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

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?

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)