defaultClient *http.Client}var clientWrapperTrace = &httptrace.ClientTrace{GotConn: traceTransport.GotConn}func (c *ClientWrapper) Do(req *http.Request) (*http.Response, error) {    req = req.WithContext(httptrace.WithClientTrace(req.Context(), clientWrapperTrace))    return c.defaultClient.Do(req)}但是，追踪失败http.Client，没有输出GotConn。有人可以帮助我们找出上述代码的问题吗？http去谷歌API安卓发布者

Answer 1

1. 来自的请求无法google/oauth2被 追踪httptrace。您ClientWrapper传递的 withcontext.WithValue将在这里被忽略，并且 oauth2 有它自己的 http.Client，它只是使用from context.Value的Transport方法。*http.Client

2. 来自 androidpublisher 的请求可以通过 httptrace 跟踪，如下所示：

ctx := httptrace.WithClientTrace(context.Background(), clientWrapperTrace)r, err := c.VerifyProduct(ctx, packageName, productID, token)

1. 如果您只想计算请求，我认为覆盖http.Client.Transport是一种简单的方法。

type TraceTransport struct {

}

func (t *TraceTransport) RoundTrip(req *http.Request) (*http.Response, error) {

    fmt.Printf("RoundTrip hook %v\n", req.URL)

    return http.DefaultTransport.RoundTrip(req)

}

func NewClientTrace(jsonKey []byte) (*Client, error) {

    cli := &http.Client{Transport: &TraceTransport{}}

    ctx := context.WithValue(context.Background(), oauth2.HTTPClient, cli)

    // ...

    service, err := androidpublisher.NewService(ctx, option.WithHTTPClient(conf.Client(ctx)))

    // ....

}