Hey, I agree with the direction of the PR. Given that is_paused serves several critical functions, overloading it to include draining behavior would likely cause unintended side effects across the system. By keeping "draining" as a distinct, transient state, we can avoid those complications while effectively solving the need for graceful task completion. This will also significant improvement for managing Dags during upgrades.
On Wed, 9 Sep 2026 at 20:15, Elad Kalif <[email protected]> wrote: > > The drain here is a transient which eventually converges to pause. > > I agree. drain is intermediate state. When draining is completed the status > should be changed to paused. > > On Wed, Sep 9, 2026 at 1:49 PM Jarek Potiuk <[email protected]> wrote: > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > >
