[jira] [Created] (AIRFLOW-2855) Need to Check Validity of Cron Expression When Process DAG File/Zip File

["Xiaodong DENG (JIRA)" <ji...@apache.org>]

Xiaodong DENG created AIRFLOW-2855:
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             Summary: Need to Check Validity of Cron Expression When Process DAG File/Zip File
                 Key: AIRFLOW-2855
                 URL: https://issues.apache.org/jira/browse/AIRFLOW-2855
             Project: Apache Airflow
          Issue Type: Improvement
          Components: DAG
            Reporter: Xiaodong DENG
            Assignee: Xiaodong DENG


*schedule_interval* of DAGs can either be *datetime* or a *Cron expression*.

When it's a Cron expression, there is no mechanism to check its validity at this moment. If there is anything wrong with the Cron expression itself, it will cause issues when methods _*following_schedule(**)*_  and _*previous_schedule()*_ are invoked (will affect scheduling). However, exceptions will only be written into logs. From Web UI, it’s hard for users to identify this issue & the source while no new task can be initiated (especially for users who’re not very familiar with Cron).

 It may be good to show error messages in web UI when a DAG's Cron expression (as schedule_interval) can not be parsed by *croniter* properly.

 



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