每个请求图像大小调整期间的竞争条件

Question

根据预先定义的预设，您可以根据请求调整图像大小，然后将其附加到已调整大小的图像文件名，并保存在同一目录中。在调整大小期间，如果两个请求拉动相同的图像，您如何处理竞争条件？

建议的解决方案是：

import os
import time

import my_threadsafe_cache_module as cache
from my_image_resizer import resize_by_preset_name


def resize_on_demand(preset, original_image_filepath, *args, **kwargs):
    """
    Args:
        preset: A string containing the name of your pre-defined preset.
        original_image_filepath: A string containing the original filepath.
        args, kwargs: Passed to resize_by_preset_name
    """
    resized_filename = ('_' + preset).join(os.path.splitext(original_image_filepath))
    if os.path.exists(resized_filename):
        return resized_filename

    # If the image does not exist, we shall create the resized version.
    cache_key = cache.get('RESIZE_' + resized_filename) # Should return None or True
    if cache_key is None:
        try: # Ensure that the cache key is always deleted
            cache.set('RESIZE_' + resized_filename, True, 5) # 5 indicates seconds
            resize_by_preset_name(preset, original_image_filepath, *args, **kwargs)
        finally:
            cache.delete('RESIZE_' + resized_filename) # Delete the cache key
    else: # We wait until cache_key is not None
        while cache_key is not None:
            time.sleep(1)
            cache_key = cache.get('RESIZE_' + resized_filename)

    return resized_filename

这是正确的做法吗？什么可能陷阱？