Allow overriding the date from the DagRun conf

[stacimc]

Fixes

Description

Adds an option to the DagRun conf to let you override the date of a run of a dated provider DAG.

When you manually run a dated DAG, it is always passed in today's date. This option allows you to pass in any arbitrary date you'd like. While I don't necessarily expect this to be used frequently in production, it has come in handy many times for local testing.

Testing Instructions

To trigger a DAG using a date override, select the Trigger DAG w/ config option seen here:

Then pass your chosen date in using a YYYY-MM-DD format like this:
{"date": "2022-04-10"}

Pick a dated DAG, like Europeana:

• Try running it normally by enabling the DAG locally and letting a scheduled run start. Verify that it correctly uses the scheduled date.
• Try running it manually without a DagRun conf. Verify that it uses today's date.
• Try triggering the DAG w/ a config and pass in a different date. Verify the custom date is used. You should see a message in the logs like Using date <date> from dagrun conf.

Notes

• The DAG will error if nonsense data or an incorrectly formatted date is passed in.
• You can set a date override on any provider DAG, even a non-dated one. In this case it simply won't do anything.

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

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[krysal]

The code looks good to me, though, what is this date used for? It's not totally clear to me.

Is there a place where we can find these configuration parameters with their descriptions or use cases documented? Yesterday I was looking to limit the number of records pulled, and I wasn't sure if there is a param for it (there is an Airflow Variable but something for an individual DAG run? would be nice to add it if it's not already done).

[stacimc]

The code looks good to me, though, what is this date used for? It's not totally clear to me.

This is the ingestion date that's used in dated DAGs. Typically, the logical date of the DagRun is passed in automatically. The goal of this PR is to allow a dev a way to override that to whatever date we want, because otherwise there isn't currently an easy way to run ingestion for an arbitrary day.

(A recent use case for me was testing with Finnish Museums. I wanted to reproduce a bug that only happens on certain days, and found it useful to be able to easily kick off ingestion for specific dates.)

Is there a place where we can find these configuration parameters with their descriptions or use cases documented?

There isn't, but there is an issue to add documentation! WordPress/openverse#1427 Couldn't agree more, it's easy to forget what the available options are.

Yesterday I was looking to limit the number of records pulled, and I wasn't sure if there is a param for it (there is an Airflow Variable but something for an individual DAG run? would be nice to add it if it's not already done).

The ingestion_limit Airflow variable is what you're thinking of, and you're right that it applies to all DAGs. Having that available as an option for individual DAG runs sounds like it could be very handy! I made WordPress/openverse#1329 to track it, thanks 😄

[AetherUnbound]

Great idea! I can't test this locally at this time, but the implementation & test look 💯

[AetherUnbound]

Finally able to test, works great!