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==Install Redis Caching for Magento==
[[File:Img-redis.jpg|frameless|right|Install Redis Cache Magento ]]
How to install redis for backend caching?  You see alot of talk about using apc and memcached for Magento caching, but if you are looking for a more stable caching, then redis is for you.

===1) Install Redis and phpRedis===

This can be done using yum, which makes this step pretty easy.

 yum install redis php-pecl-redis

 service redis start

 chkconfig redis on

Now to verify that redis is chkconfig on

 chkconfig --list redis

===2) Install Cm_Cache_Backend_Redis Magento Extension===

This is the extension that is required on versions of CE 1.7.0.2 and older, as Magento 1.8.0.0 it comes pre installed.

 wget -O Cm_Cache_Backend_Redis.tar.gz https://github.com/colinmollenhour/Cm_Cache_Backend_Redis/tarball/master

 tar xzf Cm_Cache_Backend_Redis.tar.gz 

 cd colinmollenhour-Cm_Cache_Backend_Redis-*/

 cp -r Cm /path/to/magento/app/code/local/

 cp -r lib/Credis /path/to/magento/lib/

 cat > /path/to/magento/app/etc/modules/Cm_Cache.xml <<eof
 <?xml version="1.0" encoding="UTF-8"?>
 <config>
    <modules>
        <Cm_Cache>
            <active>true</active>
            <codePool>local</codePool>
        </Cm_Cache>
    </modules>
 </config>
 eof

===3) Install Credis Library===

Again not needed if you are using Magento 1.8.0.0 or higher, as its already included in the base install

 wget -O credis.tar.gz https://github.com/colinmollenhour/credis/tarball/master

 tar xzf credis.tar.gz

 cd colinmollenhour-credis-*/

 cp -r ./* /path/to/magento/lib/Credis/

 cd /path/to/magento/

 chown -R username. lib/Credis/

 chown -R username. app/code/local/Cm/

 chown -R username. app/etc/modules/Cm_Cache.xml

===4) Configure Magento to use Redis ===
Now comes the fun part, you are going to need to setup redis in your local.xml file.

I recommend always making a backup copy of your local.xml file before making any changes to it

 cp app/etc/local.xml app/etc/local.xml-bk-$(date +%F)

Now lets install redis as a backend cache

 vim app/etc/local.xml

Now add the following to your configuration for redis using TCP

 <!-- 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 unique string to enable persistent connections. E.g.: sess-db0;
     <database>0</database> <!-- Redis database number; protection against accidental data loss is improved by not sharing databases -->
     <password></password> <!-- Specify if your Redis server requires authentication -->
     <force_standalone>0</force_standalone>  <!-- 0 for phpredis, 1 for standalone PHP -->
     <connect_retries>1</connect_retries>    <!-- Reduces errors due to random connection failures; a value of 1 will not retry after the first failure -->
     <read_timeout>10</read_timeout>         <!-- Set read timeout duration; phpredis does not currently support setting read timeouts -->
     <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, lz4 (as l4z) and snappy -->
     <use_lua>0</use_lua> <!-- Set to 1 if Lua scripts should be used for some operations -->
   </backend_options>
 </cache>

If you are using a Socket for your redis instance

 <cache>
   <backend>Cm_Cache_Backend_Redis</backend>
   <backend_options>
     <server>/var/tmp/redis-multi_path/to/my.sock</server> <!-- or absolute path to unix socket -->
     <port></port>
     <persistent></persistent> <!-- Specify unique string to enable persistent connections. E.g.: sess-db0;
     <database>0</database> <!-- Redis database number; protection against accidental data loss is improved by not sharing databases -->
     <password></password> <!-- Specify if your Redis server requires authentication -->
     <force_standalone>0</force_standalone>  <!-- 0 for phpredis, 1 for standalone PHP -->
     <connect_retries>1</connect_retries>    <!-- Reduces errors due to random connection failures; a value of 1 will not retry after the first failure -->
     <read_timeout>10</read_timeout>         <!-- Set read timeout duration; phpredis does not currently support setting read timeouts -->
     <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, lz4 (as l4z) and snappy -->
     <use_lua>0</use_lua> <!-- Set to 1 if Lua scripts should be used for some operations -->
   </backend_options>
 </cache>

===Clearning your Magento Cache===

Now the last step is a giving, any time you make any changes to your Magento configuration/template is to clear your sessions and cache.  You do NOT want problems later, because you forgot to clear them and you now find a problem.  Sometimes problems show their heads up to a week or so, so clear cache/session and see if you have any problems/issues.

If you were using files prior to the change

 rm -r /path/magento/var/session/* /path/magento/var/cache/*

If you were using memcache prior to change

 echo "flush_all" | nc 127.0.0.1 11211
 
or if using a sock

 echo "flush_all" | nc -U /path/to/socket

===How to flush your Redis Cache===

Now you will want to flush your redis cache anytime you make a change to your site. The fastest way to do this is to run the following command via the command line.

 echo 'flushall' | redis-cli -h 127.0.0.1 -p 6379
or
 echo 'flushall' | redis-cli -s /path/to/sock

===How to Check if your Redis Cache is Working===

To verify you are getting connections to your redis instance

 echo 'info' | redis-cli -h 127.0.0.1 -p 6379 | grep connections
or
 echo 'info' | nc -U /path/to/socket | grep connections

===Additioanl Articles===
 --> [[How to install Redis on a Centos 6.4 Server]]
 --> [[Magento Connect is not Working]]
 --> [[Changing the Minimum Search Query - MySQL Full Text Only]]
 --> [[Install Redis Caching for Magento]]
 --> [[Install Redis Full Page Caching for Magento Enterprise]]
 --> [[Basic Redis commands - Cheat Sheet]]