Joseph Doherty
78 lines
3.9 KiB
C#
78 lines
3.9 KiB
C#
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Health;
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namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring;
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/// <summary>
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/// In-memory state for a single site's health, stored by the central aggregator.
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/// Immutable: every state transition produces a new instance which the aggregator
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/// installs into its <c>ConcurrentDictionary</c> via an atomic compare-and-swap.
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/// This makes handing the reference straight to UI callers safe — a consumer can
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/// never observe a torn or half-applied update.
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/// </summary>
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public sealed record SiteHealthState
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{
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/// <summary>Gets the unique identifier of the site this state record belongs to.</summary>
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public required string SiteId { get; init; }
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/// <summary>
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/// The latest full <see cref="SiteHealthReport"/> received for the site, or
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/// <c>null</c> if the site is known only via heartbeats and has not yet sent
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/// a report.
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/// </summary>
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public SiteHealthReport? LatestReport { get; init; }
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/// <summary>
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/// Time the latest full <see cref="SiteHealthReport"/> was processed, or
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/// <c>null</c> if the site is known only via heartbeats and has not yet sent
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/// a report. Used by the UI to surface report staleness during failover;
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/// the <c>null</c> case must be rendered as "no report yet" rather than as a
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/// timestamp (a <c>default</c> sentinel would display as year-0001).
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/// </summary>
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public DateTimeOffset? LastReportReceivedAt { get; init; }
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/// <summary>
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/// Time the most recent signal of any kind (full report OR heartbeat) was
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/// received. Drives offline detection — heartbeats from the standby keep the
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/// site marked online even when the active node is unable to produce a report
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/// (mid-failover, brief stalls). Heartbeat cadence is owned by the Cluster
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/// Infrastructure / SiteCommunicationActor (every
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/// CommunicationOptions.TransportHeartbeatInterval — 5s by default).
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/// </summary>
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public DateTimeOffset LastHeartbeatAt { get; init; }
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/// <summary>
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/// Gets the instant this site was first observed by the aggregator (via a
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/// report or a heartbeat); <c>null</c> only for states not built by the
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/// aggregator (hand-constructed fixtures). Anchors metrics-staleness for a
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/// site that has NEVER delivered a report (review 01 round-2 N3): with
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/// <see cref="LastReportReceivedAt"/> null the staleness check previously
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/// skipped the site forever. <see cref="LastHeartbeatAt"/> cannot anchor
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/// this — every heartbeat advances it.
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/// </summary>
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public DateTimeOffset? FirstSeenAt { get; init; }
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/// <summary>Gets the sequence number of the last accepted health report, used to reject out-of-order duplicates.</summary>
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public long LastSequenceNumber { get; init; }
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/// <summary>Gets a value indicating whether the site is currently considered online.</summary>
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public bool IsOnline { get; init; }
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/// <summary>
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/// Gets a value indicating whether the site is online (heartbeats still
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/// arriving) but has sent no full <see cref="SiteHealthReport"/> within
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/// <see cref="HealthMonitoringOptions.MetricsStaleTimeout"/>. This is a signal
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/// <em>distinct</em> from liveness: a site whose HealthReportSender died keeps
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/// heartbeating and would otherwise show "online with frozen metrics forever".
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/// Cleared whenever a fresh report is processed. Heartbeats never set or clear
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/// it — they say nothing about the metrics pipeline.
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/// </summary>
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public bool IsMetricsStale { get; init; }
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/// <summary>
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/// Gets the instant of the last online↔offline flip, or <c>null</c> if the
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/// site has never changed status since it was first observed. Answers "when
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/// did this site drop / come back". Not moved by report/heartbeat traffic that
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/// leaves the online/offline status unchanged, nor by the metrics-stale flag.
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/// </summary>
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public DateTimeOffset? LastStatusChangeAt { get; init; }
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}
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