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Memcached

Table of contents

1. About Memcache
2. Memcached Users
3. Ubuntu 11.10 Installation and setup using CLI
4. Configuring Memcache
5. Use Memcache with Drupal 7.x
6. Use Memcache with Drupal 6.x

About Memcache

• from memcached.org
• It is free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.
• It is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.
• It is simple yet powerful.
• Its simple design promotes quick deployment, ease of development, and solves many problems facing large data caches.
• Its API is available for most popular languages.

Memcached Users

Memcached should not be underestimated. Its use will make a big difference for websites with TBs and PBs of files/DBs. It’s just used by no less than the following big websites:

• LiveJournal
• Wikipedia
• Flickr
• Bebo
• Twitter
• Typepad
• Yellowbot
• Youtube
• Digg
• WordPress.com
• Craigslist
• Mixi

Ubuntu 11.10 Installation and setup using CLI

1. Install memcached

   sudo apt-get install memcached libmemcached-tools
   sudo apt-get install memcached libmemcached-tools
   

2. Install memcached php extension using PECL

   sudo apt-get install php5-dev php-pear make
   sudo pecl install memcache
   

3. Edit your php.ini file

   sudo vim /etc/php5/apache2/php.ini
   

   Then, insert the following line into it:

   extension=memcache.so
   

4. Restart apache and start memcache

   sudo service apache2 restart
   sudo service apache2 restart
   

5. That’s it, you’re done. The following are optionals:

   To check if memcache is running, run

   sudo service memcached status
   

   Note that memcache’s default port is 11211. To check if it is active and listening to that port, run

   netstat -tap | grep memcached
   

   To check the status and stats, use memstat tool, where 127.0.0.1 is the local or public IP address.

   memstat 127.0.0.1:11211
   

   If memstat is not yet installed, install it with

   sudo apt-get install memstat
   

Configuring Memcache

Configuring memcache can be done by editing the configuration file that can be found in /etc/memcached.conf.

To edit

sudo vim /etc/memcached.conf

To change default memory (64 MB), look for the following lines:

# Start with a cap of 64 megs of memory. It's reasonable, and the daemon default
# Note that the daemon will grow to this size, but does not start out holding this much
# memory
-m 64

To effect changes, restart memcache and apache2.

sudo service memcached restart
sudo service apache2 restart

Use Memcache with Drupal 7.x

1. Edit php.ini file.

   sudo vim /etc/php5/apache2/php.ini
   

   Append the following line:

   memcache.hash_strategy=consistent
   

2. Install and activate a drupal module Drupal Memcache

3. Edit settings.php of Drupal isntance to include:

   $conf['cache_backends'][] = 'sites/all/modules/memcache/memcache.inc';
   $conf['cache_default_class'] = 'MemCacheDrupal';
   $conf['memcache_key_prefix'] = 'unique';
   

   where unique is whatever word you want. This is important if you have multiple instances of drupal running with memcache in a single server.

Use Memcache with Drupal 6.x

Perform the same steps in Drupal 7.x except step No. 3.

For step 3, include the following, instead:

$conf['cache_inc'] ='sites/all/modules/memcache/memcache.inc';