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Current implementation uses a caching library called Stash (, via Stash-bundle. If this changes, then the configuration format will most likely change as well.). Stash supports the following cache driversbackends: FileSystem, Memcache, APC, Sqlite, XCacheRedis and BlackHole.

Use of Memcached or Redis is a requirement for use in Clustering setup, for overview of clustering feature see Clustering. 

If eZ Publish Platform changes to another cache system, configuration will change in the future, changes to configuration in StashBundle is listed here:

Cache service

The cache system is exposed as a "cache" service, and can be reused by any other service as described on the Persistence cache page.

...

stash:
    caches:
        default:
            # With the version of Stash bundled with For eZ Publish Platform 5.1versions andprior to 5.2 this is called "handlers:4/2014.07, use "handlers" instead of "drivers"!
            drivers:
                - FileSystem
            inMemory: false
            registerDoctrineAdapter: false

...

stash:
    caches:
        default:
            # With the version of Stash bundled with For eZ Publish Platform 5.1versions andprior to 5.2 this is called "handlers:4/2014.07, use "handlers" instead of "drivers"!
            drivers:
                - BlackHole
            inMemory: true
            registerDoctrineAdapter: false

...

If you want to change to another drivercache backend, see in Stash drivers backend configuration below for what kind of settings you have available.

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The "default" here refers to the name of the cache pool as specified in the stash configuration block shown above, if your install has several repositories (databases), then make sure every group of sites using different repositories also uses a different cache pool to avoid unwanted effects.
NB: We plan to make this more native in the future, so this setting will someday not be needed.

Stash

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cache backend configuration

General settings

To check which cache settings are available for your installation, run the following command in your terminal :

php ezpublish/console config:dump-reference stash

FileSystem

This cache driver backend is using local filesystem, by default the Symfony cache folder, as this is per server, it does not support multi server (cluster) setups!

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stash:
    caches:
        default:
            # With the version of Stash bundled with For eZ Publish Platform 5.1versions andprior to 5.2 this is called "handlers:4/2014.07, use "handlers" instead of "drivers"!
            drivers:
                - FileSystem
            inMemory: true
            registerDoctrineAdapter: false
            FileSystem:
                keyHashFunction: 'crc32'

FileSystem

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cache backend troubleshooting

By default, Stash Filesystem driver cache backend stores cache to a sub-folder named after the environment (i.e. ezpublish/cache/dev, ezpublish/cache/prod). This can lead to the following issue : if different environments are used for operations, persistence cache (manipulating content, mostly) will be affected and cache can become inconsistent.

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1. Manual

   Always use the same environment, for web, command line, cronjobs...
   
   

2. Share stash cache across Symfony environments (prod / dev)

Either by using another Stash drivercache backend, or by setting Stash to use a shared cache folder that does not depend on the environment. 
In ezpublish.yml:

...

This will store stash cache to ezpublish/cache/common.

APC

This cache driver backend is using shard memory using APC's user cache feature, as this is per server, it does not support multi server (cluster) setups, unless you use PHP-FPM on a dedicated server (this way, user cache can be shared among all the workers in one pool).

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Memcache

This cache driver backend is using Memcached, a distributed caching solution, this is the only supported cache solution for multi server (cluster) setups!

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✲ All settings but servers are only available with memcached php extension, for more information on these settings and which version of php-memcached they are available in, see: http://php.net/Memcached
✸ If you are on eZ Publish 5.1, make sure to update Stash and StashBundle to get access to these settings.

Example with Memcache

stash:
    caches:
        default:
            # With the version of Stash bundled with For eZ Publish Platform 5.1versions andprior to 5.2 this is called "handlers:4/2014.07, use "handlers" instead of "drivers"!
            drivers: [ Memcache ]
            inMemory: true
            registerDoctrineAdapter: false
            Memcache:
                prefix_key: ezdemo_
                retry_timeout: 1
                servers:
                    -
                        server: 127.0.0.1
                        port: 11211

Memory consumption issues with Redis

If you use the Redis cache driver and encounter problems with high memory consumption, you can use the following (non-SiteAccess-aware) settings:

ezpublish:
    stash_cache:
        igbinary: true/false
        lzf: true/false

• ezpublish.stash_cache.igbinary enables you to use the igbinary PHP extension to serialize objects stored in cache.
  • Recommended enabled in most use cases.
• ezpublish.stash_cache.lzf enables you to use the LZF PHP extension to compress serialized objects stored in cache.
  • Compression consumes some more CPU. A scenario where it improves overall performance is when Redis memory and/or network bandwidth is limited, with spare CPU capacity on PHP server.

These options in combination results in around 1/2 memory usage for API caching compared to not being enabled, igbinary accounts for ~75% of that and LZF the remaining ~25% when configured for max compression.

After changing these settings you need to clear cache and purge Redis content .