[Cache] Redis: Do not remove items expired due to a time discrepancy

sbelyshkin · sbelyshkin · commit 5af1ff6a632e · 2021-09-28T18:05:37.000+07:00
diff --git a/src/Symfony/Component/Cache/Adapter/RedisEphemeralTagAwareAdapter.php b/src/Symfony/Component/Cache/Adapter/RedisEphemeralTagAwareAdapter.php
@@ -120,6 +120,17 @@ public function clear(string $prefix = ''): bool
         return parent::clear($prefix);
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    protected function evictExpiredItems(array $expiredItemKeys)
+    {
+        // Although it's better to remove big stale items explicitly to free up the memory for recomputed values,
+        // thereby preventing possible evictions of other still fresh items, we keep these keys for other clients
+        // as a measure of stampede protection in multi-server setups assuming that we got these keys most likely
+        // because of (presumably small) time discrepancy between hosts. Anyway, Redis will delete them soon.
+    }
+
     /**
      * {@inheritdoc}
      */
