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https://github.com/silverstripe/silverstripe-framework
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Provides an interface for classes to implement their own flush() functionality. This function gets called early in a request on all implementations of Flushable when flush=1|all is requested in the URL. This fix came out of an issue where Requirements combined files were not being cleaned up after dev/build?flush=1, due to the fact that flush would only occur when you called it while on a page that used those combined files, but not in any other contexts. This will now call flush on any implementors of Flushable regardless of the context of where flush was called.
155 lines
5.6 KiB
Markdown
155 lines
5.6 KiB
Markdown
# Caching
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## Built-In Caches
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The framework uses caches to store infrequently changing values.
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By default, the storage mechanism is simply the filesystem, although
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other cache backends can be configured. All caches use the `[api:SS_Cache]` API.
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The most common caches are manifests of various resources:
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* PHP class locations (`[api:SS_ClassManifest]`)
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* Template file locations and compiled templates (`[api:SS_TemplateManifest]`)
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* Configuration settings from YAML files (`[api:SS_ConfigManifest]`)
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* Language files (`[api:i18n]`)
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Flushing the various manifests is performed through a GET
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parameter (`flush=1`). Since this action requires more server resources than normal requests,
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executing the action is limited to the following cases when performed via a web request:
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* The [environment](/topics/environment-management) is in "dev mode"
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* A user is logged in with ADMIN permissions
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* An error occurs during startup
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## The Cache API
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The `[api:SS_Cache]` class provides a bunch of static functions wrapping the Zend_Cache system
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in something a little more easy to use with the SilverStripe config system.
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A `Zend_Cache` has both a frontend (determines how to get the value to cache,
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and how to serialize it for storage) and a backend (handles the actual
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storage).
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Rather than require library code to specify the backend directly, cache
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consumers provide a name for the cache backend they want. The end developer
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can then specify which backend to use for each name in their project's
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configuration. They can also use 'all' to provide a backend for all named
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caches.
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End developers provide a set of named backends, then pick the specific
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backend for each named cache. There is a default File cache set up as the
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'default' named backend, which is assigned to 'all' named caches.
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## Using Caches
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Caches can be created and retrieved through the `SS_Cache::factory()` method.
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The returned object is of type `Zend_Cache`.
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:::php
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// foo is any name (try to be specific), and is used to get configuration
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// & storage info
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$cache = SS_Cache::factory('foo');
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if (!($result = $cache->load($cachekey))) {
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$result = caluate some how;
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$cache->save($result);
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}
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return $result;
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Normally there's no need to remove things from the cache - the cache
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backends clear out entries based on age and maximum allocated storage. If you
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include the version of the object in the cache key, even object changes
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don't need any invalidation. You can force disable the cache though,
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e.g. in development mode.
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:::php
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// Disables all caches
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SS_Cache::set_cache_lifetime('any', -1, 100);
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You can also specifically clean a cache.
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Keep in mind that `Zend_Cache::CLEANING_MODE_ALL` deletes all cache
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entries across all caches, not just for the 'foo' cache in the example below.
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:::php
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$cache = SS_Cache::factory('foo');
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$cache->clean(Zend_Cache::CLEANING_MODE_ALL);
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A single element can be invalidated through its cache key.
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:::php
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$cache = SS_Cache::factory('foo');
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$cache->remove($cachekey);
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In order to increase the chance of your cache actually being hit,
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it often pays to increase the lifetime of caches ("TTL").
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It defaults to 10 minutes (600s) in SilverStripe, which can be
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quite short depending on how often your data changes.
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Keep in mind that data expiry should primarily be handled by your cache key,
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e.g. by including the `LastEdited` value when caching `DataObject` results.
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:::php
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// set all caches to 3 hours
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SS_Cache::set_cache_lifetime('any', 60*60*3);
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## Alternative Cache Backends
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By default, SilverStripe uses a file-based caching backend.
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Together with a file stat cache like [APC](http://us2.php.net/manual/en/book.apc.php)
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this is reasonably quick, but still requires access to slow disk I/O.
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The `Zend_Cache` API supports various caching backends ([list](http://framework.zend.com/manual/1.12/en/zend.cache.backends.html))
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which can provide better performance, including APC, Xcache, ZendServer, Memcached and SQLite.
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## Cleaning caches on flush=1 requests
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If `?flush=1` is requested in the URL, e.g. http://mysite.com?flush=1, this will trigger a call to `flush()` on
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any classes that implement the `Flushable` interface. Using this, you can trigger your caches to clean.
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See [reference documentation on Flushable](/reference/flushable) for implementation details.
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### Memcached
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This backends stores cache records into a [memcached](http://www.danga.com/memcached/)
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server. memcached is a high-performance, distributed memory object caching system.
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To use this backend, you need a memcached daemon and the memcache PECL extension.
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:::php
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// _config.php
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SS_Cache::add_backend(
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'primary_memcached',
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'Memcached',
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array(
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'host' => 'localhost',
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'port' => 11211,
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'persistent' => true,
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'weight' => 1,
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'timeout' => 5,
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'retry_interval' => 15,
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'status' => true,
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'failure_callback' => ''
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)
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);
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SS_Cache::pick_backend('primary_memcached', 'any', 10);
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### APC
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This backends stores cache records in shared memory through the [APC](http://pecl.php.net/package/APC)
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(Alternative PHP Cache) extension (which is of course need for using this backend).
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:::php
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SS_Cache::add_backend('primary_apc', 'APC');
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SS_Cache::pick_backend('primary_apc', 'any', 10);
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### Two-Levels
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This backend is an hybrid one. It stores cache records in two other backends:
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a fast one (but limited) like Apc, Memcache... and a "slow" one like File or Sqlite.
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:::php
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SS_Cache::add_backend('two_level', 'Two-Levels', array(
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'slow_backend' => 'File',
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'fast_backend' => 'APC',
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'slow_backend_options' => array(
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'cache_dir' => TEMP_FOLDER . DIRECTORY_SEPARATOR . 'cache'
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)
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));
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SS_Cache::pick_backend('two_level', 'any', 10);
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