fix(historian): #694 page raw reads at a strict gateway's learned ceiling; opt-in EventReadHorizon

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.
2026-10-13 00:52:12 -04:00
parent a5a0496176
commit 3c3513ea3e
23 changed files with 1461 additions and 79 deletions
@@ -94,4 +94,19 @@ public sealed class HistorianDataSourceReverseEventsGuardTests
                $"{type.FullName} must declare SupportedAggregates itself, not inherit the interface default");
        }
    }
+
+    [Fact]
+    public void Every_implementation_declares_its_raw_page_limit_itself()
+    {
+        // Gitea #694: the default (0 = no limit) is what a strict-ceiling Gateway must NOT report — a wrapper that inherited
+        // it would bring back BadTooManyOperations for every page larger than the gateway's ceiling.
+        foreach (var type in ProductionImplementations())
+        {
+            var map = type.GetInterfaceMap(typeof(IHistorianDataSource));
+            var getter = map.TargetMethods[Array.FindIndex(map.InterfaceMethods,
+                m => m.Name == "get_" + nameof(IHistorianDataSource.MaxRawValuesPerRead))];
+            getter.DeclaringType.ShouldBe(type,
+                $"{type.FullName} must declare MaxRawValuesPerRead itself, not inherit the interface default");
+        }
+    }
 }