Caching: the layers and how to invalidate them #

This page is for developers who use a cache component (Symfony Cache, Laravel's Cache, Django's cache framework, Rails' Rails.cache). Exponential has several caches, each with an id and tags, handled by eZCache (kernel/classes/ezcache.php), and most of them are invalidated by the kernel when content is published. The usual reason "my change does not show" is one of these layers (Caches).

Contents #

1. The layers
2. Clearing
3. Fragment caching in templates
4. Caching data in PHP
5. Under persistent workers
6. Compared with other frameworks

The layers #

Content view caching is site.ini [ContentSettings] ViewCaching (enabled shipped). The full list with ids and tags: Caches guide.

Clearing #

php bin/php/ezcache.php --clear-tag=ini --allow-root-user
php bin/php/ezcache.php --clear-id=template-override --allow-root-user
./console exp:cache status
./console exp:velocity deploy          # the usual way after a code change: everything in the right order

exp:velocity deploy clears caches in an order chosen so that a page rendered by old code is never cached again (Servers and deployment). An extension can add its own cache to the list with site.ini [Cache] CacheItems[] and a [Cache_<id>] block, so ezcache.php and Setup > Caches can clear it.

Fragment caching in templates #

{cache-block keys=array( 'expdemo-stats', $current_user.contentobject_id ) expiry=300}
  {def $stats = fetch( 'expdemo', 'stats', hash() )} ... {undef $stats}
{/cache-block}

Data from your own tables does not trigger the publish clear: choose an expiry, or use ignore_content_expiry and clear the template-block cache yourself when your data changes. Key by everything the output depends on, including the user when the fragment is personal (Template caches).

Caching data in PHP #

There is no PSR-6 or PSR-16 cache pool in the kernel. Expensive results are stored through the cluster file handler, so they work on one server and on a cluster:

$file = eZClusterFileHandler::instance( eZSys::cacheDirectory() . '/expdemo/stats.cache' );
$stats = $file->processCache(
    function ( $path, $mtime ) { return json_decode( (string)file_get_contents( $path ), true ); },
    function ( $path ) {
        $stats = expDemoStats::compute();
        return array( 'content' => $stats, 'binarydata' => json_encode( $stats ), 'scope' => 'expdemo-stats' );
    },
    300 );

While one process generates, others wait instead of generating the same data (Caching in applications). Cache files must be written through eZClusterFileHandler::instance(), not with direct file calls. With the sevenx_valkey_cache extension an installation keeps the content view cache and the compiled INI cache in Valkey or Redis (sevenx_valkey_cache).

Under persistent workers #

Velocity keeps PHP processes between requests: a static variable survives into the next request. Never keep user-specific data in statics; process memory is not shared between workers, so it is not a shared cache either.

Compared with other frameworks #

The difference that matters: content caches are invalidated by publishing, automatically and per node; your own data needs explicit expiry or clearing.

Related pages #

• HTTP caching and reverse proxies
• View cache and cache blocks
• Cache console
• Free documentation: this page is free to copy, translate and improve under the GNU FDL 1.3.