34. The Second Level Cache¶
Note
The second level cache functionality is marked as experimental for now. It is a very complex feature and we cannot guarantee yet that it works stable in all cases.
The Second Level Cache is designed to reduce the amount of necessary database access. It sits between your application and the database to avoid the number of database hits as much as possible.
When turned on, entities will be first searched in cache and if they are not found, a database query will be fired and then the entity result will be stored in a cache provider.
There are some flavors of caching available, but is better to cache read-only data.
Be aware that caches are not aware of changes made to the persistent store by another application. They can, however, be configured to regularly expire cached data.
34.1. Caching Regions¶
Second level cache does not store instances of an entity, instead it caches only entity identifier and values. Each entity class, collection association and query has its region, where values of each instance are stored.
Caching Regions are specific region into the cache provider that might store entities, collection or queries. Each cache region resides in a specific cache namespace and has its own lifetime configuration.
Notice that when caching collection and queries only identifiers are stored. The entity values will be stored in its own region
Something like below for an entity region:
<?php
[
'region_name:entity_1_hash' => ['id' => 1, 'name' => 'FooBar', 'associationName' => null],
'region_name:entity_2_hash' => ['id' => 2, 'name' => 'Foo', 'associationName' => ['id' => 11]],
'region_name:entity_3_hash' => ['id' => 3, 'name' => 'Bar', 'associationName' => ['id' => 22]]
];
If the entity holds a collection that also needs to be cached. An collection region could look something like:
<?php
[
'region_name:entity_1_coll_assoc_name_hash' => ['ownerId' => 1, 'list' => [1, 2, 3]],
'region_name:entity_2_coll_assoc_name_hash' => ['ownerId' => 2, 'list' => [2, 3]],
'region_name:entity_3_coll_assoc_name_hash' => ['ownerId' => 3, 'list' => [2, 4]]
];
A query region might be something like:
<?php
[
'region_name:query_1_hash' => ['list' => [1, 2, 3]],
'region_name:query_2_hash' => ['list' => [2, 3]],
'region_name:query_3_hash' => ['list' => [2, 4]]
];
Note
The following data structures represents now the cache will looks like, this is not actual cached data.
34.2. Cache Regions¶
Doctrine\ORM\Cache\Region\DefaultRegion
is the default implementation.A simplest cache region compatible with all doctrine-cache drivers but does not support locking.
すべての doctrine-cache ドライバーと互換性のある最も単純なキャッシュ領域ですが、ロックはサポートしていません。
Doctrine\ORM\Cache\Region
and Doctrine\ORM\Cache\ConcurrentRegion
define contracts that should be implemented by a cache provider.
It allows you to provide your own cache implementation that might take advantage of specific cache driver.
If you want to support locking for READ_WRITE
strategies you should implement ConcurrentRegion
; CacheRegion
otherwise.
34.2.1. Cache region¶
Doctrine\ORM\Cache\Region
defines a contract for accessing a particular
cache region.
34.2.2. Concurrent cache region¶
A Doctrine\ORM\Cache\ConcurrentRegion
is designed to store concurrently managed data region.
By default, Doctrine provides a very simple implementation based on file locks Doctrine\ORM\Cache\Region\FileLockRegion
.
If you want to use an READ_WRITE
cache, you should consider providing your own cache region.
Doctrine\ORM\Cache\ConcurrentRegion
defines a contract for concurrently managed data region.
34.2.3. Timestamp region¶
Doctrine\ORM\Cache\TimestampRegion
Tracks the timestamps of the most recent updates to particular entity.
34.3. Caching mode¶
READ_ONLY
(DEFAULT)READ_ONLY (デフォルト)Can do reads, inserts and deletes, cannot perform updates or employ any locks.
読み取り、挿入、および削除を実行できますが、更新を実行したり、ロックを使用したりすることはできません。Useful for data that is read frequently but never updated.
頻繁に読み取られるが更新されないデータに役立ちます。Best performer.
最高のパフォーマー。It is Simple.
簡単です。
NONSTRICT_READ_WRITE
NONSTRICT_READ_WRITERead Write Cache doesn’t employ any locks but can do reads, inserts, updates and deletes.
読み取り書き込みキャッシュはロックを使用しませんが、読み取り、挿入、更新、および削除を実行できます。Good if the application needs to update data rarely.
アプリケーションがデータをめったに更新する必要がない場合に適しています。
READ_WRITE
読み書きRead Write cache employs locks before update/delete.
読み取り書き込みキャッシュは、更新/削除の前にロックを使用します。Use if data needs to be updated.
データを更新する必要がある場合に使用します。Slowest strategy.
最も遅い戦略。To use it a the cache region implementation must support locking.
これを使用するには、キャッシュ領域の実装でロックがサポートされている必要があります。
34.3.1. Built-in cached persisters¶
Cached persisters are responsible to access cache regions.
Cache Usage
キャッシュの使用Persister
持続するREAD_ONLY
READ_ONLY
Doctrine\ORM\Cache\Persister\Entity\ReadOnlyCachedEntityPersister
Doctrine\ORM\Cache\Persister\Entity\ReadOnlyCachedEntityPersisterREAD_WRITE
読み書き
Doctrine\ORM\Cache\Persister\Entity\ReadWriteCachedEntityPersister
Doctrine\ORM\Cache\Persister\Entity\ReadWriteCachedEntityPersisterNONSTRICT_READ_WRITE
NONSTRICT_READ_WRITE
Doctrine\ORM\Cache\Persister\Entity\NonStrictReadWriteCachedEntityPersister
Doctrine\ORM\Cache\Persister\Entity\NonStrictReadWriteCachedEntityPersisterREAD_ONLY
READ_ONLY
Doctrine\ORM\Cache\Persister\Collection\ReadOnlyCachedCollectionPersister
Doctrine\ORM\Cache\Persister\Collection\ReadOnlyCachedCollectionPersisterREAD_WRITE
読み書き
Doctrine\ORM\Cache\Persister\Collection\ReadWriteCachedCollectionPersister
Doctrine\ORM\Cache\Persister\Collection\ReadWriteCachedCollectionPersisterNONSTRICT_READ_WRITE
NONSTRICT_READ_WRITE
Doctrine\ORM\Cache\Persister\Collection\NonStrictReadWriteCachedCollectionPersister
Doctrine\ORM\Cache\Persister\Collection\NonStrictReadWriteCachedCollectionPersister
34.4. Configuration¶
Doctrine allows you to specify configurations and some points of extension for the second-level-cache
34.4.1. Enable Second Level Cache¶
To enable the second-level-cache, you should provide a cache factory.
Doctrine\ORM\Cache\DefaultCacheFactory
is the default implementation.
<?php
/** @var \Doctrine\ORM\Cache\RegionsConfiguration $cacheConfig */
/** @var \Psr\Cache\CacheItemPoolInterface $cache */
/** @var \Doctrine\ORM\Configuration $config */
$factory = new \Doctrine\ORM\Cache\DefaultCacheFactory($cacheConfig, $cache);
// Enable second-level-cache
$config->setSecondLevelCacheEnabled();
// Cache factory
$config->getSecondLevelCacheConfiguration()
->setCacheFactory($factory);
34.4.2. Cache Factory¶
Cache Factory is the main point of extension.
It allows you to provide a specific implementation of the following components:
QueryCache
stores and retrieves query cache results.
クエリ キャッシュの結果を格納および取得します。CachedEntityPersister
stores and retrieves entity results.
エンティティの結果を保存および取得します。CachedCollectionPersister
stores and retrieves query results.
クエリ結果を保存および取得します。EntityHydrator
transforms entities into a cache entries and cache entries into entities
エンティティをキャッシュ エントリに変換し、キャッシュ エントリをエンティティに変換しますCollectionHydrator
transforms collections into cache entries and cache entries into collections
コレクションをキャッシュ エントリに変換し、キャッシュ エントリをコレクションに変換します
34.4.3. Region Lifetime¶
To specify a default lifetime for all regions or specify a different lifetime for a specific region.
<?php
/** @var \Doctrine\ORM\Configuration $config */
/** @var \Doctrine\ORM\Cache\CacheConfiguration $cacheConfig */
/** @var \Doctrine\ORM\Cache\RegionsConfiguration $regionConfig */
$cacheConfig = $config->getSecondLevelCacheConfiguration();
$regionConfig = $cacheConfig->getRegionsConfiguration();
// Cache Region lifetime
$regionConfig->setLifetime('my_entity_region', 3600); // Time to live for a specific region (in seconds)
$regionConfig->setDefaultLifetime(7200); // Default time to live (in seconds)
34.4.4. Cache Log¶
By providing a cache logger you should be able to get information about all cache operations such as hits, misses and puts.
Doctrine\ORM\Cache\Logging\StatisticsCacheLogger
is a built-in implementation that provides basic statistics.
<?php /** @var \Doctrine\ORM\Configuration $config */ $logger = new \Doctrine\ORM\Cache\Logging\StatisticsCacheLogger(); // Cache logger $config->setSecondLevelCacheEnabled(true); $config->getSecondLevelCacheConfiguration() ->setCacheLogger($logger); // Collect cache statistics // Get the number of entries successfully retrieved from a specific region. $logger->getRegionHitCount('my_entity_region'); // Get the number of cached entries *not* found in a specific region. $logger->getRegionMissCount('my_entity_region'); // Get the number of cacheable entries put in cache. $logger->getRegionPutCount('my_entity_region'); // Get the total number of put in all regions. $logger->getPutCount(); // Get the total number of entries successfully retrieved from all regions. $logger->getHitCount(); // Get the total number of cached entries *not* found in all regions. $logger->getMissCount();
If you want to get more information you should implement
Doctrine\ORM\Cache\Logging\CacheLogger
and collect
all the information you want.
34.5. Entity cache definition¶
Entity cache configuration allows you to define the caching strategy and region for an entity.
エンティティ キャッシュ構成を使用すると、エンティティのキャッシュ戦略とリージョンを定義できます。usage
specifies the caching strategy:READ_ONLY
,usage はキャッシュ戦略を指定します: READ_ONLY、
NONSTRICT_READ_WRITE
, READ_WRITE
.
See Caching mode.
region
is an optional value that specifies the name of the secondregion は、秒の名前を指定するオプションの値です
level cache region.
34.6. Association cache definition¶
The most common use case is to cache entities. But we can also cache relationships. It caches the primary keys of association and cache each element will be cached into its region.
Note
for this to work, the target entity must also be marked as cacheable.
34.6.1. Cache usage¶
Basic entity cache
<?php
$em->persist(new Country($name));
$em->flush(); // Hit database to insert the row and put into cache
$em->clear(); // Clear entity manager
$country1 = $em->find('Country', 1); // Retrieve item from cache
$country1->setName('New Name');
$em->flush(); // Hit database to update the row and update cache
$em->clear(); // Clear entity manager
$country2 = $em->find('Country', 1); // Retrieve item from cache
// Notice that $country1 and $country2 are not the same instance.
Association cache
<?php
// Hit database to insert the row and put into cache
$em->persist(new State($name, $country));
$em->flush();
// Clear entity manager
$em->clear();
// Retrieve item from cache
$state = $em->find('State', 1);
// Hit database to update the row and update cache entry
$state->setName('New Name');
$em->persist($state);
$em->flush();
// Create a new collection item
$city = new City($name, $state);
$state->addCity($city);
// Hit database to insert new collection item,
// put entity and collection cache into cache.
$em->persist($city);
$em->persist($state);
$em->flush();
// Clear entity manager
$em->clear();
// Retrieve item from cache
$state = $em->find('State', 1);
// Retrieve association from cache
$country = $state->getCountry();
// Retrieve collection from cache
$cities = $state->getCities();
echo $country->getName();
echo $state->getName();
// Retrieve each collection item from cache
foreach ($cities as $city) {
echo $city->getName();
}
Note
Notice that all entities should be marked as cacheable.
34.7. Using the query cache¶
The second level cache stores the entities, associations and collections. The query cache stores the results of the query but as identifiers, entity values are actually stored in the 2nd level cache.
Note
Query cache should always be used in conjunction with the second-level-cache for those entities which should be cached.
<?php
/** @var \Doctrine\ORM\EntityManager $em */
// Execute database query, store query cache and entity cache
$result1 = $em->createQuery('SELECT c FROM Country c ORDER BY c.name')
->setCacheable(true)
->getResult();
$em->clear();
// Check if query result is valid and load entities from cache
$result2 = $em->createQuery('SELECT c FROM Country c ORDER BY c.name')
->setCacheable(true)
->getResult();
34.7.1. Cache mode¶
The Cache Mode controls how a particular query interacts with the second-level cache:
Cache::MODE_GET
- May read items from the cache, but will not add items.Cache::MODE_GET - キャッシュから項目を読み取ることができますが、項目を追加しません。Cache::MODE_PUT
- Will never read items from the cache, but will add items to the cache as it reads them from the database.Cache::MODE_PUT - キャッシュからアイテムを読み取ることはありませんが、データベースからアイテムを読み取るときにアイテムをキャッシュに追加します。Cache::MODE_NORMAL
- May read items from the cache, and add items to the cache.Cache::MODE_NORMAL - キャッシュから項目を読み取り、キャッシュに項目を追加できます。Cache::MODE_REFRESH
- The query will never read items from the cache, but will refresh items to the cache as it reads them from the database.Cache::MODE_REFRESH - クエリはキャッシュからアイテムを読み取ることはありませんが、データベースからアイテムを読み取るときにアイテムをキャッシュに更新します。
<?php
/** @var \Doctrine\ORM\EntityManager $em */
// Will refresh the query cache and all entities the cache as it reads from the database.
$result1 = $em->createQuery('SELECT c FROM Country c ORDER BY c.name')
->setCacheMode(\Doctrine\ORM\Cache::MODE_GET)
->setCacheable(true)
->getResult();
Note
The default query cache mode is `Cache::MODE_NORMAL`
34.7.2. DELETE / UPDATE queries¶
DQL UPDATE / DELETE statements are ported directly into a database and bypass the second-level cache. Entities that are already cached will NOT be invalidated. However the cached data could be evicted using the cache API or an special query hint.
Execute the UPDATE
and invalidate all cache entries
using Query::HINT_CACHE_EVICT
<?php
// Execute and invalidate
$this->_em->createQuery("UPDATE Entity\Country u SET u.name = 'unknown' WHERE u.id = 1")
->setHint(\Doctrine\ORM\Query::HINT_CACHE_EVICT, true)
->execute();
Execute the UPDATE
and invalidate all cache entries
using the cache API
<?php
// Execute
$this->_em->createQuery("UPDATE Entity\Country u SET u.name = 'unknown' WHERE u.id = 1")
->execute();
// Invoke Cache API
$em->getCache()->evictEntityRegion('Entity\Country');
Execute the UPDATE
and invalidate a specific cache entry
using the cache API
<?php
// Execute
$this->_em->createQuery("UPDATE Entity\Country u SET u.name = 'unknown' WHERE u.id = 1")
->execute();
// Invoke Cache API
$em->getCache()->evictEntity('Entity\Country', 1);
34.8. Using the repository query cache¶
As well as Query Cache
all persister queries store only identifier values for an individual query.
All persisters use a single timestamp cache region to keep track of the last update for each persister,
When a query is loaded from cache, the timestamp region is checked for the last update for that persister.
Using the last update timestamps as part of the query key invalidate the cache key when an update occurs.
<?php
// load from database and store cache query key hashing the query + parameters + last timestamp cache region..
$entities = $em->getRepository('Entity\Country')->findAll();
// load from query and entities from cache..
$entities = $em->getRepository('Entity\Country')->findAll();
// update the timestamp cache region for Country
$em->persist(new Country('zombieland'));
$em->flush();
$em->clear();
// Reload from database.
// At this point the query cache key is no longer valid, the select goes straight to the database
$entities = $em->getRepository('Entity\Country')->findAll();
34.9. Cache API¶
Caches are not aware of changes made by another application. However, you can use the cache API to check / invalidate cache entries.
<?php
/** @var \Doctrine\ORM\Cache $cache */
$cache = $em->getCache();
$cache->containsEntity('Entity\State', 1) // Check if the cache exists
$cache->evictEntity('Entity\State', 1); // Remove an entity from cache
$cache->evictEntityRegion('Entity\State'); // Remove all entities from cache
$cache->containsCollection('Entity\State', 'cities', 1); // Check if the cache exists
$cache->evictCollection('Entity\State', 'cities', 1); // Remove an entity collection from cache
$cache->evictCollectionRegion('Entity\State', 'cities'); // Remove all collections from cache
34.10. Limitations¶
34.10.1. Composite primary key¶
Composite primary key are supported by second level cache, however when one of the keys is an association the cached entity should always be retrieved using the association identifier. For performance reasons the cache API does not extract from composite primary key.
<?php
#[Entity]
class Reference
{
#[Id]
#[ManyToOne(targetEntity: Article::class, inversedBy: 'references')]
#[JoinColumn(name: 'source_id', referencedColumnName: 'article_id')]
private Article|null $source = null;
#[Id]
#[ManyToOne(targetEntity: Article::class, inversedBy: 'references')]
#[JoinColumn(name: 'target_id', referencedColumnName: 'article_id')]
private $target;
}
// Supported
/** @var Article $article */
$article = $em->find('Article', 1);
// Supported
/** @var Article $article */
$article = $em->find('Article', $article);
// Supported
$id = ['source' => 1, 'target' => 2];
$reference = $em->find('Reference', $id);
// NOT Supported
$id = ['source' => new Article(1), 'target' => new Article(2)];
$reference = $em->find('Reference', $id);
34.10.2. Distributed environments¶
Some cache driver are not meant to be used in a distributed environment. Load-balancer for distributing workloads across multiple computing resources should be used in conjunction with distributed caching system such as memcached, redis, riak …
Caches should be used with care when using a load-balancer if you don’t share the cache. While using APC or any file based cache update occurred in a specific machine would not reflect to the cache in other machines.
34.10.3. Paginator¶
Count queries generated by Doctrine\ORM\Tools\Pagination\Paginator
are not cached by second-level cache.
Although entities and query result are cached, count queries will hit the
database every time.