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.
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).
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).
- M1/M2: when the 1 ms pre-window margin (boundary row + stored samples, e.g. a
>16-sample tie cluster at start-1ms / lastTs-1ms) uses up the cap + 16 budget,
re-read ONCE asking for cap + m + 16 (m = pre-window rows seen); fail
BadTooManyOperations only if the re-read is still short because of them. The
raw budget is no longer clamped at the gateway default ceiling (AVEVA always
emits the boundary row, so page sizes 999,985-1,000,000 always came back
short); the #688 clamp stays on the per-sample aggregate path only.
- Merge trap: NumValuesPerNode 0 => int.MaxValue, never through the clamp.
- L3: the forward end is exclusive ([start, end), the IHistorianDataSource
contract); a point read (start == end, the tie-cluster over-fetch) inclusive.
- RequestStartFor never goes before the Unix epoch (#686's walk-back floor).
- L4 (docs): an Uncertain native row for an all-NULL interval is unverified live.
An AVEVA Full raw read leads with a row stamped at the query start (the value in
effect, Quality=133, or a no-data NULL row); it was returned as a stored sample.
Raw reads now use the #681 classification (RawAggregateReader.RequestStartFor /
IsWindowSample — one authority, by timestamp, since a stored NULL looks the same
on the wire): request from 1 ms early with NumValuesPerNode + 16 rows, keep rows
at or after StartTime, drain the whole stream. A full page still holds exactly
the cap, so #669 paging/resume/tie-cluster reads are unchanged; a margin that
swallows the allowance fails the node rather than ending paging early.
ReturnBounds is not plumbed on any backend (documented).
AVEVA answers one extra row for the interval before the window; it was mapped as
a result stamped before StartTime (N+1 values). Rows whose interval lies outside
the requested span (either direction) are now dropped after the drained stream.
An Uncertain (opc 64-191) interval kept no value (opc >= 192 was the only data
test); it now carries its value as UncertainDataSubNormal | Calculated.
Docs: AVEVA's TWA excludes NULL-gap time while the SQL backends bridge it;
end-to-end per-interval values also need historiangw#27.
1. Uncapped reverse raw read on a forward-only backend = ONE forward read of the
window, filtered and reversed in memory (was a segment-by-segment walk).
2. Segment width is aimed at ~half the row budget from the density just observed
(overflow: from the truncated read's own sample span) and carried page to page
in HistoryContinuationState.SegmentWidthTicks.
3. The walk starts no later than now + 1 day and never reads before the epoch.
4. Request bounds are rounded outward to the millisecond, so a row AVEVA
fabricates at a rounded-up query start cannot land inside the segment.
5. Budget M = max(1, MaxTieClusterOverfetch); reads ask M + 2 rows, completeness is
'short OR last row past the segment', and a read crowded by rows before the
segment is re-read once (<= 2M + 4). A cluster of exactly M, neighbouring
clusters each within M, and M <= 1 are all served; only one timestamp over M
is refused. ServerHistorianOptions text updated.
6. The raw and events tie-path oversized-cluster refusal is BadTooManyOperations
(was BadHistoryOperationUnsupported), consistent with the walk.
7. GatewayHistorianDataSource.ReadRawAsync: a caller cancellation is not a backend
failure; NumValuesPerNode = 0 is sent as int.MaxValue (the client package and
the gateway reject max_values <= 0, so every uncapped Gateway raw read failed);
a MaxValuesCeiling refusal is a HistoryReadLimitExceededException.
8. Tests: upper-edge filter, epoch floor, look-ahead, ms alignment, exact/adjacent
clusters, minimal budget, carried density, and the walk over the real Gateway
source + FakeHistorianGatewayClient (OpcUaServer internals visible to it).
#669 turned an end-only capped HistoryRead-Raw into a reverse read (start > end)
for every backend; the gateway rejects start > end (InvalidArgument), so on the
default Gateway backend every end-only capped and every explicit reverse raw read
failed the node and was counted as a backend health failure.
- IHistorianDataSource.SupportsReverseRaw (default false; SqlServer/QuestDB/Null
true, Gateway false; guard test pins that every production backend declares it).
- OtOpcUaNodeManager sends a reverse window only to a backend that declares it;
otherwise ReverseRawReader walks (lo, hi] back in bounded forward segment reads
(1 min, x4 while sparse; each <= MaxTieClusterOverfetch + 1 rows; a full read is
re-read narrower, never answered truncated; filtered on sample timestamps, which
also drops AVEVA's fabricated query-start rows; stops at the Unix epoch). A
one-timestamp tie cluster over the bound => BadTooManyOperations.
- ServeRawPagedAsync maps HistoryReadLimitExceededException to BadTooManyOperations.
- GatewayHistorianDataSource.ReadRawAsync refuses start > end unsent, without
recording a health failure.
Average, Count, Minimum, Maximum, Range, Start, End, Delta and Minimum/MaximumActualTime are evaluated
on the Gateway backend from forward ReadRaw reads with BucketPlan + AggregateEvaluator, so Gateway
matches SqlServer/QuestDB exactly (values, status bits, interval-start stamps, #677 reverse).
- Window read [start - 1 ms, end] so AVEVA's initial-value row never lands in a bucket; a pre-window
row proves earlier data only with a non-Bad OPC quality (histsdk puts a value on every NULL row).
- Earlier data otherwise from a 2-row [1970, start) probe; later data from a 2-row [end, now+1d]
look-ahead; both ignore rows stamped at their query start/end.
- No gateway stream is ever abandoned (a client-side cancel makes the gateway evict its shared
historian session); past ServerHistorian:MaxTimeWeightedRawRows the bounded stream is drained, then
BadTooManyOperations. The gateway's max_values-ceiling InvalidArgument maps to the same limit; a
caller cancellation is not a backend fault.
- TimeAverage/Total stay AVEVA-native (no prior-sample read for exact Part 13 bounds), now stamped with
the interval start (PENDING the live leg: histsdk's tail+43 start_time field is unverified) and
carrying the Calculated bits.
- Served set: GatewayHistorianDataSource.ServedAggregates (12). Live AVEVA leg open (VPN).
IHistorianDataSource.SupportedAggregates (default: every HistoryAggregateType)
is the one authority for both ServerCapabilities/AggregateFunctions (i=2997) and
HistoryServerCapabilities/AggregateFunctions (i=11201) and for the up-front
BadAggregateNotSupported in HistoryRead-Processed. Gateway declares
AggregateModeMapper.Served (4), SqlServer/QuestDB AggregateFamilies.Served (17),
Null none. Only the folder references are trimmed; the SDK's calculator
factories stay so live AggregateFilter subscriptions keep working.
Co-Authored-By: Claude <noreply@anthropic.com>
- IHistorianDataSource.SupportsReverseEvents (default false; SqlServer/QuestDB true; Gateway/Null declare false).
The node manager checks it BEFORE calling the source: an end-only capped events read becomes reverse only on
a supporting backend (Gateway, the default, keeps the pre-#675 forward [MinValue, EndTime) paging), and an
explicit reverse read on a non-supporting backend is BadHistoryOperationUnsupported without a call.
- Removed the broad catch (NotSupportedException) in the events path: a NotSupportedException from inside a
backend is now logged as a backend fault (Error), not an 'unsupported' Warning.
- Null declares the reverse overload itself; guard test: every production IHistorianDataSource declares both
the reverse overload and the capability (positive-control scan of all four backends).
- Conformance: capability reported + oversized reverse tie cluster (forward over-fetch reversed == reverse
read order; capped reverse read stopping inside the cluster flags truncation) on SqlServer + QuestDB.
- docs/Historian.md: end-only capped events read is backward on SqlServer/QuestDB, forward on Gateway.
- IHistorianDataSource.ReadEventsAsync(..., bool reverse, ...) overload: reverse = Part 11 window (lo, hi]
newest-first by (time, id) DESC. Default forwards forward reads and throws NotSupportedException for
reverse (Null); Gateway refuses explicitly (ascending-only stream). Server answers
BadHistoryOperationUnsupported instead of silently returning the earliest N ascending.
- SqlServer / QuestDB serve reverse natively (ORDER BY time DESC, id DESC + TOP/LIMIT).
- Node manager: reverse event reads page with continuation points; direction stored in the cursor
(HistoryContinuationState.Reverse) so a resume continues in the cursor's direction; reverse tie clusters
over-fetched forward and sliced from the newest end (SliceTieCluster(reverse:)); end-only reads with a
cap page backward from EndTime (mirrors raw).
- Resumed event pages over-fetch by the boundary skip, so every non-final page is a full cap page.
- Tests: node-manager reverse paging (ties, clusters, coarse resolution, overfetch bound, resume
direction both ways, end-only, unsupported backend); shared EventReadConformance on SqlServer +
QuestDB; over-the-wire reverse paging; offline Gateway pin of the UTC DateTime.MaxValue bound through
the published client's proto conversion (in-process gRPC capture) and FILETIME.
- docs/Historian.md event paging section.
Adds <summary>/<param>/<returns>/<inheritdoc> where missing and removes
project bookkeeping IDs (task/tracking refs) from shipped code comments,
so the docs read cleanly and CommentChecker is quiet except for known
false positives (PLC/protocol terms, event/IEqualityComparer inheritdoc).
Doc/comment-only; no logic changed; solution builds clean.
The HistorianGateway driver is now the sole historian read/write+alarm backend, so the
Wonderware sidecar projects are dead code. Removes the 5 Wonderware projects (driver,
.Client, .Client.Contracts, + their 2 test projects) from the solution and tree, and fully
retires the vestigial 'Historian.Wonderware' driver type (UI/probe-only; it had no driver
factory): the Host probe registration, the AdminUI driver-config surface (driver page,
tag-config editor/model/validator entry, address picker/builder, driver-type catalog +
dropdown + edit-router entries), and their tests. Prunes the now-unused Wonderware
connection fields (Host/Port/UseTls/ServerCertThumbprint/SharedSecret) from
AlarmHistorianOptions (keeping Enabled + the SQLite store-and-forward knobs) and refreshes
the stale XML docs that named Wonderware as the production backend.
Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii
Addresses T7/T8/T11 code-review minors: route the sync dispose through DisposeAsync
so a double Dispose()+DisposeAsync() stays a no-op; cover the sync path.
Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii
Joseph Doherty