code: public void shutdown() {
          clientExecutionTimer.shutdown();
          httpRequestTimer.shutdown();
          IdleConnectionReaper.removeConnectionManager(httpClient.getHttpClientConnectionManager());
          httpClient.getHttpClientConnectionManager().shutdown();
      }
docs: Shuts down this HTTP client object, releasing any resources that might be held open. This is
  an optional method, and callers are not expected to call it, but can if they want to
  explicitly release any open resources. Once a client has been shutdown, it cannot be used to
  make more requests.