Go를 사용한 교차 애플리케이션 추적

http.HandleFunc("/users", usersHandler)
http.HandleFunc(newrelic.WrapHandleFunc(app, "/users", usersHandler))

txn := app.StartTransaction("transactionName")
// req is a *http.Request, this marks the transaction as a web transaction
txn.SetWebRequestHTTP(req)

// writer is a http.ResponseWriter, use the returned writer in place of the original
writer = txn.SetWebResponse(writer)
writer.WriteHeader(500)

defer txn.End()

// Cross application tracing not enabled
txn := app.StartTransaction("transactionName")
defer txn.End()

// old code
// writer.WriteHeader(http.StatusInternalServerError)

// replace with this
txn := app.StartTransaction("transactionName")
txn.SetWebRequest(req)
writer = txn.SetWebResponse(writer)
writer.WriteHeader(http.StatusInternalServerError)

func useNewRoundTripper(txn *newrelic.Transaction) (*http.Response, error) {
    client := &http.Client{}
    client.Transport = newrelic.NewRoundTripper(client.Transport)
    req, _ := http.NewRequest("GET", "http://api.example.com/", nil)
    req = newrelic.RequestWithTransactionContext(req, txn)
    return client.Do(req)
}

func external(txn *newrelic.Transaction, req *http.Request) (*http.Response, error) {
    s := newrelic.StartExternalSegment(txn, req)
    response, err := http.DefaultClient.Do(req)
    s.Response = response
    s.End()
    return response, err
}

func noGoodForCat(txn *newrelic.Transaction, url string) (*http.Response, error) {
    // CAT headers not inserted
    defer newrelic.ExternalSegment{
        StartTime: txn.StartSegmentNow(),
        URL:       url,
    }.End()

    return http.Get(url)
}