如何跟踪http.客户端与httptrace在Go

Question

根据这个文档，我们可以用这种方式跟踪http.Client和httptrace

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
}

我们希望将httptrace应用于NewWithClient的http.Client参数来进行HTTP跟踪。

我们已经尝试过的

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)
}
func NewClientTrace(jsonKey []byte) (*Client, error) {
cli := &http.Client{
Transport: traceTransport,
Timeout:   time.Duration(10) * time.Second,
}
cliWrapper := &ClientWrapper{defaultClient: cli}
ctx := context.WithValue(context.Background(), oauth2.HTTPClient, cliWrapper)
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
}
type Client struct {
service *androidpublisher.Service
}
func (c *Client) VerifyProduct(
ctx context.Context,
packageName string,
productID string,
token string,
) (*androidpublisher.ProductPurchase, error) {
ps := androidpublisher.NewPurchasesProductsService(c.service)
result, err := ps.Get(packageName, productID, token).Context(ctx).Do()
return result, err
}
// test codes
c, err := NewClientTrace([]byte(privateKey)) 
if err != nil {
return
}
packageName := "package.name"
productID := "product_id"
token := "xxxxx"
r, err := c.VerifyProduct(context.Background(), packageName, productID, token)

但是，跟踪http.Client失败，没有GotConn输出。有没有人能帮我们解决一下以上代码的问题?

Answer 1

1. 来自google/oauth2的请求无法被httptrace跟踪。通过context.WithValue传递的ClientWrapper在这里将被忽略，oauth2有自己的http。客户端，它只是使用*http.Client的Transport方法从context.Value.

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)

3. 如果你只是想计数请求，我认为覆盖http.Client.Transport是一个简单的方法。

type TraceTransport struct {
}
func (t *TraceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
fmt.Printf("RoundTrip hook %vn", 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)))
// ....
}