feat: add MQTT will message delivery on abnormal disconnect (Gap 6.2)
Adds WillMessage class, SetWill/ClearWill/GetWill methods to MqttSessionStore, PublishWillMessage that dispatches via OnPublish delegate (or tracks as delayed when DelayIntervalSeconds > 0), and 10 unit tests covering all will message behaviors.
This commit is contained in:
Joseph Doherty
146
tests/NATS.Server.Tests/Mqtt/MqttFlowControllerTests.cs
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146
tests/NATS.Server.Tests/Mqtt/MqttFlowControllerTests.cs
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// Go reference: server/mqtt.go — mqttMaxAckPending, flow control logic.
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using NATS.Server.Mqtt;
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using Shouldly;
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namespace NATS.Server.Tests.Mqtt;
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public sealed class MqttFlowControllerTests
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{
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// 1. TryAcquire succeeds when under limit
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[Fact]
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public async Task TryAcquire_succeeds_when_under_limit()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 1024);
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var result = await fc.TryAcquireAsync("sub-1");
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result.ShouldBeTrue();
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}
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// 2. TryAcquire fails when at limit
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[Fact]
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public async Task TryAcquire_fails_when_at_limit()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 1);
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var first = await fc.TryAcquireAsync("sub-1");
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var second = await fc.TryAcquireAsync("sub-1");
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first.ShouldBeTrue();
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second.ShouldBeFalse();
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}
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// 3. Release allows next acquire
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[Fact]
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public async Task Release_allows_next_acquire()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 1);
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var first = await fc.TryAcquireAsync("sub-1");
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first.ShouldBeTrue();
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// At limit — second should fail
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var atLimit = await fc.TryAcquireAsync("sub-1");
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atLimit.ShouldBeFalse();
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fc.Release("sub-1");
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// After release a slot is available again
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var afterRelease = await fc.TryAcquireAsync("sub-1");
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afterRelease.ShouldBeTrue();
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}
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// 4. GetPendingCount tracks pending
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[Fact]
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public async Task GetPendingCount_tracks_pending()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 10);
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await fc.AcquireAsync("sub-1");
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await fc.AcquireAsync("sub-1");
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await fc.AcquireAsync("sub-1");
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fc.GetPendingCount("sub-1").ShouldBe(3);
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}
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// 5. GetPendingCount decrements on release
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[Fact]
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public async Task GetPendingCount_decrements_on_release()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 10);
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await fc.AcquireAsync("sub-1");
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await fc.AcquireAsync("sub-1");
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await fc.AcquireAsync("sub-1");
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fc.Release("sub-1");
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fc.GetPendingCount("sub-1").ShouldBe(2);
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}
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// 6. GetPendingCount returns zero for unknown subscription
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[Fact]
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public void GetPendingCount_zero_for_unknown()
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{
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using var fc = new MqttFlowController();
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fc.GetPendingCount("does-not-exist").ShouldBe(0);
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}
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// 7. RemoveSubscription cleans up
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[Fact]
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public async Task RemoveSubscription_cleans_up()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 10);
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await fc.AcquireAsync("sub-1");
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fc.SubscriptionCount.ShouldBe(1);
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fc.RemoveSubscription("sub-1");
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fc.SubscriptionCount.ShouldBe(0);
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}
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// 8. SubscriptionCount tracks independent subscriptions
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[Fact]
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public async Task SubscriptionCount_tracks_subscriptions()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 10);
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await fc.AcquireAsync("sub-a");
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await fc.AcquireAsync("sub-b");
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await fc.AcquireAsync("sub-c");
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fc.SubscriptionCount.ShouldBe(3);
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}
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// 9. DefaultMaxAckPending can be updated via UpdateLimit
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[Fact]
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public void DefaultMaxAckPending_can_be_updated()
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{
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using var fc = new MqttFlowController(defaultMaxAckPending: 1024);
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fc.DefaultMaxAckPending.ShouldBe(1024);
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fc.UpdateLimit(512);
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fc.DefaultMaxAckPending.ShouldBe(512);
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}
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// 10. Dispose cleans up all subscriptions
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[Fact]
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public async Task Dispose_cleans_up_all()
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{
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var fc = new MqttFlowController(defaultMaxAckPending: 10);
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await fc.AcquireAsync("sub-x");
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await fc.AcquireAsync("sub-y");
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await fc.AcquireAsync("sub-z");
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fc.SubscriptionCount.ShouldBe(3);
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fc.Dispose();
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fc.SubscriptionCount.ShouldBe(0);
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}
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}
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202
tests/NATS.Server.Tests/Mqtt/MqttWillMessageTests.cs
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202
tests/NATS.Server.Tests/Mqtt/MqttWillMessageTests.cs
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// Unit tests for MQTT will message delivery on abnormal disconnection.
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// Go reference: golang/nats-server/server/mqtt.go — mqttDeliverWill ~line 490,
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// TestMQTTWill server/mqtt_test.go:4129
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using NATS.Server.Mqtt;
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using Shouldly;
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namespace NATS.Server.Tests.Mqtt;
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public class MqttWillMessageTests
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{
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// Go ref: mqtt.go mqttSession will field — will message is stored on CONNECT with will flag.
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[Fact]
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public void SetWill_stores_will_message()
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{
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var store = new MqttSessionStore();
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var will = new WillMessage { Topic = "client/status", Payload = "offline"u8.ToArray(), QoS = 0, Retain = false };
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store.SetWill("client-1", will);
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var stored = store.GetWill("client-1");
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stored.ShouldNotBeNull();
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stored.Topic.ShouldBe("client/status");
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stored.Payload.ShouldBe("offline"u8.ToArray());
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}
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// Go ref: mqttDeliverWill — on graceful DISCONNECT, will is cleared (not delivered).
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[Fact]
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public void ClearWill_removes_will()
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{
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var store = new MqttSessionStore();
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var will = new WillMessage { Topic = "client/status", Payload = "offline"u8.ToArray() };
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store.SetWill("client-2", will);
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store.ClearWill("client-2");
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store.GetWill("client-2").ShouldBeNull();
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}
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// Go ref: TestMQTTWill server/mqtt_test.go:4129 — will is published on abnormal disconnect.
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[Fact]
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public void PublishWillMessage_publishes_on_abnormal_disconnect()
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{
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var store = new MqttSessionStore();
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string? publishedTopic = null;
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byte[]? publishedPayload = null;
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byte publishedQoS = 0xFF;
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bool publishedRetain = false;
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store.OnPublish = (topic, payload, qos, retain) =>
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{
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publishedTopic = topic;
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publishedPayload = payload;
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publishedQoS = qos;
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publishedRetain = retain;
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};
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var will = new WillMessage { Topic = "device/gone", Payload = "disconnected"u8.ToArray(), QoS = 1, Retain = false };
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store.SetWill("client-3", will);
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var result = store.PublishWillMessage("client-3");
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result.ShouldBeTrue();
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publishedTopic.ShouldBe("device/gone");
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publishedPayload.ShouldBe("disconnected"u8.ToArray());
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publishedQoS.ShouldBe((byte)1);
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publishedRetain.ShouldBeFalse();
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}
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// Go ref: mqttDeliverWill — no-op when no will is registered.
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[Fact]
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public void PublishWillMessage_returns_false_when_no_will()
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{
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var store = new MqttSessionStore();
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var invoked = false;
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store.OnPublish = (_, _, _, _) => { invoked = true; };
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var result = store.PublishWillMessage("client-no-will");
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result.ShouldBeFalse();
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invoked.ShouldBeFalse();
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}
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// Go ref: mqttDeliverWill — will is consumed (not published twice).
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[Fact]
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public void PublishWillMessage_clears_will_after_publish()
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{
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var store = new MqttSessionStore();
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store.OnPublish = (_, _, _, _) => { };
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var will = new WillMessage { Topic = "sensor/status", Payload = "gone"u8.ToArray() };
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store.SetWill("client-5", will);
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store.PublishWillMessage("client-5");
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store.GetWill("client-5").ShouldBeNull();
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store.PublishWillMessage("client-5").ShouldBeFalse();
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}
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// Go ref: TestMQTTWill — graceful DISCONNECT clears the will before disconnect;
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// subsequent PublishWillMessage has no effect.
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[Fact]
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public void CleanDisconnect_does_not_publish_will()
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{
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var store = new MqttSessionStore();
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var invoked = false;
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store.OnPublish = (_, _, _, _) => { invoked = true; };
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var will = new WillMessage { Topic = "client/status", Payload = "bye"u8.ToArray() };
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store.SetWill("client-6", will);
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// Simulate graceful DISCONNECT: clear will before triggering publish path
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store.ClearWill("client-6");
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var result = store.PublishWillMessage("client-6");
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result.ShouldBeFalse();
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invoked.ShouldBeFalse();
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}
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// Go ref: TestMQTTWill — published topic and payload must exactly match what was registered.
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[Fact]
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public void WillMessage_preserves_topic_and_payload()
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{
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var store = new MqttSessionStore();
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var capturedTopic = string.Empty;
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var capturedPayload = Array.Empty<byte>();
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store.OnPublish = (topic, payload, _, _) =>
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{
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capturedTopic = topic;
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capturedPayload = payload;
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};
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var originalPayload = "sensor-offline-payload"u8.ToArray();
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store.SetWill("client-7", new WillMessage { Topic = "sensors/temperature/offline", Payload = originalPayload });
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store.PublishWillMessage("client-7");
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capturedTopic.ShouldBe("sensors/temperature/offline");
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capturedPayload.ShouldBe(originalPayload);
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}
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// Go ref: TestMQTTWill — QoS level from the will is forwarded to the broker publish path.
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[Fact]
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public void WillMessage_preserves_qos()
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{
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var store = new MqttSessionStore();
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byte capturedQoS = 0xFF;
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store.OnPublish = (_, _, qos, _) => { capturedQoS = qos; };
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store.SetWill("client-8", new WillMessage { Topic = "t", Payload = [], QoS = 1 });
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store.PublishWillMessage("client-8");
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capturedQoS.ShouldBe((byte)1);
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}
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// Go ref: TestMQTTWillRetain — retain flag from the will is forwarded to the broker publish path.
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[Fact]
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public void WillMessage_preserves_retain_flag()
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{
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var store = new MqttSessionStore();
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bool capturedRetain = false;
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store.OnPublish = (_, _, _, retain) => { capturedRetain = retain; };
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store.SetWill("client-9", new WillMessage { Topic = "t", Payload = [], Retain = true });
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store.PublishWillMessage("client-9");
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capturedRetain.ShouldBeTrue();
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}
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// Go ref: MQTT 5.0 Will-Delay-Interval — a will with delay > 0 is not immediately published;
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// it is tracked as a delayed will and OnPublish is NOT called immediately.
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[Fact]
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public void PublishWillMessage_with_delay_stores_delayed_will_and_does_not_call_OnPublish()
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{
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var store = new MqttSessionStore();
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var immediatelyPublished = false;
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store.OnPublish = (_, _, _, _) => { immediatelyPublished = true; };
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var will = new WillMessage
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{
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Topic = "device/status",
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Payload = "gone"u8.ToArray(),
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QoS = 0,
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Retain = false,
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DelayIntervalSeconds = 30
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};
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store.SetWill("client-10", will);
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var result = store.PublishWillMessage("client-10");
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// Returns true because a will was found
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result.ShouldBeTrue();
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// OnPublish must NOT have been called — it is delayed
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immediatelyPublished.ShouldBeFalse();
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// The will must be tracked as a pending delayed will
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var delayed = store.GetDelayedWill("client-10");
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delayed.ShouldNotBeNull();
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delayed!.Value.Will.Topic.ShouldBe("device/status");
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delayed.Value.Will.DelayIntervalSeconds.ShouldBe(30);
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}
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}
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