apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/RetryableRestTemplate.java/RetryableRestTemplate/canRetry
class RetryableRestTemplate:  private boolean canRetry(Throwable e, HttpMethod method) {
    Throwable nestedException = e.getCause();
    if (method == HttpMethod.GET) {
      return nestedException instanceof SocketTimeoutException
             || nestedException instanceof HttpHostConnectException
             || nestedException instanceof ConnectTimeoutException;
    }
    return nestedException instanceof HttpHostConnectException
           || nestedException instanceof ConnectTimeoutException;
  }