From 68f309b6782057d1eeb8e9ab5c397e8f8949be8b Mon Sep 17 00:00:00 2001
From: Sergey Belyshkin <sbelyshkin@gmail.com>
Date: Wed, 30 Mar 2022 18:52:37 +0700
Subject: [PATCH] [Cache] Optimize caching of tags

---
 .../Cache/Adapter/TagAwareAdapter.php         | 36 +++++++++----------
 .../Tests/Adapter/TagAwareAdapterTest.php     | 14 ++++----
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php b/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
index 7e7395b71281a..732d024290982 100644
--- a/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/TagAwareAdapter.php
@@ -39,7 +39,6 @@ class TagAwareAdapter implements TagAwareAdapterInterface, TagAwareCacheInterfac
     use LoggerAwareTrait;
 
     public const TAGS_PREFIX = "\0tags\0";
-    private const MAX_NUMBER_OF_KNOWN_TAG_VERSIONS = 1000;
 
     private array $deferred = [];
     private AdapterInterface $pool;
@@ -79,8 +78,7 @@ static function (array $items, array $itemTags) {
         );
         self::$setTagVersions ??= \Closure::bind(
             static function (array $items, array $tagVersions) {
-                $now = null;
-                foreach ($items as $key => $item) {
+                foreach ($items as $item) {
                     $item->newMetadata[CacheItem::METADATA_TAGS] = array_intersect_key($tagVersions, $item->newMetadata[CacheItem::METADATA_TAGS] ?? []);
                 }
             },
@@ -343,14 +341,16 @@ public function __destruct()
     private function getTagVersions(array $tagsByKey, bool $persistTags): array
     {
         $tagVersions = [];
-        $fetchTagVersions = false;
+        $fetchTagVersions = $persistTags;
 
         foreach ($tagsByKey as $tags) {
             $tagVersions += $tags;
-
+            if ($fetchTagVersions) {
+                continue;
+            }
             foreach ($tags as $tag => $version) {
                 if ($tagVersions[$tag] !== $version) {
-                    unset($this->knownTagVersions[$tag]);
+                    $fetchTagVersions = true;
                 }
             }
         }
@@ -364,14 +364,10 @@ private function getTagVersions(array $tagsByKey, bool $persistTags): array
         foreach ($tagVersions as $tag => $version) {
             $tags[$tag.static::TAGS_PREFIX] = $tag;
             $knownTagVersion = $this->knownTagVersions[$tag] ?? [0, null];
-            if ($fetchTagVersions || $knownTagVersion[1] !== $version || $now - $knownTagVersion[0] >= $this->knownTagVersionsTtl) {
-                // reuse previously fetched tag versions up to the ttl
+            if ($fetchTagVersions || $now > $knownTagVersion[0] || $knownTagVersion[1] !== $version) {
+                // reuse previously fetched tag versions until the expiration
                 $fetchTagVersions = true;
             }
-            unset($this->knownTagVersions[$tag]); // For LRU tracking
-            if ([0, null] !== $knownTagVersion) {
-                $this->knownTagVersions[$tag] = $knownTagVersion;
-            }
         }
 
         if (!$fetchTagVersions) {
@@ -380,20 +376,24 @@ private function getTagVersions(array $tagsByKey, bool $persistTags): array
 
         $newTags = [];
         $newVersion = null;
+        $expiration = $now + $this->knownTagVersionsTtl;
         foreach ($this->tags->getItems(array_keys($tags)) as $tag => $version) {
-            if (!$version->isHit()) {
+            unset($this->knownTagVersions[$tag = $tags[$tag]]); // update FIFO
+            if (null !== $tagVersions[$tag] = $version->get()) {
+                $this->knownTagVersions[$tag] = [$expiration, $tagVersions[$tag]];
+            } elseif ($persistTags) {
                 $newTags[$tag] = $version->set($newVersion ??= random_bytes(6));
+                $tagVersions[$tag] = $newVersion;
+                $this->knownTagVersions[$tag] = [$expiration, $newVersion];
             }
-            $tagVersions[$tag = $tags[$tag]] = $version->get();
-            $this->knownTagVersions[$tag] = [$now, $tagVersions[$tag]];
         }
 
-        if ($newTags && $persistTags) {
+        if ($newTags) {
             (self::$saveTags)($this->tags, $newTags);
         }
 
-        if (\count($this->knownTagVersions) > $maxTags = max(self::MAX_NUMBER_OF_KNOWN_TAG_VERSIONS, \count($newTags) << 1)) {
-            array_splice($this->knownTagVersions, 0, $maxTags >> 1);
+        while ($now > ($this->knownTagVersions[$tag = array_key_first($this->knownTagVersions)][0] ?? \INF)) {
+            unset($this->knownTagVersions[$tag]);
         }
 
         return $tagVersions;
diff --git a/src/Symfony/Component/Cache/Tests/Adapter/TagAwareAdapterTest.php b/src/Symfony/Component/Cache/Tests/Adapter/TagAwareAdapterTest.php
index 5d6c52892b45f..c242c0dadaa3c 100644
--- a/src/Symfony/Component/Cache/Tests/Adapter/TagAwareAdapterTest.php
+++ b/src/Symfony/Component/Cache/Tests/Adapter/TagAwareAdapterTest.php
@@ -12,7 +12,6 @@
 namespace Symfony\Component\Cache\Tests\Adapter;
 
 use PHPUnit\Framework\MockObject\MockObject;
-use Psr\Cache\CacheItemInterface;
 use Psr\Cache\CacheItemPoolInterface;
 use Symfony\Component\Cache\Adapter\AdapterInterface;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
@@ -67,15 +66,18 @@ public function testKnownTagVersionsTtl()
 
         $pool->save($item);
         $this->assertTrue($pool->getItem('foo')->isHit());
-        $this->assertTrue($pool->getItem('foo')->isHit());
 
-        sleep(20);
+        $tagsPool->deleteItem('baz'.TagAwareAdapter::TAGS_PREFIX); // tag invalidation
 
-        $this->assertTrue($pool->getItem('foo')->isHit());
+        $this->assertTrue($pool->getItem('foo')->isHit()); // known tag version is used
 
-        sleep(5);
+        sleep(10);
 
-        $this->assertTrue($pool->getItem('foo')->isHit());
+        $this->assertTrue($pool->getItem('foo')->isHit()); // known tag version is still used
+
+        sleep(1);
+
+        $this->assertFalse($pool->getItem('foo')->isHit()); // known tag version has expired
     }
 
     public function testInvalidateTagsWithArrayAdapter()