feat: add slow consumer per-kind tracking with account counters (Gap 5.5)

Adds SlowConsumerTracker class for per-ClientKind slow consumer counting with configurable threshold callbacks, and extends Account with atomic IncrementSlowConsumers/SlowConsumerCount/ResetSlowConsumerCount members. Includes 10 unit tests covering concurrency, threshold firing, and reset.
2026-02-25 11:33:58 -05:00
parent 774717d57c
commit 7e5c6e4fd9
3 changed files with 222 additions and 0 deletions
--- a/tests/NATS.Server.Tests/SlowConsumerStallGateTests.cs
+++ b/tests/NATS.Server.Tests/SlowConsumerStallGateTests.cs
@@ -0,0 +1,153 @@
+using NATS.Server;
+using NATS.Server.Auth;
+using Shouldly;
+
+namespace NATS.Server.Tests;
+
+/// <summary>
+/// Tests for <see cref="SlowConsumerTracker"/> and <see cref="Account"/> slow-consumer counters.
+/// Go reference: server/client.go — handleSlowConsumer, markConnAsSlow.
+/// </summary>
+public class SlowConsumerStallGateTests
+{
+    // ── SlowConsumerTracker ────────────────────────────────────────────────────
+
+    [Fact]
+    public void RecordSlowConsumer_increments_total_count()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Router);
+
+        tracker.TotalCount.ShouldBe(3L);
+    }
+
+    [Fact]
+    public void RecordSlowConsumer_increments_per_kind_count()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Gateway);
+
+        tracker.GetCount(ClientKind.Client).ShouldBe(2L);
+        tracker.GetCount(ClientKind.Gateway).ShouldBe(1L);
+    }
+
+    [Fact]
+    public void GetCount_returns_zero_for_unrecorded_kind()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        tracker.GetCount(ClientKind.Leaf).ShouldBe(0L);
+    }
+
+    [Fact]
+    public void Multiple_kinds_tracked_independently()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Router);
+        tracker.RecordSlowConsumer(ClientKind.Gateway);
+        tracker.RecordSlowConsumer(ClientKind.Leaf);
+
+        tracker.GetCount(ClientKind.Client).ShouldBe(1L);
+        tracker.GetCount(ClientKind.Router).ShouldBe(1L);
+        tracker.GetCount(ClientKind.Gateway).ShouldBe(1L);
+        tracker.GetCount(ClientKind.Leaf).ShouldBe(1L);
+        tracker.GetCount(ClientKind.System).ShouldBe(0L);
+        tracker.TotalCount.ShouldBe(4L);
+    }
+
+    [Fact]
+    public void OnThresholdExceeded_fires_when_threshold_reached()
+    {
+        var tracker = new SlowConsumerTracker(threshold: 3);
+        ClientKind? firedKind = null;
+        tracker.OnThresholdExceeded(k => firedKind = k);
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        firedKind.ShouldBeNull();
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        firedKind.ShouldBeNull();
+
+        tracker.RecordSlowConsumer(ClientKind.Router);
+        firedKind.ShouldBe(ClientKind.Router);
+    }
+
+    [Fact]
+    public void OnThresholdExceeded_not_fired_below_threshold()
+    {
+        var tracker = new SlowConsumerTracker(threshold: 5);
+        var fired = false;
+        tracker.OnThresholdExceeded(_ => fired = true);
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Client);
+
+        fired.ShouldBeFalse();
+    }
+
+    [Fact]
+    public void Reset_clears_all_counters()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        tracker.RecordSlowConsumer(ClientKind.Client);
+        tracker.RecordSlowConsumer(ClientKind.Router);
+        tracker.TotalCount.ShouldBe(2L);
+
+        tracker.Reset();
+
+        tracker.TotalCount.ShouldBe(0L);
+        tracker.GetCount(ClientKind.Client).ShouldBe(0L);
+        tracker.GetCount(ClientKind.Router).ShouldBe(0L);
+    }
+
+    // ── Account slow-consumer counters ────────────────────────────────────────
+
+    [Fact]
+    public void Account_IncrementSlowConsumers_tracks_count()
+    {
+        var account = new Account("test-account");
+
+        account.SlowConsumerCount.ShouldBe(0L);
+
+        account.IncrementSlowConsumers();
+        account.IncrementSlowConsumers();
+        account.IncrementSlowConsumers();
+
+        account.SlowConsumerCount.ShouldBe(3L);
+    }
+
+    [Fact]
+    public void Account_ResetSlowConsumerCount_clears()
+    {
+        var account = new Account("test-account");
+
+        account.IncrementSlowConsumers();
+        account.IncrementSlowConsumers();
+        account.SlowConsumerCount.ShouldBe(2L);
+
+        account.ResetSlowConsumerCount();
+
+        account.SlowConsumerCount.ShouldBe(0L);
+    }
+
+    [Fact]
+    public void Thread_safety_concurrent_increments()
+    {
+        var tracker = new SlowConsumerTracker();
+
+        Parallel.For(0, 1000, _ => tracker.RecordSlowConsumer(ClientKind.Client));
+
+        tracker.TotalCount.ShouldBe(1000L);
+        tracker.GetCount(ClientKind.Client).ShouldBe(1000L);
+    }
+}