Halt ingestion when WordPress Photo Directory reaches last page

[stacimc]

Fixes

Fixes WordPress/openverse#1372 by @AetherUnbound

Description

The WordPress Photo Directory DAG was failing to halt ingestion gracefully when it reached the end of its data. Instead, it raises a 400 when attempting to access a page number beyond the total page count. This is especially bad if skip_ingestion_errors is enabled, because it will retry infinitely.

To fix this we need to make a HEAD request to get the total page count. This information is only available in the headers and not response_json, so we are not able to fetch it in get_batch_data. This PR makes this additional request on the first batch, and then halts ingestion during get_should_continue when we reach the final page.

Testing Instructions

At the time this PR was written, this DAG detects 53 pages of results. To test it locally, I recommend editing the initial current_page variable in the __init__ method to 52, so the DAG will run quickly and hit the last page:

def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        <...>

        self.current_page = 52

After making the edit, run the DAG and verify that it stops gracefully when the last page has been reached. You should be able to see a log that looks like:

The final page of data has been processed. Halting ingestion.

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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[sarayourfriend]

This LGTM and tests fine locally. Thank you for the good instructions.

I was wondering if you had considered any alternative solutions to this, perhaps ones that would add the ability to get the headers to the base class? I had one idea for how to do it so that it would always be available as part of response_json but didn't want to get into it if you thought it was a YAGNI type situation.

Anyway, LGTM either way and the solution makes sense for this DAG.

[krysal]

Nice! I was thinking about the general solution for the response headers as well but that seemed to require much refactorization of other DAGs for just using it here. I like this.

Good code coverage in testing too! It's appreciated.

[sarayourfriend]

I have at least one idea that wouldn't require any refactors of other DAGs, but would be a little obscure: subclass dict and add a headers attribute. Then map the JSON response into the dict subclass and add the headers to the headers attribute.

[stacimc]

I was wondering if you had considered any alternative solutions to this, perhaps ones that would add the ability to get the headers to the base class?

We definitely can, but I wasn't aware of any other cases where we needed it (although I could be wrong). I'd say I have a slight preference to refactoring more fully if/when another use case arises... although the dict subclassing idea is pretty slick @sarayourfriend 🤩

[sarayourfriend]

I'd say I have a slight preference to refactoring more fully if/when another use case arises

I like this as well 🚀