feat(sessions): add UnattachedSessionGraceSeconds to reap never-subscribed idle sessions
A client that opens a session and vanishes before it ever streams (e.g. OtOpcUa's GalaxyDriver on a failed start) pinned a session slot and a live x86 worker for the full DefaultLeaseSeconds (1800 s), because detach-grace only applies to sessions that once had a subscriber. MxGateway:Sessions:UnattachedSessionGraceSeconds (int, default 0 = off, validated >= 0) makes the existing lease sweep reap a Ready session that has never attached an event subscriber once it has been idle (no unary activity) for the window, with the close reason unattached-grace-expired. Ready-only, idle-from-last-activity and first-subscriber-cancels keep it from catching slow starts or unary-only clients. GatewaySession.ExtendLease had no production callers and did not fit the rule, so it is removed; tests move leases through TouchClientActivity.
This commit is contained in:
Joseph Doherty
@@ -1129,8 +1129,8 @@ public sealed class SessionManagerTests
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GatewaySession expiredSession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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GatewaySession activeSession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-2", ownerKeyId: null, CancellationToken.None);
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DateTimeOffset now = DateTimeOffset.UtcNow;
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expiredSession.ExtendLease(now.AddSeconds(-1));
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activeSession.ExtendLease(now.AddMinutes(5));
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SetLeaseExpiry(expiredSession, now.AddSeconds(-1));
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SetLeaseExpiry(activeSession, now.AddMinutes(5));
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int closedCount = await manager.CloseExpiredLeasesAsync(now, CancellationToken.None);
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@@ -1194,6 +1194,130 @@ public sealed class SessionManagerTests
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Assert.Equal(0, snapshot.OpenSessions);
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}
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/// <summary>
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/// With <c>UnattachedSessionGraceSeconds</c> set, a session that never attached an event
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/// subscriber and has been idle for the window is reaped by the ordinary lease sweep even
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/// though its 30-minute lease is nowhere near expiry. This is the knob for clients that
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/// open a session and vanish (OtOpcUa's GalaxyDriver on a failed start): without it each
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/// such open pins an x86 worker for <c>DefaultLeaseSeconds</c>.
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/// </summary>
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/// <returns>A task that represents the asynchronous operation.</returns>
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[Fact]
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public async Task CloseExpiredLeasesAsync_ReapsNeverSubscribedSessionAfterUnattachedGrace()
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{
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FakeWorkerClient workerClient = new();
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FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
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using GatewayMetrics metrics = new();
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SessionManager manager = CreateManager(
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new FakeSessionWorkerClientFactory(workerClient),
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metrics: metrics,
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options: CreateOptions(unattachedSessionGraceSeconds: 60),
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timeProvider: clock);
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GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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clock.Advance(TimeSpan.FromSeconds(59));
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int closedBefore = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(0, closedBefore);
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Assert.Equal(SessionState.Ready, session.State);
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clock.Advance(TimeSpan.FromSeconds(1));
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int closedAfter = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(1, closedAfter);
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Assert.Equal(SessionState.Closed, session.State);
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Assert.Equal(1, workerClient.ShutdownCount);
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Assert.False(manager.TryGetSession(session.SessionId, out _));
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Assert.Equal(1, metrics.GetSnapshot().SessionsClosed);
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Assert.Equal(0, metrics.GetSnapshot().OpenSessions);
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}
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/// <summary>
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/// The window is an idle timeout, not a hard deadline from open: unary activity restarts
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/// it, so a client that only ever reads and writes (never streams) is not reaped while it
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/// keeps calling.
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/// </summary>
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/// <returns>A task that represents the asynchronous operation.</returns>
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[Fact]
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public async Task CloseExpiredLeasesAsync_UnattachedGrace_IsRestartedByUnaryActivity()
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{
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FakeWorkerClient workerClient = new();
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FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
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SessionManager manager = CreateManager(
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new FakeSessionWorkerClientFactory(workerClient),
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options: CreateOptions(unattachedSessionGraceSeconds: 60),
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timeProvider: clock);
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GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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clock.Advance(TimeSpan.FromSeconds(59));
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await manager.InvokeAsync(session.SessionId, CreateCommand(MxCommandKind.Ping), CancellationToken.None);
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clock.Advance(TimeSpan.FromSeconds(59));
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int closedWhileActive = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(0, closedWhileActive);
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Assert.Equal(SessionState.Ready, session.State);
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clock.Advance(TimeSpan.FromSeconds(1));
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int closedAfterIdle = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(1, closedAfterIdle);
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Assert.Equal(SessionState.Closed, session.State);
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}
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/// <summary>
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/// A session that ever had an event subscriber is outside this knob's remit — once it has
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/// streamed, detach-grace and the normal lease govern it — and a session with a subscriber
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/// attached right now is never idle.
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/// </summary>
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/// <param name="keepSubscriberAttached">Whether the subscriber is still attached at sweep time.</param>
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/// <returns>A task that represents the asynchronous operation.</returns>
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[Theory]
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[InlineData(true)]
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[InlineData(false)]
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public async Task CloseExpiredLeasesAsync_UnattachedGrace_DoesNotReapSessionThatSubscribed(bool keepSubscriberAttached)
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{
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FakeWorkerClient workerClient = new();
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FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
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SessionManager manager = CreateManager(
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new FakeSessionWorkerClientFactory(workerClient),
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options: CreateOptions(detachGraceSeconds: 0, unattachedSessionGraceSeconds: 60),
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timeProvider: clock);
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GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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IDisposable subscriber = session.AttachEventSubscriber(maxSubscribers: 1);
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if (!keepSubscriberAttached)
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{
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subscriber.Dispose();
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}
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clock.Advance(TimeSpan.FromSeconds(61));
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int closedCount = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(0, closedCount);
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Assert.Equal(SessionState.Ready, session.State);
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Assert.Equal(0, workerClient.ShutdownCount);
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subscriber.Dispose();
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}
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/// <summary>
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/// The knob is off by default: a never-subscribed idle session lives for its full lease.
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/// </summary>
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/// <returns>A task that represents the asynchronous operation.</returns>
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[Fact]
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public async Task CloseExpiredLeasesAsync_UnattachedGrace_IsDisabledByDefault()
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{
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FakeWorkerClient workerClient = new();
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FakeTimeProvider clock = new(DateTimeOffset.UtcNow);
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SessionManager manager = CreateManager(
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new FakeSessionWorkerClientFactory(workerClient),
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options: CreateOptions(),
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timeProvider: clock);
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GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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clock.Advance(TimeSpan.FromMinutes(20));
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int closedCount = await manager.CloseExpiredLeasesAsync(clock.GetUtcNow(), CancellationToken.None);
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Assert.Equal(0, closedCount);
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Assert.Equal(SessionState.Ready, session.State);
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}
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/// <summary>Verifies that an expired-lease sweep leaves a session with an active event subscriber open.</summary>
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/// <returns>A task that represents the asynchronous operation.</returns>
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[Fact]
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@@ -1203,7 +1327,7 @@ public sealed class SessionManagerTests
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SessionManager manager = CreateManager(new FakeSessionWorkerClientFactory(workerClient));
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GatewaySession session = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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DateTimeOffset now = DateTimeOffset.UtcNow;
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session.ExtendLease(now.AddSeconds(-1));
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SetLeaseExpiry(session, now.AddSeconds(-1));
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using IDisposable eventSubscriber = session.AttachEventSubscriber(maxSubscribers: 1);
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int closedCount = await manager.CloseExpiredLeasesAsync(now, CancellationToken.None);
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@@ -1310,8 +1434,8 @@ public sealed class SessionManagerTests
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DateTimeOffset now = DateTimeOffset.UtcNow;
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// Both leases are far in the future, so only the fault can reap the faulted session.
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faultedSession.ExtendLease(now.AddMinutes(30));
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healthySession.ExtendLease(now.AddMinutes(30));
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SetLeaseExpiry(faultedSession, now.AddMinutes(30));
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SetLeaseExpiry(healthySession, now.AddMinutes(30));
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faultedSession.MarkFaulted("test fault");
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int closedCount = await manager.CloseExpiredLeasesAsync(now, CancellationToken.None);
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@@ -1372,8 +1496,8 @@ public sealed class SessionManagerTests
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GatewaySession firstSession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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GatewaySession secondSession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-2", ownerKeyId: null, CancellationToken.None);
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DateTimeOffset now = DateTimeOffset.UtcNow;
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firstSession.ExtendLease(now.AddSeconds(-1));
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secondSession.ExtendLease(now.AddSeconds(-1));
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SetLeaseExpiry(firstSession, now.AddSeconds(-1));
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SetLeaseExpiry(secondSession, now.AddSeconds(-1));
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int closedCount = await manager.CloseExpiredLeasesAsync(now, CancellationToken.None);
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@@ -1425,8 +1549,8 @@ public sealed class SessionManagerTests
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GatewaySession failingSession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-1", ownerKeyId: null, CancellationToken.None);
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GatewaySession healthySession = await manager.OpenSessionAsync(CreateOpenRequest(), "client-2", ownerKeyId: null, CancellationToken.None);
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DateTimeOffset now = DateTimeOffset.UtcNow;
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failingSession.ExtendLease(now.AddSeconds(-1));
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healthySession.ExtendLease(now.AddSeconds(-1));
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SetLeaseExpiry(failingSession, now.AddSeconds(-1));
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SetLeaseExpiry(healthySession, now.AddSeconds(-1));
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SessionManagerException exception = await Assert.ThrowsAsync<SessionManagerException>(
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async () => await manager.CloseExpiredLeasesAsync(now, CancellationToken.None));
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@@ -1592,7 +1716,8 @@ public sealed class SessionManagerTests
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int defaultLeaseSeconds = 1800,
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int detachGraceSeconds = 0,
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int workerReadyWaitTimeoutMs = 0,
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int faultedGraceSeconds = 0)
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int faultedGraceSeconds = 0,
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int unattachedSessionGraceSeconds = 0)
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{
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return new GatewayOptions
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{
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@@ -1604,6 +1729,7 @@ public sealed class SessionManagerTests
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DetachGraceSeconds = detachGraceSeconds,
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WorkerReadyWaitTimeoutMs = workerReadyWaitTimeoutMs,
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FaultedGraceSeconds = faultedGraceSeconds,
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UnattachedSessionGraceSeconds = unattachedSessionGraceSeconds,
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},
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Worker = new WorkerOptions
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{
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