potiuk opened a new pull request #18362: URL: https://github.com/apache/airflow/pull/18362
Default isolation level for the MSSQL database is READ_COMMITTED but its implementation in MSSQL might cause random deadlocks for select queries - because by default MSSQL uses shared locks for READ_COMMITTED transaction isolation that might cause deadlocks with the UPDATE statements which create exclusive locks. This change switches the MSSQL DB used during tests to have READ_COMMITTED_SNAPSHOTS enabled and it adds check at the Airflow startup to make sure that if the MSSQL database is used, the READ_COMMITTED_SNAPSHOTS is set and documentation is added to describe it. It also allows to revert removal of 2017 version of mssql which was done in the faith that removal of 2017 will remove the flaky random test failures. <!-- Thank you for contributing! 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. Feel free to ping committers for the review! In case of existing issue, reference it using one of the following: closes: #ISSUE related: #ISSUE How to write a good git commit message: http://chris.beams.io/posts/git-commit/ --> --- **^ Add meaningful description above** Read the **[Pull Request Guidelines](https://github.com/apache/airflow/blob/main/CONTRIBUTING.rst#pull-request-guidelines)** for more information. 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/main/UPDATING.md). -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
