docs: public HttpResponse doAction(HttpRequest request, String form, HttpMethod method)
          throws ClientException, ServerException {
          request.validate();
          
          // try refresh credentials if CredentialProvider set
          this.config.refreshCredentials();
          
          try {
              int retryTimes = 0;
              HttpResponse response = null;
  
              boolean httpInvoke = false;
              if (request instanceof HttpInvokeFunctionRequest) {
                  httpInvoke = true;
              }
  
              do {
                  if (!httpInvoke
                      || !ANONYMOUS.equals(((HttpInvokeFunctionRequest) request).getAuthType())) {
                      signRequest(request, form, method, httpInvoke);
                  }
  
                  PrepareUrl prepareUrl = prepareUrl(request.getPath(), request.getQueryParams());
  
                  response = HttpResponse.getResponse(prepareUrl.getUrl(), request, method,
                      config.getConnectTimeoutMillis(), config.getReadTimeoutMillis());
  
                  retryTimes++;
  
                  if (httpInvoke) {
                      return response;
                  }
  
              } while (500 <= response.getStatus() && AUTO_RETRY && retryTimes < MAX_RETRIES);
  
              if (response.getStatus() >= 500) {
                  String requestId = response.getHeader(HeaderKeys.REQUEST_ID);
                  String stringContent =
                      response.getContent() == null ? "" : new String(response.getContent());
                  ServerException se;
                  try {
                      se = new Gson().fromJson(stringContent, ServerException.class);
                  } catch (JsonParseException e) {
                      se = new ServerException("InternalServiceError",
                          "Failed to parse response content", requestId);
                  }
                  se.setStatusCode(response.getStatus());
                  se.setRequestId(requestId);
                  throw se;
              } else if (response.getStatus() >= 300) {
                  ClientException ce;
                  if (response.getContent() == null) {
                      ce = new ClientException("SDK.ServerUnreachable",
                          "Failed to get response content from server");
                  } else {
                      try {
                          ce = new Gson()
                              .fromJson(new String(response.getContent()), ClientException.class);
                      } catch (JsonParseException e) {
                          ce = new ClientException("SDK.ResponseNotParsable",
                              "Failed to parse response content", e);
                      }
                  }
                  if (ce == null) {
                      ce = new ClientException("SDK.UnknownError", "Unknown client error");
                  }
                  ce.setStatusCode(response.getStatus());
                  ce.setRequestId(response.getHeader(HeaderKeys.REQUEST_ID));
                  throw ce;
              }
              return response;
          } catch (InvalidKeyException exp) {
              throw new ClientException("SDK.InvalidAccessSecret",
                  "Speicified access secret is not valid.");
          } catch (SocketTimeoutException exp) {
              throw new ClientException("SDK.ServerUnreachable",
                  "SocketTimeoutException has occurred on a socket read or accept.");
          } catch (IOException exp) {
              throw new ClientException("SDK.ServerUnreachable",
                  "Server unreachable: " + exp.toString());
          } catch (NoSuchAlgorithmException exp) {
              throw new ClientException("SDK.InvalidMD5Algorithm",
                  "MD5 hash is not supported by client side.");
          } catch (URISyntaxException e) {
              throw new ClientException("SDK.InvalidURL", "url is not valid: " + e.getMessage());
          }
      }