浏览器中的图像缓存 - app-engine-patch 应用程序

我在浏览器中为应用程序引擎应用程序缓存图像时遇到一些问题 我正在发送上次修改、过期和缓存控制标头，但每次都会从服务器加载图像。 这是代码的标题部分：

响应['内容类型'] = '图像/jpg'

响应['上次修改'] = current_time.strftime('%a, %d %b %Y %H:%M:%S GMT')

响应['过期'] = current_time + timedelta(天=30)

响应['缓存控制'] = '公共，最大年龄=2592000'

这是我在 dpaste 中修复副本的示例代码here http://dpaste.com/hold/154503/

def view_image(request, key):
  data = memcache.get(key)  
  if data is not None:  
    if(request.META.get('HTTP_IF_MODIFIED_SINCE') >= data['Last-Modified']):  
      data.status_code = 304  
    return data  
  else:  
    image_content_blob = #some code to get the image from the data store  
    current_time = datetime.utcnow()
    response = HttpResponse()
    last_modified = current_time - timedelta(days=1)
    response['Content-Type'] = 'image/jpg'
    response['Last-Modified'] = last_modified.strftime('%a, %d %b %Y %H:%M:%S GMT')
    response['Expires'] = current_time + timedelta(days=30)
    response['Cache-Control']  = 'public, max-age=315360000'
    response['Date']           = current_time
    response.content = image_content_blob

    memcache.add(image_key, response, 86400)
    return response