Script file access (design docs/plans/2026-09-28-script-file-access-design.md): Files.ReadTextAsync /
ReadLinesAsync / ExistsAsync on site ScriptGlobals (+ Instance.Files), backed by the site-singleton
ScriptFileReader. The one host-mediated exception to the System.IO ban - scripts still never name a
System.IO type. OFF by default: ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots (empty = every call
throws Disabled) + MaxFileBytes (1 MiB, validated 1..64 MiB, roots must be absolute). Guard: fully
qualified, no device paths / ADS, canonical path strictly inside a root (directory-boundary match), no
reparse point on the file or any directory below the root, size cap before and during the read.
Errors are one Commons type, ScriptFileAccessException(+ScriptFileAccessFailure); Commons.Types.Scripts
joins the default script imports on every surface so it binds by short name. Mirrored on
ScriptCompileSurface (CompileFiles, parity-pinned) and the Test Run sandbox (binds, refuses Disabled).
Inbound (central) scripts do not get it.
Rig: docker/recipes (sample RecipeValueName,RecipeValue files incl. an invalid one) bind-mounted
read-only at /app/recipes on both site-a nodes with AllowedRoots [/app/recipes]. The TestMesMachine
SimDelmiaRecipe simulator now reads + parses the downloaded file, converts each value to its recipe tag's
type and loads it all-or-nothing (14 new TestDelmiaReceiver attributes); verify-mes-test-machine.sh
group A covers accept / re-download / invalid lines / NotFound / OutsideAllowedRoots, VERIFY_GROUPS
selects groups (rig: AD).
A null resetValue encoded to null, which wrote an empty string and then handed the
waiter a null target (= any change), fast-pathing on the stale cache and reinstating
the race the overload exists to close. The context parameter is now non-nullable and
the accessor throws ArgumentException before any write. Also: additive-timeout note on
all surfaces, batch-failure message no longer names the bool overload, and the
error-message/batch-failure branches are pinned.
Claude-Session: https://claude.ai/code/session_01XPsuy2ZZ5Gbyfpt8PrK5BV
Second slice of the 2026-09-09 whole-system review remediation
(docs/plans/2026-09-09-arch-review.md §10), on top of the High slice 146a1323.
Runtime/devices: SR-2 alarm on-trigger integration scope; SR-3 correlated NativeAlarmActor
subscribe retry; SR-4 immutable audited DB target; SR-5 ordered InstanceActor stop/flush;
SR-12 rehydration fence; SR-13 S&F gate recheck per delivery; DC-4 no OPC UA security
downgrade; DC-5 alarm snapshot for every new subscriber; ORCH-1 sync-dispose joins the pump.
Management/UI: MG-2 site scope on audit tree + Flow Debugger Replay; MG-3 stale-probe memo
removed; MG-4 server-owned bulk-deploy deadline; UI-5 sandbox runs in a killable child
process (new CentralUI.SandboxWorker project); UI-14 bounded sandbox output/IPC.
Edge/audit: EI-1 relay audit ownership; EI-2 SkipBodyCapture suppresses error text; EI-3/EI-11
error-field redaction + caps; EI-4 single relay deadline, pre-execution-only retry; EI-5
authenticated relay provenance; EI-10 body cap before audit read.
Persistence/contracts: DL-1 global Instance.UniqueName unique index + conflict translation;
DL-2 DataConnection protocol config encrypted at rest (migration
20260909203046_EnforceGlobalInstanceNamesAndProtectProtocolConfiguration — coordinated
central upgrade, old binaries cannot read protected rows); DL-3 bounded Replay paging;
DL-6 cross-site Overwrite of a deployed instance rejected; XC-4 proto descriptor contract test.
Config/hygiene: XC-1 central listener isolation by local port; XC-2/XC-3 inert SMTP + cron
keys removed from rig settings; CM-2 env2 bootstrap guard enabled; DC-6 deploy site exit code;
DC-7 notifier retries only explicit standby rejection; XC-5 ClusterClient purged from docs.
Gates recorded in the report: build 0/0, 9 397 passed / 0 failed, rig redeployed on all
eight nodes with the migration applied. 46 Low findings remain open.
Task 5 code-review follow-ups:
- I1: ExternalSystemHelper gates its TraceStepScope on a new isTraced ctor arg
(default false for direct construction), not on `_traceSink is not null` — a
traced run without an inline collector still writes durable ScriptLog rows
that must name their step.
- I2 (design §5): an inline shared script now SHARES its caller's ScriptLogger
via the new `sharedLog` ctor param — one line cap, one anchor, one closing
row. Consequence documented on the Log property: a shared script's lines
carry the PARENT run's ExecutionId and land on the parent's ScriptRun node.
- M3: TraceCapturingLogger swallows a throwing formatter — most of what it
captures is best-effort "audit write failed" warnings logged from inside a
catch block, and a formatting exception must not escape that path.
- Tests: ApiCall step attribution, traced-without-collector, shared-script
logger sharing, nested batch/wait scope attribution + unwind, throwing
formatter; test (c) now also pins the anti-recursion property (EmitLog must
log through the undecorated logger).
CompileSurfaceParityTests stays red until Task 7 mirrors Log on ScriptCompileSurface.
A traced run refused before launch — by the per-script in-flight cap
(MaxConcurrentRunsPerScript) or by MinTimeBetweenRuns — emitted no ScriptTrace row at
all, so the Flow Debugger reported NO_TRIGGER_WITHIN_WINDOW ("no value-change trigger on
this attribute, or no device echo"), which is wrong in both cases and sends the operator
to check the wrong things.
Both guards now leave a Failed ScriptTrace/ScriptRun row naming the guard that refused
the run, parented to the writing execution and carrying the trigger detail. The new
ScriptRunLauncher.EmitSuppressedRun reuses EmitScriptRun with elapsedMs 0 and no
collector (a shed run has no reply to ride on — the row reaches the debugger via
PullTraceEvents / Replay), resolving the writer and identity providers from a fresh
scope because it runs on the actor thread. Best-effort, never throws, no-op untraced.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
Every emit site hands FlowTraceCollector the same AuditEvent it hands the
writer, but redaction and payload capping lived inside the writers, which
return a NEW filtered record — so the inline copy that rides
ScriptCallResult.TraceEvents / RouteToCallResponse.TraceEvents was the RAW
event: no per-target SQL-parameter redaction, no header scrubbing, no 8 KB /
64 KB truncation. Live and Replay of the same execution could therefore show
different payloads, and the 500-event-only cap left the reply free to breach
the 4 MB gRPC receive limit — which would fail a real call, since the same
reply carries the script's return value.
The collector now applies the host IAuditRedactor itself (outside the lock;
the writers keep their own idempotent Apply) and enforces a byte budget
(DefaultMaxBytes = 1 MB over the redacted DetailsJson) alongside the event
cap, flagging Truncated when either trips. It moves to Commons
(Types/Debugging) so the central FlowDebugRunner can share it.
The redactor is a singleton, so ScriptRunLauncher resolves it from the ROOT
provider and keeps constructing the collector before the try — the traced
ScriptRun row is emitted from the catch blocks too, including the
shed-at-dequeue path that throws before the DI scope exists.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
The Flow Debugger trace arm was recorded when a traced write was ISSUED, not
when the DCL acknowledged it. A write the device rejected (or that timed out)
left the arm standing for the whole TraceArmWindowSeconds (30 s), so the next
unrelated subscription update on that attribute was stamped with the debugger's
execution id and spawned a traced, parented run — the debugger drew a "device
echo" of a write that never landed.
The write's continuation runs off the actor's dispatcher, so it cannot touch
_traceArms directly; it Tells self a new DisarmTrace message instead, handled in
a Receive<>. The disarm is keyed on the writer's execution id, so a late failure
cannot steal an arm a newer traced write has since taken.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
A Flow Debugger live run (execution 1130c01f) spent 108 of a 176 ms site script run
between the cached DB write completing and Notify.Send starting: the immediate-
completion telemetry awaited two autocommit SQLite transactions on the consolidated
LocalDb file (RecordAttemptAsync + RecordTerminalAsync), on the script thread, each a
WAL fsync on a Docker volume; the submit row was a third. The audit half of the same
forwarder was already a channel write, so the tracking half was the whole cost.
OperationTrackingStore is now a single-writer queue: Record*Async enqueue an ordered
work item and return; one background pump drains the bounded channel (8192, wait
backpressure - tracking never drops) and applies each batch (<=256) in ONE transaction,
falling back to per-row apply when a batch fails so a poison row cannot take its
neighbours. Preserved invariants: FIFO across enqueue/attempt/terminal; read-your-
writes (GetStatusAsync and ReadChangedSinceAsync barrier on every write queued before
them, skipped when idle) so Tracking.Status, the telemetry actor's status join and
central's PullSiteCalls never see a stale row; timestamps stamped when recorded;
PurgeTerminalAsync returns after the purge lands; DisposeAsync drains the queue before
closing; sync Dispose keeps its documented in-flight-writes-fail semantics. New public
FlushAsync() is the explicit barrier. Accepted: a queued-but-unapplied row is lost on a
hard crash (ms window); S&F buffer and audit rows are unaffected.
No interface, forwarder or ScriptRuntimeContext change. Tests: write returns while
another connection holds the DB write lock and lands once released (fails on the old
store: 31 s); reads see 100 ordered attempts + terminal; DisposeAsync drains 200
queued rows; write after dispose throws ObjectDisposed. Existing tests that poke the
SQLite file right after a store call now FlushAsync first.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
Review of Task 3: the sink invoke sat before WriteAsync/ForwardAsync inside the
best-effort try, so a throwing sink would have silently dropped the durable
row. GuardTraceSink wraps the delegate in every helper ctor (and Collect
guards EmitTrace); pinned by a throwing-sink test. ScriptRunLauncher no longer
allocates a collector for a traced run with no reply target (Nobody) — the
list would never be read. FlowTraceCollector.Complete pinned at unit level;
Snapshot documented as a non-closing peek.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
ScriptRuntimeContext caches a trace sink (null on an untraced run, so the
production path is byte-identical) and threads it into the ExternalSystem /
Database / Notify helpers and AuditingDbConnection→AuditingDbCommand (onAudit).
All eight outbound emit sites hand the SAME AuditEvent instance to the sink
first, then to the writer/forwarder. FlowTraceCollector gains Completed +
Complete(): ScriptRunLauncher closes the collector where it builds the reply
snapshot, so un-awaited calls finishing after the run returned never mutate a
list the reply was built from. Cap (500) unchanged. Plan 2026-09-06 D5.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
Flow Debugger (design 2026-09-05 §5.3): a traced SetStaticAttributeCommand on a data-sourced
attribute records (attribute → writer, expiry) for TraceArmWindowSeconds (new option,
default 30, validated > 0); the next DCL echo for that attribute is published with the
writer's SourceExecutionId + Trace whatever its value, and the arm is consumed once. Static
writes publish Trace directly. Untraced writes never arm (pinned).
Claude-Session: https://claude.ai/code/session_01GSLkkHKz9JrAtmJjmQK3cP
Flow Debugger (design 2026-09-05 §5.1/§5.4): ScriptRunLauncher emits one ScriptRun row per
traced run on every exit path (OccurredAtUtc = run start), replies with the run's
ExecutionId (always) and the collector snapshot (traced only). ScriptActor forwards
ScriptCallRequest.Trace and, for a value-change trigger fired by a traced stamped change,
parents the run to the writer with trigger detail in Extra; every other trigger stays a root.
Claude-Session: https://claude.ai/code/session_01GSLkkHKz9JrAtmJjmQK3cP
Flow Debugger (design 2026-09-05 §5.1/§5.2): the context is the single funnel for
SetAttribute / WriteBatchAndWait / WaitInternal, so it emits the write/wait rows (collector
first, then the best-effort IAuditWriter whose redactor applies the payload cap), stamps
Trace on SetStaticAttributeCommand and ScriptCallRequest, and hands the flag + sink to the
inline CallShared child context. Untraced contexts emit nothing (pinned).
Claude-Session: https://claude.ai/code/session_01GSLkkHKz9JrAtmJjmQK3cP
Review finding on ab08ecd3: each Good re-armed the watchdog from 'now', so Goods arriving faster than the floor starved the retry. Pinned by FlappingGood_DoesNotDeferTheRetry (12 Goods over 1.2 s; naive re-arm measured 1.43 s, guarded ~0.3 s).
Claude-Session: https://claude.ai/code/session_019ZxXT5sxZs5XrtdwYzJDPV
Task 4 review fix-ups: RepeatedFailures gaps[1] lower bound 600→500 (two compounding jitter draws bottom out at 512 ms); SubscribeToDcl also clears _tagPathToAttributes and its prune is documented as defensive (PreStart is the only caller).
Also from the Task 3 review: FailedSubscribeResponse_IsRetried guards the failure path again (large ceiling); HandleSubscribeTagsResponse reads state instead of get-or-create; SubscribeToDcl prunes stale retry state on re-entry; doc comments refreshed.
Claude-Session: https://claude.ai/code/session_019ZxXT5sxZs5XrtdwYzJDPV
FailedSubscribeResponse_IsRetried and LostSubscribeResponse_IsRetried_AndSuccessStopsRetrying now pin the in-flight ceiling to the retry interval: a lost reply is re-sent only once the outstanding request is presumed lost, by design.
Claude-Session: https://claude.ai/code/session_019ZxXT5sxZs5XrtdwYzJDPV
HandleEnsureInstanceStarted, HandleDeploymentStateQuery, and HandleEnable each
called GetAllDeployedConfigsAsync — materializing every deployed config,
including every ConfigJson blob — just to FirstOrDefault one row. A
volume-restore reconcile healing hundreds of instances turned that into
hundreds of full-table reads.
Add SiteStorageService.GetDeployedConfigAsync(name) (single-row, full
projection incl. ConfigJson, for callers that (re)start an Instance Actor)
and GetDeployedConfigMetadataAsync(name) (single-row, ConfigJson-free
projection, for callers that only need DeploymentId/RevisionHash/IsEnabled).
Switch the three call sites; leave decisions/semantics identical.
HandleEnsureInstanceStarted gets its own _deployedConfigLoader seam,
deliberately separate from the existing _configLoader (still used by the
boot-time load, which legitimately needs every row) so a test overriding one
cannot accidentally gate the other. Generation fencing (StoreGenerationAtRead,
Medium wave T1) is untouched: the generation is still captured on the actor
thread before the read dispatches.
Tests: new SiteStorageServiceTests lock in that both projections return the
same values GetAllDeployedConfigsAsync().FirstOrDefault(...) did. The three
row-101 ensure-started race tests (ReconcileStartsInstanceTests) are ported
to the new seam and still pass, proving generation fencing survives the
projection. Proof of failure: since this is a pure I/O-cost fix with no
observable behavior change, the new/changed tests were confirmed to fail to
even compile against the unfixed code (stash/unstash) — GetDeployedConfigAsync,
GetDeployedConfigMetadataAsync, and the deployedConfigLoader ctor param don't
exist there.
P1-1 — the row-67 ensure-started self-heal re-read the durable row off-thread but
captured no _storeWriteGeneration and never ran IsStoreSnapshotStale, unlike the boot
load and the reconcile sweep. A Disable or Delete committing inside that window left the
result carrying an enabled config that passed every guard (neither command sets any of
the three pipeline markers ShouldAttemptEnsureStart re-checks), so the heal started an
instance the operator had just stopped — PERMANENTLY, since the sweep iterates store rows
only and has no runtime→store stop leg. The generation is now captured at dispatch,
threaded on EnsureInstanceStartedResult and checked on landing, and the comment claiming
the stored row already covered this is corrected. The heal reads through _configLoader,
the same seam the boot load and sweep use (identical production call), so a test can hold
the read open across a committed disable/delete.
P1-2 — the "static overrides reset on redeployment" invariant was racy in both
directions. ApplyDeployment created the successor Instance Actor first and only then
dispatched the clear, queued behind a full config-JSON write, so the successor's PreStart
override load routinely won and applied the PREDECESSOR's overrides — keys absent from
the new config included — to in-memory state for the actor's lifetime while the disk
ended cleared; a later restart then silently flipped the values. The clear is now
dispatched BEFORE CreateInstanceActor and handed to the actor as a gate its override load
chains behind; the persistence task joins the same task, so a failed clear still fails the
deploy exactly as before. Leg 2: the predecessor's PostStop flush was fire-and-forget and
could commit up to one coalescing window AFTER the clear (the Deployment Manager gates the
clear on Terminated), durably resurrecting overrides — PostStop now waits for it, bounded
at 5s with a Warning on overrun.
Tests: new RedeployStaticOverrideResetTests (5) pins both legs plus the gate mechanism and
first-deploy behaviour; three new cases in ReconcileStartsInstanceTests pin the discarded
disable/delete heals and that an unraced heal still starts. InstanceActorTests'
StaticOverride_ResetOnRedeployment comment claimed to simulate an ordering the production
path did not have — corrected.
Alarm on-trigger runs (ScriptRunLauncher.RunAlarmScriptAsync) bypassed the
stuck-script watchdog, the script-error health counter, and
ScriptRunSummaryRecorder entirely, even though they run on the same bounded
ScriptExecutionScheduler pool as instance scripts. A wedged alarm body cost a
pool thread forever with no site event and no detach/replace, and a timed-out
or failed on-trigger run was invisible to health monitoring and the run
summary.
Bring the alarm path to parity with the instance-script path (RunScriptAsync):
capture the worker slot/run stamp in the first synchronous segment and arm
ArmStuckScriptWatchdog with the same detach-and-replace semantics and gauge;
resolve ScriptRunSummaryRecorder/ISiteEventLogger from the same DI provider and
thread RecordStarted/RecordCompleted/RecordFailed/RecordTimedOut; increment
ISiteHealthCollector.IncrementScriptError on both the timeout and general
failure catch blocks. LaunchAlarmScript/RunAlarmScriptAsync now take
healthCollector and serviceProvider parameters, passed from AlarmActor's
existing _healthCollector/_serviceProvider fields. No change to the
enqueue-anchored deadline, the shed cap, or "a stop does NOT cancel an
in-flight run" semantics.
Adds AlarmScriptWatchdogTests (previously zero coverage of LaunchAlarmScript):
wedged-worker detach + replacement, timeout-at-dequeue health counter
increment, and successful-completion summary recording. All three fail
against the pre-fix code (verified via stash) and pass after.
ReadStoreSnapshotAsync's snapshot is read off the actor thread and consumed only
when its piped message lands. Row 101 guarded the DEFINITIONS half of that race;
the CONFIG half was left to machinery whose reach is time-limited, and both legs
of the instance reconcile sweep were reachable through it:
- Row-72 leg: a read dispatched before a deploy's persist, landing after the
deploy completed AND after the pipeline released ownership, carries the
revision the deploy replaced. TryRestartStaleInstance then "repairs" the
instance BACKWARD, re-deploying the snapshot's own superseded ConfigJson.
InstanceIsOwnedByADeployPipeline covers only in-flight deploys, and the
per-revision claim has never seen the old revision, so nothing stopped it.
- Row-78 leg: a read dispatched before a delete/disable commits still shows an
enabled row while the actor is already stopped, so StartStoredInstance
resurrects it — and delete clears _sweepAttemptedRevisions, freeing the claim.
Both verified real by neutralising the freshness check and re-running the new
tests (the fail-before site event literally reads "running revision rev-2 is
stale, applying stored revision rev-1"; the deleted instance came back).
_definitionsWriteGeneration becomes _storeWriteGeneration, covering both tables
(the snapshot is one consistent read and is discarded whole, so one counter is
the right shape); DefinitionsGenerationAtRead -> StoreGenerationAtRead on both
internal records. The generation is now bumped at BOTH ends of every mutation —
when the off-thread write is dispatched and when its completion message lands —
because the config paths advance actor state before the write, so an
initiation-only bump would let an in-window read look fresh. Disable, delete and
the init-failure rollback have no actor-thread completion message of their own,
so a minimal StoreWriteCompleted self-message carries the bump for them.
CDC-replicated writes, snapshot resyncs, restored files and
SiteReconciliationActor's fetch deliberately do NOT bump: discovering exactly
those is the sweep's reason to exist.
A stale sweep result is now dropped WHOLE (no overlay apply, no start, no
restart). A stale boot load cannot be dropped — startup must finish — so it
re-dispatches LoadDeployedConfigs(); a fifth consecutive superseded read is
applied anyway with a Warning, and a late one arriving after the boot completed
is dropped rather than looping against the S5 retry timer.
Tests: three fail-before regressions (backward restart, resurrection, boot
re-read) plus two guard twins pinning that the legitimate row-72 restart and
row-78 start still fire on a current-generation snapshot. The row-101
definitions tests keep passing; FreshEmptySweepSnapshot's hardcoded generation
moves 1 -> 2 now that one artifact apply bumps at both ends.
Docs: Component-SiteRuntime.md's stale-snapshot paragraph now describes the
whole snapshot (both halves, both consumers, the boot re-dispatch, the
CDC-no-bump rule), the components mirror follows, and the arbitration memo gains
§11 extending §10 to the config half.
An off-thread snapshot read racing an artifact apply could land after the
apply populated the overlay; its stale absences then tombstoned and stopped
just-applied LIVE connections, which nothing re-creates until an instance
redeploy (the removal evicts the hash slot the overlay push is gated on).
Each read now captures a definitions-write generation at dispatch; a stale
result is discarded whole (additions too — a stale row would reconfigure a
live connection backward). Deterministic repro fails before the fix; a
fresh-generation guard test pins that row-90 disappearance still fires.
`DataConnectionManagerActor.HandleCreateConnection` is create-only (warns and
returns for a name it already holds), so `EnsureDclConnection`'s documented
"a changed config re-issues the create so the DCL adopts it" was never true on
ANY node: a corrected endpoint/credential/backup/failover-count took effect only
when the connection was next built from scratch (node restart, singleton
failover, remove-then-re-add), while the DM's hash cache recorded it as applied.
Rows 89/90 made that honest with a Warning; this closes it.
New `ReconfigureConnectionCommand` (Commons, same shape as the create):
- `DeploymentManagerActor.EnsureDclConnection` now has three outcomes off its one
per-name hash slot — unchanged -> nothing at all, new -> create, CHANGED ->
reconfigure — and logs "Reconfigured DCL connection {Connection}
(protocol={Protocol}) in place" at Information in place of the old Warning. The
winner-resolution / arbitration / tombstone logic is untouched; only what
happens after a change is detected changed.
- `DataConnectionManagerActor` FORWARDS the command to the owning connection
actor, falling back to a create for a name it does not hold, so the command is
safe whatever the manager's state.
- `DataConnectionActor` handles it in ALL THREE states and never stashes it — a
connection pointed at a wrong or dead endpoint lives in Connecting/Reconnecting,
which is exactly when a correction arrives; stashed it would wait on the broken
configuration forever. Handling replaces protocol/primary/backup/failover-count,
re-arms endpoint selection to Primary (the new config's primary is the intent,
whatever the old config had failed over to), and calls the new shared
`SwapAdapter` helper — now used by both failover sites too, so the swap exists
once: unhook + fire-and-forget dispose -> _factory.Create -> rewire -> bump
_adapterGeneration LAST. `BecomeReconnecting(afterReconfigure: true)` then
reconnects immediately (StartSingleTimer replaces any armed reconnect, so no
racing attempts) with the unstable-disconnect accounting and failover check
suppressed — the link was dropped on purpose, and counting it as an unstable
cycle could trip a failover onto the NEW backup before the new primary had been
tried once. ReSubscribeAll/ReSubscribeAllAlarms then re-issue everything from
the untouched subscription registries. Idempotent: a reconfigure carrying the
configuration already in force is a no-op.
Stop-and-recreate was rejected as destructive: subscriptions live inside
DataConnectionActor and InstanceActor cancels its subscribe-retry timer on first
success, so a rebuilt actor would have no subscribers and nothing would ever
re-subscribe.
Tests: new DataConnectionReconfigureTests (7; 5 fail / 2 pass against a
behavioural revert). DclConnectionArbitrationTests gains two row-97 tests and its
CDC-arrival test now asserts the second push is a reconfigure; its ping-pong
guard also asserts zero reconfigures, since a flip would now show up there.
SiteRuntime-010 renamed to ..._ReissuesReconfigureCommand. 3 fail against a
reverted EnsureDclConnection. DataConnectionLayer.Tests 327/327,
SiteRuntime.Tests 643/643, solution build 0 warnings.
Docs: Component-DataConnectionLayer.md gains an "In-place reconfiguration"
section under Endpoint Redundancy; Component-SiteRuntime.md, and the
docs/components/ mirrors, updated; the arbitration decision memo gains an
appended §9 postscript resolving its residual 1 (residuals 2 and 3 stay open).
The compile cache was a `static` class, so its entry table and its Hits/Count
counters were one process-global blob every test class in the SiteRuntime
assembly wrote into. Row 91 last wave neutered the resulting flakes (per-test
GUID keys + one-sided counter bounds), but the shared mutable state itself
remained: any test calling Clear() evicted entries other parallel classes had
just inserted, and a Clear() from a class outside the serialized collection
would degrade the others to recompiles and re-open the row-91 flake class.
PREMISE CORRECTION: the register speculated production clears "per-instance or
per-deployment script entries" and offered ClearKeys(prefix) as the natural fit.
There are NO production callers of Clear() at all — grep of src/ finds only
GetOrAdd (ScriptCompilationService.CompileCore). Clear() existed solely so
tests could reset the global. A key-scoped API would therefore have been new
production surface built for nobody, so the instance-scoped seam is the fix and
Clear() is deleted outright rather than migrated.
- SiteScriptCompileCache: `internal static class` -> `internal sealed class`;
Cache/EvictionLock/_hits/_accessSequence become instance fields. LRU batch
eviction, the double-checked sweep and the ConcurrentDictionary.ToArray()
snapshot are byte-for-byte the same policy. Clear() removed.
- ScriptCompilationService owns one cache. Public ctor (the DI path) builds its
own; a new internal ctor takes one for tests. Production N4 sharing is
unchanged and now rests on the DI SINGLETON registration — the one service
instance is threaded to DeployCompileValidator and to every Instance Actor —
so that lifetime is load-bearing and is pinned by a new registration test.
- Tests: all three Clear() callers migrated off it. Each test now owns its cache,
which lets the assertions get STRONGER — the row-91 workarounds are retired:
Hits/Count are exact again (no >= baseline bounds), the per-test GUID key
token is gone, and ForeignEntrySlack (512 entries of allowance on the bound)
drops to the racing-thread count in the concurrency test. New test
SeparateCaches_DoNotShareEntriesOrCounters pins the scoping directly: filling
one cache past MaxEntries leaves another's entry, hit count and identity
intact. DeploymentWarmThenGateTests additionally asserts Count == 1 now that
its counter is private.
- The [Collection("SiteScriptCompileCache")] serialization from row 91 is
RELAXED (removed from all three classes) — they no longer touch any shared
state, so there is nothing left to serialize.
- Docs: Component-SiteRuntime.md gains the ownership/singleton note and drops
the Clear() reference; DeploymentManagerActor / DeployCompileValidator /
ServiceCollectionExtensions comments corrected to say where the cache lives.
Build: 0 warnings. SiteRuntime.Tests 643/643, three consecutive full-parallel
runs. AuditLog.Tests correlation classes (other ScriptCompilationService
consumers) green.
Closes deferred-work-register rows 89 and 90, and corrects their premise twice.
THE RULE
The `data_connection_definitions` store wins wherever it has an opinion; an
instance's flattened `Connections` entry is a deploy-time snapshot and is
authoritative only for names the store has never owned (the deploy-only site,
where that table is legitimately empty).
PREMISE CORRECTION 1 — the peer's DCL is EMPTY, not stale
`DeploymentManagerActor` is a `site-{SiteId}`-scoped singleton and the only
sender of Create/RemoveConnectionCommand, to its OWN node's `dcl-manager`
(which exists on every node but is populated only where the singleton runs).
So the standby serves nothing. The real defect is that `_createdConnections`
is in-memory per singleton incarnation: a restart or failover rebuilds every
connection from the flattened snapshots and silently discards a newer
connection-only artifact deploy. Row 89 is therefore create-time, not
message-delivery, and NOT replication-specific — the same loss happens on an
unreplicated single-node restart.
PREMISE CORRECTION 2 — a changed config never reached a LIVE connection either
`DataConnectionManagerActor.HandleCreateConnection` is create-only (warns and
returns on a name it holds), so `EnsureDclConnection`'s documented "re-issues
the create so the DCL adopts the new configuration" has never been true on any
node. Now surfaced with a Warning saying exactly that, once per changed config.
Not fixed here: stop-and-recreate drops every tag subscription and InstanceActor
cancels its subscribe-retry timer on first success, so nothing re-subscribes.
MECHANISM
`data_connection_definitions` gains its first production reader. It is read on
the SAME off-thread task as the deployed configs (`ReadStoreSnapshotAsync`), by
the boot load and every sweep tick, into an actor-thread-confined arbitration
overlay applied BEFORE the boot batch and BEFORE the sweep's repair loop. A
CDC-delivered definition change converges within one tick on whichever node runs
the singleton — no new cross-node message. A failed definitions read yields null
and leaves the overlay untouched (distinct from an empty list, which is a real
answer); clearing it would reintroduce the ping-pong through the error path.
THE PING-PONG, KILLED BY CONSTRUCTION
§7.4 of the sweep memo rejected a store-level pass because two sources would
flip the single per-name hash slot, recreating the actor every tick. That is a
property of WHERE the hash is computed: every ensure path now resolves the
winner BEFORE hashing, so only one configuration can ever occupy the slot. The
artifact-deploy path writes its rows into the overlay in the same pass, closing
the same flip arriving through the other door.
REMOVAL (row 90)
Both removal paths share `RemoveConnectionCentrally` and record an in-memory
tombstone, so a centrally removed connection is not resurrected by the next
instance start — a pre-existing bug. Tombstones are deliberately not persisted;
a definition row reappearing clears one.
TESTS
tests/.../Actors/DclConnectionArbitrationTests.cs — 8 tests. Fail-before
(behavioral revert: overlay inert + tombstone check disabled): 5 fail, 3 pass;
the 3 passers are the two deploy-only regression guards and the ping-pong guard.
DOCS
New decision memo docs/plans/2026-08-17-dcl-connection-arbitration-decision.md
(topology, rule, ping-pong mechanism, tombstones, residuals); Component-SiteRuntime,
Component-DataConnectionLayer + their docs/components mirrors; the §7.4 residual in
the sweep memo marked closed with its premise corrected.
An Instance Actor started by a self-heal came up with NO DCL connection actors,
so every tag it subscribed was answered "Unknown connection: <name>" by the DCL
manager indefinitely. Proven live 2026-08-16 by the row-78 close-out probe: the
sweep correctly started the replication-seeded instances, then every subscribe
failed for 6+ min until a second pair restart.
Root cause is narrower than the register assumed. A DCL connection actor is
never created from data_connection_definitions -- that table has no production
reader at all (GetAllDataConnectionDefinitionsAsync is called only by a test).
It exists only as a side effect of starting an instance, from the Connections
map inside that instance's own flattened config, via EnsureDclConnections.
That ensure was the CALLER's job and only two of the four callers made it:
CreateInstanceActorBatch (boot) ensured OK
ApplyDeployment (deploy) ensured OK
StartStoredInstance MISSING <- row-67 ensure-started + row-78 sweep
HandleEnableResult MISSING <- enabling a disabled instance
The two misses are the two paths added after the original pair -- the signature
of a convention living at call sites instead of in the funnel.
It was never replication-specific: the boot load reads only ENABLED configs, so
a node booting with an instance disabled never creates its connections either,
and enabling it afterwards hit the identical dead end on an ordinary
unreplicated site.
Fix: EnsureDclConnections moves into CreateInstanceActor, already documented as
the single Instance Actor creation funnel (it is where the running revision is
stamped for the same reason), and the two caller-side calls are removed. Placed
before the already-exists guard so the two paths that already called it keep
their exact previous semantics. No new message, option or DCL change -- it
reuses EnsureDclConnection's existing per-name hash guard, so steady state is
silent. Structural rather than another guard: a fifth start path cannot forget.
Deliberately NOT done, with rationale in the memo: a sweep pass over
data_connection_definitions. It would not have fixed row 85 (that table is empty
on a site that has only ever received instance deploys), and re-hashing from it
would fight the deploy path over the same per-name hash slot, recreating
connection actors and dropping live subscriptions on a loop. Two residual
sibling gaps (connection-only artifact deploy replicating to a peer that never
adopts it, and the mirror-image removal case) are recorded in the memo and the
component docs as open, not silently skipped.
Tests: SelfHealCreatesDclConnectionTests, 7 tests asserting on the
CreateConnectionCommand messages sent to a recording DCL stand-in. Verified
fail-before against a behavioral revert (call removed from the funnel, restored
at the two original sites): 4 fail / 3 pass, the 3 being steady-state silence
plus two refactor guards that must pass on both sides.
Docs: sweep design memo gains section 7; Component-SiteRuntime,
Component-DataConnectionLayer, docs/components/SiteRuntime and
docs/components/DataConnectionLayer updated (the deploy-flow step ordering in
docs/components/SiteRuntime was stale as written).
The site's deployed_configurations rows are the durable truth about what should be
running; the set of live Instance Actors is what IS running. Nothing kept the two in
agreement after boot, and nothing surfaced a disagreement.
Row 78 (availability, proven live 2026-08-15) -- deployed_configurations is one of
LocalDb's ten replicated tables, so on a replicated pair a config can appear in a
node's file with no local actor involved at all: the CDC sync applier writes the row
directly. Live sequence: site-a-b's reconcile fetched 4 configs at its solo boot; the
pair was then restarted with a fresh site-a-a file and snapshot replication seeded
site-a-a's table within ~5s -- AFTER its boot-time load had read an empty table, and
invisibly to its own reconcile (central rightly reported "0 fetched", because central's
view of the site was correct). Enabled instances sat dead with their configs present
until yet another restart. Row 67's EnsureInstanceStartedCommand only covers configs
the reconcile itself FETCHES; this is the same gap through a side door.
Row 72 (silent divergence) -- for a STALE ReconcileGapItem the pass writes the newer
config via StoreDeployedConfigIfNewerAsync, a pure file write, while the running
Instance Actor keeps executing the previously compiled config until the next restart
or redeploy. Nothing said "stored revision != running revision".
Both are closed by one periodic sweep owned by the Deployment Manager singleton
(ScadaBridge:SiteRuntime:InstanceSweepIntervalSeconds, default 60, validated >= 0;
0 disables). Each tick re-reads the durable rows off-thread and, on the actor thread,
for every ENABLED stored config either starts a missing Instance Actor (row 78) or --
when the running one's revision no longer matches the stored one -- re-applies the
stored config through the ordinary redeploy path (row 72).
A sweep was chosen over a LocalDb change hook deliberately: a hook covers only the
replication arrival path, and only on the half of the fleet running with replication
enabled, whereas the sweep is arrival-path-agnostic (replication seeding, post-boot
snapshot resync, a hand-restored file, any future path). It is also not available --
ILocalDb 0.3.0 exposes no change-notification or applied-rows callback, so a hook would
mean a new upstream capability in scadaproj plus an in-process bus into this singleton,
a cross-repo change to close a site-local gap.
Row 72's decision is to CONVERGE, not merely warn. The stored row is what central
successfully deployed; an actor serving the config central believes was replaced is the
actual fault, and a surface-only warning leaves the operator to issue by hand exactly
the redeploy the sweep would have performed. Reusing HandleDeploy means the compile
gate, warm-then-gate ordering, redeploy-supersede, the static-override / native-alarm
reset and all-or-nothing-per-instance are the production ones, not a second
implementation -- and a stop still does NOT cancel an in-flight script run, exactly as
for a central redeploy.
Guards, shared with row 67 via the extracted InstanceIsOwnedByADeployPipeline predicate
and the shared StartStoredInstance helper:
- a DISABLED instance is never started (config row, no actor is its correct state);
- the sweep defers to any deploy pipeline owning the instance (compile warm in flight,
predecessor still terminating, deployment awaiting its persistence/init join), so it
can never interleave with a real redeploy -- that window has the config stored and no
actor, which an unguarded sweep would answer by creating a child whose actor name is
still registered;
- inert until boot-time Instance Actor creation has finished, so a tick between
staggered batches does not "heal" instances the boot load is about to create;
- ONE repair attempt per (instance, revision) pair -- this is what stops a periodic
self-heal becoming a restart loop for an actor that dies during init, or for a stored
config the compile gate rejects (a rejection leaves the running instance untouched:
the gate returns before anything is stopped);
- reads never overlap, so a slow read cannot stack ticks into duplicate repairs.
A sweep that finds nothing is completely silent -- no log above Trace, no site event.
A repair emits the same Warning `deployment` site-event pattern as row 67 with the
trigger named ("deployment-manager sweep self-heal") so it is distinguishable from a
startup-reconcile heal; a stale-revision restart names BOTH revisions and a rejected
one adds an Error event. The synthetic redeploy replies to the singleton itself rather
than NoSender, because dead letters are a monitored site health metric.
CreateInstanceActor gains a revisionHash parameter and is the single creation funnel
that records it, so the stale check covers every path that can start an Instance Actor;
a missing entry reads as "unknown", never "stale", so a future path bypassing the funnel
degrades to no-op rather than to spurious restarts.
Fail-before by behavioral revert (sweep timer left unarmed): 5 of 10 new tests fail,
including both live symptoms -- the row-78 repro ("A replication-seeded config for an
enabled instance left no running Instance Actor") and the row-72 repro, whose snapshot
still shows the rev-1 value 111 while the store holds rev-2's 222. The 5 negative
guards (disabled / in-flight redeploy / matching revisions / silent-when-healthy /
interval-zero) are green in both states, as they must be.
SiteRuntime 626/626, Host 505/505, AuditLog 383/383.
Design note: docs/plans/2026-08-15-instance-sweep-self-heal-design.md
An external system's MaxRetries/RetryDelay existed on the central entity but never
reached a site and had no management surface, so every ExternalSystem.CachedCall
buffered with the S&F engine default (DefaultMaxRetries 50 x DefaultRetryInterval
30s ~= 25 min to park) whatever central had configured. The sibling
DatabaseConnectionArtifact had always carried its equivalents.
The consumption end was already wired: ExternalSystemClient.CachedCallAsync already
read system.MaxRetries/RetryDelay and passed them to EnqueueAsync with the 0-as-unset
convention. Only the transport and persistence were missing.
Commons
- ExternalSystemArtifact gains MaxRetries/RetryDelay as optional positional params
(0 / TimeSpan.Zero = unset), matching DatabaseConnectionArtifact rather than going
nullable, so it maps 1:1 onto the entity and the proto3 scalars.
- Create/UpdateExternalSystemCommand gain nullable MaxRetries/RetryDelay, following
the existing TimeoutSeconds "omit to preserve" convention. Both additive.
Central
- ManagementActor create maps both; update preserves-if-null.
- ArtifactDeploymentService projects them onto the artifact.
Wire
- site_command.proto ExternalSystemArtifactDto gains max_retries=7 /
retry_delay=8 (google.protobuf.Duration), mirroring DatabaseConnectionArtifactDto.
Additive: a pre-existing site decodes them as 0/absent, which IS the unset value,
so old behaviour is preserved. Vendored C# regenerated via docker/regen-proto.sh
sitecommand; csproj Protobuf item re-commented, no message types added or removed.
Site
- external_systems gains max_retries / retry_delay_ms via AddColumnIfMissing,
DEFAULT 0 = unset. Storage upsert, repository SELECT/mapping (new ordinals 6/7
appended so existing ones are untouched), apply path, and the legacy migrator's
explicit column list all carry them.
Replicated-table decision: external_systems IS in SiteLocalDbSetup.ReplicatedTables,
so this was checked against the AckTime/native_alarm_state precedent. Real columns
are correct here, not a JSON bag: the table has no general-purpose config column
(auth_configuration and method_definitions are both semantically specific),
timeout_seconds already set the additive-column precedent on this exact table, and
sibling database_connections stores the same two values as plain columns. Verified in
LocalDb source that RegisterReplicated re-reads PRAGMA table_info every boot and its
install script is DROP-then-CREATE, so capture triggers rebuild over the new column
set automatically, and SiteStorageSchema.Apply runs before registration on the same
boot. The only cost is the ReplicatedTable.ComputeDigest change, which the sync
handshake compares fail-closed - a mixed-version pair refuses to sync loudly instead
of diverging silently. Both-nodes-together is already the standing site-pair rule, so
no new operational constraint; recorded in topology-guide.md.
Also fixed: ArtifactDiff.CompareExternalSystem never compared MaxRetries/RetryDelay,
so a bundle import that changed a system's retry budget previewed as "Identical" -
harmless while the values were inert, a live behaviour change now.
No EF migration: the central ExternalSystemDefinitions columns already exist
(InitialSchema). Central UI already had both form fields.
Tests: site storage round-trip + unset-default, site apply path, central artifact
projection, proto round-trip (via the shared sample), management create/preserve,
CLI option parse + alias, and diff reporting. Fail-before verified on the two core
tests (expected 7 got 0 on the read path; expected 9 got 0 on the apply path).
Docs: Component-ExternalSystemGateway, Component-StoreAndForward, Component-CLI,
components/StoreAndForward, components/SiteRuntime, deployment/topology-guide,
CLI README (which was also missing --timeout-seconds entirely).
SiteReconciliationActor's node-STARTUP fetch healed the config FILE but never the
RUNTIME. Instance Actors are created from exactly two paths -- the Deployment
Manager's boot-time SQLite load and an explicit deploy/enable command -- and the
reconcile pass runs AFTER that boot load has already read storage. So a config
reconcile restored started no actor: an enabled, successfully-deployed instance
whose config was missing at boot (lost volume, first boot after a restore,
rehomed data dir) stayed dead until the NEXT restart, whose load finally picked
it up. Proven live on site-a 2026-08-15: "Reconcile: fetched + stored config"
with no "InstanceActor started" after it, and a debug snapshot answering
instanceNotFound.
The pass now raises a fire-and-forget EnsureInstanceStartedCommand (new Commons
Deployment message) for every ENABLED instance it healed, routed through the
deployment-manager singleton PROXY so Instance Actors stay under the singleton no
matter which node's reconcile found the gap.
The handler is deliberately advisory:
- idempotent -- no-op when the actor is already running, which both nodes'
reconcile actors legitimately trigger for the same instance;
- enabled-state-aware -- it re-reads the durable row, which is the authority on
both the config body and enabled/disabled, so a disable landing after the
fetch still wins and the instance stays stopped;
- it defers to any in-flight deploy/redeploy/warm for the instance, which keeps
the deploy gate's ordering guarantees and the all-or-nothing-per-instance rule
intact -- this never applies a config, it only starts one already persisted;
- a missing row is a quiet no-op, the normal case on an unreplicated site whose
peer node healed its own file.
The heal is no longer silent: a successful reconcile start emits a Warning log
line and an operational `deployment` site event, because reaching it means the
node booted without a config for an instance that should have been running.
Joseph Doherty