def start_upload(self):
    clean_flag = False
    # 检查是否能够正常接入
    self.check_access()
    # 获取桶内是否存在分片上传信息
    upload_id_list = self.get_upload_id_list()
    # 是否清理未完成的分片
    if upload_id_list:
        clean_flag = self.clean_unfinished_upload(upload_id_list)
    upload_id = self.check_object_exist(upload_id_list, clean_flag)
    part_number_list = self.check_part_number_list(upload_id)
    file_index_list = self.split_source_file()
    # 分片上传文件
    if VIRTUAL_FILE_FLAG:
        self.upload_virtual_file_part(upload_id, file_index_list, part_number_list)
    else:
        self.upload_part(upload_id, file_index_list, part_number_list)
    # 合并文件
    self.complete_upload(upload_id, len(file_index_list))