Joseph Doherty
d28e3e64f1
Bisecting the gap above a truncated read halved below the 1 ms request granularity (requests are ms-rounded, so it re-sent identical requests) and bisected the WHOLE gap even when the burst ended right above the row it saw: a 1,026-row burst ending 100 days ago took 46 reads. After an empty top-anchored segment the walk now gallops up from the known row ((known + d, top], d x4, following each truncated read), then bisects the bracket, with halving floored at the granularity (the Min kept; a crowded gallop falls back to top-anchored halving). Burst: 18 reads, 0 repeated requests; dense tag stopped 2 days ago: 26 (gallop alone crawled: 94). Walk fuzzed at 4,000 seeds locally (400 in-tree). Docs: measured counts; CLAUDE.md gateway prerequisites list RuntimeDb:EventReadMaxRows.
296 lines
16 KiB
C#
296 lines
16 KiB
C#
using Opc.Ua;
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using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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using HistorianRead = ZB.MOM.WW.OtOpcUa.Core.Abstractions.HistoryReadResult;
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namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;
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/// <summary>
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/// Gitea #689 / #691: the reverse walk-back (<see cref="ReverseWalk"/> through <see cref="ReverseRawReader"/>) driven
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/// directly, without a server: a randomized exactness check against a brute-force answer, and the sizing properties.
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/// </summary>
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public sealed class ReverseWalkTests
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{
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private static CancellationToken Ct => TestContext.Current.CancellationToken;
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private static readonly DateTime T0 = new(2026, 10, 12, 18, 0, 0, DateTimeKind.Utc);
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private static DataValueSnapshot At(long ticks, double v) =>
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new(v, StatusCodes.Good, new DateTime(ticks, DateTimeKind.Utc), new DateTime(ticks, DateTimeKind.Utc));
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/// <summary>
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/// A randomized walk over AVEVA-shaped forward reads (inclusive end, a fabricated row at the query start — optionally
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/// stamped at the start rounded UP to the millisecond — counted against the cap): every page is exactly the brute-force
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/// newest-first answer over <c>(lo, hi]</c>, ties in the backend's forward order reversed, whatever the carried width
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/// — and a timestamp over the tie budget is the only refusal.
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/// </summary>
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[Fact]
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public async Task A_walked_page_is_exactly_the_newest_N_over_the_window_on_random_data()
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{
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var failures = new List<string>();
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for (var seed = 0; seed < 400; seed++)
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{
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var rng = new Random(seed);
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var series = RandomSeries(rng, out var maxCluster);
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var source = new AvevaShapedSource(series, roundUp: rng.Next(2) == 0);
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var tieBudget = rng.Next(4) switch { 0 => 1, 1 => 3, 2 => 8, _ => 65536 };
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var want = (uint)rng.Next(1, 40);
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var span = Ts(series[^1]) - Ts(series[0]);
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var hi = Ts(series[0]) + (long)(rng.NextDouble() * 1.2 * span) + rng.Next(0, 3);
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var lo = Ts(series[0]) - TimeSpan.TicksPerSecond + (long)(rng.NextDouble() * (hi - Ts(series[0])) * 0.8);
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if (rng.Next(5) == 0) lo = 0; // an end-only read
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var hint = rng.Next(3) switch
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{
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0 => default,
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1 => new ReverseWalkHint(rng.Next(1, 10)),
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_ => new ReverseWalkHint((long)(rng.NextDouble() * TimeSpan.TicksPerHour)),
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};
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if (rng.Next(2) == 0)
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{
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// A TRUE empty stretch (#691): between two adjacent distinct timestamps, or from the floor to the first row.
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var k = rng.Next(series.Count);
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var from = k == 0 ? (rng.Next(2) == 0 ? 0 : DateTime.UnixEpoch.Ticks) : Ts(series[k - 1]);
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var to = Ts(series[k]);
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if (to > from) hint = hint with { EmptyFromTicks = from, EmptyToTicks = to };
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}
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// Page on: each next page resumes just below the previous page's oldest timestamp with the hint it returned —
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// so the hints the walk itself produces (width, proven-empty stretch) are exercised too.
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for (var pageNo = 0; pageNo < 6 && hi > Math.Max(lo, DateTime.UnixEpoch.Ticks); pageNo++)
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{
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var expected = series.Where(s => Ts(s) > Math.Max(lo, DateTime.UnixEpoch.Ticks) && Ts(s) <= hi)
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.Select((s, i) => (s, i)).OrderByDescending(x => Ts(x.s)).ThenByDescending(x => x.i)
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.Take((int)want).Select(x => (double)x.s.Value!).ToList();
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try
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{
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var page = await ReverseRawReader.ReadAsync(source, "T", new DateTime(hi, DateTimeKind.Utc),
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new DateTime(lo, DateTimeKind.Utc), want, tieBudget, T0.AddDays(1), hint, Ct);
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var got = page.Samples.Select(s => (double)s.Value!).ToList();
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if (!got.SequenceEqual(expected))
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{
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failures.Add($"seed {seed} page {pageNo}: got [{string.Join(",", got)}] expected [{string.Join(",", expected)}]");
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break;
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}
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if (page.Hint.WidthTicks <= 0) failures.Add($"seed {seed}: no width carried");
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if (got.Count < want) break;
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hint = page.Hint;
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hi = Ts(page.Samples[^1]) - 1;
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}
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catch (HistoryReadLimitExceededException)
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{
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if (maxCluster <= tieBudget) failures.Add($"seed {seed}: refused with no cluster over {tieBudget} (max {maxCluster})");
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break;
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}
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}
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if (source.MaxCap > 2L * Math.Max(Math.Max(tieBudget, ReverseWalk.DiscoveryRows), 2 * want + 16) + 4)
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failures.Add($"seed {seed}: asked for {source.MaxCap} rows");
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if (source.BadRequests > 0) failures.Add($"seed {seed}: {source.BadRequests} invalid requests");
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}
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failures.ShouldBeEmpty();
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}
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/// <summary>
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/// #689: the carried width sizes a resumed page from N, not from the tie budget — the live symptom was 32,770 rows
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/// per page for N = 3 on a 1 Hz tag once the width had grown over a few pages.
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/// </summary>
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[Fact]
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public async Task A_resumed_page_on_a_dense_tag_reads_about_N_rows_with_the_default_tie_budget()
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{
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var series = Enumerable.Range(0, 200_000).Select(i => At(T0.Ticks + i * TimeSpan.TicksPerSecond, i)).ToList();
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var source = new AvevaShapedSource(series);
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var hi = new DateTime(Ts(series[^1]), DateTimeKind.Utc);
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var hint = default(ReverseWalkHint);
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for (var page = 1; page <= 30; page++)
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{
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source.Reset();
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var result = await ReverseRawReader.ReadAsync(source, "T", hi, DateTime.MinValue, 3, 65536, hi.AddHours(1), hint, Ct);
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result.Samples.Count.ShouldBe(3);
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hint = result.Hint;
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hi = result.Samples[^1].SourceTimestampUtc!.Value.AddTicks(-1);
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if (page > 1) source.RowsReturned.ShouldBeLessThanOrEqualTo(30, $"page {page}");
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}
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}
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/// <summary>
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/// #689: a dense tag that stopped long ago. The walk's ×4 growth across the empty stretch overshoots into far more
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/// rows than one read takes; the truncated read only shows the OLDEST of them, so the walk must not keep re-entering
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/// that stretch — it searches the gap above the newest row it saw (gallop up, then bisect). Measured: 26 reads.
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/// </summary>
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[Fact]
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public async Task A_dense_tag_below_a_long_empty_stretch_is_found_in_a_bounded_number_of_reads()
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{
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// 10 Hz for 3 hours, ending two days before "now".
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var start = T0.AddDays(-2).AddHours(-3);
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var series = Enumerable.Range(0, 108_000).Select(i => At(start.Ticks + i * TimeSpan.TicksPerMillisecond * 100, i)).ToList();
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var source = new AvevaShapedSource(series);
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var page = await ReverseRawReader.ReadAsync(source, "T", T0, DateTime.MinValue, 3, 65536, T0, default(ReverseWalkHint), Ct);
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page.Samples.Select(s => (double)s.Value!).ShouldBe([107_999d, 107_998d, 107_997d]);
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source.Reads.ShouldBeLessThanOrEqualTo(30);
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source.RowsReturned.ShouldBeLessThanOrEqualTo(30 * (ReverseWalk.DiscoveryRows + 2));
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}
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/// <summary>
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/// #691: the end of a walk proves the rest of the window empty in about one read — after two empty segments the walk
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/// asks once for the whole remainder down to the floor — instead of one read per ×4 growth step to 1970 (~14 reads).
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/// </summary>
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[Fact]
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public async Task Running_out_of_rows_proves_the_rest_of_the_window_empty_in_a_few_reads()
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{
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var series = Enumerable.Range(0, 5).Select(i => At(T0.Ticks + i * TimeSpan.TicksPerSecond, i)).ToList();
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var source = new AvevaShapedSource(series);
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var page = await ReverseRawReader.ReadAsync(source, "T", T0.AddSeconds(4), DateTime.MinValue, 10, 65536, T0,
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default(ReverseWalkHint), Ct);
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page.Samples.Select(s => (double)s.Value!).ShouldBe([4d, 3d, 2d, 1d, 0d]);
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source.Reads.ShouldBeLessThanOrEqualTo(4, "one segment holding the rows, two empty ones, then the remainder at once");
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}
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/// <summary>
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/// #691: a page's last complete read proves the stretch below its oldest row empty, and the continuation carries it:
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/// the next page steps straight over it to the floor instead of walking it again.
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/// </summary>
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[Fact]
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public async Task A_resumed_page_steps_over_the_stretch_the_previous_page_proved_empty()
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{
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var series = Enumerable.Range(0, 25).Select(i => At(T0.Ticks + i * TimeSpan.TicksPerSecond, i)).ToList();
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var source = new AvevaShapedSource(series);
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var now = T0.AddHours(1);
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// Page 1: an hour of nothing above the rows; the remainder probe reads all 25 and proves (1970, row 0) empty.
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var p1 = await ReverseRawReader.ReadAsync(source, "T", now, DateTime.MinValue, 10, 65536, now, default(ReverseWalkHint), Ct);
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p1.Samples.Select(s => (double)s.Value!).ShouldBe(Enumerable.Range(15, 10).Reverse().Select(i => (double)i));
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p1.Hint.HasEmptyStretch.ShouldBeTrue();
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p1.Hint.EmptyFromTicks.ShouldBeLessThanOrEqualTo(DateTime.UnixEpoch.Ticks);
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p1.Hint.EmptyToTicks.ShouldBe(Ts(series[0]));
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var hint = p1.Hint;
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var hi = p1.Samples[^1].SourceTimestampUtc!.Value.AddTicks(-1);
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for (var page = 2; page <= 3; page++)
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{
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source.Reset();
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var p = await ReverseRawReader.ReadAsync(source, "T", hi, DateTime.MinValue, 10, 65536, now, hint, Ct);
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p.Samples.Count.ShouldBe(page == 2 ? 10 : 5);
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source.Reads.ShouldBe(1, $"page {page} reads its rows and steps over the proven-empty stretch to the floor");
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hint = p.Hint;
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hi = p.Samples[^1].SourceTimestampUtc!.Value.AddTicks(-1);
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}
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}
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/// <summary>
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/// #691.4 review: a burst just over the discovery read, sub-millisecond spaced, ending 100 days ago. The search for
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/// the top of the burst above the truncated read never re-sends an identical request (halving below the 1 ms request
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/// granularity did), and gallops up from the truncated read's newest row instead of bisecting the whole 100-day gap
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/// down to the millisecond (was 46 reads).
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/// </summary>
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[Fact]
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public async Task Bisecting_above_a_truncated_read_never_resends_an_identical_request()
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{
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var end = T0.AddDays(-100);
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var count = ReverseWalk.DiscoveryRows + 2;
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var series = Enumerable.Range(0, count).Select(i => At(end.Ticks - (count - 1 - i) * 1_000, i)).ToList(); // 0.1 ms apart
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var source = new AvevaShapedSource(series);
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var page = await ReverseRawReader.ReadAsync(source, "T", T0, DateTime.MinValue, 3, 65536, T0, default(ReverseWalkHint), Ct);
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page.Samples.Select(s => (double)s.Value!).ShouldBe([count - 1d, count - 2d, count - 3d]);
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source.RepeatedRequests.ShouldBe(0, string.Join("\n", source.Log));
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source.Reads.ShouldBeLessThanOrEqualTo(22, string.Join("\n", source.Log));
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}
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private static long Ts(DataValueSnapshot s) => s.SourceTimestampUtc!.Value.Ticks;
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/// <summary>Random ascending series: bursts, gaps, sub-millisecond stamps and tie clusters.</summary>
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private static List<DataValueSnapshot> RandomSeries(Random rng, out int maxCluster)
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{
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var list = new List<DataValueSnapshot>();
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var t = T0.Ticks - rng.Next(0, 3) * TimeSpan.TicksPerDay;
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var count = rng.Next(1, 400);
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maxCluster = 1;
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var v = 0;
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while (list.Count < count)
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{
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t += rng.Next(6) switch
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{
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0 => rng.Next(1, 10), // sub-millisecond
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1 => rng.Next(1, 5) * TimeSpan.TicksPerMillisecond, // dense
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2 => rng.Next(1, 3) * TimeSpan.TicksPerSecond,
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3 => rng.Next(1, 120) * TimeSpan.TicksPerMinute, // a gap
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_ => rng.Next(1, 1000) * TimeSpan.TicksPerMillisecond,
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};
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var ties = rng.Next(8) == 0 ? rng.Next(2, 12) : 1;
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maxCluster = Math.Max(maxCluster, ties);
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for (var k = 0; k < ties; k++) list.Add(At(t, v++));
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}
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return list;
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}
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/// <summary>AVEVA-shaped forward-only raw source (see the fuzz test's summary).</summary>
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private sealed class AvevaShapedSource(IReadOnlyList<DataValueSnapshot> series, bool roundUp = false) : IHistorianDataSource
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{
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public long MaxCap { get; private set; }
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public long RowsReturned { get; private set; }
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public int Reads { get; private set; }
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public int BadRequests { get; private set; }
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/// <summary>Requests that repeated an earlier request exactly (start, end, cap) — read-only, so pure waste.</summary>
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public int RepeatedRequests { get; private set; }
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private readonly HashSet<(DateTime, DateTime, uint)> _seen = [];
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/// <summary>Every request, for failure messages.</summary>
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public List<string> Log { get; } = [];
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public void Reset() { MaxCap = 0; RowsReturned = 0; Reads = 0; RepeatedRequests = 0; _seen.Clear(); Log.Clear(); }
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public bool SupportsReverseRaw => false;
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public Task<HistorianRead> ReadRawAsync(string fullReference, DateTime startUtc, DateTime endUtc, uint maxValuesPerNode,
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CancellationToken cancellationToken)
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{
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Reads++;
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if (!_seen.Add((startUtc, endUtc, maxValuesPerNode))) RepeatedRequests++;
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Log.Add($"[{startUtc:O} .. {endUtc:O}] cap {maxValuesPerNode}");
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if (startUtc > endUtc || maxValuesPerNode == 0 || startUtc < DateTime.UnixEpoch) BadRequests++;
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MaxCap = Math.Max(MaxCap, maxValuesPerNode);
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var stamp = roundUp && startUtc.Ticks % TimeSpan.TicksPerMillisecond != 0
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? new DateTime(startUtc.Ticks - startUtc.Ticks % TimeSpan.TicksPerMillisecond + TimeSpan.TicksPerMillisecond, DateTimeKind.Utc)
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: startUtc;
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var prior = series.LastOrDefault(s => s.SourceTimestampUtc <= startUtc);
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var rows = new List<DataValueSnapshot>
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{
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prior is null
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? new DataValueSnapshot(-1d, StatusCodes.BadNoData, stamp, stamp)
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: new DataValueSnapshot(-2d, prior.StatusCode, stamp, stamp),
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};
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rows.AddRange(series.Where(s => s.SourceTimestampUtc >= startUtc && s.SourceTimestampUtc <= endUtc));
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var page = rows.Take((int)Math.Min(int.MaxValue, maxValuesPerNode)).ToList();
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RowsReturned += page.Count;
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return Task.FromResult(new HistorianRead(page, null));
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}
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public Task<HistorianRead> ReadProcessedAsync(string fullReference, DateTime startUtc, DateTime endUtc, TimeSpan interval,
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HistoryAggregateType aggregate, CancellationToken cancellationToken) => throw new NotSupportedException();
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public Task<HistorianRead> ReadAtTimeAsync(string fullReference, IReadOnlyList<DateTime> timestampsUtc,
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CancellationToken cancellationToken) => throw new NotSupportedException();
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public Task<HistoricalEventsResult> ReadEventsAsync(string? sourceName, DateTime startUtc, DateTime endUtc, int maxEvents,
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CancellationToken cancellationToken) => throw new NotSupportedException();
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public HistorianHealthSnapshot GetHealthSnapshot() => NullHistorianDataSource.Instance.GetHealthSnapshot();
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public void Dispose() { }
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}
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}
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