详解Golang net/http包中的RoundTripper接口

type RoundTripper interface {
	RoundTrip(*Request) (*Response, error)
}

package http_otel
import (
	"net/http"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
)
type OtelRoundTripper struct {
	original http.RoundTripper
}
func (ort *OtelRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	tracer := otel.Tracer("")
	ctx, span := tracer.Start(req.Context(), req.URL.Path)
	defer span.End()
	req = req.WithContext(ctx)
	resp, err := ort.original.RoundTrip(req)
	if err != nil {
		span.RecordError(err)
		span.SetStatus(codes.Error, err.Error())
	} else {
		attrs := []attribute.KeyValue{
			{
				Key:   "http.status_code",
				Value: attribute.IntValue(resp.StatusCode),
			},
			{
				Key:   "http.method",
				Value: attribute.StringValue(req.Method),
			},
			{
				Key:   "http.route",
				Value: attribute.StringValue(req.URL.RequestURI()),
			},
			{
				Key:   "http.scheme",
				Value: attribute.StringValue(req.URL.Scheme),
			},
			{
				Key:   "http.user_agent",
				Value: attribute.StringValue(req.UserAgent()),
			},
		}
		span.SetAttributes(attrs...)
	}
	return resp, err
}
func New() *OtelRoundTripper {
	return &OtelRoundTripper{
		original: tripper,
	}
}

package main
import (
    "bytes"
    "fmt"
    "xxx/http-otel"
    "io"
    "net/http"
)
func main() {
    reader := bytes.NewReader([]byte(`{"foo":"bar"}`))
    request, err := http.NewRequest("POST", "http://xxx.com/user/list", reader)
    if err != nil {
       panic(err)
    }
    request = request.WithContext(traceCtx) // traceCtx 指上文的 context，这里使用伪代码作演示
    request.Header.Set("Content-Type", "application/json")
    client := http.Client{Transport: http_otel.New()}
    resp, err := client.Do(request)
    if err != nil {
       panic(err)
    }
    defer resp.Body.Close()
    b, err := io.ReadAll(resp.Body)
    fmt.Println(string(b), err)
}