气流-尝试运行TaskInstance时从sqlalchemy引发的错误

我正在测试气流结构内部爬行器的执行情况。如果我运行下面的脚本,一切正常,有效载荷也会打印出来。

from airflow import DAG
from airflow.models import BaseOperator, TaskInstance
from hooks.crawler_hook import CrawlerHook

from datetime import datetime
import time

class CrawlerOperator(BaseOperator):
    def __init__(self, conn_id=None, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.conn_id = conn_id

    def execute(self):
        hook = CrawlerHook(conn_id=self.conn_id)
        print(hook.run())

if __name__ == "__main__":
    CrawlerOperator(task_id='test_run').execute()

但当我试图在DAG中运行TaskInstance时,我遇到了一个错误,无法理解为什么:

if __name__ == "__main__":
    with DAG(dag_id="DAG1", start_date=datetime.now(), catchup=False) as dag:
        to = CrawlerOperator(task_id="test_run")
        ti = TaskInstance(task=to)
        ti.run()

错误是:

Traceback (most recent call last):
  File "/home/../.env/lib/python3.8/site-packages/airflow/utils/session.py", line 67, in wrapper
    return func(*args, **kwargs)
  File "/home/../.env/lib/python3.8/site-packages/airflow/models/taskinstance.py", line 1123, in get_dagrun
    dr = session.query(DagRun).filter(DagRun.dag_id == self.dag_id, DagRun.run_id == self.run_id).one()
  File "/home/../.env/lib/python3.8/site-packages/sqlalchemy/orm/query.py", line 3500, in one
    raise orm_exc.NoResultFound("No row was found for one()")
sqlalchemy.orm.exc.NoResultFound: No row was found for one()

有什么建议吗?