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.
A tie cluster's truncated read left the width at one tick; once the gap
above it was under two milliseconds nothing floored it, so segHi
stepped down one tick per read: 30 rows at one ms 0.3 s below hi with a
carried 1 s width took 10,006 identical reads (S8). (a) The top-anchored
width is floored at the granularity, Min kept; (b) a segment no wider
than the granularity is the unit that escalates to
MaxTieClusterOverfetch and then refuses - per millisecond, exact for the
ms-resolution Gateway (documented). Both are needed: the floor alone
loops on crowded reads with a small tie budget. S8 is a repo test
(4 shapes, reads <= 30, 0 repeated requests); random-data tests now
measure the refusal unit as rows in any 1 ms window. Reviewer harness,
5,000 seeds x default/MSONLY/CROWD: worst page 70 reads (default/MSONLY),
63 (CROWD) at M=65536, p99.9 27-37; no page over 500 reads at any tie
budget.
The last pages of a deep reverse page-through on a forward-only backend
each walked down to 1970 one x4 growth step at a time (~14-16 reads,
~2.5 s live). After two empty segments the walk now asks once per page
for the whole remainder at the page budget (a truncated answer is
discarded and the walk carries on), and the stretch the page's last
complete read proved empty rides the continuation point
(HistoryContinuationState.EmptyFromTicks/EmptyToTicks, session-held, so
no versioning) so the next page steps over it. Fuzz now pages with the
walk's own hints and with true random empty stretches.
ReverseRawReader aimed every segment at half of MaxTieClusterOverfetch
(~32k rows by default) and carried that width page to page, so a paged
'latest N' read on a dense Gateway tag fetched ~32,770 rows per page
(2-5 s live) to return N. The walk now lives in a generic ReverseWalk
core: segments are aimed at ~N+8 rows (page budget 2N+16), a discovery
segment (first without a hint / after an empty one) may read 1,024, and
the tie budget is only the ceiling a single-timestamp cluster escalates
to. A truncated read never re-enters the stretch below its newest row
until the gap above it is bisected. Tests: per-page row counts on a
dense tag (node manager + walk), randomized exactness fuzz (walk and
node-manager paging), dense-tag-below-a-long-gap read bound.
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.
IHistorianDataSource.TimestampResolutionTicks (default 1; QuestDB 10). A drained tie
cluster now steps off T by the resolution, so a forward one-value-per-page read on a
microsecond backend no longer re-reads the same sample forever (C1). QuestDB AtTime
results carry the client's original request time (M3); regression for the NEXT seek
skipping a tombstone (M1). Conformance backend wires the real writer and updater.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
A reverse read (start > end) with a small NumValuesPerNode resumed through
the tie-cluster path, which drained the cluster and stepped FORWARD to
T + 1 tick - outside a reverse window - so the read ended with GoodNoData
after one sample. SliceTieCluster now steps down to T - 1 tick for a
reverse read (terminal at the excluded end), and the node manager slices
the over-fetched cluster in the read's own direction so the skip count is
not applied from the wrong end. Forward paging is unchanged.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
HistoryRead is served server-side by IHistorianDataSource; nothing ever dispatched
to a driver's IHistoryProvider. Removes IHistoryProvider, the OpcUaClient history
passthrough, DriverCapability.HistoryRead (+ resilience tier rows and AdminUI row),
HistoryReadStatusException and its node-manager catches, and the tests that only
covered them. Shared result types and HistoryAggregateNotSupportedException stay
(moved to Historian/HistoryReadContracts.cs). A stored ResilienceConfig still
carrying a HistoryRead key parses (diagnostic only; new test).
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
The tests probe a free port (bind 0, release) and start the SDK server later; under a
highly parallel run another test can take the port in between and the SDK fails with
'Failed to establish tcp listener sockets for Ipv4 and IPv6.'. OpcUaHostStart.StartAsync
builds a fresh host + server on a fresh port per attempt (up to 5) when the failure is a
bind failure; all 45 start sites in OpcUaServer.Tests, OpcUaServer.IntegrationTests and
Runtime.Tests use it. Per-attempt GUID ApplicationUris are hoisted out of the host factory
because a changed URI against a reused PKI store fails with 'Cannot access private key'.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
H1 (HIGH): write-routing key now (AddressSpaceRealm, bareId), not bare-only.
A raw s=<RawPath> and a UNS s=<Area/Line/Equip/Eff> can collide as bare
strings; the bare-only key let a colliding raw+UNS pair route to the WRONG
driver ref (last-writer-wins). The realm the node manager resolves (RealmOf)
is now threaded through IOpcUaNodeWriteGateway.WriteAsync -> RouteNodeWrite ->
_driverRefByNodeId keyed by (realm, bareId). New regression test:
Colliding_raw_and_uns_bare_ids_route_to_their_own_driver_by_realm.
M1 (MEDIUM): discovered-node injection made coherently DORMANT. HandleDiscoveredNodes
hard-short-circuits (single enforcement point; _discoveredByDriver never
populates so the re-inject tail is inert too), with a clear log pointing at the
/raw browse-commit flow. New pin: Discovered_nodes_are_ignored_dormant_in_v3;
the 16+2 v2 injection scenarios re-pointed to an accurate skip reason
(DiscoveryInjectionDormantV3).
M2 (MEDIUM): realm-qualified dual-node self-correction tests —
Failed_uns_write_reverts_uns_node_and_leaves_raw_node_untouched +
Raw_realm_revert_reverts_raw_node_only (the second fails if the realm is dropped).
L1: removed the = AddressSpaceRealm.Uns defaults from the consequential
node-manager mutation methods (WriteValue/WriteAlarmCondition/MaterialiseAlarmCondition/
EnsureFolder/EnsureVariable/UpdateFolderDisplayName/UpdateTagAttributes/
RaiseNodesAddedModelChange/Remove*/RevertOptimisticWriteIfNeeded) + the
AttributeValueUpdate/AlarmStateUpdate records, so the compiler forces explicit
realm; read-only accessors + internal builders retain their defaults.
L3: fixed the stale VirtualTagHostActor class comment (V3NodeIds.Uns, not the
retired EquipmentNodeIds.Variable).
Also: DeploymentArtifactRawUnsParityTests — Raw/UNS node-set byte-parity
round-trip between AddressSpaceComposer.Compose and DeploymentArtifact.ParseComposition.
Claude-Session: https://claude.ai/code/session_01LVneM3eh1UtJxEisFXgmox
C1 (critical): a boundary tie cluster larger than NumValuesPerNode could
silently truncate a resumed read to GoodNoData, permanently dropping the
un-emitted ties — the (timestamp, skip) cursor cannot advance past a single
timestamp the fixed-(start,end,cap) backend keeps re-returning. Now detected
and failed LOUDLY per node with BadHistoryOperationUnsupported + a log naming
the tag/timestamp/cap; documented in Historian.md with the larger-cap remedy.
Regression test Raw_tie_cluster_larger_than_page_fails_loudly_not_silently.
I3: build HistoryData before Save() so a projection failure can never orphan a
stored continuation cursor.
N1 (YAGNI): drop the never-produced HistoryReadKind enum + Processed-only
Aggregate/IntervalTicks fields from HistoryContinuationState — only Raw pages.
N3: ComputeResumeCursor guards its documented non-empty precondition.
I1: document InMemoryHistoryContinuationStore's eventual-consistency (test double).
Build clean, 182/182 OpcUaServer tests pass.
The Wonderware historian backend is single-shot — it returns up to
NumValuesPerNode samples with a null continuation point — so paging is
synthesised server-side, time-based, for the only count-capped arm (Raw):
- A full page (count == NumValuesPerNode, NumValuesPerNode > 0) emits an
opaque 16-byte continuation point and stores a resume cursor; a short page
(or NumValuesPerNode == 0 "all values") emits none.
- A resume read takes the stored cursor, reads the next page from the boundary
forward, and emits a fresh CP only if that page is also full.
- The resume cursor is tie-safe (HistoryPaging.ComputeResumeCursor /
TrimBoundaryDuplicates): the next page resumes from the boundary timestamp
INCLUSIVE and drops the head ties already returned, so samples sharing the
boundary SourceTimestamp are neither duplicated nor skipped.
Continuation points are bound to the OPC UA session via the SDK's
ISession.SaveHistoryContinuationPoint / RestoreHistoryContinuationPoint store
(SessionHistoryContinuationStore) — capped by ServerConfiguration.
MaxHistoryContinuationPoints (default 100, oldest-evicted) and disposed on
session close. releaseContinuationPoints is honoured via an override of
HistoryReleaseContinuationPoints (the base dispatcher routes release-only reads
there, never to the per-details arms). An unknown / evicted / released point
resumes to BadContinuationPointInvalid.
Processed and AtTime stay single-shot: neither details type carries a client
count cap, so the single-shot backend returns the complete result in one read
and there is no "full page" signal to page on (spec-conformant). Modified-value
history remains out of scope.
The pure paging decisions + CP store contract are unit-tested via HistoryPaging
+ InMemoryHistoryContinuationStore; the full multi-page round trip is driven
end-to-end through the node manager with an in-memory store + a series-backed
fake historian (the in-process harness is session-less).
Joseph Doherty