drogna

A demonstration harness. Every number in it is invented.

Version 1 record

This page describes software that has been retired. It is accurate about Version 1 and is not a description of what runs now — see the current site and the archive.

C-14 Publisher

Status: built

  • Code: services/publisher/ — atomic.py for the single visible step, catalogue.py for the current-run pointer, manifest.py for the run manifest and publish.py for the announcement
  • Delivered by: specs/009-control-loop
  • Covered by: services/publisher/tests/, tests/integration/test_publication_atomicity.py and tests/integration/test_new_run_servable.py
  • Not present: the run manifest it writes has no schema master, and records no run sequence — see the coverage store and the scheduler

Responsibility: make completed runs visible atomically; announce them. Owns the failure mode of: partial visibility.

What it does

When a model run finishes, the publisher makes it visible in one step and marks it current. No reader ever observes a partially written field. It then announces the new run as an event on the control namespace.

Why atomicity is a component and not a detail

A gridded forecast is many files, or many variables in one file, written over a period of time. Without an explicit publication step, a reader can arrive halfway and get a field whose temperature is from the new run and whose salinity is from the old one. Nothing errors. The values are all plausible. The sound speed derived from them is wrong in a way that no validation catches.

That is the failure mode this component exists to own, and it is the reason the publication step is a named component rather than the last four lines of the model runner.

Why it announces

Consumers subscribe to the announcement. Nothing polls the query layer asking whether anything has changed, because the query layer has no notification mechanism and polling it would be an invented one. The announcement is how the control loop closes: the run that the scheduler decided on becomes a fact that the telemetry, the planner and the client all hear about at the same moment.

Requirements: FR-30, FR-31. Feature: 009.