Joseph Doherty
45 lines
2.2 KiB
C#
45 lines
2.2 KiB
C#
namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
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/// <summary>
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/// Flow Debugger step logs (design 2026-09-09 D6): the ambient "which step is running right now"
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/// marker used to attribute runtime-sourced log lines to a step node.
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///
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/// <para>A <c>ScriptLog</c> row names its owning step explicitly (D2), but the runtime lines the
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/// node logs on the script's behalf are produced deep inside a helper — the helper knows its
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/// pre-minted step <c>EventId</c>, the logging call site does not. Rather than thread that id
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/// through every internal call, the helpers open a scope around their body and
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/// <see cref="ScriptLogger"/> reads <see cref="Current"/> when no explicit id is supplied.</para>
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///
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/// <para><see cref="AsyncLocal{T}"/> so the value flows through the helper's own awaits and
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/// nowhere else: it is captured by continuations started inside the scope and is invisible to
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/// concurrent runs on other threads of the script execution pool. Lines logged outside any scope
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/// see <see langword="null"/> and fall back to the execution's anchor row (D2).</para>
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/// </summary>
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public static class TraceStepScope
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{
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private static readonly AsyncLocal<Guid?> _current = new();
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/// <summary>The step <c>EventId</c> owning the currently executing helper body, or <see langword="null"/> outside any scope.</summary>
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public static Guid? Current => _current.Value;
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/// <summary>
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/// Sets the current step for the scope's lifetime; restores the previous value on dispose,
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/// so nested scopes (a helper calling another helper) unwind correctly.
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/// </summary>
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/// <param name="stepEventId">The pre-minted <c>EventId</c> of the step row this body belongs to.</param>
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/// <returns>A handle that restores the previous ambient value when disposed.</returns>
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public static IDisposable Enter(Guid stepEventId)
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{
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var prev = _current.Value;
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_current.Value = stepEventId;
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return new Restore(prev);
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}
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/// <summary>Restores the ambient step id captured at <see cref="Enter"/> time.</summary>
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private sealed class Restore(Guid? prev) : IDisposable
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{
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/// <inheritdoc />
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public void Dispose() => _current.Value = prev;
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}
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}
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