[PR] [v3-3-test] Fix Dag scheduling stall after switching to a coarser cron (#72498) [airflow]

["github-actions[bot] (via GitHub)" <gi...@apache.org>]

github-actions[bot] opened a new pull request, #72679:
URL: https://github.com/apache/airflow/pull/72679

   * Fix Dag scheduling stall after switching to a coarser cron
   
   Changing a Dag's schedule to a coarser cron (e.g. hourly to daily) could
   make the realigned next run collide with the logical_date of the run
   already on record. The scheduler would then loop on "run already exists;
   skipping dagrun creation" forever instead of advancing, since every input
   to the recompute (the DAG's static start_date, the stale reference run)
   is a fixed constant that reproduces the identical collision every time.
   
   A single-step guard for this class of collision already existed for the
   narrower case of a CronTriggerTimetable-to-CronDataIntervalTimetable
   switch. A single step turns out to always be enough for both shipped
   _DataIntervalTimetable subclasses, but only because of invariants that
   are specific to them and aren't enforced anywhere -- a custom Timetable
   isn't guaranteed to uphold them. Retry a bounded number of times instead
   of assuming one step suffices, and fail loudly if that budget is
   exhausted rather than looping unbounded, which would otherwise hang the
   scheduler's main loop for every Dag if a future _get_next implementation
   ever stopped strictly advancing.
   
   * Simplify the coarser-schedule-stall guard to a single bounded retry
   
   Only one advance past the previous run's start is provably necessary
   for both shipped _DataIntervalTimetable subclasses; a second retry was
   unproven margin that only existed to satisfy a synthetic test case, not
   any real or documented timetable behavior. A bounded while loop implied
   that margin was load-bearing. Replacing it with a single retry followed
   by a loud failure keeps the same fail-fast guarantee -- a custom
   Timetable needing more than one step is still caught immediately rather
   than silently retried -- while matching what the invariant actually
   proves.
   
   * Use ValueError for timetable alignment guard
   
   * Avoid exposing timetable internals in error message
   
   * Simplify schedule change test runner helper
   
   * Clarify zero-length interval test wording
   
   * Clarify coarser schedule regression test comment
   (cherry picked from commit 31117014f3c5a8cd4d4acd4223309eb344e21981)
   
   Co-authored-by: Jason(Zhe-You) Liu <68...@users.noreply.github.com>


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: commits-unsubscribe@airflow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org

Re: [PR] [v3-3-test] Fix Dag scheduling stall after switching to a coarser cron (#72498) [airflow]

["vatsrahul1001 (via GitHub)" <gi...@apache.org>]

vatsrahul1001 merged PR #72679:
URL: https://github.com/apache/airflow/pull/72679


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: commits-unsubscribe@airflow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org