Zend_Cache backend using Redis with full support for tags

This Zend_Cache backend allows you to use a Redis server as a central cache storage. Tags are fully supported without the use of TwoLevels cache so this backend is great for use on a single machine or in a cluster. Works with any Zend Framework project including all versions of Magento!

FEATURES

• Uses the phpredis PECL extension for best performance (requires master branch or tagged version newer than Aug 19 2011).
• Falls-back to standalone PHP if phpredis isn't available using the Credis library.
• Tagging is fully supported, implemented using the Redis "set" and "hash" datatypes for efficient tag management.
• Key expiry is handled automatically by Redis, and the cache is safe to use with the "allkeys-lru" maxmemory-policy config option.
• Supports unix socket connection for even better performance on a single machine.
• Supports configurable compression for memory savings. Can choose between gzip, lzf and snappy and can change configuration without flushing cache.
• Uses transactions to prevent race conditions between saves, cleans or removes causing unexpected results.
• Unit tested!

INSTALLATION (Magento)

1. Install redis (2.4+ required)

• The recommended "maxmemory-policy" is "volatile-lru". All data keys are volatile and tag sets are not to prevent tag data from being lost. Just be sure the "maxmemory" is high enough to accomodate all of the tag data with lots of room left for the key data.

2. Install phpredis (optional)

• For 2.4 support you must use the "master" branch or a tagged version newer than Aug 19, 2011.
• phpredis is optional, but it is much faster than standalone mode
• phpredis does not support setting read timeouts at the moment (see pull request #260). If you receive read errors, this might be the reason.

3. Install this module using modman

• modman clone git://github.com/colinmollenhour/Cm_Cache_Backend_Redis.git

4. Edit app/etc/local.xml to configure:

   <!-- This is a child node of config/global -->
   <cache>
     <backend>Cm_Cache_Backend_Redis</backend>
     <backend_options>
       <server>127.0.0.1</server> <!-- or absolute path to unix socket -->
       <port>6379</port>
       <persistent></persistent> <!-- Specify a unique string like "cache-db0" to enable persistent connections. -->
       <database>0</database>
       <password></password>
       <force_standalone>0</force_standalone>  <!-- 0 for phpredis, 1 for standalone PHP -->
       <connect_retries>1</connect_retries>    <!-- Reduces errors due to random connection failures -->
       <read_timeout>10</read_timeout>         <!-- Set read timeout duration -->
       <automatic_cleaning_factor>0</automatic_cleaning_factor> <!-- Disabled by default -->
       <compress_data>1</compress_data>  <!-- 0-9 for compression level, recommended: 0 or 1 -->
       <compress_tags>1</compress_tags>  <!-- 0-9 for compression level, recommended: 0 or 1 -->
       <compress_threshold>20480</compress_threshold>  <!-- Strings below this size will not be compressed -->
       <compression_lib>gzip</compression_lib> <!-- Supports gzip, lzf and snappy -->
     </backend_options>
   </cache>
   
   <!-- This is a child node of config/global for Magento Enterprise FPC -->
   <full_page_cache>
     <backend>Cm_Cache_Backend_Redis</backend>
     <backend_options>
       <server>127.0.0.1</server> <!-- or absolute path to unix socket -->
       <port>6379</port>
       <persistent></persistent> <!-- Specify a unique string like "cache-db0" to enable persistent connections. -->
       <database>1</database> <!-- Separate database 1 to keep FPC separately -->
       <password></password>
       <force_standalone>0</force_standalone>  <!-- 0 for phpredis, 1 for standalone PHP -->
       <connect_retries>1</connect_retries>    <!-- Reduces errors due to random connection failures -->
       <lifetimelimit>57600</lifetimelimit>    <!-- 16 hours of lifetime for cache record -->
       <compress_data>0</compress_data>        <!-- DISABLE compression for EE FPC since it already uses compression -->
     </backend_options>
   </full_page_cache>
   

RELATED / TUNING

• Automatic cleaning is optional and not recommended since it is slow and uses lots of memory.
• Occasional (e.g. once a day) garbage collection is recommended if the entire cache is infrequently cleared and automatic cleaning is not enabled. The best solution is to run a cron job which does the garbage collection. (See "Example Garbage Collection Script" below.)
• Compression will have additional CPU overhead but may be worth it for memory savings and reduced traffic. For high-latency networks it may even improve performance. Use the Magento Cache Benchmark to analyze your real-world compression performance and test your system's performance with different compression libraries.
  • gzip - Slowest but highest compression. Most likely you will not want to use above level 1 compression.
  • lzf - Fastest compress, fast decompress. Install: sudo pecl install lzf
  • snappy - Fastest decompress, fast compress. Download and install: snappy and php-snappy
• Monitor your redis cache statistics with my modified munin plugin.
• Enable persistent connections. Make sure that if you have multiple configurations connecting the persistent string is unique for each configuration so that "select" commands don't cause conflicts.
• Use the stats.php script to inspect your cache to find oversized or wasteful cache tags.

Example Garbage Collection Script (Magento)

<?php count($argc) or die('<pre>:P</pre>');
ini_set('memory_limit','1024M');
set_time_limit(0);
error_reporting(E_ALL | E_STRICT);
require_once 'app/Mage.php';
Mage::app()->getCache()->getBackend()->clean('old');
// uncomment this for Magento Enterprise Edition
// Enterprise_PageCache_Model_Cache::getCacheInstance()->getFrontend()->getBackend()->clean('old');

Release Notes

• November 19, 2012: Added read_timeout option. (Feature only supported in standalone mode, will be supported by phpredis when pull request #260 is merged)
• October 29, 2012: Added support for persistent connections. (Thanks samm-git!)
• October 12, 2012: Improved memory usage and efficiency of garbage collection and updated recommendation.
• September 17, 2012: Added connect_retries option (default: 1) to prevent errors from random connection failures.
• July 10, 2012: Added password authentication support.
• Mar 1, 2012: Using latest Credis_Client which adds auto-reconnect for standalone mode.
• Feb 15, 2012: Changed from using separate keys for data, tags and mtime to a single hash per key.
• Nov 10, 2011: Changed from using phpredis and redisent to Credis (which wraps phpredis). Implemented pipelining.

@copyright  Copyright (c) 2012 Colin Mollenhour (http://colin.mollenhour.com)
This project is licensed under the "New BSD" license (see source).