Joseph Doherty
57ae69a05e
R08 1.4: raw and modified history reads share HistoryReadPaging. A read stopped by the caller's cap releases the server continuation point. The raw path also passed releaseContinuationPoints = (cp != null), which released page two instead of reading it, so every raw read was silently truncated to its first server page. R08 1.5: DefaultSubscriptionAdapter removes its Subscription from the SDK Session on delete/dispose (and a failed CreateAsync removes it too), so re-targeted alarm subscriptions no longer accumulate in Session.Subscriptions. Refs #747 Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
67 lines
3.3 KiB
C#
67 lines
3.3 KiB
C#
using Opc.Ua;
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using Serilog;
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namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
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/// <summary>
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/// The client-side HistoryRead paging loop shared by the raw and modified reads. Continuation pages are
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/// READ (<c>releaseContinuationPoints = false</c>) while the caller still wants values; a read stopped by the
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/// caller's own cap while the server still holds a cursor releases that cursor so it does not occupy one of the
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/// session's continuation-point slots until eviction.
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/// </summary>
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internal static class HistoryReadPaging
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{
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private static readonly ILogger Logger = Log.ForContext(typeof(HistoryReadPaging));
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/// <summary>Reads (or, with <paramref name="releaseContinuationPoints"/>, releases) one page.</summary>
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/// <param name="continuationPoint">The cursor to resume, or <see langword="null"/> for the first page.</param>
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/// <param name="releaseContinuationPoints"><see langword="true"/> to release the cursor instead of reading.</param>
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/// <param name="ct">The caller's cancellation token.</param>
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/// <returns>The per-node result, or <see langword="null"/> when the response carried none.</returns>
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public delegate Task<HistoryReadResult?> PageReader(
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byte[]? continuationPoint, bool releaseContinuationPoints, CancellationToken ct);
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/// <summary>Reads pages until the server finishes or the caller's cap is reached.</summary>
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/// <typeparam name="T">The element type extracted from each page.</typeparam>
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/// <param name="readPage">Issues one HistoryRead for the single node.</param>
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/// <param name="extract">Extracts the page's elements from a result.</param>
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/// <param name="maxValues">The caller's cap; <c><= 0</c> means no cap (follow every continuation point).</param>
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/// <param name="nodeId">The node being read, for refusal messages.</param>
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/// <param name="ct">The caller's cancellation token.</param>
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/// <returns>Every element read.</returns>
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/// <exception cref="ServiceResultException">A page was refused (see <see cref="HistoryReadStatus"/>).</exception>
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public static async Task<List<T>> ReadAllAsync<T>(
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PageReader readPage, Func<HistoryReadResult, IEnumerable<T>> extract, int maxValues, NodeId nodeId,
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CancellationToken ct)
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{
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var all = new List<T>();
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byte[]? continuationPoint = null;
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while (true)
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{
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var result = await readPage(continuationPoint, false, ct).ConfigureAwait(false);
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if (result == null) return all;
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HistoryReadStatus.ThrowIfRefused(result.StatusCode, nodeId);
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all.AddRange(extract(result));
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continuationPoint = result.ContinuationPoint;
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if (continuationPoint is not { Length: > 0 }) return all;
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if (maxValues > 0 && all.Count >= maxValues) break;
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}
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// Stopped by the client's own cap: the server still holds a cursor for this session. Release it; failing to
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// is not worth failing a read whose values are already in hand.
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try
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{
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await readPage(continuationPoint, true, ct).ConfigureAwait(false);
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}
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catch (Exception ex) when (ex is not OperationCanceledException)
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{
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Logger.Warning(ex, "Releasing the HistoryRead continuation point for {NodeId} failed", nodeId);
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}
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return all;
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}
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}
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