fix(site-runtime): reuse exited detached worker slots in script scheduler (review 2026-10-21 01/SR-M1)

2026-10-22 08:29:09 -04:00
parent 96cab3f3d7
commit 7541a38762
2 changed files with 91 additions and 11 deletions
@@ -118,4 +118,44 @@ public class ScriptExecutionSchedulerTests
            await Task.Delay(50);
        Assert.True(condition(), "condition not met within timeout");
    }
+
+    /// <summary>
+    /// Repeatedly wedging + detaching a worker must reuse the vacated slot rather than grow the
+    /// slot table without bound (review 2026-10-21 01/SR-M1).
+    /// </summary>
+    [Fact]
+    public async Task DetachedWorkerSlot_IsReused_SlotTableStaysBounded()
+    {
+        using var scheduler = new ScriptExecutionScheduler(1);
+
+        for (var round = 0; round < 6; round++)
+        {
+            var gate = new ManualResetEventSlim(false);
+            var started = new TaskCompletionSource<(int Slot, long Stamp)>();
+            var wedged = Task.Factory.StartNew(() =>
+            {
+                var slot = ScriptExecutionScheduler.CurrentWorkerSlot!.Value;
+                started.SetResult((slot, scheduler.CurrentRunStamp(slot)));
+                gate.Wait();
+            }, CancellationToken.None, TaskCreationOptions.None, scheduler);
+
+            var (s, stamp) = await started.Task;
+            Assert.Equal(WorkerDetachOutcome.Detached, scheduler.TryDetachWorker(s, stamp));
+            gate.Set();
+            await wedged;
+
+            // Wait for the detached worker to exit and hand its slot back.
+            var deadline = DateTime.UtcNow.AddSeconds(5);
+            while (scheduler.DetachedThreadCount != 0 && DateTime.UtcNow < deadline)
+                await Task.Delay(10);
+            Assert.Equal(0, scheduler.DetachedThreadCount);
+            await Task.Delay(50);
+        }
+
+        // 1 live + at most 1 free/in-flight detached slot, never 1 + 6.
+        Assert.True(scheduler.SlotCount <= 2, $"slot table grew to {scheduler.SlotCount}");
+        // The pool still works afterwards.
+        var ran = await Task.Factory.StartNew(() => 42, CancellationToken.None, TaskCreationOptions.None, scheduler);
+        Assert.Equal(42, ran);
+    }
 }