@Override
 public void downloadTemplateToStorage(
     DataObject template, AsyncCompletionCallback<DownloadAnswer> callback) {
   if (template != null) {
     long templateId = template.getId();
     DataStore store = template.getDataStore();
     if (isTemplateUpdateable(templateId, store.getId())) {
       if (template.getUri() != null) {
         initiateTemplateDownload(template, callback);
       } else {
         s_logger.info("Template url is null, cannot download");
         DownloadAnswer ans = new DownloadAnswer("Template url is null", Status.UNKNOWN);
         callback.complete(ans);
       }
     } else {
       s_logger.info("Template download is already in progress or already downloaded");
       DownloadAnswer ans =
           new DownloadAnswer(
               "Template download is already in progress or already downloaded", Status.UNKNOWN);
       callback.complete(ans);
     }
   }
 }
  private void initiateTemplateDownload(
      DataObject template, AsyncCompletionCallback<DownloadAnswer> callback) {
    boolean downloadJobExists = false;
    TemplateDataStoreVO vmTemplateStore = null;
    DataStore store = template.getDataStore();

    vmTemplateStore = _vmTemplateStoreDao.findByStoreTemplate(store.getId(), template.getId());
    if (vmTemplateStore == null) {
      vmTemplateStore =
          new TemplateDataStoreVO(
              store.getId(),
              template.getId(),
              new Date(),
              0,
              Status.NOT_DOWNLOADED,
              null,
              null,
              "jobid0000",
              null,
              template.getUri());
      vmTemplateStore.setDataStoreRole(store.getRole());
      vmTemplateStore = _vmTemplateStoreDao.persist(vmTemplateStore);
    } else if ((vmTemplateStore.getJobId() != null) && (vmTemplateStore.getJobId().length() > 2)) {
      downloadJobExists = true;
    }

    Long maxTemplateSizeInBytes = getMaxTemplateSizeInBytes();
    if (vmTemplateStore != null) {
      start();
      VirtualMachineTemplate tmpl = _templateDao.findById(template.getId());
      DownloadCommand dcmd =
          new DownloadCommand((TemplateObjectTO) (template.getTO()), maxTemplateSizeInBytes);
      dcmd.setProxy(getHttpProxy());
      if (downloadJobExists) {
        dcmd =
            new DownloadProgressCommand(
                dcmd, vmTemplateStore.getJobId(), RequestType.GET_OR_RESTART);
      }
      if (vmTemplateStore.isCopy()) {
        dcmd.setCreds(TemplateConstants.DEFAULT_HTTP_AUTH_USER, _copyAuthPasswd);
      }
      EndPoint ep = _epSelector.select(template);
      if (ep == null) {
        String errMsg =
            "There is no secondary storage VM for downloading template to image store "
                + store.getName();
        s_logger.warn(errMsg);
        throw new CloudRuntimeException(errMsg);
      }
      DownloadListener dl = new DownloadListener(ep, store, template, _timer, this, dcmd, callback);
      ComponentContext.inject(dl); // initialize those auto-wired field in download listener.
      if (downloadJobExists) {
        // due to handling existing download job issues, we still keep
        // downloadState in template_store_ref to avoid big change in
        // DownloadListener to use
        // new ObjectInDataStore.State transition. TODO: fix this later
        // to be able to remove downloadState from template_store_ref.
        s_logger.info("found existing download job");
        dl.setCurrState(vmTemplateStore.getDownloadState());
      }

      try {
        ep.sendMessageAsync(dcmd, new UploadListener.Callback(ep.getId(), dl));
      } catch (Exception e) {
        s_logger.warn(
            "Unable to start /resume download of template "
                + template.getId()
                + " to "
                + store.getName(),
            e);
        dl.setDisconnected();
        dl.scheduleStatusCheck(RequestType.GET_OR_RESTART);
      }
    }
  }