可以通过使用 Airflow 的 hooks 和 sensors，实现在连续 2 次任务失败时进行通知。

以下是一个示例代码：

1. 创建一个 CustomSensor 继承 BaseSensorOperator，实现连续任务失败的检测逻辑：

from airflow.sensors.base import BaseSensorOperator
from airflow.hooks.base_hook import BaseHook
from typing import Optional, Tuple

class CustomSensor(BaseSensorOperator):

    def __init__(self,
                 task_id: str,
                 conn_id: str,
                 num_failures: int,
                 *args,
                 **kwargs) -> None:
        super().__init__(task_id=task_id, *args, **kwargs)
        self.conn_id = conn_id
        self.num_failures = num_failures
    
    def poke(self, context) -> bool:
        hook = BaseHook.get_hook(conn_id=self.conn_id)
        result = hook.get_results()
        if len(result) > self.num_failures:
            return True
        return False

2. 在 DAG 中使用该 CustomSensor：

from airflow import DAG
from datetime import datetime, timedelta
from custom_plugins import CustomSensor

default_args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2022, 1, 1),
    'email': ['youremail@yourdomain.com']
    'email_on_failure': True,
    'email_on_retry': False,
    'retries': 3,
    'retry_delay': timedelta(minutes=5),
}

with DAG('my_dag', default_args=default_args, schedule_interval=timedelta(days=1)) as dag:
    task_a = BashOperator(task_id='task_a', bash_command='echo 1')
    task_b = BashOperator(task_id='task_b', bash_command='echo 2')

    check_task = CustomSensor(
        task_id='check_task',
        num_failures=2,
        conn_id='my_conn',
        poke_interval=timedelta(minutes=1)
    )

    notify_task = EmailOperator(
        task_id='notify_task',
        subject='Two consecutive task failures',
        to='youremail@yourdomain