> The drain here is a transient which eventually converges to pause. Yep. That was my thinking. You summarized it all in one sentence :)
On Wed, Sep 9, 2026 at 7:03 AM Dheeraj Turaga <[email protected]> wrote: > Hi Amogh, > > On Jarek's thought, I agree with him that just changing the pause behavior > is probably not a good idea. > I can see instances where a user may want to instantly pause a dag in one > case > but want to drain a dag in another case. I myself have such a need for > different dags. > > For example, during airflow upgrades, I would like to gracefully drain my > whole instance before upgrade. > While during regular operation, I may want to prevent my dag from launching > further tasks. > > The drain here is a transient which eventually converges to pause. > > Draining keeps task scheduling enabled, and only automated dagrun creation > paths are gated. > *is_paused* is set to true only when the dagrun are completed. Manual > triggers are still allowed > simialr to the behavior when *is_paused* set to false. > > It would be great to get your thoughts on the PR once you get a chance to > play with it. > > Dheeraj > > On Tue, Sep 8, 2026 at 11:19 PM Amogh Desai <[email protected]> wrote: > > > Yep, *is_paused* does more than block new runs. The scheduler checks it > > directly when deciding which > > tasks to run next. That is what freezes downstream tasks today, and it is > > also why I would push back on > > "same is_paused but two buttons." > > > > If you are suggesting that "Pause and drain" sets *is_paused=True* right > > away, those two checks still need a way > > to know "this one is a soft pause, let it keep going." That means adding > a > > second flag anyway, just hidden behind > > the same name. And *is_paused* shows up in other places like backfill > pause > > logic and asset triggered runs. Each of > > those would need checking to make sure a "soft paused" Dag still acts > like > > an active one everywhere except the one > > spot it should not. From the PR, it avoids all that by keeping > > *is_paused=False* during drain, so every existing check > > keeps working as it should. It only adds new checks in a few places that > > decide whether to start a new run. > > > > Thanks & Regards, > > Amogh Desai > > > > > > On Tue, Sep 8, 2026 at 4:29 PM Jarek Potiuk <[email protected]> wrote: > > > > > I like the idea Amogh. I think **just changing** pause behaviour might > > not > > > be good idea for compatibility (someone might rely on it's current > > > behaviour). > > > > > > But maybe we could have different behaviour of two > > > different buttons/behaviour: "Pause" (current behaviour - stop current > > > tasks and it's downstream), "Pause and drain" - set the Dag to "paused" > > but > > > let the running dag_runs to continue until completion. > > > > > > It might however require some scheduler changes - I think currently > > > is_paused is used to select run-eligible tasks ? > > > > > > J. > > > > > > > > > On Tue, Sep 8, 2026 at 7:41 AM Amogh Desai <[email protected]> > > wrote: > > > > > > > Thanks for picking a 4-year-old issue. > > > > The ask itself makes sense. > > > > > > > > One design question that might eventually come up in this thread / PR > > is: > > > > why do we need a new persisted state > > > > instead of just changing what is_paused does? i.e: keep gating new > run > > > > creation on is_paused, but stop freezing > > > > downstream tasks in created runs. That would get you graceful > draining > > > > without a schema change or migration. > > > > > > > > From my reading, doing that would silently change the semantics of > > > > *is_paused*. Today, freezes downstream tasks in-flight. > > > > Some operators pause specifically to stop a run's progress, not just > to > > > > block new ones. Folding drain behavior into *is_paused* > > > > might change that for everyone already relying on the current freeze > + > > > > pause behavior, with no option to opt out, yes? > > > > Worth clarifying. > > > > > > > > Thanks & Regards, > > > > Amogh Desai > > > > > > > > > > > > On Sun, Sep 6, 2026 at 3:15 AM Dheeraj Turaga < > [email protected] > > > > > > > wrote: > > > > > > > > > Hey Everyone, > > > > > > > > > > I wanted to start this discussion to get feedback on PR #72407, > which > > > > > proposes adding a "draining" scheduling state to Airflow. > > > > > > > > > > The Problem > > > > > > > > > > Currently, pausing a DAG stops it mid-flight. While running tasks > are > > > > > allowed to finish, queued and downstream tasks remain stranded > until > > > the > > > > > DAG is unpaused. There is currently no native way to stop starting > > new > > > > runs > > > > > while allowing those already in flight to complete. > > > > > > > > > > This is a significant pain point during upgrades and maintenance. > The > > > > > current workaround as described in the four-year-old Issue #22006 > > > > requires > > > > > users to manually rewrite every DAG schedule to None, wait for runs > > to > > > > > drain, and then restore the schedules afterward. This process is > > > invasive > > > > > and prone to error. > > > > > > > > > > Proposed Solution: The draining State > > > > > > > > > > The PR introduces a draining state that sits between active and > > paused. > > > > Key > > > > > behaviors include: > > > > > > > > > > - No New Scheduled Runs: The scheduler creates no new runs for a > > > > draining > > > > > DAG (including scheduled, asset-triggered, and partitioned/rollup > > > paths). > > > > > - Completion of In-Flight Runs: is_paused remains false during > the > > > > drain, > > > > > meaning task instances in existing runs are still scheduled and > > finish > > > > > normally. > > > > > - Automatic Convergence: Once no unfinished runs remain, the > > > scheduler > > > > > automatically moves the DAG to the paused state and writes a > > > > > drain_completed audit log entry. > > > > > > > > > > The core property of this feature is that draining is transient, > not > > a > > > > > third resting state; it always converges to paused. > > > > > > > > > > Implementation Details > > > > > > > > > > Explicit run creation via manual triggers, TriggerDagRunOperator, > > asset > > > > > materialization, or backfills remains allowed during draining, > > > mirroring > > > > > the behavior of a paused DAG. An earlier revision that blocked > these > > > > > actions was reverted to ensure draining is not stricter than the > > state > > > it > > > > > converges into. > > > > > > > > > > Links: > > > > > > > > > > - PR: https://github.com/apache/airflow/pull/72407 > > > > > - Issue: https://github.com/apache/airflow/issues/22006 > > > > > > > > > > Thanks, > > > > > Dheeraj > > > > > > > > > > > > > > >
