Load Balancing: Clear request cache in cache version accessor on cache version update to prevent unnecessary cache roll forwards (#20831)

* Clear request cache on version update

* Update src/Umbraco.Core/Cache/IRepositoryCacheVersionAccessor.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/Umbraco.Core/Cache/IRepositoryCacheVersionAccessor.cs

@@ -20,7 +20,14 @@ public interface IRepositoryCacheVersionAccessor
     /// <returns>
     /// The cache version if found, or <see langword="null"/> if the version doesn't exist or the request is a client-side request.
     /// </returns>
-    public Task<RepositoryCacheVersion?> GetAsync(string cacheKey);
+    Task<RepositoryCacheVersion?> GetAsync(string cacheKey);
+
+    /// <summary>
+    /// Notifies of a version change on a given cache key.
+    /// </summary>
+    /// <param name="cacheKey">Key of the changed version.</param>
+    void VersionChanged(string cacheKey)
+    { }
 
     /// <summary>
     /// Notifies the accessor that caches have been synchronized.
@@ -29,5 +36,5 @@ public interface IRepositoryCacheVersionAccessor
     /// This method is called after cache synchronization to temporarily bypass version checking,
     /// preventing recursive sync attempts while repositories reload data from the database.
     /// </remarks>
-    public void CachesSynced();
+    void CachesSynced();
 }

src/Umbraco.Core/Cache/RepositoryCacheVersionService.cs

@@ -88,6 +88,7 @@ internal class RepositoryCacheVersionService : IRepositoryCacheVersionService
         _logger.LogDebug("Setting cache for {EntityType} to version {Version}", typeof(TEntity).Name, newVersion);
         await _repositoryCacheVersionRepository.SaveAsync(new RepositoryCacheVersion { Identifier = cacheKey, Version = newVersion.ToString() });
         _cacheVersions[cacheKey] = newVersion;
+        _repositoryCacheVersionAccessor.VersionChanged(cacheKey);
 
         scope.Complete();
     }

src/Umbraco.Web.Common/Cache/RepositoryCacheVersionAccessor.cs

@@ -77,5 +77,17 @@ public class RepositoryCacheVersionAccessor : IRepositoryCacheVersionAccessor
         return databaseVersion;
     }
 
+
+    /// <inheritdoc />
+    public void VersionChanged(string cacheKey)
+    {
+        var removed = _requestCache.Remove(cacheKey);
+        if (removed is false)
+        {
+            _logger.LogDebug("Cache version for key {CacheKey} wasn't removed from request cache, possibly missing HTTP context", cacheKey);
+        }
+    }
+
+    /// <inheritdoc />
     public void CachesSynced() => _requestCache.ClearOfType<RepositoryCacheVersion>();
 }