potiuk opened a new pull request #6988: [AIRFLOW-2516] Fix mysql deadlocks URL: https://github.com/apache/airflow/pull/6988 Deadlocks were occuring in mysql when task_instance was modified by two queries at the same time. One query used state as selection criteria and updated it in the same query where second query just updated the state for the same table. The first query locked state index first and primary index afterwards, the second query locked primary index first and state afterwards - leading to deadlocks. This change splits the first query into two independent ones. First query makes select FOR UPDATE and selects all the task instances to act on (this will lock primary index only) and second updates all affected task instances. Note that performance impact for that is neglectable because this query is only run once every scheduler loop and the second part of it (looping through task instances) will only happen in case there are some manually modified DagRun states - so it is only run to correct some wrong states of DagRun. This should happen very infrequently. - [x] Description above provides context of the change - [x] Commit message contains [\[AIRFLOW-XXXX\]](https://issues.apache.org/jira/browse/AIRFLOW-XXXX) or `[AIRFLOW-XXXX]` for document-only changes - [x] Unit tests coverage for changes (not needed for documentation changes) - [x] Commits follow "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)" - [x] Relevant documentation is updated including usage instructions. - [x] I will engage committers as explained in [Contribution Workflow Example](https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst#contribution-workflow-example). In case of fundamental code change, Airflow Improvement Proposal ([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvements+Proposals)) is needed. In case of a new dependency, check compliance with the [ASF 3rd Party License Policy](https://www.apache.org/legal/resolved.html#category-x). In case of backwards incompatible changes please leave a note in [UPDATING.md](https://github.com/apache/airflow/blob/master/UPDATING.md). Read the [Pull Request Guidelines](https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst#pull-request-guidelines) for more information.
---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
