Close a change batch on its own window so a library scan cannot grow it without bound

1 files changed, 123 insertions, 0 deletions

diff --git a/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/LibraryChangedNotifierTests.cs b/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/LibraryChangedNotifierTests.cs
new file mode 100644
index 0000000000..cdb261de8d
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/EntryPoints/LibraryChangedNotifierTests.cs
@@ -0,0 +1,123 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Emby.Server.Implementations.EntryPoints;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Controller.Session;
+using MediaBrowser.Model.Configuration;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.EntryPoints;
+
+public class LibraryChangedNotifierTests
+{
+    // How long a test waits for the notifier's timer callback to run. Generous: the assertions are
+    // about a batch being sent at all, not about how promptly.
+    private static readonly TimeSpan _flushTimeout = TimeSpan.FromSeconds(15);
+
+    private readonly Mock<ILibraryManager> _libraryManager = new();
+    private readonly Mock<IServerConfigurationManager> _configurationManager = new();
+    private readonly Mock<ISessionManager> _sessionManager = new();
+    private readonly Mock<IUserManager> _userManager = new();
+    private readonly Mock<IProviderManager> _providerManager = new();
+    private readonly ServerConfiguration _configuration = new();
+
+    private int _flushCount;
+
+    public LibraryChangedNotifierTests()
+    {
+        _configurationManager.SetupGet(e => e.Configuration).Returns(_configuration);
+
+        // Reading the session list is the first thing a flush does, so it stands in for "a batch was
+        // sent" without having to mock a whole user library behind it.
+        _sessionManager.SetupGet(e => e.Sessions)
+            .Returns(() =>
+            {
+                Interlocked.Increment(ref _flushCount);
+                return [];
+            });
+    }
+
+    [Fact]
+    public async Task OnLibraryItemUpdated_BatchSizeCapReached_SendsWithoutWaitingForWindow()
+    {
+        // Long enough that only the size cap can close the batch.
+        _configuration.LibraryUpdateDuration = 3600;
+
+        var notifier = CreateNotifier();
+        await notifier.StartAsync(TestContext.Current.CancellationToken);
+
+        for (var i = 0; i < LibraryChangedNotifier.MaxBatchSize; i++)
+        {
+            RaiseItemUpdated();
+        }
+
+        Assert.True(await WaitForFlushAsync(1), "The batch was not sent once it hit the size cap.");
+
+        await notifier.StopAsync(TestContext.Current.CancellationToken);
+        notifier.Dispose();
+    }
+
+    [Fact]
+    public async Task OnLibraryItemUpdated_ChangesNeverPause_StillSendsOnTheWindow()
+    {
+        // A scan changes items continuously. The window must run from the first change of a batch, or
+        // the batch never closes and holds every item it named alive for the length of the scan.
+        _configuration.LibraryUpdateDuration = 1;
+
+        var notifier = CreateNotifier();
+        await notifier.StartAsync(TestContext.Current.CancellationToken);
+
+        var stopwatch = Stopwatch.StartNew();
+        while (stopwatch.Elapsed < _flushTimeout && Volatile.Read(ref _flushCount) == 0)
+        {
+            // Well below the window, and well below the size cap over the whole loop.
+            RaiseItemUpdated();
+            await Task.Delay(25, TestContext.Current.CancellationToken);
+        }
+
+        Assert.True(Volatile.Read(ref _flushCount) > 0, "The batch was never sent while changes kept arriving.");
+
+        await notifier.StopAsync(TestContext.Current.CancellationToken);
+        notifier.Dispose();
+    }
+
+    private LibraryChangedNotifier CreateNotifier()
+        => new(
+            _libraryManager.Object,
+            _configurationManager.Object,
+            _sessionManager.Object,
+            _userManager.Object,
+            NullLogger<LibraryChangedNotifier>.Instance,
+            _providerManager.Object);
+
+    // A folder passes the notifier's item filter without needing any of BaseItem's static services.
+    private void RaiseItemUpdated()
+        => _libraryManager.Raise(
+            e => e.ItemUpdated += null,
+            _libraryManager.Object,
+            new ItemChangeEventArgs { Item = new Folder { Id = Guid.NewGuid() } });
+
+    private async Task<bool> WaitForFlushAsync(int expected)
+    {
+        var stopwatch = Stopwatch.StartNew();
+        while (stopwatch.Elapsed < _flushTimeout)
+        {
+            if (Volatile.Read(ref _flushCount) >= expected)
+            {
+                return true;
+            }
+
+            await Task.Delay(25, TestContext.Current.CancellationToken);
+        }
+
+        return false;
+    }
+}