[GitHub] [airflow] malthe commented on issue #17010: Add support for custom Trigger Rule logic

[GitBox <gi...@apache.org>]

malthe commented on issue #17010:
URL: https://github.com/apache/airflow/issues/17010#issuecomment-966888936


   I think something like `TriggerRule.WAIT_ALL & TriggerRule.ONE_SUCCESS` is easier to understand than the existing `TriggerRule.NONE_FAILED_OR_SKIPPED` rule.
   
   Following the ideas in #19361 – it seems that these ideas can combine, e.g.
   
   ```python
      ...
      trigger_rule=TriggerRule.WAIT_ALL & TriggerRule.ONE_SUCCESS & TriggerRule.MONDAY
   ```
   Those are all static rules that can be combined with boolean logic such as `&`, `|` and `~` (not).
   
   In #19361 there is also `CronTimeFilter` which could be turned into a trigger rule as well – in the example above, `TriggerRule.MONDAY` is really just a predefined cron-based time filter.
   
   Like timetables (see [AIP-39](https://cwiki.apache.org/confluence/display/AIRFLOW/AIP-39+Richer+scheduler_interval)), there could be support for custom implementations, but it might be reasonable to start with a set of builtin classes which can then be combined as proposed above.
   
   In some scheduling systems, there is support for custom calendars such as "bank holidays". This seems like a good case for a custom implementation since there is no clear single solution. There are Python libraries such as [holidays](https://pypi.org/project/holidays/) that address official holidays, but an organization might have a need for much more specific calendars.


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