Forecast: fetch raw forcing data only on rank 0

[mxkpp]

In support of adding multiprocessing capability to the forecast workflow, this changes the forecast forcing data fetcher to run only on MPI rank 0, since the other ranks download the same information.

This should be tested with a branch of the same name for MSWM, Fcst Mgr, and RTE, see other PRs:

NGWPC/nwm-msw-mgr#43

NGWPC/nwm-fcst-mgr#10

NGWPC/nwm-rte#42

Additions

Removals

Changes

• forcing_extraction.retrieve_forcing(self._job_meta) is called only by rank 0 now, and previously was called by all ranks (but previously the workflow was running with a single rank).

Testing

1. I confirmed that the files downloaded by rank 0 are equivalent to those downloaded by rank 1, which confirms that this is a safe change, that multiprocessing workflows will receive the proper inputs.
2. regrid.py pytests passed for HRR and RAP.

Screenshots

Notes

Todos

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Target Environment support

• Linux