8000 [Cache] Prevent stampede at warmup using flock() · symfony/symfony@0ac2777 · GitHub
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nicolas-grekasnicolas-grekas
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[Cache] Prevent stampede at warmup using flock()
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3 files changed

+162
-18
lines changed

3 files changed

+162
-18
lines changed

‎src/Symfony/Component/Cache/LockRegistry.php

Lines changed: 130 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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<?php
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/*
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* This file is part of the Symfony package.
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*
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* (c) Fabien Potencier <fabien@symfony.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Symfony\Component\Cache;
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use Psr\Cache\CacheItemInterface;
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use Psr\Cache\CacheItemPoolInterface;
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/**
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* LockRegistry is used internally by existing adapters to protect against cache stampede.
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*
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* It does so by wrapping the computation of items in a pool of locks.
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* Foreach each apps, there can be at most 20 concurrent processes that
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* compute items at the same time and only one per cache-key.
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*
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* @author Nicolas Grekas <p@tchwork.com>
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*/
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class LockRegistry
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{
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private static $save;
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private static $openedFiles = array();
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private static $lockedFiles = array();
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/**
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* The number of items in this list controls the max number of concurrent processes.
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8000 */
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private static $files = array(
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'AbstractAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'AdapterInterface.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'ApcuAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'ArrayAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'ChainAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'DoctrineAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'FilesystemAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'MemcachedAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'NullAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'PdoAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'PhpArrayAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'PhpFilesAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'ProxyAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'RedisAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'SimpleCacheAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'TagAwareAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'TagAwareAdapterInterface.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'TraceableAdapter.php',
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__DIR__.\DIRECTORY_SEPARATOR.'Adapter'.\DIRECTORY_SEPARATOR.'TraceableTagAwareAdapter.php',
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);
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/**
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* Defines a set of existing files that will be used as keys to acquire locks.
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*
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* @return array The previously defined set of files
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*/
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public static function setFiles(array $files): array
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{
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$previousFiles = self::$files;
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self::$files = $files;
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foreach (self::$openedFiles as $k => $file) {
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flock($file, LOCK_UN);
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fclose($file);
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}
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self::$openedFiles = self::$lockedFiles = array();
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return $previousFiles;
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}
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/**
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* @internal
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*/
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public static function save(string $key, CacheItemPoolInterface $pool, CacheItemInterface $item, callable $callback, float $startTime, &$value): bool
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{
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self::$save = self::$save ?? \Closure::bind(
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function (CacheItemPoolInterface $pool, CacheItemInterface $item, $value, float $startTime) {
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if ($item instanceof CacheItem && $startTime && $item->expiry > $endTime = microtime(true)) {
84+
$item->newMetadata[CacheItem::METADATA_EXPIRY] = $item->expiry;
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$item->newMetadata[CacheItem::METADATA_CTIME] = 1000 * (int) ($endTime - $startTime);
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}
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$pool->save($item->set($value));
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return $value;
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},
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null,
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CacheItem::class
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);
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$key = self::$files ? crc32($key) % \count(self::$files) : -1;
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if ($key < 0 || (self::$lockedFiles[$key] ?? false) || !$lock = self::open($key)) {
98+
$value = (self::$save)($pool, $item, $callback($item), $startTime);
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return true;
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}
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try {
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// race to get the lock in non-blocking mode
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if (flock($lock, LOCK_EX | LOCK_NB)) {
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self::$lockedFiles[$key] = true;
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$value = (self::$save)($pool, $item, $callback($item), $startTime);
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return true;
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}
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// if we failed the race, retry locking in blocking mode to wait for the winner
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flock($lock, LOCK_SH);
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} finally {
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flock($lock, LOCK_UN);
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self::$lockedFiles[$key] = false;
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}
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return false;
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}
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private static function open(int $key)
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{
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if ($h = self::$openedFiles[$key] ?? null) {
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return $h;
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}
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if ($h = fopen(self::$files[$key], 'rb')) {
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return self::$openedFiles[$key] = $h;
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}
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}
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}

‎src/Symfony/Component/Cache/Tests/LockRegistryTest.php

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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<?php
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/*
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* This file is part of the Symfony package.
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*
6+
* (c) Fabien Potencier <fabien@symfony.com>
7+
*
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* For the full copyright and license information, please view the LICENSE
9+
* file that was distributed with this source code.
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*/
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namespace Symfony\Component\Cache\Tests;
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use PHPUnit\Framework\TestCase;
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use Symfony\Component\Cache\LockRegistry;
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class LockRegistryTest extends TestCase
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{
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public function testFiles()
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{
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$lockFiles = LockRegistry::setFiles(array());
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LockRegistry::setFiles($lockFiles);
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$expected = array_map('realpath', glob(__DIR__.'/../Adapter/*'));
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$this->assertSame($expected, $lockFiles);
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}
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}

‎src/Symfony/Component/Cache/Traits/GetTrait.php

Lines changed: 6 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -11,9 +11,9 @@
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namespace Symfony\Component\Cache\Traits;
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14-
use Psr\Cache\CacheItemInterface;
1514
use Psr\Cache\CacheItemPoolInterface;
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use Symfony\Component\Cache\CacheItem;
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use Symfony\Component\Cache\LockRegistry;
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/**
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* An implementation for CacheInterface that provides stampede protection via probabilistic early expiration.
@@ -36,6 +36,7 @@ public function get(string $key, callable $callback, float $beta = null)
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3737
private function doGet(CacheItemPoolInterface $pool, string $key, callable $callback, float $beta)
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{
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retry:
3940
$t = 0;
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$item = $pool->getItem($key);
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$recompute = !$item->isHit() || INF === $beta;
@@ -63,24 +64,11 @@ private function doGet(CacheItemPoolInterface $pool, string $key, callable $call
6364
return $item->get();
6465
}
6566

66-
static $save = null;
67-
68-
if (null === $save) {
69-
$save = \Closure::bind(
70-
function (CacheItemPoolInterface $pool, CacheItemInterface $item, $value, float $startTime) {
71-
if ($item instanceof CacheItem && $startTime && $item->expiry > $endTime = microtime(true)) {
72-
$item->newMetadata[CacheItem::METADATA_EXPIRY] = $item->expiry;
73-
$item->newMetadata[CacheItem::METADATA_CTIME] = 1000 * (int) ($endTime - $startTime);
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}
75-
$pool->save($item->set($value));
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return $value;
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},
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null,
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CacheItem::class
81-
);
67+
if (!LockRegistry::save($key, $pool, $item, $callback, $t, $value)) {
68+
$beta = 0;
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goto retry;
8270
}
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84-
return $save($pool, $item, $callback($item), $t);
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return $value;
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}
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}

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