workflow.py 文件源码

def cached_data(self, name, data_func=None, max_age=60):
        """Return cached data if younger than ``max_age`` seconds.

        Retrieve data from cache or re-generate and re-cache data if
        stale/non-existant. If ``max_age`` is 0, return cached data no
        matter how old.

        :param name: name of datastore
        :param data_func: function to (re-)generate data.
        :type data_func: ``callable``
        :param max_age: maximum age of cached data in seconds
        :type max_age: ``int``
        :returns: cached data, return value of ``data_func`` or ``None``
            if ``data_func`` is not set

        """
        serializer = manager.serializer(self.cache_serializer)

        cache_path = self.cachefile('%s.%s' % (name, self.cache_serializer))
        age = self.cached_data_age(name)

        if (age < max_age or max_age == 0) and os.path.exists(cache_path):

            with open(cache_path, 'rb') as file_obj:
                self.logger.debug('Loading cached data from : %s',
                                  cache_path)
                return serializer.load(file_obj)

        if not data_func:
            return None

        data = data_func()
        self.cache_data(name, data)

        return data