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-12 Scheduler

Status: built

  • Code: services/scheduler/ — policy.py for the minimum interval, outstanding.py for the duplicate-request register, and run_id.py for the deterministic run identifier
  • Delivered by: specs/009-control-loop
  • Covered by: services/scheduler/tests/, tests/integration/test_monitor_scheduler_handoff.py and tests/integration/test_control_loop_startup.py
  • Not present: the run identifier is derived from the seed and an ordinal by hashing, so a published run's name cannot be read back as the sequence it was, and the run manifest records no run sequence for want of one. The coverage store's naming rule puts the sequence in the name and the scheduler has not adopted it

Responsibility: decide whether a model run is warranted. Owns the failure mode of: thrashing.

What it does

It receives divergence requests from the monitor and decides whether to start a model run. It enforces a minimum interval between runs and rejects duplicate outstanding requests.

Why it is a separate component

Because "the forecast is wrong" and "we should therefore recompute it now" are different judgements, and merging them produces a system that recomputes whenever it is wrong, which is exactly when computing is most expensive and least likely to help.

Separating them also means the policy lives in one readable place. The minimum interval, the deduplication rule, and any future rule about time of day or resource availability are all scheduling policy, and scheduling policy is one of the few genuinely bespoke pieces of logic in the system rather than plumbing.

Thrashing

The failure mode it owns is a loop that spends all its time reacting: a run starts, the forecast changes, the residual moves, another request arrives, and the system never reaches a state where anyone can ask whether the forecast is any good. The minimum interval is the crude form of the defence and the duplicate-request rejection is the precise one.

Requirements: FR-27. Feature: 009.