From 971b177d27ec43fca1ed6c027971190508bc5063 Mon Sep 17 00:00:00 2001
From: Trevor North <trevor@blubolt.com>
Date: Thu, 20 Feb 2020 16:09:42 +0000
Subject: [PATCH] Fix versioned namespace clears

When using namespace versioning to achieve atomic cache clears, only
delete cache keys matching the old/current version.

This resolves tag inconsistency issues whereby the process running the
clear would delete keys set against the new version by more recently
spawned concurreny processes. Most seriously this could result in newly
set data keys remaining, but with empty associated tag sets meaning the
invalidation via tags was no longer possible.

Clearing specific prefixes is not supported when using versioned
namespaces as it is desirable to clear all old keys as they will no
longer be used and would otherwise eventually fill cache memory.
---
 src/Symfony/Component/Cache/Traits/AbstractTrait.php | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/Symfony/Component/Cache/Traits/AbstractTrait.php b/src/Symfony/Component/Cache/Traits/AbstractTrait.php
index f9a1d8fdafa2..7639424ea78c 100644
--- a/src/Symfony/Component/Cache/Traits/AbstractTrait.php
+++ b/src/Symfony/Component/Cache/Traits/AbstractTrait.php
@@ -111,9 +111,14 @@ public function hasItem($key)
      */
     public function clear(/*string $prefix = ''*/)
     {
-        $prefix = 0 < \func_num_args() ? (string) func_get_arg(0) : '';
         $this->deferred = [];
         if ($cleared = $this->versioningIsEnabled) {
+            if ('' === $namespaceVersionToClear = $this->namespaceVersion) {
+                foreach ($this->doFetch([static::NS_SEPARATOR.$this->namespace]) as $v) {
+                    $namespaceVersionToClear = $v;
+                }
+            }
+            $namespaceToClear = $this->namespace.$namespaceVersionToClear;
             $namespaceVersion = substr_replace(base64_encode(pack('V', mt_rand())), static::NS_SEPARATOR, 5);
             try {
                 $cleared = $this->doSave([static::NS_SEPARATOR.$this->namespace => $namespaceVersion], 0);
@@ -124,10 +129,13 @@ public function clear(/*string $prefix = ''*/)
                 $this->namespaceVersion = $namespaceVersion;
                 $this->ids = [];
             }
+        } else {
+            $prefix = 0 < \func_num_args() ? (string) func_get_arg(0) : '';
+            $namespaceToClear = $this->namespace.$prefix;
         }
 
         try {
-            return $this->doClear($this->namespace.$prefix) || $cleared;
+            return $this->doClear($namespaceToClear) || $cleared;
         } catch (\Exception $e) {
             CacheItem::log($this->logger, 'Failed to clear the cache: '.$e->getMessage(), ['exception' => $e]);