diff --git a/docs/Historian.md b/docs/Historian.md
index 0c4963d9..e6801b31 100644
--- a/docs/Historian.md
+++ b/docs/Historian.md
@@ -765,8 +765,11 @@ data.
refusal of the remembered one. A **raised** ceiling (or a switch to streaming) is noticed by the only reads it matters to: when a
read bounded by the remembered ceiling comes back full without proving completeness, it is re-probed **once** at its full budget
— served ⇒ the ceiling is forgotten; refused naming a larger ceiling ⇒ that one is learned and the read re-issued at it; refused
- naming the same ceiling ⇒ the bounded result stands. No timer: a TTL would only add refusals for reads that already fit; the cost
- of the rule is one refused re-probe per genuinely over-ceiling read (which fails either way). So an uncapped read (`NumValuesPerNode = 0`, which used to be refused outright on a strict gateway, even for a 10-row
+ naming the same ceiling ⇒ the bounded result stands. Raw and AtTime re-probe immediately. Per-sample aggregates (#696) reuse
+ a refusal for **30 seconds** before re-probing a full stream; within that period an oversized window still fails honestly with
+ `BadTooManyOperations`. A lowered ceiling is still re-learned immediately; a raise becomes visible on the next incomplete
+ aggregate read after the cooldown. So an uncapped read (`NumValuesPerNode = 0`, which used to be refused outright on a strict
+ gateway, even for a 10-row
window) and a page size within 16 of the ceiling are now served when the window fits. A ceiling-bounded read is answered only
when it is **provably complete** — the stream came back short of the ceiling, or reached `EndTime` (or, capped, filled the page);
a stream that delivered the whole ceiling short of `EndTime` may be truncated and fails **`BadTooManyOperations`** (not a backend
@@ -828,6 +831,17 @@ data.
refusing; doubling the look-back allowance does not skip that final usable budget. Reverse paging retries a crowded segment
with a smaller in-window budget derived from the learned ceiling and the observed pre-window rows.
+**Missing tags (#653).** Gateway Raw, Processed and AtTime first check the tag catalog. An empty exact-name catalog result or an explicit
+`NotFound` returns no data without a history RPC: Raw is empty; AtTime and Processed return null/`BadNoData` at the
+requested times or bucket timestamps. Unsupported aggregate validation still runs first. A bounded per-data-source cache
+holds at most 4,096 tag names, with **5 seconds** for absence and **60 seconds** for presence, so newly provisioned tags become
+visible after the short negative expiry. Catalog faults and cancellation never become missing-tag cache entries. The adapter drains the filtered catalog stream and checks exact names, avoiding older gateways that misparse a missing `GetTagMetadata` response as `Internal`. Empty
+AtTime/Processed requests need no check. Events and modified-history capability checks are unaffected.
+
+**Stopped-tag reverse discovery (#696).** On a strict Gateway, a truncated remainder probe retains its oldest-row evidence
+and density. Gap discovery uses the learned ceiling's available budget; ordinary page reads keep their page-sized budget.
+Only complete segments contribute to a page, preserving newest-first order, bounds, ties and continuation hints.
+
### Gateway AtTime is evaluated from raw reads (#693)
> ⚠️ **Client-visible (#693).** Gateway AtTime used to pass AVEVA's own interpolated answer (the gateway's `ReadAtTime`) through,
diff --git a/docs/plans/2026-10-13-historian-653-696-results.md b/docs/plans/2026-10-13-historian-653-696-results.md
new file mode 100644
index 00000000..df052676
--- /dev/null
+++ b/docs/plans/2026-10-13-historian-653-696-results.md
@@ -0,0 +1,36 @@
+# Missing-tag and Gateway performance fixes — 2026-10-13
+
+Follow-up to pushed `97668d26` / PR #699. Implements #653 and the remaining #696 items 2/3 under the approved bounded design.
+
+## Changes
+
+- **#653:** Raw, Processed and AtTime check tag presence before history RPCs. The bounded 4,096-name cache uses a 5-second negative and 60-second positive lifetime. Only explicit absence or NotFound is cached as missing; failures and cancellation propagate. Raw is empty; AtTime and Processed retain requested/bucket timestamps with null/BadNoData. Unsupported aggregate validation runs first.
+- **Live compatibility adjustment:** the deployed gateway misparses missing `GetTagMetadata` replies as `Internal` (`InvalidDataException: GetTagInfo response ended unexpectedly`). The adapter therefore checks the filtered tag catalog and compares exact names, fully draining the stream before declaring presence/absence. It never turns the parser error into a missing tag. Wildcard matches alone do not prove presence, and a trailing stream fault cannot enter the cache.
+- **#696 item 2:** a truncated remainder probe seeds strict-ceiling reverse discovery with its observed rows/density; gap searches use the available discovery budget. Complete segments alone contribute to the newest-first page. Regression: a 7,200-row stopped 1 Hz tag, ceiling 1,000, requested latest three one day later, previously 17 raw calls; now meets a maximum of 12 with exactly 7199/7198/7197 returned. Ordinary page sizing and event discovery behavior are unchanged.
+- **#696 item 3:** per-sample aggregates reuse a ceiling refusal for 30 seconds instead of immediately re-probing on every full stream. The next incomplete aggregate read after expiry notices a raised ceiling; a lowered ceiling is re-learned immediately. Raw and AtTime re-probes remain immediate. During the cooldown an oversized aggregate remains BadTooManyOperations, never a truncated result.
+
+## Verification evidence
+
+New regressions failed before fixes: all initial 12 cases failed (missing preflight/caching, 17 discovery reads, duplicate aggregate refusal). The four catalog wire cases failed with the metadata adapter and pass with the catalog adapter. Final Gateway suite: 434 passed, six environment-gated skips.
+
+Independent read-only review found no important defects. Concurrent cold requests can duplicate a metadata/catalog check; cache access and capacity mutations are locked. No single-flight guarantee was introduced. Catalog RPC contract streams all matches; the upstream SDK pages the native tag-query results, with no configured browse result ceiling.
+
+## Live #653 confirmation
+
+Measured the updated GatewayHistorianDataSource through the real adapter and local gateway against the existing remote AVEVA connection. Temporary historian:read key had a two-hour expiry and was revoked after the run. No historian writes/provisioning and no gateway deployment changes.
+
+Nonexistent tag: `OtOpcUa.Issue653.Nonexistent.20261013`.
+
+| Operation, five consecutive runs | Elapsed milliseconds | Result |
+|---|---|---|
+| Raw | 228, 0, 0, 0, 0 | empty |
+| Count processed | 2, 0, 0, 0, 0 | six null/BadNoData buckets |
+| AtTime | 1, 0, 0, 0, 0 | null/BadNoData at requested time |
+
+These used one data source/cache: the first Raw call is cold, subsequent calls are cached. The prior direct-client measurement took ~30.6 seconds for missing-tag Raw/Aggregate and ~61.3 seconds for AtTime. Direct client RPCs are not modified; the fast-fail protection is in OtOpcUa.
+
+**Control limitation:** SysTimeSec catalog presence succeeded, but its Raw RPC twice timed out upstream with DeadlineExceeded at ~30 seconds. The data source propagated IOException/communication failure rather than returning no data. A fresh control using the original package client (no data-source presence checks) also timed out with DeadlineExceeded after 30,656 ms, confirming this timeout is independent of the new checks. The earlier direct-client control had succeeded. This run therefore verifies missing-tag fast-fail and failure propagation, not healthy-tag live history behavior. No end-to-end deployed OPC UA claim is made.
+
+#694 remains open for native aggregate rerun after historiangw#27. No sibling gateway code changed.
+
+Full final-tree solution: 14,600 passed, 609 skipped, 0 failed across 62 suites. `dotnet test ZB.MOM.WW.OtOpcUa.slnx --verbosity quiet`, exit 0. Includes 122 passing OPC UA integration tests and 268 passing host integration tests (12 host skips). Environment-gated suites are included in the skip count.
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs
index cc3ed941..854bfda5 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs
@@ -68,7 +68,8 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
internal int MaxPreWindowRows => _maxPreWindowRows;
/// A strict gateway's row ceiling, learned from its first refusal (#691.3).
- private readonly GatewayRowCeiling _ceiling = new();
+ private readonly GatewayRowCeiling _ceiling;
+ private readonly GatewayTagPresenceCache _tags;
private readonly object _healthLock = new();
private DateTime? _lastSuccessUtc;
@@ -107,6 +108,8 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
_logger = logger;
_maxRawRows = maxRawRows;
_time = timeProvider ?? TimeProvider.System;
+ _ceiling = new GatewayRowCeiling(_time);
+ _tags = new GatewayTagPresenceCache(_client, _time);
}
///
@@ -126,6 +129,11 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
try
{
+ if (!await _tags.ExistsAsync(fullReference, cancellationToken).ConfigureAwait(false))
+ {
+ RecordOutcome(success: true, error: null);
+ return new HistoryReadResult([], ContinuationPoint: null);
+ }
var samples = await ReadRawWindowAsync(fullReference, startUtc, endUtc, maxValuesPerNode, cancellationToken)
.ConfigureAwait(false);
var snapshots = SampleMapper.ToSnapshots(samples);
@@ -351,6 +359,11 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
if (plan.BucketCount == 0) return new HistoryReadResult([], ContinuationPoint: null);
try
{
+ if (!await _tags.ExistsAsync(fullReference, cancellationToken).ConfigureAwait(false))
+ {
+ RecordOutcome(success: true, error: null);
+ return new HistoryReadResult(plan.Assemble(new Dictionary(), t => AggregateEvaluator.NoData(t, _time.GetUtcNow().UtcDateTime)), ContinuationPoint: null);
+ }
var byBucket = new Dictionary();
foreach (var request in NativeAggregatePlan.Requests(plan))
{
@@ -390,6 +403,11 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
try
{
var now = _time.GetUtcNow().UtcDateTime;
+ if (plan.BucketCount > 0 && !await _tags.ExistsAsync(fullReference, cancellationToken).ConfigureAwait(false))
+ {
+ RecordOutcome(success: true, error: null);
+ return new HistoryReadResult(plan.Assemble(new Dictionary(), t => AggregateEvaluator.NoData(t, now)), ContinuationPoint: null);
+ }
var values = await RawAggregateReader
.ReadAsync(_client, _ceiling, fullReference, aggregate, plan, _maxRawRows, now, cancellationToken)
.ConfigureAwait(false);
@@ -460,6 +478,11 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
try
{
var now = _time.GetUtcNow().UtcDateTime;
+ if (timestampsUtc.Count > 0 && !await _tags.ExistsAsync(fullReference, cancellationToken).ConfigureAwait(false))
+ {
+ RecordOutcome(success: true, error: null);
+ return MissingAtTime(timestampsUtc, now);
+ }
var values = await GatewayAtTimeReader
.ReadAsync(_client, _ceiling, fullReference, timestampsUtc, now, cancellationToken, valueType)
.ConfigureAwait(false);
@@ -488,6 +511,12 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
{
try
{
+ if (timestampsUtc.Count > 0 && !await _tags.ExistsAsync(fullReference, cancellationToken).ConfigureAwait(false))
+ {
+ RecordOutcome(success: true, error: null);
+ return MissingAtTime(timestampsUtc, _time.GetUtcNow().UtcDateTime);
+ }
+
var samples = await _client
.ReadAtTimeAsync(fullReference, timestampsUtc, cancellationToken)
.ConfigureAwait(false);
@@ -669,6 +698,10 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
return result;
}
+ /// No-data values for a missing tag, stamped with the client's requested times.
+ private static HistoryReadResult MissingAtTime(IReadOnlyList times, DateTime now) =>
+ new(times.Select(t => AtTimeEvaluator.Evaluate(t, null, null, now, now)).ToArray(), ContinuationPoint: null);
+
/// Classifies actual gRPC/package transport failures without treating refusals as outages (#697).
private static bool IsTransportFailure(Exception ex) => ex switch
{
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayReadLimits.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayReadLimits.cs
index a4467136..56951345 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayReadLimits.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayReadLimits.cs
@@ -76,13 +76,15 @@ internal static class GatewayReadLimits
/// the read is re-issued at N; refused naming C again ⇒ the C-bounded result stands (no repeat).
///
///
-/// Why no TTL. A raise only matters to a read that needs more than C, and such a read re-probes anyway
-/// (rule 3), so a timer would only add refusals for reads that fit. The cost of the rule is one refused re-probe per
-/// genuinely over-ceiling read — a read that fails BadTooManyOperations whatever is done.
+/// Re-probe timing (#696). Raw and AtTime reads re-probe incomplete streams immediately. Per-sample
+/// aggregate reads opt into a 30-second cooldown after a refusal; a full stream during it remains a request
+/// limit, never a truncated answer. After the cooldown the next incomplete read detects a raised ceiling.
///
///
-internal sealed class GatewayRowCeiling
+internal sealed class GatewayRowCeiling(TimeProvider? timeProvider = null)
{
+ private readonly TimeProvider _time = timeProvider ?? TimeProvider.System;
+ private long _lastRefusalTicks;
private int _learned; // 0 = unknown / not strict
/// The learned ceiling (0 = none).
@@ -93,8 +95,9 @@ internal sealed class GatewayRowCeiling
/// The max_values the read wants.
/// One drained read with the given budget.
/// True when a pass with the given budget delivered it all without proving completeness.
+ /// Aggregate-only opt-in: reuse a refusal for 30 seconds before re-probing an incomplete read.
/// The result and the budget it was read with.
- public async Task<(T Result, int Budget)> ReadAsync(int budget, Func> pass, Func needsMore)
+ public async Task<(T Result, int Budget)> ReadAsync(int budget, Func> pass, Func needsMore, bool deferRecentReprobe = false)
{
var learned = Learned;
if (learned <= 0 || learned >= budget) return await AttemptAsync(budget, pass).ConfigureAwait(false);
@@ -102,6 +105,10 @@ internal sealed class GatewayRowCeiling
var bounded = await AttemptAsync(learned, pass).ConfigureAwait(false);
if (bounded.Budget < learned || !needsMore(bounded.Result, bounded.Budget)) return bounded;
+ // #696: aggregate reads may reuse a recent refusal for 30 seconds. Raw paging keeps immediate re-probes.
+ if (deferRecentReprobe && _time.GetUtcNow().UtcTicks - Volatile.Read(ref _lastRefusalTicks) < TimeSpan.FromSeconds(30).Ticks)
+ return bounded;
+
// Rule 3: full at a possibly stale ceiling — re-probe once at the full budget.
int fresh;
try
@@ -114,10 +121,16 @@ internal sealed class GatewayRowCeiling
{
// fall through (outside the catch)
}
- Volatile.Write(ref _learned, fresh);
+ Learn(fresh);
return fresh > learned ? (await pass(fresh).ConfigureAwait(false), fresh) : bounded;
}
+ private void Learn(int ceiling)
+ {
+ Volatile.Write(ref _lastRefusalTicks, _time.GetUtcNow().UtcTicks);
+ Volatile.Write(ref _learned, ceiling);
+ }
+
private async Task<(T Result, int Budget)> AttemptAsync(int budget, Func> pass)
{
int ceiling;
@@ -129,7 +142,7 @@ internal sealed class GatewayRowCeiling
{
// fall through to the retry (outside the catch, so a second refusal is not nested in this one)
}
- Volatile.Write(ref _learned, ceiling);
+ Learn(ceiling);
return (await pass(ceiling).ConfigureAwait(false), ceiling);
}
}
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagPresenceCache.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagPresenceCache.cs
new file mode 100644
index 00000000..19760334
--- /dev/null
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayTagPresenceCache.cs
@@ -0,0 +1,36 @@
+using Grpc.Core;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway;
+
+/// Bounded metadata cache (#653). Missing tags expire quickly; failures never become missing tags.
+internal sealed class GatewayTagPresenceCache(IHistorianGatewayClient client, TimeProvider time)
+{
+ internal const int Capacity = 4096;
+ private readonly object _sync = new();
+ private readonly Dictionary _entries = new(StringComparer.Ordinal);
+
+ public async Task ExistsAsync(string tag, CancellationToken ct)
+ {
+ ct.ThrowIfCancellationRequested();
+ lock (_sync)
+ if (_entries.TryGetValue(tag, out var entry) && time.GetUtcNow() < entry.Expires) return entry.Exists;
+
+ bool exists;
+ try { exists = await client.TagExistsAsync(tag, ct).ConfigureAwait(false); }
+ catch (Exception ex) when (IsNotFound(ex)) { exists = false; }
+ ct.ThrowIfCancellationRequested();
+ lock (_sync)
+ {
+ if (!_entries.ContainsKey(tag) && _entries.Count >= Capacity) _entries.Remove(_entries.Keys.First());
+ _entries[tag] = (exists, time.GetUtcNow().AddSeconds(exists ? 60 : 5));
+ }
+ return exists;
+ }
+
+ private static bool IsNotFound(Exception ex)
+ {
+ for (Exception? e = ex; e is not null; e = e.InnerException)
+ if (e is RpcException { StatusCode: StatusCode.NotFound }) return true;
+ return false;
+ }
+}
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/HistorianGatewayClientAdapter.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/HistorianGatewayClientAdapter.cs
index c7a323d1..b4ceefd3 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/HistorianGatewayClientAdapter.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/HistorianGatewayClientAdapter.cs
@@ -81,6 +81,17 @@ public sealed class HistorianGatewayClientAdapter : IHistorianGatewayClient, IDi
return new HistorianGatewayClientAdapter(HistorianGatewayClient.Create(clientOptions));
}
+ ///
+ public async Task TagExistsAsync(string tag, CancellationToken ct)
+ {
+ // #653: older gateway SDKs misparse a missing GetTagInfo response as Internal. A catalog query proves
+ // absence without guessing from an error. Even a glob-like tag is checked by exact name, never by row count.
+ var found = false;
+ await foreach (var name in _inner.BrowseTagNamesAsync(tag, ct).ConfigureAwait(false))
+ found |= string.Equals(name, tag, StringComparison.OrdinalIgnoreCase);
+ return found; // drain first: a trailing stream fault must propagate and must not become a cache entry
+ }
+
///
public IAsyncEnumerable ReadRawAsync(
string tag, DateTime startUtc, DateTime endUtc, int maxValues, CancellationToken ct) =>
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/IHistorianGatewayClient.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/IHistorianGatewayClient.cs
index eef687c0..f356d52d 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/IHistorianGatewayClient.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/IHistorianGatewayClient.cs
@@ -11,6 +11,12 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway;
///
public interface IHistorianGatewayClient : IAsyncDisposable
{
+ /// Checks the tag catalog; false means explicitly absent, while failures propagate.
+ /// Historian tag name.
+ /// Cancellation token.
+ /// Whether the historian contains the tag.
+ Task TagExistsAsync(string tag, CancellationToken ct);
+
/// Streams raw historian samples for a tag over a time window.
/// The historian tag name to read.
/// Inclusive start of the requested time window (UTC).
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/RawAggregateReader.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/RawAggregateReader.cs
index 6f144c77..7f64e36f 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/RawAggregateReader.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/RawAggregateReader.cs
@@ -188,7 +188,7 @@ internal static class RawAggregateReader
var requested = MaxValuesFor(maxWindowRows);
var (pass, maxValues) = await ceiling.ReadAsync(requested,
budget => ReadWindowAsync(client, tag, aggregate, plan, requestStart, budget, maxWindowRows, ct),
- (r, budget) => !r.OverCap && r.Received >= budget).ConfigureAwait(false);
+ (r, budget) => !r.OverCap && r.Received >= budget, deferRecentReprobe: true).ConfigureAwait(false);
var (buckets, earliest, latest, received, overCap) = pass;
if (overCap) throw LimitExceeded(tag, maxWindowRows);
if (received >= maxValues) throw BudgetExhausted(tag, maxWindowRows, requested, maxValues);
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseRawReader.cs b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseRawReader.cs
index 93572869..5491bb4f 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseRawReader.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseRawReader.cs
@@ -126,7 +126,7 @@ internal static class ReverseRawReader
(budget < Math.Max(1, maxTieCluster)
? "the backend's row ceiling (HistorianGateway Historian:ReadLimits:MaxValuesCeiling)."
: "ServerHistorian:MaxTieClusterOverfetch.")),
- ct)
+ ct, useDiscoveryBudgetForGaps: limit > 0)
.ConfigureAwait(false);
return new ReverseRawPage(rows, next.WidthTicks) { Hint = next };
}
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseWalk.cs b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseWalk.cs
index 014c760d..79816766 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseWalk.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/ReverseWalk.cs
@@ -123,13 +123,14 @@ internal static class ReverseWalk
/// What the previous page of the same read carried (default = none).
/// Builds the exception for a timestamp holding more than M rows.
/// Cancellation.
+ /// Use ceiling-sized discovery and retain truncated remainder rows (#696, strict raw backends only).
/// At most rows, newest first, and the hint for the next page.
public static async Task<(List Rows, ReverseWalkHint Next)> WalkAsync(
Func>> read,
Func ticksOf,
IComparer? tieOrder,
DateTime hi, DateTime lo, uint want, int tieBudget, long resolutionTicks, DateTime nowUtc,
- ReverseWalkHint hint, Func tooManyAtOneTimestamp, CancellationToken ct)
+ ReverseWalkHint hint, Func tooManyAtOneTimestamp, CancellationToken ct, bool useDiscoveryBudgetForGaps = false)
{
var resolution = Math.Max(1L, resolutionTicks);
var granularity = Math.Max(Alignment, resolution);
@@ -206,7 +207,8 @@ internal static class ReverseWalk
var segLo = segHi - stopTicks <= w ? stopTicks : segHi - w;
var start = Utc(AlignDown(segLo, granularity));
var end = Utc(AlignUp(segHi + 1, granularity));
- var segBudget = discovering && !probe ? discoveryBudget : pageBudget;
+ var segBudget = (discovering && !probe) || (useDiscoveryBudgetForGaps && (probe || known > 0))
+ ? discoveryBudget : pageBudget;
var cap = segBudget + 2;
IReadOnlyList rows;
var narrowed = false;
@@ -220,10 +222,14 @@ internal static class ReverseWalk
if (probe)
{
- // Deep history below: the probe saw only its oldest rows. Carry on walking from the same segHi.
+ // #696: strict-ceiling discovery retains the rows/density instead of discarding the remainder probe.
probed = true;
- narrowed = true;
- break;
+ if (!useDiscoveryBudgetForGaps)
+ {
+ narrowed = true;
+ break;
+ }
+ probe = false;
}
var leading = 0;
@@ -284,7 +290,7 @@ internal static class ReverseWalk
// Rows exist at lastInner; what lies above it is unknown. Aim at about half the page budget at the
// density the truncated rows showed (their span, not the segment's — it may open on an empty stretch).
var aimed = inner > 1 && lastInner > firstInner
- ? (long)Math.Min((double)(lastInner - firstInner) * (pageBudget / 2.0) / (inner - 1), maxWidth)
+ ? (long)Math.Min((double)(lastInner - firstInner) * ((useDiscoveryBudgetForGaps ? segBudget : pageBudget) / 2.0) / (inner - 1), maxWidth)
: resolution;
known = lastInner;
knownWidth = Math.Max(resolution, aimed);
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/FakeHistorianGatewayClient.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/FakeHistorianGatewayClient.cs
index 5ee232b0..80decb3f 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/FakeHistorianGatewayClient.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/FakeHistorianGatewayClient.cs
@@ -12,6 +12,17 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests;
///
public sealed class FakeHistorianGatewayClient : IHistorianGatewayClient
{
+ public bool TagExistsResult = true;
+ public int TagExistsCallCount;
+ public Exception? TagExistsThrows;
+ public Task TagExistsAsync(string tag, CancellationToken ct)
+ {
+ ct.ThrowIfCancellationRequested();
+ TagExistsCallCount++;
+ if (TagExistsThrows is { } error) throw error;
+ return Task.FromResult(TagExistsResult);
+ }
+
// ---- ReadRaw -------------------------------------------------------------------------------
public IReadOnlyList RawSamples = Array.Empty();
public string? LastReadRawTag;
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayCeilingPagingTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayCeilingPagingTests.cs
index 0ca4db5d..17c5d312 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayCeilingPagingTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayCeilingPagingTests.cs
@@ -385,6 +385,21 @@ public sealed class GatewayCeilingPagingTests : IDisposable
finally { await host.DisposeAsync(); }
}
+ [Fact]
+ public async Task A_stopped_dense_tag_under_a_strict_ceiling_is_found_with_bounded_discovery_cost()
+ {
+ var stored = PerSecond(7200);
+ var fake = Gateway(stored, Ceiling);
+ var ds = new GatewayHistorianDataSource(fake, NullLogger.Instance);
+ await ds.ReadRawAsync("T", At(0), At(1), 5000, Ct);
+ fake.RawCalls.Clear();
+ var page = await ReverseRawReader.ReadAsync(ds, "T", At(7200).AddDays(1), DateTime.UnixEpoch,
+ 3, 65536, At(7200).AddDays(1), 0, Ct);
+ page.Samples.Select(s => s.Value).ShouldBe(new object?[] { 7199d, 7198d, 7197d });
+ fake.RawCalls.Count.ShouldBeLessThanOrEqualTo(12);
+ EveryRequestFits(fake);
+ }
+
// ---- F3: rows crowding the look-back before a page start ---------------------------------------------------------------
[Theory]
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayMissingTagTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayMissingTagTests.cs
new file mode 100644
index 00000000..992ae6fd
--- /dev/null
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayMissingTagTests.cs
@@ -0,0 +1,126 @@
+using Google.Protobuf.WellKnownTypes;
+using Grpc.Core;
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests;
+
+public sealed class GatewayMissingTagTests
+{
+ private static CancellationToken Ct => TestContext.Current.CancellationToken;
+ private static readonly DateTime Now = new(2026, 10, 13, 8, 0, 0, DateTimeKind.Utc);
+ private sealed class Clock : TimeProvider
+ {
+ public DateTime Current = Now;
+ public override DateTimeOffset GetUtcNow() => new(Current);
+ }
+ private static GatewayHistorianDataSource Source(FakeHistorianGatewayClient fake, Clock? clock = null, bool native = false) =>
+ new(fake, NullLogger.Instance, timeProvider: clock, atTimeFromRaw: !native);
+
+ [Theory]
+ [InlineData("Raw")]
+ [InlineData("AtTime")]
+ [InlineData("NativeAtTime")]
+ [InlineData("Count")]
+ [InlineData("TimeAverage")]
+ public async Task A_missing_tag_returns_no_data_without_a_history_RPC(string kind)
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsResult = false };
+ var ds = Source(fake, native: kind == "NativeAtTime");
+ var result = kind switch
+ {
+ "Raw" => await ds.ReadRawAsync("Missing", Now.AddMinutes(-1), Now, 10, Ct),
+ "AtTime" or "NativeAtTime" => await ds.ReadAtTimeAsync("Missing", [Now], Ct),
+ _ => await ds.ReadProcessedAsync("Missing", Now.AddMinutes(-1), Now, TimeSpan.FromMinutes(1),
+ kind == "Count" ? HistoryAggregateType.Count : HistoryAggregateType.TimeAverage, Ct),
+ };
+ if (kind == "Raw") result.Samples.ShouldBeEmpty();
+ else
+ {
+ result.Samples.Count.ShouldBe(1);
+ result.Samples[0].Value.ShouldBeNull();
+ (result.Samples[0].StatusCode & 0xFFFF0000u).ShouldBe(0x809B0000u);
+ result.Samples[0].SourceTimestampUtc.ShouldBe(kind.Contains("AtTime") ? Now : Now.AddMinutes(-1));
+ }
+ fake.TagExistsCallCount.ShouldBe(1);
+ (fake.ReadRawCallCount + fake.ReadAggregateCallCount + fake.ReadAtTimeCallCount).ShouldBe(0);
+ ds.GetHealthSnapshot().TotalFailures.ShouldBe(0);
+ }
+
+ [Fact]
+ public async Task Negative_cache_expires_so_a_newly_provisioned_tag_can_be_read()
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsResult = false };
+ var clock = new Clock(); var ds = Source(fake, clock);
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsResult = true;
+ fake.RawSamples = [new HistorianSample { Timestamp = Timestamp.FromDateTime(Now.AddSeconds(-1)), NumericValue = 42, OpcQuality = 192 }];
+ (await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct)).Samples.ShouldBeEmpty();
+ fake.TagExistsCallCount.ShouldBe(1);
+ clock.Current = Now.AddSeconds(5);
+ (await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct)).Samples.Single().Value.ShouldBe(42d);
+ fake.TagExistsCallCount.ShouldBe(2);
+ }
+
+ [Fact]
+ public async Task Positive_cache_avoids_checks_per_page_and_expires_after_a_minute()
+ {
+ var fake = new FakeHistorianGatewayClient(); var clock = new Clock(); var ds = Source(fake, clock);
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsCallCount.ShouldBe(1);
+ clock.Current = Now.AddSeconds(60);
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsCallCount.ShouldBe(2);
+ }
+
+ [Fact]
+ public async Task An_explicit_nested_NotFound_is_cached_as_missing()
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsThrows = new InvalidOperationException("wrapper",
+ new RpcException(new Status(StatusCode.NotFound, "absent"))) };
+ var ds = Source(fake);
+ (await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct)).Samples.ShouldBeEmpty();
+ (await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct)).Samples.ShouldBeEmpty();
+ fake.TagExistsCallCount.ShouldBe(1);
+ fake.ReadRawCallCount.ShouldBe(0);
+ }
+
+ [Fact]
+ public async Task The_presence_cache_is_bounded_and_a_displaced_entry_is_checked_again()
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsResult = false }; var ds = Source(fake);
+ for (var i = 0; i <= GatewayTagPresenceCache.Capacity; i++)
+ await ds.ReadRawAsync($"T{i}", Now.AddMinutes(-1), Now, 10, Ct);
+ await ds.ReadRawAsync("T0", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsCallCount.ShouldBe(GatewayTagPresenceCache.Capacity + 2);
+ }
+
+ [Fact]
+ public async Task Caller_cancellation_is_not_cached_as_missing()
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsThrows = new OperationCanceledException() }; var ds = Source(fake);
+ await Should.ThrowAsync(() => ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct));
+ fake.TagExistsThrows = null;
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsCallCount.ShouldBe(2);
+ }
+
+ [Theory]
+ [InlineData(StatusCode.Unavailable)]
+ [InlineData(StatusCode.PermissionDenied)]
+ [InlineData(StatusCode.Internal)]
+ public async Task A_metadata_fault_is_not_cached_as_a_missing_tag(StatusCode code)
+ {
+ var fake = new FakeHistorianGatewayClient { TagExistsThrows = new RpcException(new Status(code, "failure")) };
+ var ds = Source(fake);
+ await Should.ThrowAsync(() => ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct));
+ fake.TagExistsThrows = null;
+ await ds.ReadRawAsync("T", Now.AddMinutes(-1), Now, 10, Ct);
+ fake.TagExistsCallCount.ShouldBe(2);
+ fake.ReadRawCallCount.ShouldBe(1);
+ }
+}
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayStrictCeilingTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayStrictCeilingTests.cs
index 2dbd50ae..5b6f0e80 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayStrictCeilingTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayStrictCeilingTests.cs
@@ -57,6 +57,30 @@ public sealed class GatewayStrictCeilingTests
public override DateTimeOffset GetUtcNow() => new(now);
}
+ private sealed class MovingClock : TimeProvider
+ {
+ public DateTime Current = Now;
+ public override DateTimeOffset GetUtcNow() => new(Current);
+ }
+
+ [Fact]
+ public async Task Aggregate_ceiling_re_probes_wait_thirty_seconds_then_notice_a_raised_limit()
+ {
+ var fake = Store(100, ceiling: 50);
+ var clock = new MovingClock();
+ var ds = new GatewayHistorianDataSource(fake, NullLogger.Instance, timeProvider: clock);
+ Task Read() => ds.ReadProcessedAsync("T", At(0), At(100), TimeSpan.FromSeconds(100), HistoryAggregateType.Count, Ct);
+ await Should.ThrowAsync(Read);
+ await Should.ThrowAsync(Read);
+ Refusals(fake).ShouldBe(1);
+ fake.MaxValuesCeiling = 200;
+ await Should.ThrowAsync(Read);
+ Refusals(fake).ShouldBe(1);
+ clock.Current = Now.AddSeconds(30);
+ (await Read()).Samples.Single().Value.ShouldBe(100);
+ ds.MaxRawValuesPerRead.ShouldBe(200 - RawAggregateReader.PreWindowAllowance);
+ }
+
// ---- raw, uncapped ---------------------------------------------------------------------------------------------------
[Fact]
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagCatalogWireTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagCatalogWireTests.cs
new file mode 100644
index 00000000..23fb00f2
--- /dev/null
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayTagCatalogWireTests.cs
@@ -0,0 +1,90 @@
+using System.Net;
+using Grpc.Core;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Server.Kestrel.Core;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
+using ZB.MOM.WW.OtOpcUa.Runtime.Historian;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests;
+
+public sealed class GatewayTagCatalogWireTests
+{
+ private static CancellationToken Ct => TestContext.Current.CancellationToken;
+
+ [Theory]
+ [InlineData("Pump1", true)]
+ [InlineData("Missing", false)]
+ [InlineData("Pump*", false)]
+ public async Task Presence_is_proved_by_exact_names_without_using_the_broken_metadata_parser(string tag, bool expected)
+ {
+ var service = new TagsService();
+ await using var server = await StartAsync(service);
+ using var adapter = Create(server.Port);
+ (await adapter.TagExistsAsync(tag, Ct)).ShouldBe(expected);
+ service.Filter.ShouldBe(tag);
+ service.MetadataCalls.ShouldBe(0);
+ service.Completed.ShouldBe(1);
+ }
+
+ [Fact]
+ public async Task A_catalog_stream_fault_after_a_matching_name_is_not_cached_as_presence()
+ {
+ var service = new TagsService { FailAfterRow = true };
+ await using var server = await StartAsync(service);
+ using var adapter = Create(server.Port);
+ var source = new GatewayHistorianDataSource(adapter, NullLogger.Instance);
+ var now = DateTime.UtcNow;
+ await Should.ThrowAsync(() => source.ReadRawAsync("Pump1", now.AddMinutes(-1), now, 10, Ct));
+ service.FailAfterRow = false; service.Names = [];
+ (await source.ReadRawAsync("Pump1", now.AddMinutes(-1), now, 10, Ct)).Samples.ShouldBeEmpty();
+ service.BrowseCalls.ShouldBe(2);
+ }
+
+ private static HistorianGatewayClientAdapter Create(int port) => HistorianGatewayClientAdapter.Create(
+ new ServerHistorianOptions { Endpoint = $"http://127.0.0.1:{port}", ApiKey = "histgw_test_key", UseTls = false },
+ NullLoggerFactory.Instance);
+
+ private sealed class TagsService : HistorianTags.HistorianTagsBase
+ {
+ public int MetadataCalls, BrowseCalls, Completed;
+ public string? Filter;
+ public bool FailAfterRow;
+ public string[] Names = ["Pump1", "Pump2"];
+ public override Task GetTagMetadata(GetTagMetadataRequest request, ServerCallContext context)
+ {
+ MetadataCalls++;
+ throw new RpcException(new Status(StatusCode.Internal, "GetTagInfo response ended unexpectedly."));
+ }
+ public override async Task BrowseTagNames(BrowseTagNamesRequest request, IServerStreamWriter stream, ServerCallContext context)
+ {
+ BrowseCalls++; Filter = request.Filter;
+ foreach (var name in Names)
+ {
+ await stream.WriteAsync(new TagName { Name = name }, context.CancellationToken);
+ if (FailAfterRow) throw new RpcException(new Status(StatusCode.Internal, "catalog failure"));
+ }
+ Completed++;
+ }
+ }
+
+ private sealed class Server(WebApplication app, int port) : IAsyncDisposable
+ {
+ public int Port => port;
+ public async ValueTask DisposeAsync() { await app.StopAsync(); await app.DisposeAsync(); }
+ }
+ private static async Task StartAsync(TagsService service)
+ {
+ var builder = WebApplication.CreateSlimBuilder();
+ builder.Logging.ClearProviders();
+ builder.WebHost.ConfigureKestrel(k => k.Listen(IPAddress.Loopback, 0, o => o.Protocols = HttpProtocols.Http2));
+ builder.Services.AddGrpc(); builder.Services.AddSingleton(service);
+ var app = builder.Build(); app.MapGrpcService(); await app.StartAsync();
+ return new Server(app, new Uri(app.Urls.First()).Port);
+ }
+}