From 2a609e1ecac1fb89ae85707edb4abe00ee2cca10 Mon Sep 17 00:00:00 2001
From: Mole <nikolajlauridsen@protonmail.ch>
Date: Fri, 14 Nov 2025 14:14:28 +0100
Subject: [PATCH] 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>
---
 .../Cache/IRepositoryCacheVersionAccessor.cs         | 11 +++++++++--
 .../Cache/RepositoryCacheVersionService.cs           |  1 +
 .../Cache/RepositoryCacheVersionAccessor.cs          | 12 ++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/Umbraco.Core/Cache/IRepositoryCacheVersionAccessor.cs b/src/Umbraco.Core/Cache/IRepositoryCacheVersionAccessor.cs
index 61ae733fe1..af304dc19e 100644
--- a/src/Umbraco.Core/Cache/IRepositoryCacheVersionAccessor.cs
+++ b/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();
 }
diff --git a/src/Umbraco.Core/Cache/RepositoryCacheVersionService.cs b/src/Umbraco.Core/Cache/RepositoryCacheVersionService.cs
index 541e9f032e..09269f92e1 100644
--- a/src/Umbraco.Core/Cache/RepositoryCacheVersionService.cs
+++ b/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();
     }
diff --git a/src/Umbraco.Web.Common/Cache/RepositoryCacheVersionAccessor.cs b/src/Umbraco.Web.Common/Cache/RepositoryCacheVersionAccessor.cs
index b96e2546e1..4485c80834 100644
--- a/src/Umbraco.Web.Common/Cache/RepositoryCacheVersionAccessor.cs
+++ b/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>();
 }