Prevent unbounded queue history retention

.gitignore

@@ -34,6 +34,9 @@ bld/
 [Tt]est[Rr]esult*/
 [Bb]uild[Ll]og.*
 
+# Generated test result artifacts
+Tests/**/[Rr]esults/
+
 # NUNIT
 *.VisualState.xml
 TestResult.xml

Libraries/Esiur/Core/AsyncQueue.cs

@@ -50,7 +50,8 @@ public class AsyncQueue<T> : AsyncReply<T>
     int currentId = 0;
     int currentFlushId;
 
-    public List<AsyncQueueItem<T>> Processed = new();
+    bool captureProcessedItems;
+    List<AsyncQueueItem<T>> processed = new();
 
     List<AsyncQueueItem<T>> list = new List<AsyncQueueItem<T>>();
     //Action<T> callback;
@@ -63,6 +64,34 @@ public class AsyncQueue<T> : AsyncReply<T>
     //return this;
     //}
 
+    /// <summary>
+    /// Enables or disables retaining delivered queue items for diagnostics.
+    /// Capture is disabled by default, and disabling it discards retained items.
+    /// </summary>
+    public void SetProcessedCapture(bool enabled)
+    {
+        lock (queueLock)
+        {
+            captureProcessedItems = enabled;
+
+            if (!enabled)
+                processed = new();
+        }
+    }
+
+    /// <summary>
+    /// Atomically returns and removes the delivered queue items retained since the previous drain.
+    /// </summary>
+    public List<AsyncQueueItem<T>> DrainProcessed()
+    {
+        lock (queueLock)
+        {
+            var result = processed;
+            processed = new();
+            return result;
+        }
+    }
+
     public void Add(AsyncReply<T> reply)
     {
         lock (queueLock)
@@ -121,13 +150,16 @@ public class AsyncQueue<T> : AsyncReply<T>
                     Trigger(list[i].Reply.Result);
                     resultReady = false;
 
-                    var p = list[i];
-                    p.Delivered = DateTime.Now;
-                    p.Ready = p.Reply.ReadyTime;
-                    p.BatchSize = batchSize;
-                    p.FlushId = flushId;
-                    //p.HasResource = p.Reply. (p.Ready - p.Arrival).TotalMilliseconds > 5;
-                    Processed.Add(p);
+                    if (captureProcessedItems)
+                    {
+                        var p = list[i];
+                        p.Delivered = DateTime.Now;
+                        p.Ready = p.Reply.ReadyTime;
+                        p.BatchSize = batchSize;
+                        p.FlushId = flushId;
+                        //p.HasResource = p.Reply. (p.Ready - p.Arrival).TotalMilliseconds > 5;
+                        processed.Add(p);
+                    }
 
                     list.RemoveAt(i);
 

Libraries/Esiur/Protocol/EpConnection.cs

@@ -378,11 +378,21 @@ public partial class EpConnection : NetworkConnection, IStore
     }
 
 
+    /// <summary>
+    /// Enables or disables retaining delivered resource queue items for diagnostics.
+    /// Capture is disabled by default.
+    /// </summary>
+    public void SetFinishedQueueCapture(bool enabled)
+    {
+        _queue.SetProcessedCapture(enabled);
+    }
+
+    /// <summary>
+    /// Atomically returns and removes the retained delivered resource queue items.
+    /// </summary>
     public List<AsyncQueueItem<EpResourceQueueItem>> GetFinishedQueue()
     {
-        var l = _queue.Processed.ToArray().ToList();
-        _queue.Processed.Clear();
-        return l;
+        return _queue.DrainProcessed();
     }
 
     void init()

Tests/Distribution/Queueing/Client/Program.cs

@@ -7,9 +7,9 @@
 // Table III (λ, μ, R̄, δ̄, D̄, P99(D), queue length, batch B).
 //
 // Each replication uses an identical configuration; the server
-// runs StartUpdatesLocal back-to-back, and the client snapshots
-// the cumulative finished-queue length between replications so
-// that each replication's evaluation sees only its own items.
+// runs StartUpdatesLocal back-to-back, and the client drains the
+// captured finished queue between replications so that each
+// replication's evaluation sees only its own items.
 //
 // Usage:
 //   dotnet run -- --host 127.0.0.1 --port 10901 \
@@ -52,20 +52,20 @@ Console.WriteLine($"[Client-T4-R] {delays.Length * alphas.Length} configurations
 var wh = new Warehouse();
 var serviceResource = await wh.Get<EpResource>($"ep://{host}:{port}/sys/queueing");
 var service = (dynamic)serviceResource;
+serviceResource.ResourceConnection.SetFinishedQueueCapture(true);
 
 // ---------- replication coordinator state ----------
 //
 // The server's StartUpdatesLocal fires `trials` PropertyChanged events
 // across a single call. We count incoming events; when `trials` arrive,
-// the current replication is complete. We then slice off this rep's
-// portion of the cumulative finished-queue and hand it to QueueEval.
+// the current replication is complete. We then drain this rep's
+// finished-queue items and hand them to QueueEval.
 //
 // `repDone` is signaled once per replication so the orchestrator coroutine
 // can drive the next call.
 
 int eventsThisRep = 0;
 TaskCompletionSource<bool> repDone = new(TaskCreationOptions.RunContinuationsAsynchronously);
-int finishedQueueBaseline = 0; // cumulative length BEFORE current rep started
 
 serviceResource.PropertyChanged += (object? sender, PropertyChangedEventArgs e) =>
 {
@@ -100,10 +100,8 @@ foreach (var delay in delays)
             repDone = new TaskCompletionSource<bool>(
                 TaskCreationOptions.RunContinuationsAsynchronously);
 
-            // Snapshot the cumulative finished-queue length right before this rep
-            // so we can slice off only this rep's portion afterwards.
-            var preQueue = service.ResourceConnection.GetFinishedQueue();
-            finishedQueueBaseline = preQueue.Count;
+            // Discard any straggler notifications from the previous replication.
+            serviceResource.ResourceConnection.GetFinishedQueue();
 
             // Kick off the server-driven trial sequence (fire-and-forget;
             // completion is signalled via PropertyChanged → repDone).
@@ -112,15 +110,10 @@ foreach (var delay in delays)
             // Wait until `trials` PropertyChanged events have been received.
             await repDone.Task;
 
-            // The server completed `trials` events; slice off this rep's
-            // portion of the cumulative finished-queue. GetFinishedQueue()
-            // returns IReadOnlyList<AsyncQueueItem<T>>; we forward the
-            // typed sliced subset directly to Evaluate which is generic
-            // on T (the property's runtime payload type).
-            var fullQueue = service.ResourceConnection.GetFinishedQueue();
-            var typedQueue = SliceQueue(fullQueue, finishedQueueBaseline);
-
-            var repResult = EsiurQueueEval.Evaluate(typedQueue);
+            // The server completed `trials` events; drain this replication's
+            // captured queue items and evaluate them directly.
+            var repQueue = serviceResource.ResourceConnection.GetFinishedQueue();
+            var repResult = EsiurQueueEval.Evaluate(repQueue);
             reps.Add(repResult);
 
             Console.WriteLine($"  rep {rep + 1}/{replications}: " +
@@ -158,19 +151,3 @@ static string GetArg(string[] args, string key, string def)
     int i = Array.IndexOf(args, key);
     return (i >= 0 && i + 1 < args.Length) ? args[i + 1] : def;
 }
-
-// ----------------------------------------------------------------
-// Slice the cumulative finished-queue down to only the items added
-// during the current replication.
-//
-// The queue is dynamically typed (returned from a dynamic-dispatched
-// member) and its element type is AsyncQueueItem<T> where T is the
-// runtime payload type of the observed property. We rely on the DLR
-// to bind the LINQ Skip<T>/ToList<T> generic methods at runtime, just
-// as the original code does with the Evaluate<T> call below it.
-// ----------------------------------------------------------------
-static dynamic SliceQueue(dynamic fullQueue, int skipCount)
-{
-    return System.Linq.Enumerable.ToList(
-        System.Linq.Enumerable.Skip(fullQueue, skipCount));
-}

Tests/Unit/AsyncQueueTests.cs

@@ -0,0 +1,77 @@
+using Esiur.Core;
+
+namespace Esiur.Tests.Unit;
+
+public class AsyncQueueTests
+{
+    [Fact]
+    public void ProcessedCapture_IsDisabledByDefault()
+    {
+        var queue = new AsyncQueue<int>();
+        var delivered = new List<int>();
+        queue.Then(delivered.Add);
+
+        for (var i = 0; i < 100; i++)
+            queue.Add(new AsyncReply<int>(i));
+
+        Assert.Equal(Enumerable.Range(0, 100), delivered);
+        Assert.Empty(queue.DrainProcessed());
+    }
+
+    [Fact]
+    public void DrainProcessed_ReturnsCapturedItemsExactlyOnce()
+    {
+        var queue = new AsyncQueue<int>();
+        queue.SetProcessedCapture(true);
+
+        for (var i = 0; i < 100; i++)
+            queue.Add(new AsyncReply<int>(i));
+
+        var processed = queue.DrainProcessed();
+
+        Assert.Equal(100, processed.Count);
+        Assert.Equal(Enumerable.Range(1, 100), processed.Select(x => x.Sequence));
+        Assert.All(processed, x => Assert.NotEqual(default, x.Delivered));
+        Assert.Empty(queue.DrainProcessed());
+    }
+
+    [Fact]
+    public void DisablingCapture_DiscardsHistoryAndStopsCapturing()
+    {
+        var queue = new AsyncQueue<int>();
+        queue.SetProcessedCapture(true);
+        queue.Add(new AsyncReply<int>(1));
+
+        queue.SetProcessedCapture(false);
+        queue.Add(new AsyncReply<int>(2));
+
+        Assert.Empty(queue.DrainProcessed());
+    }
+
+    [Fact]
+    public async Task DrainProcessed_DoesNotLoseItemsDuringConcurrentAdds()
+    {
+        const int itemCount = 1000;
+        var queue = new AsyncQueue<int>();
+        var sequences = new HashSet<int>();
+        queue.SetProcessedCapture(true);
+
+        var producer = Task.Run(() =>
+            Parallel.For(0, itemCount, i => queue.Add(new AsyncReply<int>(i))));
+
+        while (!producer.IsCompleted)
+        {
+            foreach (var item in queue.DrainProcessed())
+                Assert.True(sequences.Add(item.Sequence));
+
+            await Task.Yield();
+        }
+
+        await producer;
+
+        foreach (var item in queue.DrainProcessed())
+            Assert.True(sequences.Add(item.Sequence));
+
+        Assert.Equal(Enumerable.Range(1, itemCount), sequences.OrderBy(x => x));
+    }
+}