worker(alarms): route ForcedMode/watch-list/failover via AlarmCommandHandler; emit provider-mode-changed event
This commit is contained in:
Joseph Doherty
@@ -37,8 +37,14 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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private readonly MxAccessEventQueue eventQueue;
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private readonly Func<IMxAccessAlarmConsumer> consumerFactory;
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private readonly Action? threadAffinityCheck;
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private readonly IMxAccessComObjectFactory? comFactory;
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private readonly Func<IReadOnlyList<AlarmSubtagTarget>, IMxAccessAlarmConsumer>? standbyFactory;
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private readonly MxAccessEventMapper mapper = new MxAccessEventMapper();
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private readonly object syncRoot = new object();
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private AlarmDispatcher? dispatcher;
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private FailoverAlarmConsumer? failoverConsumer;
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private EventHandler<AlarmProviderModeChange>? providerModeChangedHandler;
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private string subscribeSessionId = string.Empty;
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private bool disposed;
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/// <summary>Initializes a new alarm command handler with the given event queue.</summary>
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@@ -79,10 +85,49 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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MxAccessEventQueue eventQueue,
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Func<IMxAccessAlarmConsumer> consumerFactory,
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Action? threadAffinityCheck)
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: this(eventQueue, consumerFactory, threadAffinityCheck, comFactory: null, standbyFactory: null)
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{
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}
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/// <summary>
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/// Full constructor that also threads the MXAccess COM-object factory and
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/// an optional standby-consumer seam so the subscribe path can build the
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/// subtag / failover consumers required by
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/// <see cref="SubscribeAlarmsCommand.ForcedMode"/> and
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/// <see cref="SubscribeAlarmsCommand.WatchList"/>.
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/// </summary>
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/// <param name="eventQueue">The event queue.</param>
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/// <param name="consumerFactory">
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/// Factory for the PRIMARY (alarmmgr) consumer — the existing
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/// wnwrap-backed source. Used alone in alarmmgr mode and as the primary
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/// of the failover composite in auto mode.
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/// </param>
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/// <param name="threadAffinityCheck">Optional STA thread-affinity guard.</param>
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/// <param name="comFactory">
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/// The MXAccess COM-object factory used to build the
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/// <see cref="LmxSubtagAlarmSource"/> backing the subtag consumer. May be
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/// <see langword="null"/> when a <paramref name="standbyFactory"/> is
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/// supplied (tests) or when only the alarmmgr path is ever exercised.
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/// </param>
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/// <param name="standbyFactory">
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/// Optional seam that builds the STANDBY (subtag) consumer from a watch
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/// list. Defaults to a <see cref="SubtagAlarmConsumer"/> over an
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/// <see cref="LmxSubtagAlarmSource"/> built from
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/// <paramref name="comFactory"/>. Tests inject a fake so they need no
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/// live COM factory.
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/// </param>
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public AlarmCommandHandler(
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MxAccessEventQueue eventQueue,
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Func<IMxAccessAlarmConsumer> consumerFactory,
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Action? threadAffinityCheck,
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IMxAccessComObjectFactory? comFactory,
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Func<IReadOnlyList<AlarmSubtagTarget>, IMxAccessAlarmConsumer>? standbyFactory)
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{
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this.eventQueue = eventQueue ?? throw new ArgumentNullException(nameof(eventQueue));
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this.consumerFactory = consumerFactory ?? throw new ArgumentNullException(nameof(consumerFactory));
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this.threadAffinityCheck = threadAffinityCheck;
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this.comFactory = comFactory;
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this.standbyFactory = standbyFactory;
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}
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/// <summary>Gets a value indicating whether the handler is subscribed.</summary>
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@@ -92,10 +137,10 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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}
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/// <inheritdoc />
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public void Subscribe(string subscription, string sessionId)
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public void Subscribe(SubscribeAlarmsCommand command, string sessionId)
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{
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if (disposed) throw new ObjectDisposedException(nameof(AlarmCommandHandler));
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if (subscription is null) throw new ArgumentNullException(nameof(subscription));
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if (command is null) throw new ArgumentNullException(nameof(command));
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threadAffinityCheck?.Invoke();
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lock (syncRoot)
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@@ -106,17 +151,31 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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"AlarmCommandHandler already has an active subscription; " +
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"call Unsubscribe before issuing another SubscribeAlarms command.");
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}
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IMxAccessAlarmConsumer consumer = consumerFactory()
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subscribeSessionId = sessionId ?? string.Empty;
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IMxAccessAlarmConsumer consumer = BuildConsumer(command)
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?? throw new InvalidOperationException("Alarm consumer factory returned null.");
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MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(
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eventQueue, new MxAccessEventMapper());
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dispatcher = new AlarmDispatcher(consumer, sink, sessionId ?? string.Empty);
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// When the selected consumer is a failover composite, surface its
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// provider switches onto the worker's event queue so connected
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// gateway clients can observe degraded/recovered state. The handler
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// is unsubscribed/disposed on Unsubscribe/Dispose below.
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if (consumer is FailoverAlarmConsumer failover)
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{
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failoverConsumer = failover;
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providerModeChangedHandler = OnProviderModeChanged;
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failover.ProviderModeChanged += providerModeChangedHandler;
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}
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MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(eventQueue, mapper);
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dispatcher = new AlarmDispatcher(consumer, sink, subscribeSessionId);
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try
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{
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dispatcher.Subscribe(subscription);
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dispatcher.Subscribe(command.SubscriptionExpression ?? string.Empty);
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}
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catch
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{
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DetachProviderModeChanged();
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try { dispatcher.Dispose(); } catch { /* swallow */ }
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dispatcher = null;
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throw;
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@@ -124,6 +183,89 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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}
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}
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/// <summary>
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/// Selects and builds the alarm consumer from the command's
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/// <see cref="SubscribeAlarmsCommand.ForcedMode"/> and
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/// <see cref="SubscribeAlarmsCommand.WatchList"/>:
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/// <list type="bullet">
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/// <item><description>
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/// <c>Alarmmgr</c>, or <c>Unspecified</c> with an empty watch
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/// list: the existing primary (alarmmgr) consumer only —
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/// today's behavior.
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/// </description></item>
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/// <item><description>
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/// <c>Subtag</c>: a <see cref="SubtagAlarmConsumer"/> only.
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/// </description></item>
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/// <item><description>
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/// <c>Unspecified</c> with a non-empty watch list (auto): a
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/// <see cref="FailoverAlarmConsumer"/> over the primary and a
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/// subtag standby.
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/// </description></item>
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/// </list>
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/// </summary>
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private IMxAccessAlarmConsumer BuildConsumer(SubscribeAlarmsCommand command)
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{
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List<AlarmSubtagTarget> watchList = new List<AlarmSubtagTarget>(command.WatchList);
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if (command.ForcedMode == AlarmProviderMode.Subtag)
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{
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return BuildStandby(watchList);
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}
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if (command.ForcedMode == AlarmProviderMode.Unspecified && watchList.Count > 0)
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{
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IMxAccessAlarmConsumer primary = consumerFactory()
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?? throw new InvalidOperationException("Alarm consumer factory returned null.");
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IMxAccessAlarmConsumer standby = BuildStandby(watchList);
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AlarmFailoverConfig? failoverConfig = command.Failover;
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FailoverSettings settings = new FailoverSettings(
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failoverConfig?.ConsecutiveFailureThreshold ?? 3,
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failoverConfig?.FailbackProbeIntervalSeconds ?? 30,
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failoverConfig?.FailbackStableProbes ?? 3);
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return new FailoverAlarmConsumer(primary, standby, settings);
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}
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// Alarmmgr, or Unspecified with an empty watch list — primary only.
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return consumerFactory()
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?? throw new InvalidOperationException("Alarm consumer factory returned null.");
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}
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private IMxAccessAlarmConsumer BuildStandby(IReadOnlyList<AlarmSubtagTarget> watchList)
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{
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if (standbyFactory is not null)
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{
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return standbyFactory(watchList)
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?? throw new InvalidOperationException("Standby alarm consumer factory returned null.");
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}
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if (comFactory is null)
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{
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throw new InvalidOperationException(
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"Subtag alarm consumer requires an IMxAccessComObjectFactory; the alarm command "
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+ "handler was constructed without one and no standby factory was supplied.");
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}
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return new SubtagAlarmConsumer(new LmxSubtagAlarmSource(comFactory), watchList);
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}
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private void OnProviderModeChanged(object? sender, AlarmProviderModeChange change)
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{
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if (change is null) return;
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eventQueue.Enqueue(mapper.CreateOnAlarmProviderModeChanged(
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subscribeSessionId, change.Mode, change.Reason, change.HResult, change.AtUtc));
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}
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private void DetachProviderModeChanged()
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{
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if (failoverConsumer is not null && providerModeChangedHandler is not null)
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{
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try { failoverConsumer.ProviderModeChanged -= providerModeChangedHandler; }
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catch { /* swallow */ }
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}
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failoverConsumer = null;
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providerModeChangedHandler = null;
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}
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/// <inheritdoc />
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public void Unsubscribe()
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{
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@@ -131,6 +273,7 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
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AlarmDispatcher? toDispose;
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lock (syncRoot)
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{
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DetachProviderModeChanged();
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toDispose = dispatcher;
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dispatcher = null;
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}
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