feat: skip transcode files held by an active session

Every replica runs the transcode cleanup task against the same shared transcode
directory, so one pod deletes segments another pod is still streaming.

- read the active sessions from ITranscodeSessionStore before deleting
- keep files matching an active session manifest path or segment prefix
- abort the sweep when the store cannot be reached

Emby.Server.Implementations/ScheduledTasks/Tasks/DeleteTranscodeFileTask.cs

@@ -5,6 +5,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using MediaBrowser.Common.Configuration;
 using MediaBrowser.Controller.IO;
+using MediaBrowser.Controller.MediaEncoding;
 using MediaBrowser.Model.Globalization;
 using MediaBrowser.Model.IO;
 using MediaBrowser.Model.Tasks;
@@ -21,6 +22,7 @@ public class DeleteTranscodeFileTask : IScheduledTask, IConfigurableScheduledTas
     private readonly IConfigurationManager _configurationManager;
     private readonly IFileSystem _fileSystem;
     private readonly ILocalizationManager _localization;
+    private readonly ITranscodeSessionStore _sessionStore;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="DeleteTranscodeFileTask"/> class.
@@ -29,16 +31,19 @@ public class DeleteTranscodeFileTask : IScheduledTask, IConfigurableScheduledTas
     /// <param name="fileSystem">Instance of the <see cref="IFileSystem"/> interface.</param>
     /// <param name="configurationManager">Instance of the <see cref="IConfigurationManager"/> interface.</param>
     /// <param name="localization">Instance of the <see cref="ILocalizationManager"/> interface.</param>
+    /// <param name="sessionStore">Instance of the <see cref="ITranscodeSessionStore"/> interface.</param>
     public DeleteTranscodeFileTask(
         ILogger<DeleteTranscodeFileTask> logger,
         IFileSystem fileSystem,
         IConfigurationManager configurationManager,
-        ILocalizationManager localization)
+        ILocalizationManager localization,
+        ITranscodeSessionStore sessionStore)
     {
         _logger = logger;
         _fileSystem = fileSystem;
         _configurationManager = configurationManager;
         _localization = localization;
+        _sessionStore = sessionStore;
     }
 
     /// <inheritdoc />
@@ -78,25 +83,39 @@ public class DeleteTranscodeFileTask : IScheduledTask, IConfigurableScheduledTas
     }
 
     /// <inheritdoc />
-    public Task ExecuteAsync(IProgress<double> progress, CancellationToken cancellationToken)
+    public async Task ExecuteAsync(IProgress<double> progress, CancellationToken cancellationToken)
     {
         var minDateModified = DateTime.UtcNow.AddDays(-1);
         progress.Report(50);
 
-        DeleteTempFilesFromDirectory(_configurationManager.GetTranscodePath(), minDateModified, progress, cancellationToken);
+        IEnumerable<TranscodeSession> activeSessions;
+        try
+        {
+            activeSessions = await _sessionStore.GetActiveSessionsAsync(cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to retrieve active transcode sessions. Skipping deletion to avoid removing files in use.");
+            progress.Report(100);
+            return;
+        }
 
-        return Task.CompletedTask;
+        DeleteTempFilesFromDirectory(_configurationManager.GetTranscodePath(), minDateModified, activeSessions, progress, cancellationToken);
     }
 
     /// <summary>
-    /// Deletes the transcoded temp files from directory with a last write time less than a given date.
+    /// Deletes the transcoded temp files from directory with a last write time less than a given date,
+    /// skipping any files that belong to an active transcode session.
     /// </summary>
     /// <param name="directory">The directory.</param>
     /// <param name="minDateModified">The min date modified.</param>
+    /// <param name="activeSessions">The currently active transcode sessions.</param>
     /// <param name="progress">The progress.</param>
     /// <param name="cancellationToken">The task cancellation token.</param>
-    private void DeleteTempFilesFromDirectory(string directory, DateTime minDateModified, IProgress<double> progress, CancellationToken cancellationToken)
+    private void DeleteTempFilesFromDirectory(string directory, DateTime minDateModified, IEnumerable<TranscodeSession> activeSessions, IProgress<double> progress, CancellationToken cancellationToken)
     {
+        var activeSessionList = activeSessions.ToList();
+
         var filesToDelete = _fileSystem.GetFiles(directory, true)
             .Where(f => _fileSystem.GetLastWriteTimeUtc(f) < minDateModified)
             .ToList();
@@ -112,6 +131,13 @@ public class DeleteTranscodeFileTask : IScheduledTask, IConfigurableScheduledTas
 
             cancellationToken.ThrowIfCancellationRequested();
 
+            if (IsFileProtectedByActiveSession(file.FullName, activeSessionList))
+            {
+                _logger.LogDebug("Skipping deletion of {FilePath} as it belongs to an active transcode session.", file.FullName);
+                index++;
+                continue;
+            }
+
             FileSystemHelper.DeleteFile(_fileSystem, file.FullName, _logger);
 
             index++;
@@ -121,4 +147,24 @@ public class DeleteTranscodeFileTask : IScheduledTask, IConfigurableScheduledTas
 
         progress.Report(100);
     }
+
+    private static bool IsFileProtectedByActiveSession(string filePath, IList<TranscodeSession> activeSessions)
+    {
+        foreach (var session in activeSessions)
+        {
+            if (!string.IsNullOrEmpty(session.ManifestPath) &&
+                string.Equals(filePath, session.ManifestPath, StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+
+            if (!string.IsNullOrEmpty(session.SegmentPathPrefix) &&
+                filePath.StartsWith(session.SegmentPathPrefix, StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }