The tier system was documented, operator-authorable, and inert. Deleted rather than activated,
because its premise is gone rather than merely unused.
"Tier C" meant a driver running out-of-process behind an IDriverSupervisor that could restart its
Host without tearing down the OPC UA session. No such process exists anywhere: Galaxy reaches
MXAccess over gRPC to the external mxaccessgw sidecar (PR 7.2 retired the in-process
Galaxy.Host/Proxy/Shared projects) and FOCAS has run in-process since its managed wire client
landed 2026-04-24. Consistently, IDriverSupervisor had ZERO implementations and there was nothing
for one to implement against.
The issue understated the inertness. It says the Tier-C-only protections never engaged, implying
the Tier A/B parts did. They did not: nothing constructs MemoryTracking, MemoryRecycle or
ScheduledRecycleScheduler outside their own unit tests, so the whole Core/Stability recycle layer
was dead — meaning option (a), "pass real tiers", was never a flag flip. It would have meant
writing the wiring that never existed AND arming it.
Deleted: MemoryTracking, MemoryRecycle, ScheduledRecycleScheduler, IDriverSupervisor, the
vestigial DriverTypeRegistry (referenced only by its own tests), and the RecycleIntervalSeconds
knob — which the AdminUI let an operator author and the parser validated while it configured
nothing.
DriverTier itself SURVIVES and is load-bearing: DriverResilienceOptions.GetTierDefaults supplies
the real per-capability timeout/retry/breaker policies via DriverFactoryRegistry.GetTier and
DriverCapabilityInvokerFactory. Only the isolation-and-recycle layer above it is gone.
Deliberately NOT deleted:
- WedgeDetector came along in the same directory and is equally dead in production, but it is
tier-agnostic and is not recycle machinery — it only shares the folder. Restored rather than
swept up in a decision that was not about it.
- IDriver.GetMemoryFootprint() and FlushOptionalCachesAsync() lose their only consumer here.
Removing them touches all 12 drivers and every test stub, so they are documented as
consumerless and filed as #525 instead of buried in this diff.
Compatibility: a deployed ResilienceConfig blob still carrying "recycleIntervalSeconds" parses
cleanly (unknown keys are ignored — guarded by a new test, because a blob that suddenly failed to
parse would fall back to tier defaults and silently discard the operator's real overrides), and
the AdminUI's preserve-unknown-keys bag keeps the key rather than rewriting stored config on an
unrelated edit.
The 01/U-6 knob-inertness guard carried an explicit carve-out admitting RecycleIntervalSeconds was
dormant and out of scope; that carve-out is now gone, so the expected set is literally what the
test's name claims.
Note: Host.IntegrationTests has 2 failures (DriverProbeRegistrationTests.is_idempotent,
PrimaryGateFailoverTests) — verified pre-existing by reproducing both on clean master dc9d947b.
Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo
HistorianGateway is now the sole historian backend (read + alarm SendEvent +
continuous WriteLiveValues). Document the final state and retire the Wonderware
sidecar from the docs/config/labels:
- CLAUDE.md: rewrite the Historian section — ServerHistorian /
ContinuousHistorization / AlarmHistorian config keys, the IHistorianProvisioning
EnsureTags hook, the GatewayAlarmHistorianWriter SendEvent path + ReadEvents
dependency on gateway RuntimeDb:EventReadsEnabled=true, gateway-side
prerequisites (RuntimeDb flags + historian:read/write/tags:write scopes),
migration note, and two KNOWN-LIMITATION callouts (live-validation gate +
empty historized-ref-set recorder follow-on).
- appsettings.json: fix the stale ServerHistorian block (Host/Port/SharedSecret/
ServerCertThumbprint -> Endpoint/ApiKey/UseTls/AllowUntrustedServerCertificate/
CaCertificatePath/CallTimeout, keep MaxTieClusterOverfetch); add a disabled
ContinuousHistorization block; prune the orphaned Wonderware keys from
AlarmHistorian (keep the SQLite knobs). ApiKey env-supplied via
ServerHistorian__ApiKey (commented; valid strict JSON via _comment keys).
- README.md + docs (Historian.md, AlarmHistorian.md, Configuration.md,
ServiceHosting.md, DriverLifecycle.md, drivers/README.md, Uns.md, VirtualTags.md,
AlarmTracking.md, Client.UI.md, README.md, TestConnectProbes.md): retire the
Wonderware historian backend from current-backend descriptions; fix the stale
ServerHistorian/AlarmHistorian config tables (now gateway shape); convert
drivers/Historian.Wonderware.md to a retired stub pointing at the gateway.
- Source/UI labels (descriptive text only, no behavior change):
OtOpcUaServerHostedService.cs, HistoryPaging.cs, OtOpcUaSdkServer.cs,
HistorianAdapterActor.cs, VirtualTagModal.razor, ScriptedAlarmModal.razor,
AlarmsHistorian.razor now name the HistorianGateway backend.
Build clean (0 errors); AdminUI.Tests green (514 passed).
Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii
Joseph Doherty