总结

python3中 filter() 返回的是可迭代对象,python2中 filter() 返回的是过原列表经过函数过滤后的新列表，也就是把原本Py2中的纯列表转为了更省内存的迭代器

• 被filter修饰器过滤后的元组对象列表变为可以迭代的filter对象,
• 渲染器无法识别filter对象,也无法识别把list(iterable_filter)直接带入到参数字典中,需要用表达式转一次

  缘由

  对传给render_to_string()函数的字典参数值中,包含了被filter函数过滤后的值,被渲染后,出现了信息缺失
  

  详细

  过滤器相关代码

def filter_muted_instance_item(format_alerts):
    """屏蔽掉一个实例指定报警项"""
    muted_instance_item = set(
        [(i.ip, i.port, i.item) for i in AlertMute.objects.filter(start_time__lte=datetime.datetime.now(),
                                                                  end_time__gte=datetime.datetime.now())])
    filtered_set = filter(lambda x: (x.ip, x.port, x.item) not in muted_instance_item,  [format_alert for format_alert in format_alerts])
    return filtered_set

# # 定义修饰器 protype
# def host_item_filter(alertor_func):
#     @functools.wraps(alertor_func)
#     def modifier(*args, **kwargs):
#         kwargs['queryset'] = filter_muted_ip(kwargs['queryset'])
#         alertor_func(**kwargs)
#     return modifier

# 定义修饰器,使用wrapt包简化代码
def item_filter(filter_type='instance_item'):
    @wrapt.decorator
    def wrapper(wrapped, instance, args, kwargs):
        if filter_type == 'ip_item':
            kwargs['format_alerts'] = filter_muted_ip(kwargs['format_alerts'])
        elif filter_type == 'instance_item':
            kwargs['format_alerts'] = filter_muted_instance_item(kwargs['format_alerts'])
        return wrapped(*args, **kwargs)

    return wrapper

页面渲染相关代码

@item_filter(filter_type='instance_item')
def mail_alert(alarm_type=None, format_alerts=None, scan_time=datetime.datetime.now(), **kwargs):
    """
    使用预置的邮件模板渲染后发送报警邮件
    :param alarm_type: 报警类型
    :param format_alerts: 警报结果集
    :param scan_time: 警报产生时间
    :param kwargs: 杂项参数
    :return: 无返回项,程序内直接发送邮件
    """
    subject = "报警发送标题"
    template = "报警发送预置HTML模板"
    if alarm_type == 'dbagent_heartbeat':
        template = 'dbAlertAPP/AgentHeartbeatAlarm.html'
        subject = 'dbagent心跳报警'
        elif:
            ...........
        else:
            ..........

    # 这里注意,被filter修饰器过滤后的元组对象列表变为可以迭代的filter对象,也就是把原本Py2中的纯列表转为了更省内存的迭代器
    #         但是渲染器无法识别filter对象,也无法识别把list(iterable_filter)直接带入到参数字典中,需要用表达式转一次
    result_list = list(format_alerts)

    if kwargs.get("check_map"):
        html_string = render_to_string(template, {"results": result_list,
                                                  "scanTime": scan_time,
                                                  "checkMap": kwargs.get("check_map")
                                                  }
                                       )
    else:
        html_string = render_to_string(template, {"results": result_list,
                                                  "scanTime": scan_time,
                                                  }
                                       )

    try:
        send_mail(subject=environment_prefix+subject, message='plain_message', html_message=html_string,
                  from_email=EMAIL_HOST_USER,
                  recipient_list=get_recivers(), fail_silently=False)
    except Exception as e:
        p.error(e)