Question

我正在尝试执行包含几个Python函数的Airflow脚本。这些函数基本上查询数据库并执行一些任务。我试图执行这是Airflow，以便我能够分别监视这些功能。下面给出的是我试图执行的代码并获得以下错误

子任务：NameError：名称'task_instance'未定义

## Third party Library Imports

import psycopg2
import airflow
from airflow import DAG
from airflow.operators.python_operator import PythonOperator
from datetime import datetime, timedelta
from sqlalchemy import create_engine
import io


# Following are defaults which can be overridden later on
default_args = {
'owner': 'airflow',
'depends_on_past': False,
'start_date': datetime(2018, 1, 23, 12),
'email': ['airflow@airflow.com'],
'email_on_failure': False,
'email_on_retry': False,
'retries': 1,
'retry_delay': timedelta(minutes=5),
}

dag = DAG('sample_dag', default_args=default_args, catchup=False, schedule_interval="@once")


#######################
## Login to DB


def db_log(**kwargs):
    global db_con
    try:
    db_con = psycopg2.connect(
" dbname = 'name' user = 'user' password = 'pass' host = 'host' port = 'port' sslmode = 'require' ")
    except:
        print("Connection Failed.")
        print('Connected successfully')
        task_instance = kwargs['task_instance']
        task_instance.xcom_push(value="db_con", key="db_log")
        return (db_con)

def insert_data(**kwargs):
    v1 = task_instance.xcom_pull(key="db_con", task_ids='db_log')
    return (v1)
    cur = db_con.cursor()
    cur.execute("""insert into tbl_1 select id,bill_no,status from tbl_2 limit 2;""")

#def job_run():
#    db_log()
#    insert_data()


##########################################

t1 = PythonOperator(
task_id='Connect',
python_callable=db_log,provide_context=True,
dag=dag)

t2 = PythonOperator(
task_id='Query',
python_callable=insert_data,provide_context=True,
dag=dag)


t1 >> t2

任何人都可以为此提供帮助。感谢..

更新1：

遇到错误

AttributeError: 'NoneType' object has no attribute 'execute'

指向上面一段代码的最后一行

cur.execute("""insert into tbl_1 select id,bill_no,status from tbl_2 limit 2;""")

完整代码

完整代码：

## Third party Library Imports
import pandas as pd
import psycopg2
import airflow
from airflow import DAG
from airflow.operators.python_operator import PythonOperator
from airflow.operators.bash_operator import BashOperator
from datetime import datetime, timedelta
from sqlalchemy import create_engine
import io

# Following are defaults which can be overridden later on
default_args = {
'owner': 'airflow',
'depends_on_past': False,
'start_date': datetime(2018, 5, 29, 12),
'email': ['airflow@airflow.com']
}

dag = DAG('sample1', default_args=default_args)

## Login to DB

def db_log(**kwargs):
  global db_con
  try:
    db_con = psycopg2.connect(
       " dbname = 'name' user = 'user' password = 'pass' host = 'host' port = '5439'")
  except:
    print("I am unable to connect")
    print('Connection Task Complete')
    task_instance = kwargs['task_instance']
    task_instance.xcom_push(key="dwh_connection" , value = "dwh_connection")
    return (dwh_connection)



t1 = PythonOperator(
  task_id='DWH_Connect',
  python_callable=data_warehouse_login,provide_context=True,
  dag=dag)

#######################

def insert_data(**kwargs):
  task_instance = kwargs['task_instance']
  db_con_xcom = task_instance.xcom_pull(key="dwh_connection", task_ids='DWH_Connect')
  cur = db_con_xcom
  cur.execute("""insert into tbl_1 select limit 2 """)


##########################################

t2 = PythonOperator(
  task_id='DWH_Connect1',
  python_callable=insert_data,provide_context=True,dag=dag)

t1 >> t2

Answer 1

这是来自Python的基本错误消息。

NameError: name 'task_instance' is not defined

告诉你，当你想要使用它时，task_instance无处可寻。

任务实例在已传递给函数的上下文中提供。

Airflow使用设置

发送上下文

provide_context=True,

任务内。该定义也接受kwargs：

def insert_data(**kwargs):

这也是正确的。

<强>校正

首先需要将任务实例从上下文中删除：

task_instance = kwargs['task_instance']

然后您可以使用任务实例来使用xcom_pull。所以它看起来应该是这样的（也有一些评论）：

def insert_data(**kwargs):
    task_instance = kwargs['task_instance']
    db_con_xcom = task_instance.xcom_pull(key="db_con", task_ids='db_log')
    #return (v1)  # wrong, why return here?
    #cur = db_con.cursor()  # wrong, db_con might not be available
    cur = db_con_xcom
    cur.execute("""insert into tbl_1 select id,bill_no,status from tbl_2 limit 2;""")

Answer 2

由于问题越来越大，我认为添加第二个答案是合适的。

即使在评论编辑后＃34;我删除了代码的缩进部分＆＃34;我仍然不确定这段代码：

def db_log(**kwargs):
  global db_con
  try:
    db_con = psycopg2.connect(
       " dbname = 'name' user = 'user' password = 'pass' host = 'host' port = '5439'")
  except:
    print("I am unable to connect")
    print('Connection Task Complete')
    task_instance = kwargs['task_instance']
    task_instance.xcom_push(key="dwh_connection" , value = "dwh_connection")
    return (dwh_connection)

它应该是这样的：

def db_log(**kwargs):
  global db_con
  try:
    db_con = psycopg2.connect(
       " dbname = 'name' user = 'user' password = 'pass' host = 'host' port = '5439'")
  except:
    print("I am unable to connect")

  print('Connection Task Complete')
  task_instance = kwargs['task_instance']
  task_instance.xcom_push(key="dwh_connection" , value = "dwh_connection")
  #return (dwh_connection)  # don't need a return here

除此之外，您在其他问题（Python - AttributeError: 'NoneType' object has no attribute 'execute'）中使用PostgresHook的想法对我来说似乎很有趣。你可能想在另一个问题中追求这个想法。

气流 - 尝试执行一组Python函数

2 个答案: