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fix(historian): #691.5 a reverse walk proves the rest empty once and carries it page to page

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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.
This commit is contained in:
Joseph Doherty
2026-10-12 16:32:00 -04:00
parent d33992034d
commit 186b7d5ea5
7 changed files with 222 additions and 29 deletions
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src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/OtOpcUaNodeManager.cs
+8 -6
View File
@@ -6184,7 +6184,7 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
{
DateTime startUtc;
var boundarySkip = 0;
long segmentWidth = 0; // #686: the walk-back's width, carried page to page
var walkHint = default(ReverseWalkHint); // #686/#689/#691: the walk-back's width + proven-empty stretch, page to page
string tagname;
if (inboundCp is { Length: > 0 })
@@ -6205,7 +6205,7 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
boundarySkip = state.BoundarySkipCount;
endUtc = state.EndUtc;
numValuesPerNode = state.NumValuesPerNode;
segmentWidth = state.SegmentWidthTicks;
walkHint = state.WalkHint;
}
else
{
@@ -6243,9 +6243,9 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
{
var page = await ReverseRawReader.ReadAsync(
source, tagname, startUtc, endUtc, numValuesPerNode, MaxTieClusterOverfetch,
Clock.GetUtcNow().UtcDateTime, segmentWidth, ct)
Clock.GetUtcNow().UtcDateTime, walkHint, ct)
.ConfigureAwait(false);
segmentWidth = page.WidthHintTicks;
walkHint = page.Hint;
sourceResult = new HistorianRead(page.Samples, ContinuationPoint: null);
}
else
@@ -6324,7 +6324,8 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
if (nextStartUtc is { } resumeAt)
{
var clusterState = new HistoryContinuationState(
tagname, resumeAt, endUtc, nextSkip, numValuesPerNode, SegmentWidthTicks: segmentWidth);
tagname, resumeAt, endUtc, nextSkip, numValuesPerNode, SegmentWidthTicks: walkHint.WidthTicks,
EmptyFromTicks: walkHint.EmptyFromTicks, EmptyToTicks: walkHint.EmptyToTicks);
clusterCp = _historyContinuationStore.Save(session, clusterState);
}
@@ -6347,7 +6348,8 @@ public sealed class OtOpcUaNodeManager : CustomNodeManager2
{
HistoryPaging.ComputeResumeCursor(samples, out var nextStart, out var skip);
var nextState = new HistoryContinuationState(
tagname, nextStart, endUtc, skip, numValuesPerNode, SegmentWidthTicks: segmentWidth);
tagname, nextStart, endUtc, skip, numValuesPerNode, SegmentWidthTicks: walkHint.WidthTicks,
EmptyFromTicks: walkHint.EmptyFromTicks, EmptyToTicks: walkHint.EmptyToTicks);
// Save may return null (no session on this request) ⇒ degrade to single-shot for this node.
// Built AFTER historyData so a failure projecting samples can never orphan a stored cursor.
outboundCp = _historyContinuationStore.Save(session, nextState);