import atexit
import logging
from concurrent.futures import ThreadPoolExecutor

logger = logging.getLogger(__name__)

# 全局初始化线程池
_executor = ThreadPoolExecutor(max_workers=4, thread_name_prefix='image_embedding_')

def run_embedding_task(fn, *args, **kwargs):
    """
    提交后台任务到线程池
    """
    logger.info("Submitting embedding task to background thread...")
    return _executor.submit(fn, *args, **kwargs)

def _shutdown_executor():
    """
    优雅关闭线程池，在 Gunicorn worker 退出时触发
    """
    logger.info("Shutting down background thread pool...")
    _executor.shutdown(wait=False)

# 注册到系统退出事件，这样就不会报 _shutdown not defined 了
atexit.register(_shutdown_executor)