Backport pull request #17982 from jellyfin/release-12.z

Fix SimilarItemsManager concurrency

Original-merge: 47ba387eb36458e2b417748fbe852c27957020ad

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Cody Robibero <cody@robibe.ro>

1 files changed, 27 insertions, 2 deletions

diff --git a/Emby.Server.Implementations/Library/SimilarItems/SimilarItemsManager.cs b/Emby.Server.Implementations/Library/SimilarItems/SimilarItemsManager.cs
index fd5f292ebe..a18a17b593 100644
--- a/Emby.Server.Implementations/Library/SimilarItems/SimilarItemsManager.cs
+++ b/Emby.Server.Implementations/Library/SimilarItems/SimilarItemsManager.cs
@@ -651,7 +651,13 @@ public class SimilarItemsManager : ISimilarItemsManager
 
         try
         {
-            var stream = File.OpenRead(cachePath);
+            var stream = new FileStream(
+                cachePath,
+                FileMode.Open,
+                FileAccess.Read,
+                FileShare.ReadWrite | FileShare.Delete,
+                IODefaults.FileStreamBufferSize,
+                FileOptions.Asynchronous | FileOptions.SequentialScan);
             await using (stream.ConfigureAwait(false))
             {
                 var cache = await JsonSerializer.DeserializeAsync<SimilarItemsCache>(stream, JsonDefaults.Options, cancellationToken).ConfigureAwait(false);
@@ -675,6 +681,7 @@ public class SimilarItemsManager : ISimilarItemsManager
 
     private async Task SaveSimilarItemsCacheAsync(string cachePath, List<SimilarItemReference> references, TimeSpan cacheDuration, CancellationToken cancellationToken)
     {
+        string? tempPath = null;
         try
         {
             var directory = Path.GetDirectoryName(cachePath);
@@ -689,16 +696,34 @@ public class SimilarItemsManager : ISimilarItemsManager
                 ExpiresAt = DateTime.UtcNow.Add(cacheDuration)
             };
 
-            var stream = File.Create(cachePath);
+            tempPath = cachePath + "." + Guid.NewGuid().ToString("N", CultureInfo.InvariantCulture) + ".tmp";
+            var stream = File.Create(tempPath);
             await using (stream.ConfigureAwait(false))
             {
                 await JsonSerializer.SerializeAsync(stream, cache, JsonDefaults.Options, cancellationToken).ConfigureAwait(false);
             }
+
+            File.Move(tempPath, cachePath, true);
+            tempPath = null;
         }
         catch (IOException ex)
         {
             _logger.LogWarning(ex, "Failed to save similar items cache to {CachePath}", cachePath);
         }
+        finally
+        {
+            if (tempPath is not null)
+            {
+                try
+                {
+                    File.Delete(tempPath);
+                }
+                catch (IOException ex)
+                {
+                    _logger.LogDebug(ex, "Failed to delete temporary similar items cache file {TempPath}", tempPath);
+                }
+            }
+        }
     }
 
     private sealed class SimilarItemsCache