无法在 Airflow 的自定义运算符中传递 xcom

Unable to pass xcom in Custom Operators in Airflow

我有一个简单的线性 DAG(使用 Airflow 2.0 创建)有两个任务。我为扩展到 BaseOperator 的每个任务都有自定义运算符。以下是 dag 和运算符的代码:-

class Operator1(BaseOperator):
    @apply_defaults
    def __init__(self, **kwargs) -> None:
        super().__init__(**kwargs)
    def execute(self, context):
        ...
        logging.info('First task')
        context['task_instance'].xcom_push(key="payload", value=data)
        return data

class Operator2(BaseOperator):
    @apply_defaults
    def __init__(self, **kwargs) -> None:
        super().__init__(**kwargs)
    def execute(self, context):
        ...
        logging.info("context is ", context)
        parameters = context['task_instance'].xcom_pull(key="payload", value=data)
 

with DAG('dag_1', default_args=DEFAULT_ARGS, schedule_interval=None) as dag:
    TASK_1 = Operator1(
        task_id='task_1',
        do_xcom_push=True)
    TASK_2 = Operator2(
        task_id='task_2',
        do_xcom_push=True)
    TASK_1 >> TASK_2 

当我运行 DAG 时,我发现用于获取xcom 值的context 是空的。我在Whosebug上搜索了很多答案,并尝试了其中提到的方法,但都没有用。

真的很想得到一些关于这个问题的提示 - 如何在自定义运算符中推送和拉取 xcom 值?

我拿了你的代码 运行 它,第一个问题是 start_date 没有定义,所以它以异常结束:

Exception has occurred: AirflowException (note: full exception trace is shown but execution is paused at: _run_module_as_main)
Task is missing the start_date parameter

此外,在Operator1 class 中,data 变量未定义。我想也许您在制作代码示例时错过了它们。

除此之外代码还有效,但我认为您应该在执行 xcom_pull 操作时考虑定义 task_id 参数。

来自TaskInstancexcom_pull方法说明:

:param task_ids: Only XComs from tasks with matching ids will be pulled. Can pass None to remove the filter.

这是一个工作示例的代码,请注意,我使用两种等效的方法来执行 XComs 操作:

from airflow import DAG
from airflow.utils.dates import days_ago
from airflow.utils.decorators import apply_defaults
from airflow.models import BaseOperator


class Operator1(BaseOperator):
    @apply_defaults
    def __init__(self,  *args, **kwargs) -> None:
        super(Operator1, self).__init__(*args, **kwargs)

    def execute(self, context):
        print('First task')
        data = "valuable_data"
        more_data = "more_valueable_data"
        context['task_instance'].xcom_push(key="payload", value=data)
        self.xcom_push(context, "more_data", more_data)
        return data


class Operator2(BaseOperator):
    @apply_defaults
    def __init__(self,  *args, **kwargs) -> None:
        super(Operator2, self).__init__(*args, **kwargs)

    def execute(self, context):
        # print(f"context is  {context}")
        data = context['task_instance'].xcom_pull(
            "task_1",
            key="payload")
        more_data = self.xcom_pull(context, "task_1", key="more_data")

        print(f"Obtained data: {data}")
        print(f"Obtained more_data: {more_data}")


with DAG('dag_1',
         default_args={'owner': 'airflow'},
         start_date=days_ago(1),
         catchup=False,
         schedule_interval=None) as dag:

    TASK_1 = Operator1(
        task_id='task_1'
    )
    TASK_2 = Operator2(
        task_id='task_2'
    )
    TASK_1 >> TASK_2

日志来自 Task_2:

[2021-06-15 12:55:01,206] {taskinstance.py:1255} INFO - Exporting the following env vars:
AIRFLOW_CTX_DAG_OWNER=airflow
AIRFLOW_CTX_DAG_ID=dag_1
AIRFLOW_CTX_TASK_ID=task_2
AIRFLOW_CTX_EXECUTION_DATE=2021-06-14T00:00:00+00:00
AIRFLOW_CTX_DAG_RUN_ID=backfill__2021-06-14T00:00:00+00:00
Obtained data: valuable_data
Obtained more_data: more_valueable_data
[2021-06-15 12:55:01,227] {taskinstance.py:1159} INFO - Marking task as SUCCESS. dag_id=dag_1, task_id=task_2, execution_date=20210614T000000, start_date=20210615T120402, end_date=20210615T125501

旁注:我更改了 __init__ 方法以便也接受 *args。我正在使用 print 但可以使用 Airflow 记录器作为 self.log.info('msg') .

让我知道这是否对您有用!