Installing memcached on RedHat 5.5 to speed up Magento 1.5.0.1

Magento is a very powerful shopping cart.  Because there are so many requests to the database during each page load it’s speed is bottlenecked by MySQL.

The Magento team built in the option to use a few caching systems to help with speed.  Memcached, APC, & xcache are some available options.

Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of Magento database calls.

Install Memcached using an RPM

Memcached is not built into RedHat Enterprise Linux 5 by default.  So I’m going to install an RPM that has the software (credit):

rpm -Uhv http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS//rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm

RedHat 5.5 has some dependency issues (credit) so we’ll need to tell Yum how to correct them:

yum –enablerepo=rpmforge,rpmforge-extras install memcached

Confirm memcached is running:

memcached -h

Install the PECL extension

Now we have to allow PHP to access memcached with the PECL extension:

pecl install memcache

Add the memcache extension to the php.ini file (usually at /etc/php.ini)

extension=memcache.so

Configure memcache

vi /etc/sysconfig/memcached

Depending upon how much RAM you have to play with adjust these settings.  For my install I want to give memcache 2 GB of RAM and listen on localhost:

PORT=”11211″

USER=”memcached”

# max connection 2048

MAXCONN=”2048″

# set ram size to 2048 – 2GB

CACHESIZE=”2048″

# listen to loopback ip 127.0.0.1, for network connection use real ip e.g., 10.0.0.4

OPTIONS=”-l 127.0.0.1″

Verify the the install in PHP info:

Set up Memcached as a service

Just installing memcached by itself wont don anything.  Now we have to set it up as a service.  Register the script to start with the server:

/sbin/chkconfig –add memcached

/etc/init.d/memcached start

Intergrate memcached with Magento

Flushing Cache

Magento is now using Memcached so you wont use the native cache found in  /var/cache.  Anytime you make changes to Magento you’ll have to flush the memcached cache to see changes.  To flush the cache you’ll have to Telnet to the memcached service:

telnet localhost 11211

You’ll see an output:

Trying 127.0.0.1…

Connected to localhost.

Escape character is ‘^]’.

The just give the following command:

flush_all

That’s all you need to do.. the cache is now flushed.  You can quit the Telnet session and you’re done.

quit

Connection to localhost closed by foreign host.

$

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