fix(jobs): retry directories whose reconciliation batch was dropped

Lactose/Jobs/FileSystemCrawlJob.cs

@@ -121,19 +121,23 @@ public sealed class FileSystemCrawlJob : Job {
 
             if (changed) {
                 dirsProcessed++;
-                await ReconcileDirectory(assetDb, currentPath, files!, uploaderId, token,
+                bool reconciled = await ReconcileDirectory(assetDb, currentPath, files!, uploaderId, token,
                     (added, updated, deleted) => { filesAdded += added; filesUpdated += updated; filesDeleted += deleted; });
 
-                if (existingStates.TryGetValue(currentPath, out var existingState)) {
-                    existingState.LastMtime = currentDir.LastWriteTimeUtc;
-                } else {
-                    existingStates[currentPath] = new DirectoryScanState {
-                        Id          = Guid.NewGuid(),
-                        FolderId    = folderId,
-                        Path        = currentPath,
-                        LastMtime   = currentDir.LastWriteTimeUtc
-                    };
-                    db.DirectoryScanStates.Add(existingStates[currentPath]);
+                // Only record scan state when the reconciliation batch actually committed; a dropped
+                // batch leaves the mtime stale so the directory is retried on the next run.
+                if (reconciled) {
+                    if (existingStates.TryGetValue(currentPath, out var existingState)) {
+                        existingState.LastMtime = currentDir.LastWriteTimeUtc;
+                    } else {
+                        existingStates[currentPath] = new DirectoryScanState {
+                            Id          = Guid.NewGuid(),
+                            FolderId    = folderId,
+                            Path        = currentPath,
+                            LastMtime   = currentDir.LastWriteTimeUtc
+                        };
+                        db.DirectoryScanStates.Add(existingStates[currentPath]);
+                    }
                 }
             } else {
                 dirsSkipped++;
@@ -186,7 +190,8 @@ public sealed class FileSystemCrawlJob : Job {
     /// <param name="uploaderId">The system uploader id to backfill, if any.</param>
     /// <param name="token">Cancellation token.</param>
     /// <param name="report">Callback receiving (added, updated, deleted) counts.</param>
-    async Task ReconcileDirectory(LactoseDbContext assetDb, string dirPath, FileInfo[] files, Guid? uploaderId,
+    /// <returns>True when the batch committed; false when it was dropped due to a duplicate-key race.</returns>
+    async Task<bool> ReconcileDirectory(LactoseDbContext assetDb, string dirPath, FileInfo[] files, Guid? uploaderId,
         CancellationToken token, Action<int, int, int> report) {
         var prefix = dirPath.TrimEnd(Path.DirectorySeparatorChar) + Path.DirectorySeparatorChar;
         var lo = prefix;
@@ -260,12 +265,15 @@ public sealed class FileSystemCrawlJob : Job {
                 // same new path concurrently). The batch is dropped; the file is found next run.
                 logger.LogDebug(ex, "Dropped {Count} asset change(s) in {Path} due to a duplicate asset path.",
                     added + updated + deleted, dirPath);
+                report(0, 0, 0);
+                return false;
             } finally {
                 assetDb.ChangeTracker.Clear();
             }
         }
 
         report(added, updated, deleted);
+        return true;
     }
 
     static bool IsDuplicateKey(DbUpdateException ex) =>