* now will try locking both (newly|already)LockedImages with ten se…

…conds timeout and release lcoks in the returned hooks that will be invoked after `DbContext.SaveChange()`

* now will skip fetching new `ImageInReply` entities after locking `alreadyLockedImages` when it's empty
* rename variable `imagesKeyByUrlFilename` to `images`
* rename variable `(newly|already)Locked` to `(newly|already)LockedImages`
@ `Save()`

* rename field `LocksKeyByUrlFilename` to `GlobalLockedImagesInReplyKeyByUrlFilename`
- primary ctor param `locks`
@ ReplyContentImageSaver.cs

* now will quick exit when `newlyLocked` is empty @ `UserSaver.Save()`
@ c#/crawler

c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs

@@ -17,7 +17,7 @@ public override SaverChangeSet<ReplyPost> Save(CrawlerDbContext db)
             r => new ReplyRevision {TakenAt = r.UpdatedAt ?? r.CreatedAt, Pid = r.Pid},
             LinqKit.PredicateBuilder.New<ReplyPost>(r => Posts.Keys.Contains(r.Pid)));
 
-        replyContentImageSaver.Save(db, changeSet.NewlyAdded);
+        PostSaveHandlers += replyContentImageSaver.Save(db, changeSet.NewlyAdded).Invoke;
         PostSaveHandlers += AuthorRevisionSaver.SaveAuthorExpGradeRevisions(db, changeSet.AllAfter).Invoke;
         PostSaveHandlers += replySignatureSaver.Save(db, changeSet.AllAfter).Invoke;
 

c#/crawler/src/Tieba/Crawl/Saver/ReplyContentImageSaver.cs

@@ -1,10 +1,11 @@
 namespace tbm.Crawler.Tieba.Crawl.Saver;
 
-public class ReplyContentImageSaver(SaverLocks<string> locks)
+public class ReplyContentImageSaver(ILogger<ReplyContentImageSaver> logger)
 {
-    private static readonly ConcurrentDictionary<string, object> LocksKeyByUrlFilename = new();
+    private static readonly ConcurrentDictionary<string, ImageInReply>
+        GlobalLockedImagesInReplyKeyByUrlFilename = new();
 
-    public void Save(CrawlerDbContext db, IEnumerable<ReplyPost> replies)
+    public Action Save(CrawlerDbContext db, IEnumerable<ReplyPost> replies)
     {
         var pidAndImageList = (
                 from r in replies
@@ -19,39 +20,45 @@ from c in r.OriginalContents
                 }))
             .DistinctBy(t => (t.Pid, t.Image.UrlFilename))
             .ToList();
-        if (pidAndImageList.Count == 0) return;
-        var imagesKeyByUrlFilename = pidAndImageList.Select(t => t.Image)
+        if (pidAndImageList.Count == 0) return () => { };
+        var images = pidAndImageList.Select(t => t.Image)
             .DistinctBy(image => image.UrlFilename).ToDictionary(image => image.UrlFilename);
 
         var existingImages = (
                 from e in db.ImageInReplies.AsTracking()
-                where imagesKeyByUrlFilename.Keys.Contains(e.UrlFilename)
+                where images.Keys.Contains(e.UrlFilename)
                 select e)
             .ToDictionary(e => e.UrlFilename);
-        var newImages = imagesKeyByUrlFilename.ExceptByKey(existingImages.Keys).Keys().ToList();
-        var newlyLocked = locks.AcquireLocks(newImages);
-        var alreadyLocked = newImages.Except(newlyLocked).ToList();
+        var newImages = images
+            .ExceptByKey(existingImages.Keys).ToDictionary();
 
-        if (newlyLocked.Any(urlFilename => !LocksKeyByUrlFilename.TryAdd(urlFilename, new())))
-            throw new InvalidOperationException();
-        alreadyLocked.ForEach(urlFilename =>
-        {
-            lock (LocksKeyByUrlFilename[urlFilename])
-#pragma warning disable S108 // Either remove or fill this block of code.
-            {
-            }
-#pragma warning restore S108 // Either remove or fill this block of code.
-        });
-        existingImages = existingImages
-            .Concat((
-                from e in db.ImageInReplies.AsTracking()
-                where alreadyLocked.Contains(e.UrlFilename)
-                select e).ToDictionary(e => e.UrlFilename))
+        var newlyLockedImages = newImages
+            .Where(pair => GlobalLockedImagesInReplyKeyByUrlFilename.TryAdd(pair.Key, pair.Value))
+            .ToDictionary();
+        newlyLockedImages.Values()
+            .Where(reply => !Monitor.TryEnter(reply, TimeSpan.FromSeconds(10)))
+            .ForEach(image => logger.LogWarning(
+                "Wait for locking newly locked image {} timed out after 10s", image.UrlFilename));
+
+        var alreadyLockedImages = GlobalLockedImagesInReplyKeyByUrlFilename
+            .IntersectByKey(newImages
+                .Keys().Except(newlyLockedImages.Keys()))
             .ToDictionary();
+        alreadyLockedImages.Values()
+            .Where(reply => !Monitor.TryEnter(reply, TimeSpan.FromSeconds(10)))
+            .ForEach(image => logger.LogWarning(
+                "Wait for locking already locked image {} timed out after 10s", image.UrlFilename));
+        if (alreadyLockedImages.Count != 0)
+            existingImages = existingImages
+                .Concat((
+                    from e in db.ImageInReplies.AsTracking()
+                    where alreadyLockedImages.Keys().Contains(e.UrlFilename)
+                    select e).ToDictionary(e => e.UrlFilename))
+                .ToDictionary();
 
         (from existing in existingImages.Values
                 where existing.ExpectedByteSize == 0 // randomly respond with 0
-                join newInContent in imagesKeyByUrlFilename.Values
+                join newInContent in images.Values
                     on existing.UrlFilename equals newInContent.UrlFilename
                 select (existing, newInContent))
             .ForEach(t => t.existing.ExpectedByteSize = t.newInContent.ExpectedByteSize);
@@ -62,19 +69,28 @@ on existing.UrlFilename equals newInContent.UrlFilename
 
                 // no need to manually invoke DbContext.AddRange(images) since EF Core will do these chore
                 // https://stackoverflow.com/questions/5212751/how-can-i-retrieve-id-of-inserted-entity-using-entity-framework/41146434#41146434
-                // reuse the same instance from imagesKeyByUrlFilename
+                // reuse the same instance from existingImages
                 // will prevent assigning multiple different instances with the same key
                 // which will cause EF Core to insert identify entry more than one time leading to duplicated entry error
                 // https://github.com/dotnet/efcore/issues/30236
                 ImageInReply = existingImages.TryGetValue(t.Image.UrlFilename, out var e)
                     ? e
-                    : imagesKeyByUrlFilename[t.Image.UrlFilename]
+                    : images[t.Image.UrlFilename]
             }));
 
-        if (newlyLocked.Any(urlFilename => !LocksKeyByUrlFilename.TryRemove(urlFilename, out _)))
-            throw new InvalidOperationException();
-#pragma warning disable IDISP007 // Don't dispose injected
-        locks.Dispose();
-#pragma warning restore IDISP007 // Don't dispose injected
+        return () =>
+        {
+            try
+            {
+                if (newlyLockedImages.Any(pair =>
+                        !GlobalLockedImagesInReplyKeyByUrlFilename.TryRemove(pair)))
+                    throw new InvalidOperationException();
+            }
+            finally
+            {
+                newlyLockedImages.Values().ForEach(Monitor.Exit);
+                alreadyLockedImages.Values().ForEach(Monitor.Exit);
+            }
+        };
     }
 }

c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs

@@ -22,6 +22,7 @@ public void Save(
     {
         if (users.Count == 0) return;
         var newlyLocked = _saverLocks.Value.Acquire(users.Keys().ToList());
+        if (newlyLocked.Count == 0) return;
 
         // existingUsers may have new revisions to insert so excluding already locked users
         // to prevent inserting duplicate revision