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eZ Publish (5.x)

eZ Publish 5.x | For eZ Platform & eZ Studio topics see Technical manual and User manual, for eZ Publish 4.x and Legacy topics see eZ Publish legacy

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Introduction

Tech Note

Current implementation uses a caching library called Stash (, via Stash-bundle). Stash supports the following cache backends: FileSystemMemcache, APC, Sqlite, Redis and BlackHole.

Use of Memcached (or experimentally using 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:

Configuration change in 5.4/2014.07

StashBundle version bundled with 5.4/2014.07 and higher refers to cache backends as "drivers" where it was previously referred to as "handlers" in yml configuration

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.

Configuration

During Setup wizard and manually using ezpublish:configure console command a default configuration is generated currently using FileSystem, using %kernel.cache_dir%/stash to store cache files.

The configuration is placed in ezpublish/config/ezpublish.yml, and looks like:

Default ezpublish.yml

The default settings used during setup wizard as found in ezpublish/config/ezpublish_setup.yml:

ezpublish_setup.yml

This setting works across all installs and just caches objects within the same request thanks to the inMemory: true setting.

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

Note for "inMemory" cache with long running scripts

Use of inMemory caching with BlackHole or any other cache backend should not be used for long running scripts as it will over time return stale data, inMemory cache is not shared across requests/processes, so invalidation does not happen!

Multi repository setup

New in 5.2 is the possibility to select a specific Stash cache pool on a siteaccess or sitegroup level, the following example shows use in a sitegroup:

ezpublish.yml site group setting

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 cache backend configuration

General settings

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

FileSystem

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

We strongly discourage you from storing cache files on NFS, as it defeats the purpose of the cache: speed

Available settings

path
The path where the cache is placed, default is %kernel.cache_dir%/stash, effectively ezpublish/cache/<env>/stash
dirSplit
Number of times the cache key should be split up to avoid having to many files in each folder, default is 2.
filePermissions
The permissions of the cache file, default is 0660.
dirPermissions
The permission of the cache file directories (see dirSplit), default is 0770.
memKeyLimit

Limit on how many key to path entries are kept in memory during execution at a time to avoid having to recalculate the path on key lookups, default 200.

keyHashFunction
Algorithm used for creating paths, default md5. Use crc32 on Windows to avoid path length issues.

Issues with Microsoft Windows

If you are using a Windows OS, you may encounter an issue regarding long paths for cache directory name. The paths are long because Stash uses md5 to generate unique key that are sanitized really quickly.

Solution is to change the hash algorithm used by Stash.

Specifying key hash function

This configuration is only recommended for Windows users.

Note: You can also define the path where you want the cache files to be generated to be able to get even shorter system path for cache files.

 

FileSystem cache backend troubleshooting

By default, Stash Filesystem cache backend stores cache to a sub-folder named after the environment (i.e. ezpublish/cache/devezpublish/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.

To prevent this, there are 2 solutions :

  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 cache 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 backend is using shard memory using APC's user cache feature, as this is per server, it does not support multi server (cluster) setups.

Limitation

As APC user cache is not shared between processes, it is not possible to clear the user cache from CLI, even if you set apc.enable_cli to On. Hence publishing content from a command line script won't let you properly clear SPI Persistence cache.

Please also note that the default value for apc.shm_size is 128MB. However, 256MB is recommended for APC to work properly. For more details please refer to the APC configuration manual.

 

Available settings

ttlThe time to live of the cache in seconds, default set to 500 (8.3 minutes)
namespaceA namespace to prefix cache keys with to avoid key conflicts with other eZ Publish sites on same eZ Publish installation, default is null.

Memcache

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

Note

Stash supports both the php-memcache and php-memcached extensions. However only php-memcache is officially tested on Redhat/Centos while php-memcached is on Debian and Ubuntu. If you have both extensions installed, Stash will automatically choose php-memcached.

servers

Array of Memcached servers, with host/IP, port and weight

server: Host or IP of your Memcached server
port: Port where Memcached is listening to (defaults to 11211)
weight: Weight of the server, when using several Memcached servers

prefix_keyA namespace to prefix cache keys with to avoid key conflicts with other eZ Publish sites on same eZ Publish installation (default is an empty string).
Must be the same on all server with the same installation. See Memcached prefix_key option.
compressiondefault true. See Memcached compression option.
libketama_compatibledefault false. See Memcached libketama_compatible option
buffer_writesdefault false. See Memcached buffer_writes option 
binary_protocoldefault false. See Memcached binary_protocol option 
no_blockdefault false. See Memcached no_block option 
tcp_nodelaydefault false. See Memcached tcp_nodelay option 
connection_timeoutdefault 1000. See Memcached connection_timeout option 
retry_timeoutdefault 0. See Memcached retry_timeout option 
send_timeoutdefault 0. See Memcached send_timeout option 
recv_timeout

default 0. See Memcached recv_timeout option 

poll_timeoutdefault 1000. See Memcached poll_timeout option 
cache_lookupsdefault false. See Memcached cache_lookups option 
server_failure_limitdefault 0. See PHP Memcached documentation
socket_send_size
See Memcached socket_send_size option. ✲ ✸
socket_recv_sizeSee Memcached socket_recv_size option. ✲ ✸
serializerSee Memcached serializer option. ✲ ✸
hashSee Memcached hash option. ✲ ✸
distribution

Specifies the method of distributing item keys to the servers. See Memcached distribution option. ✲ ✸

 

✲ 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

Connection errors issue

If memcached does display connection errors when using the default (ascii) protocol, switching to binary protocol (in the stash configuration and memcached daemon) should resolve the issue.

2 Comments

  1. Hi everybody,
    When using Memcache in multi fronts installation, if the cache mechanism doesn't work after checking your eZ Publish configuration .
    Be sure to use the php5-memcached (with "d")
    It will save you probably 1 or 2 hours of debug ! (wink)

    ++

  2. When using retry_timeout option as in the example above you will get an exception like:

    [Stash\Exception\RuntimeException]
    Memcached option Memcached::OPT_RETRY_TIMEOUT not accepted by memcached extension.

    At least on Ubuntu 14.04 LTS + php5_memcached 2.1.0-6build1 + memcached 1.4.14-0ubuntu9