You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@airflow.apache.org by "fat-catTW (via GitHub)" <gi...@apache.org> on 2026/08/08 12:53:05 UTC
[PR] Flush scheduled DagRun creation state promptly [airflow]
fat-catTW opened a new pull request, #71331:
URL: https://github.com/apache/airflow/pull/71331
<!-- SPDX-License-Identifier: Apache-2.0
https://www.apache.org/licenses/LICENSE-2.0 -->
<!--
Thank you for contributing!
Please provide above a brief description of the changes made in this pull request.
Write a good git commit message following this guide: https://chris.beams.io/posts/git-commit/
Please make sure that your code changes are covered with tests.
And in case of new features or big changes remember to adjust the documentation.
For user-facing UI changes, please attach before/after screenshots (or a short
screen recording) so reviewers can assess the visual impact.
Feel free to ping (in general) for the review if you do not see reaction for a few days
(72 Hours is the minimum reaction time you can expect from volunteers) - we sometimes miss notifications.
In case of an existing issue, reference it using one of the following:
* closes: #ISSUE
* related: #ISSUE
-->
## Why
`SchedulerJobRunner._create_dag_runs()` had a TODO asking whether the scheduler should call `session.flush()` or `session.expunge_all()` while creating scheduled DagRuns.
The concern behind the TODO is that the scheduler may iterate over multiple Dags, create scheduled DagRuns, update `DagModel` scheduling fields, and create task instance rows in the same SQLAlchemy session. For larger Dags or larger batches of Dags, leaving ORM state pending until the outer transaction boundary can make it harder to reason about session growth and memory behavior.
This PR resolves that TODO by flushing after each successful scheduled DagRun creation and related `DagModel` scheduling-state update.
## Why `flush()` Instead of `expunge_all()`
The narrower operation is enough for the state observed in this path.
`session.flush()` writes pending ORM changes to the database transaction while keeping objects attached to the session. That directly addresses the observed pending/dirty scheduler state after creating a scheduled DagRun and updating the corresponding `DagModel`.
`session.expunge_all()` does something broader: it detaches every ORM object from the session. That can reduce identity-map retention, but it also carries more behavioral risk because later scheduler code may still expect ORM objects to be attached, refreshable, or tracked by the session.
To decide whether `expunge_all()` was needed, this path was checked for retained ORM objects after DagRun creation. If creating larger Dags left one tracked `DagRun` or `TaskInstance` object per created row, `flush()` would not address that memory growth because it does not clear the session identity map.
A local pressure check with 20 Dags and 500 tasks per Dag created 10,000 TaskInstance rows. After `_create_dag_runs()` returned, the observed session state was:
```text
session.new: 0
session.dirty: 0
identity_map: Counter({'DagModel': 20, 'DagVersion': 1, 'SerializedDagModel': 1, 'DagCode': 1})
```
<img width="728" height="122" alt="螢幕擷取畫面 2026-08-08 204423" src="https://github.com/user-attachments/assets/d154a3f9-27fd-441c-9072-ee57cf6a32d9" />
##### Was generative AI tooling used to co-author this PR?
<!--
If generative AI tooling has been used in the process of authoring this PR, please
change below checkbox to `[X]` followed by the name of the tool, uncomment the "Generated-by".
-->
- `[X]` Yes (please specify the tool below)
Generated-by: [Codex] following [the guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions)
---
* Read the **[Pull Request Guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#pull-request-guidelines)** for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
* For fundamental code changes, an Airflow Improvement Proposal ([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvement+Proposals)) is needed.
* When adding dependency, check compliance with the [ASF 3rd Party License Policy](https://www.apache.org/legal/resolved.html#category-x).
* For significant user-facing changes create newsfragment: `{pr_number}.significant.rst`, in [airflow-core/newsfragments](https://github.com/apache/airflow/tree/main/airflow-core/newsfragments). You can add this file in a follow-up commit after the PR is created so you know the PR number.
--
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] Flush scheduled DagRun creation state promptly [airflow]
Posted by "potiuk (via GitHub)" <gi...@apache.org>.
potiuk commented on PR #71331:
URL: https://github.com/apache/airflow/pull/71331#issuecomment-5839241949
Hello @fat-catTW - thank you for your contributions to Apache Airflow!
The Airflow community has introduced a limit of **5 open pull requests at a time** for contributors without write access to the repository. You currently have 17 open pull requests, so - as a one-time step of introducing the limit - we closed the ones where maintainers have not engaged yet:
* #69482 - Clarify Task Instance terminal state reporting
* #69764 - Restrict asset state store access to registered tasks
* #70140 - Clean up stale KubernetesPodOperator pods
* #71112 - Skip maxed out queued DagRun candidates
* #71216 - Optimize scheduler backfill completion updates
* #71287 - Isolate scheduled DagRun creation failures with savepoints
* #71331 - Flush scheduled DagRun creation state promptly
* #71697 - Allow paused Dags to finish running DagRuns
* #72561 - Respect SMTP connection sender for task email alerts
* #72871 - Reduce XCom requests when resolving mapped task inputs
* #72917 - Handle Dag run clear errors in task SDK client
* #73037 - Deduplicate API response result conversions
These pull requests stay open because maintainers are already engaged in them - they count towards your limit:
* #71214 - Store executor callback DagRun references in the database
* #71546 - Limit Glue retry task UUID scan
* #71654 - Fix Dag run filtering for null start dates
* #72715 - Allow API clients to refresh Dag bundles
* #73169 - Add missing Amazon provider unit tests
This is **not** a judgement of you or of your changes. We never told contributors before that opening many pull requests at once was a problem, so there is nothing to feel bad about - and nothing is lost: your branches, commits and the review history stay where they are.
What we ask you to do is to make your **first prioritization decision**: choose which of the pull requests above matter most to you, and reopen them (up to 5 open at a time, including the ones still open) with the "Reopen pull request" button or `gh pr reopen <PR_NUMBER> --repo apache/airflow`. Reopen the ones you are ready to follow through - keep them rebased, respond to review comments and fix failing checks.
While your pull requests are waiting for review, the most valuable thing you can do is help in other ways - reviewing other contributors' pull requests, helping with issues, and taking part in the discussions on the devlist and Slack.
Why we introduced the limit, what it means for you and how to reopen or restore a pull request is explained in https://github.com/apache/airflow/blob/main/contributing-docs/32_open_pull_request_limit.rst.
---
Drafted-by: Claude Code (Opus 5); reviewed by @potiuk before posting
--
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] Flush scheduled DagRun creation state promptly [airflow]
Posted by "potiuk (via GitHub)" <gi...@apache.org>.
potiuk closed pull request #71331: Flush scheduled DagRun creation state promptly
URL: https://github.com/apache/airflow/pull/71331
--
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