Best practices for developing own custom operators in Airflow 2.0

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We are currently in the process of developing custom operators and sensors for our Airflow (>2.0.1) on Cloud Composer. We use the official Docker image for testing/developing

As of Airflow 2.0, the recommended way is not to put them in the plugins directory of Airflow but to build them as separate Python package. This approach however seems quite complicated when developing DAGs and testing them on the Docker Airflow.

To use Airflows recommended approach we would use two separate repos for our DAGs and the operators/sensors, we would then mount the custom operators/sensors package to Docker to quickly test it there and edit it on the local machine. For further use on Composer we would need to publish our package to our private pypi repo and install it on Cloud Composer.

The old approach however, to put everything in the local plugins folder, is quite straight forward and doesnt deal with these problems.

Based on your experience what is your recommended way of developing and testing custom operators/sensors ?

airflow
1 Answers

You can put the "common" code (custom operators and such) in the dags folder and exclude it from being processed by scheduler via .airflowignore file. This allows for rather quick iterations when developing stuff.

You can still keep the DAG and "common code" in separate repositories to make things easier. you can easily use a "submodule" pattern for that (add "common" repo as submodule of the DAG repo - this way you will be able to check them out together, you can even keep different DAG directories (for different teams) with different version of the common packages this way (just submodule-link it to different versions of the packages).

I think the "package" pattern if more of a production deployment thing rather than development. Once you developed the common code locally, it would be great if you package it together in common package and version accordingly (same as any other python package). Then you can release it after testing, version it etc. etc..

In the "development" mode you can checkout the code with "recursive" submodule update and add the "common" subdirectory to PYTHONPATH. In production - even if you use git-sync, you could deploy your custom operators via your ops team using custom image (by installing appropriate, released version of your package) where your DAGS would be git-synced separately WITHOUT the submodule checkout. The submodule would only be used for development.

Also it would be worth in this case to run a CI/CD with the Dags you push to your DAG repo to see if they continue working with the "released" custom code in the "stable" branch, while running the same CI/CD with the common code synced via submodule in "development" branch (this way you can check the latest development DAG code with the linked common code).

This is what I'd do. It would allow for quick iteration while development while also turning the common code into "freezable" artifacts that could provide stable environment in production, while still allowing your DAGs to be developed and evolve quickly, while also CI/CD could help in keeping the "stable" things really stable.

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