How to get reason for failure using slack in airflow2.0 - airflow

Question

How to get the reason for the failure of an operator, without going into logs. As I want to post the reason as a notification through slack?
Thanks,
Xi

Answer 1

I can think of one way of doing this as below.
set error notifications -> https://www.astronomer.io/guides/error-notifications-in-airflow/
Also create a slack email alias for DM https://slack.com/help/articles/206819278-Send-emails-to-Slack
Other way is using the Slack API from airflow : https://medium.com/datareply/integrating-slack-alerts-in-airflow-c9dcd155105
Check the above for SlackAPIPostOperator

Answer 2

exception=context.get('exception')is the function which will give exact reason for failure
Example of on_failure_callback using slack:
step_checker = EmrStepSensor(task_id='watch_step',
job_flow_id="{{ task_instance.xcom_pull('create_job_flow',
key='return_value') }}",
step_id="{{task_instance.xcom_pull(task_ids='add_steps',key='return_value')[0] }}",
aws_conn_id='aws_default',
on_failure_callback=task_fail_slack_alert,)
def task_fail_slack_alert(context):
SLACK_CONN_ID = 'slack'
slack_webhook_token = BaseHook.get_connection(SLACK_CONN_ID).password
slack_msg = """
:red_circle: Task Failed.
*Task*: {task}
*Dag*: {dag}
*Execution Time*: {exec_date}
*Log Url*: {log_url}
*Error*:{exception}
""".format(
task=context.get('task_instance').task_id,
dag=context.get('task_instance').dag_id,
exec_date=context.get('execution_date'),
log_url=context.get('task_instance').log_url,
exception=context.get('exception')
)
failed_alert = SlackWebhookOperator(
task_id='slack_test',
http_conn_id='slack',
webhook_token=slack_webhook_token,
message=slack_msg,
username='airflow',
dag=dag)
return failed_alert.execute(context=context)