Autoscaling Controller  ·  View 18 of 37  ·  4 · Runtime

One Control Interval

Tick to actuation call, with the two halves meeting only at the record.

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Interval Tick Signal Store Decision Engine Desired State Journal Reconciler Capacity Provider 1. t0 · shard tick 2. lease still valid? 3. read signals for target 4. values + freshness 5. evaluate every policy 6. combine, damp, clamp 7. write desired capacity 8. committed · p99 2 s 9. decision + all inputs 10. read desired 11. observe actual 12. instances serving 13. apply delta · p99 3 s 14. actuation outcome One Control Interval, End to End The engine never calls the provider and the reconciler never reads a signal. The two halves meet only at the desired-state record. v 1.0 · owner Data & AI Global Practice · date 2026-09

Read this for

  • The lease check happens before the signal read, so a replica that has lost its lease spends nothing.
  • The journal write is asynchronous and after the desired-state commit — a journal outage delays explanation, never a decision.
  • The reconciler's loop is independent of the tick. It reads desired state on its own cadence and does not wait for the engine.

Budget

  • Signal read to desired-state write: p99 ≤ 2 s.
  • Desired-state write to first actuation call: p99 ≤ 3 s.
  • Both inside a 15 s interval with room for a retry.

Omitted here

  • Damping is one self-message here and a whole view in 21.
  • The provider's own latency is out of budget and measured separately as time-to-serving.
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Solution Architecture v1.0 · Data & AI Global Practice · 2026-09 · 37 views · Azure and open source18-control-interval-sequence