feat(mqtt): add JetStream-backed session and retained message persistence

Add optional IStreamStore backing to MqttSessionStore and MqttRetainedStore, enabling session and retained message state to survive process restarts via JetStream persistence. Includes ConnectAsync/SaveSessionAsync for session lifecycle, SetRetainedAsync/GetRetainedAsync with cleared-topic tombstone tracking, and 4 new parity tests covering persist/restart/clear semantics.
2026-02-25 02:42:02 -05:00
parent 7468401bd0
commit b7bac8e68e
3 changed files with 259 additions and 0 deletions
--- a/tests/NATS.Server.Tests/MqttPersistenceTests.cs
+++ b/tests/NATS.Server.Tests/MqttPersistenceTests.cs
@@ -0,0 +1,92 @@
+using NSubstitute;
+using NATS.Server.JetStream.Storage;
+using NATS.Server.Mqtt;
+
+namespace NATS.Server.Tests;
+
+// Go reference: server/mqtt.go ($MQTT_msgs, $MQTT_sess, $MQTT_rmsgs JetStream streams)
+
+public class MqttPersistenceTests
+{
+    [Fact]
+    public async Task Session_persists_across_restart()
+    {
+        // Go reference: server/mqtt.go mqttStoreSession — session survives restart
+        var store = MqttSessionStoreTestHelper.CreateWithJetStream();
+
+        await store.ConnectAsync("client-1", cleanSession: false);
+        store.AddSubscription("client-1", "topic/test", qos: 1);
+        await store.SaveSessionAsync("client-1");
+
+        // Simulate restart — new store backed by the same IStreamStore
+        var recovered = MqttSessionStoreTestHelper.CreateWithJetStream(store.BackingStore!);
+        await recovered.ConnectAsync("client-1", cleanSession: false);
+
+        var subs = recovered.GetSubscriptions("client-1");
+        subs.ShouldContainKey("topic/test");
+    }
+
+    [Fact]
+    public async Task Clean_session_deletes_existing()
+    {
+        // Go reference: server/mqtt.go cleanSession=true deletes saved state
+        var store = MqttSessionStoreTestHelper.CreateWithJetStream();
+
+        await store.ConnectAsync("client-2", cleanSession: false);
+        store.AddSubscription("client-2", "persist/me", qos: 1);
+        await store.SaveSessionAsync("client-2");
+
+        // Reconnect with clean session
+        await store.ConnectAsync("client-2", cleanSession: true);
+
+        var subs = store.GetSubscriptions("client-2");
+        subs.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public async Task Retained_message_survives_restart()
+    {
+        // Go reference: server/mqtt.go retained message persistence via JetStream
+        var retained = MqttRetainedStoreTestHelper.CreateWithJetStream();
+
+        await retained.SetRetainedAsync("sensors/temp", "72.5"u8.ToArray());
+
+        // Simulate restart
+        var recovered = MqttRetainedStoreTestHelper.CreateWithJetStream(retained.BackingStore!);
+        var msg = await recovered.GetRetainedAsync("sensors/temp");
+
+        msg.ShouldNotBeNull();
+        System.Text.Encoding.UTF8.GetString(msg).ShouldBe("72.5");
+    }
+
+    [Fact]
+    public async Task Retained_message_cleared_with_empty_payload()
+    {
+        // Go reference: server/mqtt.go empty payload clears retained
+        var retained = MqttRetainedStoreTestHelper.CreateWithJetStream();
+
+        await retained.SetRetainedAsync("sensors/temp", "72.5"u8.ToArray());
+        await retained.SetRetainedAsync("sensors/temp", ReadOnlyMemory<byte>.Empty); // clear
+
+        var msg = await retained.GetRetainedAsync("sensors/temp");
+        msg.ShouldBeNull();
+    }
+}
+
+public static class MqttSessionStoreTestHelper
+{
+    public static MqttSessionStore CreateWithJetStream(IStreamStore? backingStore = null)
+    {
+        var store = backingStore ?? new MemStore();
+        return new MqttSessionStore(store);
+    }
+}
+
+public static class MqttRetainedStoreTestHelper
+{
+    public static MqttRetainedStore CreateWithJetStream(IStreamStore? backingStore = null)
+    {
+        var store = backingStore ?? new MemStore();
+        return new MqttRetainedStore(store);
+    }
+}