feat(batch14): complete filestore write lifecycle features and tests

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/ConcurrencyTests2.Impltests.cs

@@ -1,4 +1,5 @@
 using System.Collections.Concurrent;
+using System.Diagnostics;
 using System.Reflection;
 using Shouldly;
 using ZB.MOM.NatsNet.Server;
@@ -122,6 +123,74 @@ public sealed partial class ConcurrencyTests2
         }, cfg);
     }
 
+    [Fact] // T:2494
+    public void NoRaceFileStoreWriteFullStateUniqueSubjects_ShouldSucceed()
+    {
+        var cfg = new StreamConfig
+        {
+            Name = "TEST",
+            Storage = StorageType.FileStorage,
+            Subjects = ["records.>"],
+            MaxMsgs = -1,
+            MaxBytes = 15L * 1024 * 1024 * 1024,
+            MaxAge = TimeSpan.Zero,
+            MaxMsgsPer = 1,
+            Discard = DiscardPolicy.DiscardOld,
+            Retention = RetentionPolicy.LimitsPolicy,
+        };
+
+        WithStore((fs, root) =>
+        {
+            var payload = Enumerable.Repeat((byte)'Z', 128).ToArray();
+            var errors = new ConcurrentQueue<Exception>();
+            using var cts = new CancellationTokenSource();
+
+            var writer = Task.Run(async () =>
+            {
+                while (!cts.Token.IsCancellationRequested)
+                {
+                    try
+                    {
+                        var err = InvokePrivate<Exception?>(fs, "WriteFullState");
+                        if (err != null)
+                            errors.Enqueue(err);
+                    }
+                    catch (Exception ex)
+                    {
+                        errors.Enqueue(ex);
+                    }
+
+                    try
+                    {
+                        await Task.Delay(10, cts.Token);
+                    }
+                    catch (OperationCanceledException)
+                    {
+                        break;
+                    }
+                }
+            });
+
+            for (var i = 0; i < 2_000; i++)
+            {
+                var subject = $"records.{Guid.NewGuid():N}.{i % 5}";
+                var sw = Stopwatch.StartNew();
+                fs.StoreMsg(subject, null, payload, 0).Seq.ShouldBeGreaterThan(0UL);
+                sw.Stop();
+                sw.Elapsed.ShouldBeLessThan(TimeSpan.FromMilliseconds(500));
+            }
+
+            cts.Cancel();
+            Should.NotThrow(() => writer.Wait(TimeSpan.FromSeconds(2)));
+            errors.ShouldBeEmpty();
+
+            fs.Stop();
+            var stateFile = Path.Combine(root, FileStoreDefaults.MsgDir, FileStoreDefaults.StreamStateFile);
+            File.Exists(stateFile).ShouldBeTrue();
+            new FileInfo(stateFile).Length.ShouldBeGreaterThan(0L);
+        }, cfg);
+    }
+
     private static void WithStore(Action<JetStreamFileStore, string> action, StreamConfig? cfg = null)
     {
         var root = NewRoot();