Phase 6.1 Stream B.4 follow-up — ScheduledRecycleHostedService drives registered schedulers on a fixed tick
Turns the Phase 6.1 Stream B.4 pure-logic ScheduledRecycleScheduler (shipped in PR #79) into a running background feature. A Tier C driver registers its scheduler at startup; the hosted service ticks every TickInterval (default 1 min) and invokes TickAsync on each registered scheduler. Server.Hosting: - ScheduledRecycleHostedService : BackgroundService. AddScheduler(s) must be called before StartAsync — registering post-start throws InvalidOperationException to avoid "some ticks saw my scheduler, some didn't" races. ExecuteAsync loops on Task.Delay(TickInterval, _timeProvider, stoppingToken) + delegates to a public TickOnceAsync method for one tick. - TickOnceAsync extracted as the unit-of-work so tests drive it directly without needing to synchronize with FakeTimeProvider + BackgroundService timing semantics. - Exception isolation: if one scheduler throws, the loop logs + continues to the next scheduler. A flaky supervisor can't take down the tick for every other Tier C driver. - Diagnostics: TickCount + SchedulerCount properties for tests + logs. Tests (7 new ScheduledRecycleHostedServiceTests, all pass): - TickOnce before interval doesn't fire; TickCount still advances. - TickOnce at/after interval fires the underlying scheduler exactly once. - Multiple ticks accumulate count. - AddScheduler after StartAsync throws. - Throwing scheduler doesn't poison its neighbours (logs + continues). - SchedulerCount matches registrations. - Empty scheduler list ticks cleanly (no-op + counter advances). Full solution dotnet test: 1193 passing (was 1186, +7). Pre-existing Client.CLI Subscribe flake unchanged. Production wiring (Program.cs): builder.Services.AddSingleton<ScheduledRecycleHostedService>(); builder.Services.AddHostedService(sp => sp.GetRequiredService<ScheduledRecycleHostedService>()); // During DI configuration, once Tier C drivers + their ScheduledRecycleSchedulers // are resolved, call host.AddScheduler(scheduler) for each. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
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using Microsoft.Extensions.Logging.Abstractions;
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using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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using ZB.MOM.WW.OtOpcUa.Core.Stability;
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using ZB.MOM.WW.OtOpcUa.Server.Hosting;
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namespace ZB.MOM.WW.OtOpcUa.Server.Tests;
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[Trait("Category", "Unit")]
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public sealed class ScheduledRecycleHostedServiceTests
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{
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private static readonly DateTime T0 = new(2026, 4, 19, 0, 0, 0, DateTimeKind.Utc);
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private sealed class FakeClock : TimeProvider
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{
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public DateTime Utc { get; set; } = T0;
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public override DateTimeOffset GetUtcNow() => new(Utc, TimeSpan.Zero);
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}
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private sealed class FakeSupervisor : IDriverSupervisor
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{
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public string DriverInstanceId => "tier-c-fake";
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public int RecycleCount { get; private set; }
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public Task RecycleAsync(string reason, CancellationToken cancellationToken)
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{
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RecycleCount++;
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return Task.CompletedTask;
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}
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}
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private sealed class ThrowingSupervisor : IDriverSupervisor
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{
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public string DriverInstanceId => "tier-c-throws";
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public Task RecycleAsync(string reason, CancellationToken cancellationToken)
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=> throw new InvalidOperationException("supervisor unavailable");
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}
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[Fact]
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public async Task TickOnce_BeforeInterval_DoesNotFire()
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{
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var clock = new FakeClock();
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var supervisor = new FakeSupervisor();
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var scheduler = new ScheduledRecycleScheduler(
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DriverTier.C, TimeSpan.FromMinutes(5), T0, supervisor,
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NullLogger<ScheduledRecycleScheduler>.Instance);
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance, clock);
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host.AddScheduler(scheduler);
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clock.Utc = T0.AddMinutes(1);
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await host.TickOnceAsync(CancellationToken.None);
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supervisor.RecycleCount.ShouldBe(0);
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host.TickCount.ShouldBe(1);
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}
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[Fact]
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public async Task TickOnce_AfterInterval_Fires()
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{
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var clock = new FakeClock();
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var supervisor = new FakeSupervisor();
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var scheduler = new ScheduledRecycleScheduler(
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DriverTier.C, TimeSpan.FromMinutes(5), T0, supervisor,
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NullLogger<ScheduledRecycleScheduler>.Instance);
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance, clock);
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host.AddScheduler(scheduler);
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clock.Utc = T0.AddMinutes(6);
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await host.TickOnceAsync(CancellationToken.None);
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supervisor.RecycleCount.ShouldBe(1);
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}
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[Fact]
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public async Task TickOnce_MultipleTicks_AccumulateCount()
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{
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var clock = new FakeClock();
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance, clock);
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await host.TickOnceAsync(CancellationToken.None);
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await host.TickOnceAsync(CancellationToken.None);
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await host.TickOnceAsync(CancellationToken.None);
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host.TickCount.ShouldBe(3);
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}
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[Fact]
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public async Task AddScheduler_AfterStart_Throws()
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{
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance);
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using var cts = new CancellationTokenSource();
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cts.Cancel();
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await host.StartAsync(cts.Token); // flips _started true even with cancelled token
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await host.StopAsync(CancellationToken.None);
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var scheduler = new ScheduledRecycleScheduler(
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DriverTier.C, TimeSpan.FromMinutes(5), DateTime.UtcNow, new FakeSupervisor(),
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NullLogger<ScheduledRecycleScheduler>.Instance);
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Should.Throw<InvalidOperationException>(() => host.AddScheduler(scheduler));
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}
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[Fact]
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public async Task OneSchedulerThrowing_DoesNotStopOthers()
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{
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var clock = new FakeClock();
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var good = new FakeSupervisor();
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var bad = new ThrowingSupervisor();
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var goodSch = new ScheduledRecycleScheduler(
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DriverTier.C, TimeSpan.FromMinutes(5), T0, good,
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NullLogger<ScheduledRecycleScheduler>.Instance);
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var badSch = new ScheduledRecycleScheduler(
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DriverTier.C, TimeSpan.FromMinutes(5), T0, bad,
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NullLogger<ScheduledRecycleScheduler>.Instance);
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance, clock);
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host.AddScheduler(badSch);
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host.AddScheduler(goodSch);
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clock.Utc = T0.AddMinutes(6);
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await host.TickOnceAsync(CancellationToken.None);
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good.RecycleCount.ShouldBe(1, "a faulting scheduler must not poison its neighbours");
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}
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[Fact]
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public void SchedulerCount_MatchesAdded()
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{
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance);
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var sup = new FakeSupervisor();
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host.AddScheduler(new ScheduledRecycleScheduler(DriverTier.C, TimeSpan.FromMinutes(5), DateTime.UtcNow, sup, NullLogger<ScheduledRecycleScheduler>.Instance));
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host.AddScheduler(new ScheduledRecycleScheduler(DriverTier.C, TimeSpan.FromMinutes(10), DateTime.UtcNow, sup, NullLogger<ScheduledRecycleScheduler>.Instance));
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host.SchedulerCount.ShouldBe(2);
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}
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[Fact]
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public async Task EmptyScheduler_List_TicksCleanly()
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{
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var clock = new FakeClock();
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var host = new ScheduledRecycleHostedService(NullLogger<ScheduledRecycleHostedService>.Instance, clock);
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// No registered schedulers — tick is a no-op + counter still advances.
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await host.TickOnceAsync(CancellationToken.None);
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host.TickCount.ShouldBe(1);
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}
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}
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