Joseph Doherty
65 lines
3.5 KiB
C#
65 lines
3.5 KiB
C#
using ZB.MOM.WW.OtOpcUa.Commons.Observability;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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namespace ZB.MOM.WW.OtOpcUa.Runtime.Historian;
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/// <summary>
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/// Observable-gauge instruments for the continuous-historization durable outbox, hung off the
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/// central <see cref="OtOpcUaTelemetry.Meter"/> (the same meter the Host's OpenTelemetry /
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/// Prometheus binding already scrapes), so no extra meter allowlist entry is needed.
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/// <para>
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/// The gauges read the bound outbox directly rather than Ask-ing the recorder actor: an
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/// <c>Ask</c> inside a synchronous observable-gauge callback would block the metrics-collection
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/// thread on the actor mailbox. The outbox exposes both gauge sources cheaply and
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/// non-blockingly — <see cref="IHistorizationOutbox.CountAsync"/> completes synchronously (it
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/// just reads an in-memory FIFO count) and <see cref="IHistorizationOutbox.DroppedCount"/> is a
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/// plain property. The recorder's other counters (TotalRecorded / DroppedUnsupportedKind /
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/// OutboxAppendFailures) remain available via its <c>GetStatus</c> Ask for a health hook, but are
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/// not surfaced as gauges here (Ask-in-gauge is the awkward path the plan calls out).
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/// </para>
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/// </summary>
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public static class ContinuousHistorizationMetrics
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{
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private static volatile IHistorizationOutbox? _outbox;
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static ContinuousHistorizationMetrics()
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{
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// Registered once on first touch (i.e. when BindOutbox is first called at host start). Instruments
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// are no-op until a listener attaches, so an unbound process pays nothing; the callbacks are
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// null-safe and return 0 until BindOutbox supplies the live outbox.
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OtOpcUaTelemetry.Meter.CreateObservableGauge(
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"otopcua.historization.outbox.depth",
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ObserveDepth,
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unit: "{entry}",
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description: "Un-acked entries currently held in the continuous-historization durable outbox.");
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OtOpcUaTelemetry.Meter.CreateObservableGauge(
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"otopcua.historization.outbox.dropped",
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ObserveDropped,
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unit: "{entry}",
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description: "Lifetime entries the continuous-historization outbox dropped on capacity overflow.");
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OtOpcUaTelemetry.Meter.CreateObservableGauge(
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"otopcua.historian.outbox.unreadable",
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() => _outbox?.UnreadableCount ?? 0L,
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unit: "{entry}",
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description: "Lifetime undecodable records the continuous-historization outbox skipped.");
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}
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/// <summary>Binds the process outbox the gauges observe. Called once by the Host when continuous
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/// historization is enabled; subsequent calls re-point the gauges (idempotent in practice).</summary>
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/// <param name="outbox">The durable outbox the recorder drains.</param>
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public static void BindOutbox(IHistorizationOutbox outbox)
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=> _outbox = outbox ?? throw new ArgumentNullException(nameof(outbox));
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private static long ObserveDepth()
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{
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IHistorizationOutbox? outbox = _outbox;
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if (outbox is null) return 0L;
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// CountAsync over the FasterLog outbox completes synchronously (in-memory FIFO count); read the
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// already-completed result without blocking. A (theoretical) pending result reports 0 this scrape.
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ValueTask<int> pending = outbox.CountAsync(CancellationToken.None);
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return pending.IsCompletedSuccessfully ? pending.Result : 0L;
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}
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private static long ObserveDropped() => _outbox?.DroppedCount ?? 0L;
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}
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