Autoscaling Controller  ·  View 36 of 37  ·  6 · Assurance

What It Does When It Cannot See

Fail static, then — only if declared — decay towards a schedule.

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Loss One Signal Stale past 3 intervals Signal Store Down completely blind Decision Engine Down Immediate Fail Static hold last declared No Scale-In While Blind never guess down Actuation Continues desired is durable If it persists Past a Diurnal Turn declared threshold Schedule Baseline opt-in per target Stay Frozen the default Always Alert with Cause names the source Journalled as Degraded a real outcome if declared otherwise unaffected What It Does When It Cannot See Risk / gap Security / platform Application we own Decision point Data store synchronous Freezing is right for an outage measured in minutes and increasingly wrong past a diurnal turn. Which of the two applies is a per-target declaration, not a runtime guess. v 1.0 · owner Data & AI Global Practice · date 2026-09

The decision

  • Fail static by default: when signals are stale, the engine is down, or the journal cannot be written, the fleet holds its last declared capacity.
  • Never scale in while blind. Scaling out on a stale signal wastes money; scaling in on one causes an outage.
  • Per-target opt-in to a schedule-derived baseline once blindness passes a declared threshold, for strongly diurnal targets.

Why both, and why declared

  • Freezing is safest for an outage measured in minutes and increasingly wrong as the outage passes a diurnal turn.
  • Decaying towards a schedule tracks the day but acts on a guess, which is only defensible where demand is genuinely predictable.
  • Which applies is a per-target declaration made in advance, never a runtime judgement made while blind.

Always

  • The degradation is journalled as a real outcome with its cause, and alerted naming the source that stopped publishing.
  • Actuation continues throughout: the desired-state record is durable and the reconciler does not need the engine.
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Solution Architecture v1.0 · Data & AI Global Practice · 2026-09 · 37 views · Azure and open source36-blindness-and-degradation