refactor: extract NATS.Server.Mqtt.Tests project
Move 29 MQTT test files from NATS.Server.Tests into a dedicated NATS.Server.Mqtt.Tests project. Update namespaces, add InternalsVisibleTo, and replace Task.Delay calls with PollHelper.WaitUntilAsync for proper synchronization.
This commit is contained in:
Joseph Doherty
248
tests/NATS.Server.Mqtt.Tests/Mqtt/MqttFlapperDetectionTests.cs
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248
tests/NATS.Server.Mqtt.Tests/Mqtt/MqttFlapperDetectionTests.cs
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// MQTT flapper detection tests — exponential backoff for rapid reconnectors.
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// Go reference: golang/nats-server/server/mqtt.go mqttCheckFlapper ~lines 300–360.
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using NATS.Server.Mqtt;
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using Shouldly;
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namespace NATS.Server.Mqtt.Tests.Mqtt;
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public class MqttFlapperDetectionTests
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{
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// -------------------------------------------------------------------------
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// Helper: FakeTimeProvider from Microsoft.Extensions.TimeProvider.Testing
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// -------------------------------------------------------------------------
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private static MqttSessionStore CreateStore(
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FakeTimeProvider? time = null,
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int flapThreshold = 3,
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TimeSpan? flapWindow = null) =>
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new(
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flapWindow: flapWindow ?? TimeSpan.FromSeconds(10),
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flapThreshold: flapThreshold,
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timeProvider: time);
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// -------------------------------------------------------------------------
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// 1. TrackConnectDisconnect_counts_events
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// -------------------------------------------------------------------------
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[Fact]
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public void TrackConnectDisconnect_counts_events()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — each connect increments the counter.
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var store = CreateStore();
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var s1 = store.TrackConnectDisconnect("client-a");
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s1.ConnectDisconnectCount.ShouldBe(1);
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var s2 = store.TrackConnectDisconnect("client-a");
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s2.ConnectDisconnectCount.ShouldBe(2);
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}
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// -------------------------------------------------------------------------
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// 2. Not_flapper_below_threshold
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// -------------------------------------------------------------------------
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[Fact]
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public void Not_flapper_below_threshold()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — threshold is 3; 2 events should not mark as flapper.
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var store = CreateStore();
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store.TrackConnectDisconnect("client-b");
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store.TrackConnectDisconnect("client-b");
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store.IsFlapper("client-b").ShouldBeFalse();
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}
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// -------------------------------------------------------------------------
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// 3. Becomes_flapper_at_threshold
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// -------------------------------------------------------------------------
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[Fact]
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public void Becomes_flapper_at_threshold()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — 3 events within window marks the client.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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store.TrackConnectDisconnect("client-c");
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time.Advance(TimeSpan.FromSeconds(1));
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store.TrackConnectDisconnect("client-c");
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time.Advance(TimeSpan.FromSeconds(1));
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store.TrackConnectDisconnect("client-c");
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store.IsFlapper("client-c").ShouldBeTrue();
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}
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// -------------------------------------------------------------------------
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// 4. Backoff_increases_exponentially
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// -------------------------------------------------------------------------
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[Fact]
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public void Backoff_increases_exponentially()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — backoff doubles on each new flap trigger.
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// Level 0 → 1 s, Level 1 → 2 s, Level 2 → 4 s.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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// First flap at level 0 (1 s backoff)
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store.TrackConnectDisconnect("client-d");
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store.TrackConnectDisconnect("client-d");
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var s1 = store.TrackConnectDisconnect("client-d");
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s1.BackoffLevel.ShouldBe(1); // incremented after applying level 0
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s1.BackoffUntil.ShouldNotBeNull();
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var backoff1 = s1.BackoffUntil!.Value - time.GetUtcNow().UtcDateTime;
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backoff1.TotalMilliseconds.ShouldBeInRange(900, 1100); // ~1 000 ms
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// Advance past the backoff and trigger again — level 1 (2 s)
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time.Advance(TimeSpan.FromSeconds(2));
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var s2 = store.TrackConnectDisconnect("client-d");
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s2.BackoffLevel.ShouldBe(2);
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var backoff2 = s2.BackoffUntil!.Value - time.GetUtcNow().UtcDateTime;
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backoff2.TotalMilliseconds.ShouldBeInRange(1900, 2100); // ~2 000 ms
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// Advance past and trigger once more — level 2 (4 s)
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time.Advance(TimeSpan.FromSeconds(3));
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var s3 = store.TrackConnectDisconnect("client-d");
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s3.BackoffLevel.ShouldBe(3);
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var backoff3 = s3.BackoffUntil!.Value - time.GetUtcNow().UtcDateTime;
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backoff3.TotalMilliseconds.ShouldBeInRange(3900, 4100); // ~4 000 ms
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}
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// -------------------------------------------------------------------------
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// 5. Backoff_capped_at_60_seconds
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// -------------------------------------------------------------------------
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[Fact]
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public void Backoff_capped_at_60_seconds()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — cap the maximum backoff at 60 s.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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// Trigger enough flaps to overflow past 60 s (level 6 = 64 s, which should cap at 60 s)
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for (var i = 0; i < 10; i++)
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{
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store.TrackConnectDisconnect("client-e");
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time.Advance(TimeSpan.FromMilliseconds(100));
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}
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var state = store.TrackConnectDisconnect("client-e");
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var remaining = state.BackoffUntil!.Value - time.GetUtcNow().UtcDateTime;
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remaining.TotalMilliseconds.ShouldBeLessThanOrEqualTo(60_001); // max 60 s (±1 ms tolerance)
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remaining.TotalMilliseconds.ShouldBeGreaterThan(0);
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}
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// -------------------------------------------------------------------------
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// 6. GetBackoffMs_returns_remaining
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// -------------------------------------------------------------------------
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[Fact]
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public void GetBackoffMs_returns_remaining()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — caller can query remaining backoff time.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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store.TrackConnectDisconnect("client-f");
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store.TrackConnectDisconnect("client-f");
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store.TrackConnectDisconnect("client-f"); // threshold hit
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var ms = store.GetBackoffMs("client-f");
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ms.ShouldBeGreaterThan(0);
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ms.ShouldBeLessThanOrEqualTo(1000);
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}
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// -------------------------------------------------------------------------
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// 7. GetBackoffMs_zero_when_not_flapping
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// -------------------------------------------------------------------------
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[Fact]
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public void GetBackoffMs_zero_when_not_flapping()
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{
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// Not enough events to trigger backoff — remaining ms should be 0.
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var store = CreateStore();
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store.TrackConnectDisconnect("client-g");
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store.TrackConnectDisconnect("client-g");
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store.GetBackoffMs("client-g").ShouldBe(0);
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}
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// -------------------------------------------------------------------------
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// 8. ClearFlapperState_removes_tracking
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// -------------------------------------------------------------------------
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[Fact]
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public void ClearFlapperState_removes_tracking()
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{
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// Go reference: server/mqtt.go — stable clients should have state purged.
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var store = CreateStore();
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store.TrackConnectDisconnect("client-h");
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store.TrackConnectDisconnect("client-h");
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store.TrackConnectDisconnect("client-h");
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store.IsFlapper("client-h").ShouldBeTrue();
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store.ClearFlapperState("client-h");
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store.IsFlapper("client-h").ShouldBeFalse();
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store.GetBackoffMs("client-h").ShouldBe(0);
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}
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// -------------------------------------------------------------------------
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// 9. Window_resets_after_10_seconds
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// -------------------------------------------------------------------------
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[Fact]
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public void Window_resets_after_10_seconds()
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{
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// Go reference: server/mqtt.go mqttCheckFlapper — window-based detection resets.
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// Track 2 events, advance past the window, add 1 more — should NOT be a flapper.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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store.TrackConnectDisconnect("client-i");
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store.TrackConnectDisconnect("client-i");
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// Advance past the 10 s flap window
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time.Advance(TimeSpan.FromSeconds(11));
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// Directly set the WindowStart via the returned state to simulate the old window
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// being in the past. A single new event in a new window should not cross threshold.
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store.TrackConnectDisconnect("client-i");
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store.IsFlapper("client-i").ShouldBeFalse();
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}
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// -------------------------------------------------------------------------
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// 10. CheckAndClearStableClients_clears_old
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// -------------------------------------------------------------------------
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[Fact]
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public void CheckAndClearStableClients_clears_old()
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{
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// Go reference: server/mqtt.go — periodic sweep clears long-stable flapper records.
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var time = new FakeTimeProvider(DateTimeOffset.UtcNow);
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var store = CreateStore(time);
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// Trigger flap
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store.TrackConnectDisconnect("client-j");
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store.TrackConnectDisconnect("client-j");
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var state = store.TrackConnectDisconnect("client-j");
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store.IsFlapper("client-j").ShouldBeTrue();
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// Manually backdate BackoffUntil so it's already expired
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lock (state)
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{
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state.BackoffUntil = time.GetUtcNow().UtcDateTime - TimeSpan.FromSeconds(61);
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}
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// A stable-threshold sweep of 60 s should evict the now-expired entry
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store.CheckAndClearStableClients(TimeSpan.FromSeconds(60));
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store.IsFlapper("client-j").ShouldBeFalse();
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store.GetBackoffMs("client-j").ShouldBe(0);
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}
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}
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