Cache adapters#

Cache adapters determine how cached data is stored and retrieved. Choosing the right adapter can significantly impact your application's performance.

We use the symfony/cache library which supports various cache adapters.

Silverstripe CMS tries to provide a sensible default cache implementation for your system through the DefaultCacheFactory implementation.

The DefaultCacheFactory chooses:

• PhpFilesAdapter (PHP with opcache enabled). This cache has relatively low memory defaults. We recommend increasing it for large applications, or enabling the file_cache fallback. You must have opcache.enable_cli set to true to use this cache adapter. This is so that your cache is shared between CLI and the webserver.
• FilesystemAdapter if the above isn't available

Adding an in-memory cache adapter#

The in-memory cache adapters provided by default are:

• Memcached
• Redis
• APCu

The cache adapter needs to be available before configuration has been loaded, so we use an environment variable to determine which class will be used to instantiate the in-memory cache adapter. The class must be referenced using its Fully Qualified Class Name (including namespace), and must be an instance of InMemoryCacheFactory.

CopySS_IN_MEMORY_CACHE_FACTORY="SilverStripe\Core\Cache\MemcachedCacheFactory"

Silverstripe CMS comes with three in-memory cache factories you can choose from, each with their own requirements. You can of course add your own, as well.

Memcached cache#

Memcached is a "high-performance, distributed memory object caching system". To use this cache, you must install the memcached PHP extension.

You can tell the cache adapter which Memcached server(s) to connect to by defining a DSN in the SS_MEMCACHED_DSN environment variable.

CopySS_IN_MEMORY_CACHE_FACTORY="SilverStripe\Core\Cache\MemcachedCacheFactory"
SS_MEMCACHED_DSN="memcached://localhost:11211"

Redis cache#

Redis is an "in-memory database for caching and streaming" with built-in replication and a lot of deployment options. To use this cache, you must install one of:

• predis/predis
• cachewerk/relay
• the Redis PHP extension

You can tell the cache adapter which Redis server(s) to connect to by defining a DSN in the SS_REDIS_DSN environment variable.

CopySS_IN_MEMORY_CACHE_FACTORY="SilverStripe\Core\Cache\RedisCacheFactory"
SS_REDIS_DSN="redis://verysecurepassword@localhost:6379"

APCu cache#

APCu is "an in-memory key-value store for PHP". This runs locally on the same computer as your webserver, and is only available for the webserver itself. To use this cache, you must install the APCu PHP extension.

We include this option because it requires very little effort to set up, so it may be appropriate for smaller projects. Just remember to always flush the cache with an HTTP request using ?flush=1 or the --flush CLI flag.

CopySS_IN_MEMORY_CACHE_FACTORY="SilverStripe\Core\Cache\ApcuCacheFactory"