Method get_instance

src/services/browser_captcha.py:2602–2610

(cls, db=None)

    @classmethod
    async def get_instance(cls, db=None) -> 'BrowserCaptchaService':
        if cls._instance is None:
            async with cls._lock:
                if cls._instance is None:
                    cls._instance = cls(db)
                    # 从数据库加载 browser_count 配置
                    await cls._instance._load_browser_count()
                    await cls._instance._ensure_idle_reaper()
        return cls._instance
    
    def _check_available(self):
        """检查服务是否可用"""