Joseph Doherty
d1ade5653b
A verified audit of all ~90 plan documents (2026-08-01) found ~30 .tasks.json
trackers and several plan headers still reporting 'pending'/'draft' for work
fully merged to main. Sync them so future audits don't re-litigate closed work:
- Flip ~380 stale task statuses to completed across March/May/June/July
trackers (audit-log series, milestones M5-M10, playwright waves, stillpending,
LocalDb, ClusterClient->gRPC DoD rows, and more), each verified against
code/git evidence before flipping.
- Annotate obsolete-not-done rows: ClusterClient CLI transport (never built,
HTTP shipped), TreeView Areas/Instances pages (replaced by Topology),
template-tree drag-drop (dropped for M9 menu reorder), otopcua item C
(premise superseded by #17).
- Flip stale headers: aggregated-live-alarm + kpi-rollups 'Draft not executed'
-> Delivered 2026-07-10; otopcua cutover-scope SCOPING -> DECIDED;
scadabridge-rename -> Implemented; LocalDb phase1/2 status strings ->
merged 28ca04d7.
- Fix doc drift: T9/T10 'deferred' -> shipped as SMS (Teams dropped); waitfor
sandbox follow-up shipped; followups #52/#53/#54/#162/#207 resolved; purge
TODO closed by PendingDeploymentPurgeActor; live-gate pre-existing failures
#28/#29/#31 fixed; auto-down boot-alone residual superseded by self-first
seeds; supersession banners on keep-oldest SBR + ClusterClient-era designs;
requirements-traceability 'Pending' clarified as frozen plan-generation
status.
Deliberately left pending (genuinely open, tracked in the pending-work list):
opcua-tag-browser task 19 (live smoke), ipsen tasks 7-8 (vd03 verification),
selfform task 7 (vd03 overlay, user-held), live-gate observation 1
(external-system delete orphan bug), otopcua item A + maxDepth calibration.
46 lines
2.8 KiB
Markdown
46 lines
2.8 KiB
Markdown
# Cluster Infrastructure Refinement — Design
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**Date**: 2026-03-16
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**Component**: Cluster Infrastructure (`docs/requirements/Component-ClusterInfrastructure.md`)
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**Status**: Approved — superseded in part: the keep-oldest SBR decision was replaced by the auto-down decision 2026-07-21 (`docs/plans/2026-07-21-auto-down-availability-decision.md`).
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## Problem
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The Cluster Infrastructure doc covered topology and failover behavior but lacked specification for the split-brain resolver strategy, seed node configuration, failure detection timing, and dual-node failure recovery.
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## Decisions
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### Split-Brain Resolver
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- **Keep-oldest** strategy. The longest-running node stays active on partition; the younger node downs itself.
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- Stable-after duration: 15 seconds — prevents premature downing during startup or transient instability.
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- Quorum-based strategies rejected because they cause total cluster shutdown on any partition in a two-node cluster.
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### Seed Node Configuration
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- **Both nodes are seed nodes.** No startup ordering dependency. Whichever node starts first forms the cluster.
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### Failure Detection Timing
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- Heartbeat interval: **2 seconds**.
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- Failure threshold: **10 seconds** (5 missed heartbeats).
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- Total failover time: **~25 seconds** (10s detection + 15s stable-after + singleton restart).
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- All values configurable. Defaults balance failover speed with stability.
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### Dual-Node Recovery
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- **Automatic recovery**, no manual intervention. First node up forms a new cluster from seed configuration.
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- Site clusters rebuild from SQLite (deployed configs, S&F buffer). Alarm states re-evaluate from live data.
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- Central cluster rebuilds from MS SQL. No message buffer state to recover.
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## Affected Documents
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| Document | Change |
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|----------|--------|
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| `docs/requirements/Component-ClusterInfrastructure.md` | Added 3 new sections: Split-Brain Resolution, Failure Detection Timing, Dual-Node Recovery. Updated Node Configuration to clarify both-as-seed. |
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## Alternatives Considered
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- **Static-quorum / keep-majority**: Rejected — both cause total cluster shutdown on partition in a two-node cluster. Unacceptable for SCADA availability.
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- **Single designated seed node**: Rejected — creates startup ordering dependency for no benefit in a two-node cluster.
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- **Manual recovery on dual failure**: Rejected — system already persists all state needed for automatic recovery.
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- **Fast detection (1s/5s)**: Rejected — too sensitive; brief network hiccups would trigger unnecessary failovers and full actor hierarchy rebuilds.
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- **Conservative detection (5s/30s)**: Rejected — 30 seconds of data collection downtime is too long for SCADA.
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- **Shorter stable-after (10s)**: Rejected — matching the failure threshold risks downing nodes that are slow to respond (GC pause, heavy load).
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