- I1: the poll engine belongs to a teardown generation. ShutdownAsync/Dispose
retire the current engine and install a fresh one in the same swap as the
device/tag tables, then dispose the retired one (possibly in the background
after a cancelled or over-budget shutdown). A subscription made after the
next InitializeAsync can no longer land in an engine whose late dispose tail
would dispose its CTS without cancelling it (a loop no UnsubscribeAsync could
find). Poll handles are generation-qualified (TwinCATPollHandle) because each
engine numbers handles from 1; SubscribeAsync re-homes a subscription that
raced a retirement.
- M1: a write's status feeds per-device health - Good clears that device's
comms fault and advances LastSuccessfulRead, a comms status degrades, a
refusal keeps the state.
- M2: a symbol-version re-arm bumps a per-registration epoch; an in-flight
retry that fails afterwards no longer re-imposes the backoff.
- M3: a re-arm restarts the refusal backoff at 30 s.
- M4: documented that PLC-not-in-RUN detection needs the probe.
- M5: WSTRING and multi-dimensional array encode-plan tests; the cancelled-
shutdown test asserts Unknown health and awaits its background teardown.
- M6: an infinity spelled as a string ('Infinity', '-inf') passes like a
float/double infinity; a finite overflow stays BadOutOfRange.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
- IMPORTANT: a successful probe records the PLC's ADS state; a PLC not in Run
keeps the driver Degraded with 'PLC in {state}' while LastSuccessfulRead
still advances (the device answered). RecordDeviceAnswered never restores
Healthy while any device is out of Run.
- Health is per device, rolled up worst-of: a comms fault is remembered on the
device it was seen on and only that device answering clears it (device A
answering no longer clears device B's fault).
- Refused (non-comms) dead registrations back off 30 s doubling to 10 min and
are re-armed by a symbol-version change or retried by the reconnect replay;
comms-class failures keep the every-tick retry. A retry whose failure class
changes republishes the tag's status, once.
- Bit-RMW gates are kept across generations and teardowns (never cleared).
- ShutdownAsync honours its CancellationToken: it stops waiting, finishes the
bookkeeping and throws OperationCanceledException.
- Remarks on why a superseded InitializeAsync throws OperationCanceledException.
- REAL / LREAL values (scalar or array element) outside the target range are
OverflowException -> BadOutOfRange instead of being written as Infinity.
- String / array write encoding factored into AdsTwinCATClient.PlanStringWrite
/ PlanArrayWrite; the fake runs them so a driver-level test covers the real
encode path against a fake resolved symbol.
- Timing-fragile tests use condition waits / measured probe-tick windows; the
dispose-during-shutdown test asserts ordering with a 1 s bound.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Native-subscribe isolation of an unknown symbol, LastSuccessfulRead advance
from pushes alone, a WORD bit write flipping exactly one bit (bit 16
refused), a whole-array REAL write round-trip (length mismatch refused) and a
STRING(80) write round-trip (overflow refused). Every writing case restores
the seed it touched. Skipped without the TwinCAT XAR fixture.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The poll engine already builds a per-cycle batch; TwinCAT now forwards it as
OnDataChangeBatch, so DriverInstanceActor gets one message per poll cycle
instead of one per changed tag. Because the actor subscribes ONLY the batch
event of a batch-capable driver, every native-path data change (pushes, the
BadNodeIdUnknown / refusal / unavailable snapshots) is raised through a single
RaiseDataChange that fires both the per-tag event and a fresh one-item batch.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
- Device and tag tables are build-and-swap: InitializeAsync builds a fresh
generation and publishes it by one swap under a lifecycle lock, then
releases the replaced generation; teardown swaps in empty tables. A
retained poll loop never sees a table mid-Clear (it used to read
_tagsByRawPath while a re-init only ever added to it), and each device
set is released by exactly one caller.
- A lifecycle generation makes an InitializeAsync overtaken by a shutdown
(or a newer init) release what it built instead of installing it - the
Lane A abandoned-init-overlaps-shutdown case.
- ShutdownAsync joins all probe loops together within 2 s (it awaited each
unbounded - a probe wedged in the blocking ADS Connect hung the actor's
teardown) in parallel with the poll-engine dispose, the whole bounded at
4.5 s; DisposeAsync may run concurrently and returns at once. A connect
that completes on a released device disposes its client.
- Releasing a generation disposes its native registrations, so a direct
re-init no longer leaves live notifications bound to dead DeviceStates.
- Connect gates and RMW semaphores are no longer disposed under in-flight
users (no kernel handle is ever allocated); a fault on a released device
is not recorded as driver health.
- The notification channel counts DropWrite overflows
(ITwinCATClient.DroppedNotificationCount); the probe tick warns with the
delta. A queued value whose registration was disposed is purged in the
client dispatch loop and dropped driver-side for any client.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Array tags were advertised writable but every write threw InvalidCastException
in ConvertForWrite (reported BadTypeMismatch); STRING writes went through the
Beckhoff marshaller with no length check against STRING(n) and the host's
ANSI code page, which the read side deliberately avoids.
- Array write: TwinCATArrayCodec.ToWriteElements converts exactly ArrayLength
elements to the declared type (CLR lists convert - ScadaBridge writes int[]
to Int16 nodes; a length mismatch or out-of-range element is BadOutOfRange, a
scalar value BadTypeMismatch) before any wire traffic; the ADS client plans
the layout from the resolved PLC array (TwinCATTypeGuard.CheckArray, as the
read does), encodes with TwinCATArrayCodec.Encode - the exact inverse of
Decode - and writes the raw bytes (new ITwinCATClient.WriteArrayAsync).
- STRING / WSTRING write: encoded at the PLC's declared width by
TwinCATStringCodec.EncodeString/EncodeWString (Windows-1252 or UTF-8 per
target, NUL-padded, strict: an over-long value or unrepresentable character
is OverflowException -> BadOutOfRange) and written as raw bytes.
- TwinCAT CLI read/write gain --array-length (+ --separator) for the hardware
gate.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The bit write read and wrote the parent word as a 32-bit UDInt with no parent
check: a bit beyond a 16-bit parent was written into neighbouring bytes, and a
signed parent with its sign bit set read back >= 2^31, so the checked
conversion turned any bit write into BadOutOfRange.
The write now goes through ITwinCATClient.WriteBitAsync: the ADS client
resolves the parent symbol, checks the bit against it (TwinCATBitAccess.
CheckParent, as the notification path already did), reads exactly
parent.ByteSize raw bytes, flips one bit (TwinCATBitAccess.ApplyBitWrite) and
writes the bytes back by index group/offset or variable handle. A bit beyond
the parent is BadOutOfRange, a non-integer parent BadTypeMismatch, a short
parent read BadCommunicationError (never written back), all without a health
write. The per-parent RMW lock stays in the driver.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
CompleteRead logged a Warning for every non-Good status on every poll and
latched Degraded for all of them. Now a bad tag warns once per bad episode
(re-armed when it reads Good, and on re-initialise), a comms-class status
(BadCommunicationError / BadTimeout) degrades with LastSuccessfulRead
preserved, and any other status - the device answered and refused this tag -
advances LastSuccessfulRead with no state change. Read-path exception
handlers now go through MarkCommsFault, so they never downgrade Faulted.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
In native-notification mode LastSuccessfulRead never moved past the init
stamp, so one Degraded write on a connection older than 90 s latched the
comms-loss watchdog into a full reconnect (every notification on every device
deleted and re-registered). Conversely an unreachable AMS router was swallowed
by the probe and never left Healthy.
- a native push and a successful probe now stamp LastSuccessfulRead (throttled
to one health record per 250 ms) and restore Healthy unless a device is still
probe-unreachable;
- 3 consecutive failed probe ticks write Degraded with the stamp preserved;
- a NotSupportedException write is BadNotSupported with no health write (#611);
- a reconnect replay the PLC refuses republishes the refusal's status without
degrading (it used to report BadCommunicationError + Degraded on every
reconnect for a correctly-isolated type-mismatch tag).
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Native subscribe was all-or-nothing: any registration failure other than a
type refusal disposed every registration and rethrew, so one typo'd symbol or
one unreachable PLC in a multi-device driver served zero data, churned
register/delete every reconcile tick, and left health Healthy.
Now each registration fails on its own: a refusal (the device answered: symbol
not found, PLC not ready, type mismatch) publishes its status with no health
write; any other per-tag failure publishes BadCommunicationError and degrades;
a connect failure marks the device unreachable for the rest of the call and
stores its tags as dead intents. Every failed tag is kept as a dead intent that
the probe-tick retry and the reconnect replay re-register. The ADS client now
classifies a failed symbol resolve / AddDeviceNotification by status instead of
throwing InvalidOperationException for all of them. Cancellation still tears
the partial subscription down.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The native subscribe path silently skipped a reference it could not resolve
(unknown RawPath, or a tag routed to an unconfigured device), leaving the node
on whatever status the server seeded. It now publishes one BadNodeIdUnknown
snapshot, matching the poll path.
Refs #739
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
GalaxyTelemetryTests (ActivityListener) and GatewayGalaxyDataWriterFailClosedTests
(MeterListener, filtered only by meter and instrument name) observe every Galaxy span or
measurement in the process. They now run in a collection with parallelization disabled
(F-FU6), because a parallel driver test, or its background probe seed, polluted their counts.
The stream-cancel assertion in GalaxyDriverShutdownTests goes back to a bounded wait: the
instantaneous IsCompleted check introduced in round 1 was racy.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Review fix round 2 for lane F:
- N1: the init platform seed no longer runs inline under the init token. Galaxy's Tier-A
Initialize budget is 5 s, and a cold gateway DiscoverHierarchy can spend all of it, so the
OperationCanceledException rethrow failed init, opened the Initialize breaker and cost a full
rebuild per retry. InitializeAsync now only resolves the platform source (no network) and
queues a background seed tied to a per-runtime CTS that the teardown cancels. A result that
lands after its runtime was torn down is discarded.
- N2: the seed worker serves the runtime that is live when each pass STARTS, so a request made
under a new runtime while a stale pass is in flight always gets a pass of its own.
- N3: SubscribeAsync and the subscribe-once read capture the runtime generation before
SubscribeBulk and register only if it is unchanged, atomically with the teardown's registry
Clear (_registryGate). On a mismatch they release the handles and fail the call. Re-subscribe
Rebind uses the same gate, and the production rebuild clears the registry unconditionally.
- PerPlatformProbeWatcher re-checks its stop after the SubscribeBulk await, atomically with
the record and publish. A pass that straddles StopAsync releases the handles it acquired
instead of writing the probe entry back into a cleared registry.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
- ScriptLogRateLimiter.LimitPerWindow. The ScriptLogTopicSink and
VirtualTagActor summaries now print the configured limit, not
DefaultLimitPerWindow. Tests assert "limit N/window" for a non-default
N.
- CalculationDriver.Dispose cancels, then takes _evalGate (bounded 2 s)
and disposes the gate and _evalCts. The pump and timer ticks enter the
gate through TryEnterEvalGateAsync, which stops cleanly once the
driver is disposed. Test: Dispose with a 6 s runaway run in flight
returns promptly, disposes both, and a late trigger is harmless.
- ScriptedAlarmEngine captures _shutdownToken once and disposes
_shutdownCts in Dispose when every drained task has completed. A task
stuck past the grace leaves the CTS to the GC. Lifecycle tests assert
the disposal.
- DraftValidator: CalculationNoEffectiveTrigger is skipped for a
change-triggered tag whose scriptId does not resolve. That case is
already CalculationScriptMissing or CalculationScriptNotFound, and
there are no reads to count. Both existing tests now assert the
absence (red before the change).
- docs/VirtualTags.md: System.Threading is denied as a whole namespace,
with an allow-list; the type list is now accurate (Unsafe,
RuntimeHelpers, and the ForbiddenMembers on System.Type); the resource
limits section covers the run guard and the allocation budget.
docs/ScriptEditor.md: accurate deny-list and a new "Runtime safety"
section covering timeout, refusal, quarantine after 3 timeouts,
allocation budget, lifting, and rate-limit summaries that appear only
on the source's next entry after a burst then quiet.
Refs #734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The writer concurrency fake parks on its release signal (the 300 ms delay could release the
gate early on a starved pool), the supervisor test's cross-thread hold flag is Volatile, and
the EffectiveTimeout doc now states the 1 s floor the code and tests implement.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Review fix round 1 for lane F:
- The ScanState probe watcher is seeded at InitializeAsync from a platform-only
DiscoverHierarchy query (IGalaxyPlatformSource / GatewayGalaxyPlatformSource over the owned
repository client) and re-seeded on every deploy-watcher rediscovery. The runtime never
calls DiscoverAsync on a live driver, so per-platform host status was unreachable in
production. A failed fetch logs a Warning and never fails init; re-seeds coalesce so a
deploy during an in-flight pass still gets a pass that starts after it.
- EnsureEventPumpStarted refuses while the runtime is stopping, BEFORE reusing the live pump
(that pump belongs to the dying subscriber), and the production rebuild disposes any stale
pump before wiring the new subscriber.
- TeardownRuntimeAsync closes the MX session under the caller's token linked with a 5 s
SessionCloseDeadline, so a blackholed gateway cannot hold DriverInstanceActor.PostStop for 30 s.
- A runtime generation counter, bumped by every teardown, is re-checked before each Rebind
in ResubscribeAllAsync, so a replay-gap re-snapshot that straddles a teardown cannot
resurrect handles into the cleared registry.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The SDK's DisposeAsync closes with no token, i.e. under the 30 s DefaultCallTimeout, so a
blackholed gateway parked the driver's teardown for the whole of it. CloseAsync(ct) runs the
close under the caller's token, drops the channel on a cancelled/failed close (the gateway
reaps the session on its idle lease) and leaves the session re-openable. A close followed by
the final dispose closes the gateway session once.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
- I1 ScriptRunGuard: a run refused because the previous one is still
executing is a Bad publish plus otopcua.script.run_refused, and no longer
a quarantine strike. Only a timeout (and an allocation breach) counts;
a refusal neither adds to nor resets the timeout streak; a completed run
(value or throw) resets it. On a 1 Hz trigger with a 2 s budget a single
4 s overrun is one timeout plus two refusals and must not quarantine.
Tests updated across the guard, the alarm engine, the Calculation
evaluator and the VT evaluator, plus
Refusals_neither_count_toward_nor_reset_the_timeout_streak.
- I3 ScriptedAlarmEngine: the quality bucket is tracked only after the
predicate completes (or in the inputs-not-ready path), so the tracked
bucket is the last one annotated. A refused or quarantined predicate
used to re-track the input bucket Good before the attempt and then flip
it Bad, emitting QualityChanged on every push. The run-guard tests now
count emissions (exactly 1 across N pushes, refused and quarantined
cases), with a healthy sibling's dispatch count as the positive control
that every push was processed. Both were red before the fix.
Refs #734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
- R02:H1 ScriptedAlarmHostActor gains a factory Props
(Func<(upstream, engine)>) so every incarnation builds and owns its own
engine; a supervision restart no longer re-creates the actor around a
disposed engine. The legacy instance-taking Props stays source-compatible
and is now restart-safe in the weaker sense (PreRestart marks the stop as
a restart, PostStop then detaches instead of disposing). DriverHostActor
still spawns through the legacy overload (not owned by this lane — F3).
- R02:H3 OnAlarmCommand runs every engine op under a 10 s token linked to
the actor's lifetime (DefaultCommandTimeout / Props commandTimeout) and
logs a Warning on timeout instead of suspending the mailbox on a stalled
store.
- R02:L3 DependencyMuxTagUpstreamSource.RetainOnly(loaded dep-ref union),
called after every successful load.
- R02:P6 VirtualTagActor's per-failure ScriptLogEntry is rate-limited per
tag (ScriptLogRateLimiter, 20/min + one summary); the Bad publish and the
metric are untouched.
- R07:H6 DependencyMuxActor retains the last (value, status, ts) per
ever-registered ref (through unregisters) and replays them in one batch to
a RegisterInterest(ReplayRetained: true) — VirtualTagActor, the Calculation
mux adapter and the alarm host opt in; the historization recorder does not
(a replay there would record a stale sample per deploy). CalculationDriver
records inputs regardless of _running so a replay landing before
InitializeAsync still satisfies the change-gate.
- R07:P4 CalculationEvaluator negative-caches compile failures by source
hash (one Roslyn attempt + one Warning per source until redeploy); the
driver's script-log entry fires on the Good→Bad transition or a change of
reason, matching the once-per-transition Bad publish.
- R07:H8 array results dedup structurally.
- R07:L2 ShutdownAsync drops the compiled scripts (collectible ALCs).
- R07:U5 DraftValidator rule CalculationNoEffectiveTrigger: a tag with no
timer whose change trigger is off or whose script has no literal
ctx.GetTag read can never evaluate.
Refs #734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Review 2026-10-21 G-5, G-6, G-8 ("wire them all").
- G-5: GatewayGalaxyHierarchySource now pages the DiscoverHierarchy RPC
itself (DiscoverHierarchyRawAsync) at Repository.DiscoverPageSize. The
mxaccessgw client's typed DiscoverHierarchyAsync overloads hard-code a
5000-row page and DiscoverHierarchyOptions carries no page size, so the
authored knob reached nothing; the raw request takes page_size on the
wire, so it is honoured here (non-positive → 5000). The loop keeps the
client's repeated-page-token guard.
- G-6: GalaxyDriverProbe reads ProbeTimeoutSeconds from the config and
runs under min(caller budget, configured cap) — the knob can shorten a
probe, never extend it past the host's budget. The TCP preflight now
shares that deadline instead of hanging on the caller's token alone.
- G-8: GatewayGalaxyDataWriter runs a batch as one lane per distinct tag,
concurrently and bounded at 8 (MaxConcurrentWriteLanes); same-tag
writes keep their authored order inside one lane and results land at
their request's index. Acks stay serial by design.
- GalaxyDriverForm: help text now says what the two knobs actually do.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
A timed-out script is abandoned, not stopped, and every seam re-ran it on the
next trigger, leaking one pool thread per trigger (R03:1.1, R05:2, R07:L1).
A shared ScriptRunGuard, keyed per script instance, now:
- refuses a run while that script's previous orphan is still executing
(Bad "previous evaluation still running" + otopcua.script.run_refused);
- quarantines after 3 consecutive non-completions or an allocation-budget
breach (sampled with GC.GetAllocatedBytesForCurrentThread; default 64 MB):
no further dispatch, Bad quality, one Error, otopcua.script.quarantined,
cleared on source change / redeploy / reset;
- starts the budget clock when the pool picks the run up, so starvation is
no longer charged to the script (R07:P5), and cancels the evaluator token
on timeout.
Wired into RoslynVirtualTagEvaluator, CalculationEvaluator (new async
EvaluateAsync; the driver's pump and timer ticks now await the run behind a
SemaphoreSlim gate) and ScriptedAlarmEngine (a non-completing predicate
holds state and annotates the condition BadInternalError). ScriptingOptions
(Scripting:MaxAllocBytesPerRun, Scripting:QuarantineAfterConsecutiveTimeouts)
carries the knobs; the Calculation driver config accepts the same two keys.
Tests: guard unit suite (incl. the 30-trigger runaway leaving one orphan with
a healthy sibling as positive control), per-seam refusal/quarantine/reset
tests. The S12 race test now uses one vtag id per loop: twelve concurrent
evaluations of ONE id is a shape production never produces and the guard
refuses by design.
Refs #734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Review 2026-10-21 G-4, G-7, G-11, G-10.
- G-4: PerPlatformProbeWatcher publishes its probe handles into the
driver's SubscriptionRegistry under the reserved ProbeSubscriptionId
(-1), so the EventPump's fan-out finally reaches the watcher — every
ScanState event used to be dropped as "stale after unsubscribe" and
per-platform host status never updated. ResubscribeAllAsync delegates
the reserved entry to the watcher's new ResubscribeAsync, so the probe
survives a reconnect; StopAsync removes the entry. Probe traffic is
routed by the reserved handle and never reaches the public OnDataChange.
The watcher is also built on the seam path (subscriber only), which is
what makes the wiring testable without a gateway.
- G-7: GalaxyDiscoverer.DiscoverAsync returns the hierarchy it fetched and
the driver selects its $WinPlatform/$AppEngine probe targets from that
same sweep instead of asking the gateway for the whole galaxy twice.
- G-11: OnPumpDataChange stamps LastSuccessfulRead from inbound stream
data, throttled (1 s default), so the comms-loss watchdog has honest
liveness evidence under a Degraded supervisor.
- G-10: an EventPump dispatch-loop exit that is not a cancellation now
reports a stream fault so the supervisor recreates the pump, instead of
leaving a deaf pump reporting Healthy.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
GalaxyDriver.ShutdownAsync was a no-op: the MX session, both owned gRPC
channels, the EventPump, the alarm feed, the DeployWatcher, the probe
watcher and the reconnect supervisor were released only by DisposeAsync,
which the host never calls — one leaked gateway session per respawn,
removal and /raw browse, and a watchdog Shutdown→Initialize that neither
tore down nor rebuilt anything (review 2026-10-21 G-1, G-2, G-9, G-3).
- ShutdownAsync and DisposeAsync share one ordered TeardownRuntimeAsync
(supervisor first, then deploy/probe watchers, pump, alarm feed,
session, channels); owned seams are nulled so the next InitializeAsync
rebuilds; injected seams survive a shutdown and drop only on the final
dispose. Lifecycle calls are serialised behind a gate.
- A failed production connect releases its partial runtime (no orphaned
client per watchdog retry) and lands Faulted before and after.
- StartDeployWatcherAsync stops the previous watcher before starting a
replacement, and now starts on a production instance's FIRST
InitializeAsync (the old guard returned whenever discovery had not run
here, which on a runtime instance is always).
- ReconnectSupervisor releases each cycle's CancellationTokenSource when
its loop exits and gains an awaitable StopAsync; PerPlatformProbeWatcher
gains an awaitable StopAsync.
- EventPump treats any exception under cancellation as a clean stop, so a
teardown never wakes the supervisor.
- Internal seams for tests: an IGalaxyDeployWatchSource ctor parameter and
a session-open override forwarded to the owned GalaxyMxSession.
Refs #735
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Review R08:1.1: an uncapped HistoryRead-Raw (NumValuesPerNode = 0) read a
tag's whole window into memory on every backend (SQL TOP(int.MaxValue),
QuestDB LIMIT, Gateway max_values = int.MaxValue + a second snapshot copy).
New ServerHistorian:MaxRawValuesPerRead (default 10 000; <= 0 unbounded with
a Validate() warning; 1 raised to 2). Each backend data source takes it,
reports it as IHistorianDataSource.MaxRawValuesPerRead (the Gateway: min
with a strict gateway's learned ceiling), so the node manager's existing
RawPageLimit paging serves N = 0 and N > cap as pages of at most the cap
with a continuation point. Independently, a backend raw read asking for 0
or more than the cap reads cap + 1 rows and is REFUSED
(HistoryReadLimitExceededException => BadTooManyOperations) when the window
holds more - never answered truncated, since the server's paging reads a
short answer as the last page. Bound through the Host registry, the
SqlServer/QuestDb providers and GatewayHistorian.CreateDataSource.
Tests: options (default/binding/warnings), provider binding, Gateway unit +
through a real SDK node manager (uncapped -> 999/998/998/605 + CPs), and a
conformance case for the SQL backends.
Refs #736
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
The #687/F4 crowding re-read doubled its room up to 8 re-reads with no cap, so a pathological single-ms
cluster on a streaming gateway was streamed several times over for one page. The room is now capped at
ServerHistorian:MaxTieClusterOverfetch (plumbed into GatewayHistorianDataSource as maxPreWindowRows,
default 65536); past it, or once a read has already seen more, the read is BadTooManyOperations with
PreWindowRows set.
Item 1: IHistorianDataSource.MaxRawValuesPerRead (Gateway: learned ceiling - 16 = L; 0 elsewhere, guard-tested).
RawPageLimit plans every raw page on top of #692's lookahead: with L > 0 the read (page P + boundary ties k
+ lookahead) is <= L, P = min(N, L - k - 1) (uncapped: L - k - 1); no room => straight to the tie-cluster
over-fetch (never an uncapped or underflowing request). One re-plan + re-read when the read taught a new
limit or was refused for crowding pre-window rows (HistoryReadLimitExceededException.PreWindowRows): the
page shrinks by them. Over-fetch bound min(MaxTieClusterOverfetch, L - 1); slice size never 0.
Review fixes: F1 a window starting at/before the epoch counts AVEVA's synthetic row as pre-window (a
ceiling-truncated read was reported complete); F2 the page path disables ReverseRawReader's own re-run
(cold end-only ceiling 20/N=3000 cost 3,023 reads, now <= 40); F3 crowded look-back re-read around, not
refused; F4 the #687 crowding re-read room at least doubles (up to 8 re-reads), so a cluster of hundreds
just before a resume point no longer fails on a default gateway; a crowding refusal that leaves no room
is BadTooManyOperations, never a tick-by-tick cursor.
Item 2: ServerHistorian:EventReadHorizon (default 00:00:00 = exact, unchanged). When set, every fresh
HistoryReadEvents window's earlier bound is raised to now - horizon (both directions, all backends).
Lossy by design; documented.
Item 3 (native TimeAverage/Total re-check) stays blocked on historiangw#27.
A time inside a gap of a bursty tag costs a 64-row jump read landing in the next
burst plus a bisection back across the gap (~6 reads), so the 64 + 4/time cap
refused a 1 h/day 1 Hz tag asked at noon on 30/100/300 consecutive days
(186/606/1,806 reads) that AVEVA's own AtTime served. The cap is a runaway guard
(HistoryReadDeadline bounds wall clock): now 64 + 16 per distinct time.
Regression tests for x30/x100/x300 (each <= 7 reads a time, values checked).
Docs: DateTime-hinted nodes are stepped but keep the gateway's Double (the
Gateway never historizes DateTime nodes; the SQL backends return DateTime).
H1: the walk-back reset its width after a full segment and discarded a full
whole-remainder read, so a dense tag that stopped reporting weeks ago gave up
after 65 reads (BadTooManyOperations). It now gallops (x4, whole-remainder read
after two empties) and then BISECTS once any stored row is known below — a full
segment's (incl. a full whole-remainder read's) last row, or an earlier window
read's last row: (mid, hi] empty => hi = mid; full => known = its last row;
complete with rows => done; one density-aimed segment after a full read until an
aimed segment comes back empty; below 2 ms the whole stretch from the known row
(never a 100 ns step). Stopped 1 h..365 d with 5 y history: 6-18 reads at
1/min, 21-25 at 1 Hz, 25-31 at 10 Hz.
M1: a jump read asks for 64 rows (1,000 times over 10 y: ~66k rows, was ~1M).
L1: per-request read cap 64 + 4 x distinct times with a clear message; a strict
ceiling below 4 rows is refused naming the ceiling.
L2: DateTime hints are stepped. L3: under an integer hint a NaN/inf or
out-of-Int64-range value is unusable, never saturated Good.
L5: conformance Int64 AtTime asserts the type. L4: docs name the backend
differences. Nit: the window read end is clamped to now + 1 day.
Reviewer harnesses (Scratch693Fuzz/Cost, not committed): 0 differential diffs
over 2,400 cases.
Review follow-up: on the Gateway every value is a Double (AVEVA stores a Boolean
as a 0/1 Int2), so the raw-evaluated AtTime interpolated a Boolean node to 0.5.
- IHistorianDataSource gains a default-interface overload
ReadAtTimeAsync(fullReference, timestamps, TypeCode? valueType, ct) that
forwards to the existing one (SqlServer/QuestDB/Null/fakes unchanged).
- OtOpcUaNodeManager.HistoryReadAtTime passes the node's scalar DataType
(AtTimeValueType: built-in type -> TypeCode; arrays/other types => null);
Raw and UNS NodeIds alike.
- GatewayAtTimeReader converts each raw row to the hinted kind BEFORE the shared
AtTimeEvaluator runs (Boolean = value != 0 => stepped; integers => Int64 =>
interpolated, rounded half away from zero, returned as the node's integer
type; floats Double), so the evaluator's own type branch decides.
- AtTimeEvaluator boxed every interpolated Int64 as a Double (`cond ? (long)x :
v` widens to double); its "keeping its type" test passed because Shouldly
ShouldBe compares numbers across types. Fixed (affects SqlServer/QuestDB too)
and pinned with ShouldBeOfType.
Gateway HistoryRead-AtTime passed AVEVA's own interpolation through: live it
answered the previous value as Good at a stored NULL's own time, null + Bad at
a Good sample right after a NULL, a drifted 99.99999999944 for a stored 100,
and no Interpolated bit. It is now served from raw gateway reads and evaluated
with Sql.Common's AtTimeEvaluator, as the SQL backends do (Part 11 §6.5.4).
GatewayAtTimeReader: one <=1,024-row forward window read [first-1ms, last+1ms]
for the batch, a walk-back (density-seeded, x4 growth, whole-remainder shortcut,
bisects dense history) for the first time's prev, and an 18-row probe for the
last time's next; truncated window reads continue or jump with a density-sized
margin. All bounds whole ms; a row counts only strictly inside its request
(AVEVA's boundary row never a sample); Bad rows value-less (#690); never past
now + 1 day; strict-gateway ceiling learned (#691.3) without re-probing.
10 dense times = 1 read (exact) / 3 (interpolated); 10 hourly = 12.
Kill switch ServerHistorian:GatewayAtTimeFromRaw (default true; false = the
old AVEVA passthrough). Known limit: the wire carries no data type, so numeric
tags interpolate as Double (Boolean/integer nodes are not stepped/rounded as on
the SQL backends).
1. The at-or-after bound read on a forward-only backend (Gateway) ends at
now + ReverseRawReader.LookAhead instead of DateTime.MaxValue (the gateway
only checks start <= end, so a year-9999 end reached AVEVA); a bound beyond
the horizon is not found without a read. SqlServer/QuestDB keep MaxValue:
they bind it safely and may hold samples further ahead. The Gateway fake now
refuses far-future ends, so the missing-end-bound test is no longer vacuous.
3. No data and no bound found (whole read empty) => GoodNoData, no values —
the pre-bounds answer (6.5.3.2: success only if one or both bounds exist).
A one-value page whose start bound is missing first checks there is data or
a found end bound.
4. ServerHistorian:HonorReturnBounds (default true); false ignores ReturnBounds
as before #691, including the modified-read Bad_InvalidArgument.
The start bound is the stored prior sample at its own time (walked back), never
the synthetic boundary row stamped at the query start; a stored NULL is a Bad
bound; reverse end bound walks back too.
The node manager composes the start/end bounds from each backend's existing raw
reads (one authority, HistoryBounds): at-or-before = a capped reverse read
(native, or ReverseRawReader's walk-back on a forward-only backend — never
AVEVA's synthetic boundary row), at-or-after = a capped forward read. Bounds
count toward NumValuesPerNode, the start bound leads the first page, the end
bound ends the last (carried in the continuation point). Missing bound =
Bad_BoundNotFound (null, at the bound time; one-sided reads ±1 s from the
previous value, Table 1 footnotes a/b). A modified read with ReturnBounds is
Bad_InvalidArgument (Part 11 6.5.3.3).
The .NET SDK's ReadRawModifiedDetails defaults ReturnBounds to TRUE; the
existing tests built details without setting it and now set it false.
Oracle: every row of Part 11 Table 1 over three backend shapes, plus paging
concatenation, ties, Bad bounds, microsecond truncation; conformance pins the
lookup primitives on SqlServer + QuestDB.
GatewayHistorianDataSource.ReadEventsAsync sized its result list to
maxEvents, which is int.MaxValue for NumValuesPerNode = 0: every
uncapped Gateway events read (forward on master, and the new walked
reverse one) threw 'Array dimensions exceeded' and counted as a backend
failure. Capacity is bounded at 1024. The events walk delegate moved to
ReverseEventsReader so it is tested over the real Gateway source
(forward uncapped, reverse uncapped, reverse capped).
A reverse or end-only capped events read on a backend without
SupportsReverseEvents (Gateway, Null) was refused
BadHistoryOperationUnsupported (explicit reverse) or answered with the
OLDEST N ascending (end-only, #675). It is now served newest-first by
the same ReverseWalk as raw reads: page-sized ms-aligned segments,
never answered from a read the source flagged truncated, ties sorted by
EventId (the gateway orders by event time only - the fake shuffles
them per call), one extra event walked to signal 'more', uncapped = one
forward read reversed, and the width + proven-empty stretch carried in
the events cursor. The oversized-cluster over-fetch keeps exactly the
events at T in the same order. A tie cluster over the budget is
BadTooManyOperations. Docs note the gateway's EventReadMaxRows must be
unlimited (it truncates silently).
Joseph Doherty