ReceiveAsync suspended the mailbox for the whole of every handler, so one Test Connect against a
black-holed PLC (60 s clamp) or one large deploy compose stalled every other admin operation
fleet-wide — AdminUI alarm acks/shelves, driver restarts, the next deploy.
- TestDriverConnect runs the probe on the thread pool and pipes a TestDriverConnectResult
straight to the requester (every path yields a result, never Status.Failure).
- StartDeployment serialises only the in-flight check (DB row + an actor-local compose-in-flight
flag, because the Deployment row is written at the END of the compose); the snapshot read,
validation, gzip and row write run off-actor and return as DeployComposed /
DeployComposeFailed, where the coordinator is told and the requester answered.
Tests: an alarm ack completes in < 1 s while a 60 s probe is pending and while a compose is
parked on a gated DbContext (positive controls: both still complete afterwards); a second
StartDeployment during an in-flight compose is refused.
Refs #733
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
StartDeployment read the whole config DB twice with no transaction — DraftSnapshotFactory for
the validator, then ConfigComposer for the artifact, plus clusters/nodes and Script.SourceCode
again in between. An AdminUI save landing between the two shipped an artifact the DraftValidator
never saw.
- DraftSnapshot carries ServerClusters, ClusterNodes and ApiKeys; DraftSnapshotFactory reads
every table inside one SNAPSHOT transaction on a relational provider (no-op on InMemory or
under an ambient transaction).
- ConfigComposer.Compose(DraftSnapshot) is pure over the snapshot (ordinal-sorted keys);
SnapshotAndFlattenAsync(db) delegates to it, byte-identical.
- AdminOperationsActor validates topology, estimates compile cost and composes the artifact
from the one snapshot it holds.
- Migration EnableSnapshotIsolation: ALTER DATABASE CURRENT SET ALLOW_SNAPSHOT_ISOLATION ON
(suppressTransaction; no model change).
Tests: the SQL Server snapshot read ignores a row committed mid-read (positive control: a later
read sees it); an edit injected between the Equipment and Tags reads is absent from the shipped
artifact and rejected by the next deploy; Compose(snapshot) == SnapshotAndFlattenAsync(db).
Refs #733
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
A Deployment row left in Dispatching with no NodeDeploymentState rows (HandleDispatch threw
before its SaveChanges, or the process died between the AdminOps row write and the
coordinator's Tell) was recovered with an empty expected set; the deadline then hit the
0 == 0 "race" branch and returned without touching the row, so every later StartDeployment was
refused AnotherDeploymentInFlight until someone hand-edited SQL.
- PreStart: a recovered row with no expected-ack rows is a lost dispatch. Inside the apply
deadline it is re-driven through HandleDispatch (bounded: CreatedAtUtc never moves); past it
the row is closed TimedOut with a reason naming the condition.
- HandleDispatch is idempotent on a re-dispatch (rows already seeded ARE the expected set).
- HandleDeadline takes the race branch only when _expectedAcks.Count > 0.
- The PreStart recovery read projects ArtifactBlob away (R03:3.5).
Refs #733
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Keeps the root CLAUDE.md lean by lazy-loading per-area detail (drivers, topology,
data-plane auth, alarms, historian) only when matching files are touched.
Clears CommentChecker findings in src/ (3,280 -> 209, the remainder being false
positives like PLC-5/IEEE-754/M0.0) by adding missing summaries/params/returns,
normalising inheritdoc usage, and removing Gitea/review tracking IDs while keeping
the rationale they annotated. Comment-only: comment-stripped sources are identical
to the parent commit.
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.
F1 (pre-existing): SliceTieCluster continued a forward read while next <= endUtc, but the
forward window is end-exclusive; an oversized cluster one step below EndTime resumed AT
EndTime, the resume became a start == end point read and returned the EndTime samples as
data (microsecond: EndTime 8.1 us truncated to 8.0). Continue only while next is strictly
before EndTime truncated to the backend resolution.
Tests: A_tie_cluster_just_below_the_end_time_never_resumes_onto_the_end_time (native +
microsecond; both fail on the old rule) and
A_cursor_inside_a_tie_cluster_over_fetches_without_a_normal_read_first (pins the
WithinTieCluster shortcut by per-page read count; fails with the shortcut disabled).
Docs: the oversized-cluster exception to 'every page full / no lookahead => last' (F2),
and the N + skip + 1 strict-ceiling edge note referencing #694 (F4).
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.
Joseph Doherty
dohertj2