SamWheating opened a new pull request #15714: URL: https://github.com/apache/airflow/pull/15714
<!-- 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/ --> There are two fixes included in this PR: ### 1) Enforce `READ COMMITTED` isolation when using MySQL Closes: https://github.com/apache/airflow/issues/15559 In the investigation in the above issue, we found that MySQL's default isolation level ended up causing some really weird issues when running multiple schedulers. This ended up causing skipped tasks while backfilling and caused DAGs using `depends_on_past` to completely deadlock. By enforcing `READ COMMITTED` when using MySQL we should be able to avoid these issues entirely. I don't expect that this will introduce any issues when using MySQL 5.x and/or a single scheduler, as `READ COMMITTED` is the default isolation level used by PostgreSQL. ### 2) Changing how SQLite is detected While I was in here I noticed a few places where we check for SQLite as follows: ``` if 'sqlite' in conf.get('core', 'sql_alchemy_conn') ``` While it's an unlikely occurrence, this will falsely detect sqlite in the case that it appears anywhere else in the connection string (for example, a postgres connection with a database called `not-sqlite`). I think would more reliable here to use `.startswith('sqlite')` as a SQLAlchemy connection string always starts with the dialect. --- **^ Add meaningful description above** Read the **[Pull Request Guidelines](https://github.com/apache/airflow/blob/master/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/master/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. For queries about this service, please contact Infrastructure at: [email protected]
