scale.go

// ...	
} else { // Active=False
			url := fmt.Sprintf("http://%s.%s", pa.Spec.ServiceName, pa.ObjectMeta.Namespace)
			client := &http.Client{}
			req, _ := http.NewRequest("GET", url, nil)
			req.Header.Set("knative-activator-probe", "true")
			resp, err := client.Do(req)

			if err != nil {
				logger.Errorf("Probe request to %s failed", url, zap.Error(err))
				return desiredScale, err
			}

			if resp.StatusCode != http.StatusOK {
				return desiredScale, nil
			}

			body, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				logger.Errorf("Failed to read response from probe request to %s", url, err)
				return desiredScale, nil
			}

			if string(body) == "queue-proxy" {
				return desiredScale, nil
			}
		}
	}