Upgrading Airflow to a newer version

Why you need to upgrade

Newer Airflow versions can contain Database migrations so it is recommended that you run airflow db upgrade to Upgrade your Database with the schema changes in the Airflow version you are upgrading to.

When you need to upgrade

If you have a custom deployment based on virtualenv or Docker Containers, you usually need to run the DB upgrade manually as part of the upgrade process.

In some cases the upgrade happens automatically - it depends if in your deployment, the upgrade is built-in as post-install action. For example when you are using Helm Chart for Apache Airflow with post-upgrade hooks enabled, the database upgrade happens automatically right after the new software is installed. Similarly all Airflow-As-A-Service solutions perform the upgrade automatically for you, when you choose to upgrade airflow via their UI.

How to upgrade

In order to manually upgrade the database you should run the airflow db upgrade command in your environment. It can be run either in your virtual environment or in the containers that give you access to Airflow CLI Using the Command Line Interface and the database.

Migration best practices

Depending on the size of your database and the actual migration it might take quite some time to migrate it, so if you have long history and big database, it is recommended to make a copy of the database first and perform a test migration to assess how long the migration will take. Typically “Major” upgrades might take longer as adding new features require sometimes restructuring of the database.

Post-upgrade warnings

Typically you just need to successfully run airflow db upgrade command and this is all. However in some cases, the migration might find some old, stale and probably wrong data in your database and moves it aside to a separate table. In this case you might get warning in your webserver UI about the data found.

Typical message that you might see:

Airflow found incompatible data in the <original table> table in the metadatabase, and has moved them to <new table> during the database migration to upgrade. Please inspect the moved data to decide whether you need to keep them, and manually drop the <new table> table to dismiss this warning.

When you see such message, it means that some of your data was corrupted and you should inspect it to determine whether you would like to keep or delete some of that data. Most likely the data was corrupted and left-over from some bugs and can be safely deleted - because this data would not be anyhow visible and useful in Airflow. However if you have particular need for auditing or historical reasons you might choose to store it somewhere. Unless you have specific reasons to keep the data most likely deleting it is your best option.

There are various ways you can inspect and delete the data - if you have direct access to the database using your own tools (often graphical tools showing the database objects), you can drop such table or rename it or move it to another database using those tools. If you don’t have such tools you can use the airflow db shell command - this will drop you in the db shell tool for your database and you will be able to both inspect and delete the table.

How to drop the table using Kubernetes:

  1. Exec into any of the Airflow pods - webserver or scheduler: kubectl exec -it <your-webserver-pod> python

  2. Run the following commands in the python shell:

from airflow.settings import Session

session = Session()
session.execute("DROP TABLE _airflow_moved__2_2__task_instance")

Please replace <table> in the examples with the actual table name as printed in the warning message.

Inspecting a table:

SELECT * FROM <table>;

Deleting a table:

DROP TABLE <table>;

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