HybridCache: Add ReadLock to prevent potential SQL Server deadlocks

Add ReadLock to database read operations in HybridCache services to prevent
deadlocks during concurrent content/media save operations. This extends the
fix from PR #21156 to other methods that were missing lock protection.

Methods updated with ReadLock:
- DocumentCacheService: GetNodeAsync, GetByContentType, SeedAsync, RebuildMemoryCacheByContentTypeAsync
- MediaCacheService: GetNodeAsync, GetByContentType, SeedAsync, RefreshMemoryCacheAsync, RebuildMemoryCacheByContentTypeAsync
- ContentTypeSeedKeyProvider: GetSeedKeys

src/Umbraco.PublishedCache.HybridCache/SeedKeyProviders/Document/ContentTypeSeedKeyProvider.cs

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.Options;
+using Umbraco.Cms.Core;
 using Umbraco.Cms.Core.Models;
 using Umbraco.Cms.Core.Scoping;
 using Umbraco.Cms.Core.Services.Navigation;
@@ -28,6 +29,7 @@ internal sealed class ContentTypeSeedKeyProvider : IDocumentSeedKeyProvider
     public ISet<Guid> GetSeedKeys()
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.ContentTree);
         var documentKeys = _databaseCacheRepository
             .GetDocumentKeysByContentTypeKeys(_cacheSettings.ContentTypeKeys, published: true)
             .Where(key => _publishStatusService.IsDocumentPublishedInAnyCulture(key))

src/Umbraco.PublishedCache.HybridCache/Services/DocumentCacheService.cs

@@ -121,6 +121,7 @@ internal sealed class DocumentCacheService : IDocumentCacheService
             async cancel =>
             {
                 using ICoreScope scope = _scopeProvider.CreateCoreScope();
+                scope.ReadLock(Constants.Locks.ContentTree);
                 ContentCacheNode? contentCacheNode = await _databaseCacheRepository.GetContentSourceAsync(key, preview);
 
                 // If we can resolve the content cache node, we still need to check if the ancestor path is published.
@@ -159,6 +160,7 @@ internal sealed class DocumentCacheService : IDocumentCacheService
     public IEnumerable<IPublishedContent> GetByContentType(IPublishedContentType contentType)
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.ContentTree);
         IEnumerable<ContentCacheNode> nodes = _databaseCacheRepository.GetContentByContentTypeKey([contentType.Key], ContentCacheDataSerializerEntityType.Document);
         scope.Complete();
 
@@ -237,6 +239,7 @@ internal sealed class DocumentCacheService : IDocumentCacheService
             }
 
             using ICoreScope scope = _scopeProvider.CreateCoreScope();
+            scope.ReadLock(Constants.Locks.ContentTree);
 
             IEnumerable<ContentCacheNode> cacheNodes = await _databaseCacheRepository.GetContentSourcesAsync(uncachedKeys);
 
@@ -354,6 +357,7 @@ internal sealed class DocumentCacheService : IDocumentCacheService
     public async Task RebuildMemoryCacheByContentTypeAsync(IEnumerable<int> contentTypeIds)
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.ContentTree);
 
         IEnumerable<ContentCacheNode> contentByContentTypeKey = _databaseCacheRepository.GetContentByContentTypeKey(contentTypeIds.Select(x => _idKeyMap.GetKeyForId(x, UmbracoObjectTypes.DocumentType).Result), ContentCacheDataSerializerEntityType.Document);
         scope.Complete();

src/Umbraco.PublishedCache.HybridCache/Services/MediaCacheService.cs

@@ -117,6 +117,7 @@ internal sealed class MediaCacheService : IMediaCacheService
             async cancel =>
             {
                 using ICoreScope scope = _scopeProvider.CreateCoreScope();
+                scope.ReadLock(Constants.Locks.MediaTree);
                 ContentCacheNode? mediaCacheNode = await _databaseCacheRepository.GetMediaSourceAsync(key);
                 scope.Complete();
                 return mediaCacheNode;
@@ -201,6 +202,7 @@ internal sealed class MediaCacheService : IMediaCacheService
             }
 
             using ICoreScope scope = _scopeProvider.CreateCoreScope();
+            scope.ReadLock(Constants.Locks.MediaTree);
 
             IEnumerable<ContentCacheNode> cacheNodes = await _databaseCacheRepository.GetMediaSourcesAsync(uncachedKeys);
 
@@ -231,6 +233,7 @@ internal sealed class MediaCacheService : IMediaCacheService
     public async Task RefreshMemoryCacheAsync(Guid key)
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.MediaTree);
 
         ContentCacheNode? publishedNode = await _databaseCacheRepository.GetMediaSourceAsync(key);
         if (publishedNode is not null)
@@ -257,6 +260,7 @@ internal sealed class MediaCacheService : IMediaCacheService
     public async Task RebuildMemoryCacheByContentTypeAsync(IEnumerable<int> mediaTypeIds)
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.MediaTree);
 
         IEnumerable<ContentCacheNode> contentByContentTypeKey = _databaseCacheRepository.GetContentByContentTypeKey(mediaTypeIds.Select(x => _idKeyMap.GetKeyForId(x, UmbracoObjectTypes.MediaType).Result), ContentCacheDataSerializerEntityType.Media);
 
@@ -301,6 +305,7 @@ internal sealed class MediaCacheService : IMediaCacheService
     public IEnumerable<IPublishedContent> GetByContentType(IPublishedContentType contentType)
     {
         using ICoreScope scope = _scopeProvider.CreateCoreScope();
+        scope.ReadLock(Constants.Locks.MediaTree);
         IEnumerable<ContentCacheNode> nodes = _databaseCacheRepository.GetContentByContentTypeKey([contentType.Key], ContentCacheDataSerializerEntityType.Media);
         scope.Complete();