WordPress Install Memcached Object Cache Plugin To Speed Up Blog

by on September 13, 2010 · 3 comments· LAST UPDATED September 13, 2010

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How do I install memcached cache plugin under UNIX / Linux to speed up my dynamic database-driven wordpress blog by caching data and objects in RAM to reduce the number of times an external data source must be read?

You need to install memcached caching server only if your wordpress based blog get a large numbers of hits. You need to install the following software(s) on server:

  1. memcached server : It is a caching daemon designed especially for dynamic web applications to decrease database load by storing objects in memory.
  2. php-pecl-memcache: PHP extension to work with the Memcached caching daemon through handy OO and procedural interfaces. Memcache can be used as a PHP session handler too.
  3. WordPress memcached object cache plugin : This plugin provides a persistent backend for the WordPress object cache.

Our Sample Setup

Internet
    \\
      \\
  ISP Router             +--------+
     //          +-------| mysql1 | 10.10.1.1
     //          |       +--------+
     //          |
  +-----+        |       +------+
  | lb0 |--------+-------| www1 |  10.10.1.2
  +-----+        |       +------+
vip:202.54.1.1   |
                 |       +------+
                 |-------| www2 | 10.10.1.3
                 |       +------+
                 |
                 |       +------+
  +-----+        |-------| www3 | 10.10.1.4
  | lb1 |--------+       +------+
  +-----+        |
                 |       +-----------+
                 |-------| memcache1 |  10.10.1.5
                         +-----------+
   

Where,

  • lb0 : It is a reverse proxy server that is installed on a UNIX / Linux in front of Apache Web servers hosted on www1, www2, www3. You can use nginx or any other reverse proxy server with virtual ip (connection redundancy) managed by Keepalived. This is master load balancer.
  • lb1: This is backup load balancer with nginx and keepalived.
  • www1, www2, www3 : Apache web server with php. You need install "php-pecl-memcache" and "Memcached Object Cache wordpress plugin" on all three servers.
  • mysql1 : This is MySQL server with RAID10 and fast scsi / sas disk. This server in under load and you are going to reduce the load by caching queries in RAM.
  • memcache1 : This server runs memcached with lots of RAM and it will cache mysql1 queries to decrease database load by storing objects in memory. You need to install memcached server on memcahce1. You can add memcach2 for redundancy purpose.

All of the following instructions are tested on RHEL and CentOS 5.x 64 bit servers.

Install Memcached Server

Type the following command on memache1 server. First, you need to turn on EPEL repo:
# rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
Now, install memcached using the yum command, enter:
# yum install memcached

Configure memcached

You need to edit /etc/sysconfig/memcached file, enter:
# vi /etc/sysconfig/memcached
Edit as follows:

 
PORT="11211"
USER="memcached"
MAXCONN="2048"
CACHESIZE="4096"
OPTIONS="-l 10.10.1.5"
 

Where,

  • PORT: Listen on TCP port # 11211, the default is port 11211.
  • USER: Run memcached server as memcached user.
  • MAXCONN: Use 2048 max simultaneous connections; the default is 1024.
  • CACHESIZE: Use 4096 MB (4GB) memory max to use for object storage; the default is 64 megabytes.
  • OPTIONS="-l 10.10.1.5": Listen on 10.10.1.5. This is an important option to consider as there is no other way to secure the installation. Binding to an internal or firewalled network interface is suggested. In this example, IP address 10.10.1.5 is only accessible using LAN and is behind firewalled host.

Make changes as per your setup and requirements. Save and close the file.

Turn On Service

Type the following chkconfig command to turn memcached service, enter:
# /sbin/chkconfig memcached on
## command to START the server ##
# /sbin/service memcached start
## command to STOP the server ##
# /sbin/service memcached stop
## command to RESTART the server ##
# /sbin/service memcached restart

Install php-pecl-memcache

Type the following commands on www1, www2, and www3 Apache server:
# yum -y install php-pecl-memcache
# /sbin/service httpd restart

Install Memcached Object Cache Plugin

Type the following command on www1, www2, and www3 Apache server (if you are using some sort of cluster aware file system such as GFS2 or OCFS2, than just type it on any one apache web server node):
Visit this url and grab the plugin, enter:
$ cd /tmp/
$ wget http://downloads.wordpress.org/plugin/memcached.2.0.zip
$ unzip memcached.2.0.zip

Edit object-cache.php, enter:
$ vi object-cache.php
Edit memcahe server and port connection information:

 
$buckets = array('10.10.1.5:11211');
 

Save and close the file. Finally, copy object-cache.php into your wp-content directory. In our example /var/www/html/wp-content/ directory:
$ cp object-cache.php /var/www/html/wp-content/

How Do I Verify That It Is Working?

Type the following commands to display memcache slabs (please note that the following output is taken from a small memcached server with just 512MB cache for demonstration purpose only):
# memcached-tool 10.10.1.5:11211 display
Sample outouts:

  #  Item_Size  Max_age   Pages   Count   Full?  Evicted Evict_Time OOM
  1      96B     38302s       1      42      no        0        0    0
  2     120B     37571s       1       4      no        0        0    0
  3     152B       335s       1     232      no        0        0    0
  4     192B     37763s       1      40      no        0        0    0
  5     240B     37804s       1      36      no        0        0    0
  6     304B     37595s       1      86      no        0        0    0
  7     384B       829s       4   10401      no        0        0    0
  8     480B       228s       1     972      no        0        0    0
  9     600B       106s       1     387      no        0        0    0
 10     752B     38298s       1     288      no        0        0    0
 11     944B       404s       1     143      no        0        0    0
 12     1.2K     38319s       1     258      no        0        0    0
 13     1.4K     12739s       1     176      no        0        0    0
 14     1.8K     38322s       1     230      no        0        0    0
 15     2.3K      1500s       2     491      no        0        0    0
 16     2.8K      1500s       2     648      no        0        0    0
 17     3.5K       828s       3     600      no        0        0    0
 18     4.4K     37660s       2     322      no        0        0    0
 19     5.5K     38035s       1     171      no        0        0    0
 20     6.9K     38458s       1     102      no        0        0    0
 21     8.7K     39002s       1      39      no        0        0    0
 22    10.8K     42068s       1      35      no        0        0    0
 23    13.6K     24184s       1      15      no        0        0    0
 24    16.9K     41626s       1      11      no        0        0    0
 25    21.2K     43426s       1       1      no        0        0    0
 26    26.5K     43392s       1       1      no        0        0    0
 37   308.5K      1493s       1       3     yes        0        0    0

To shows general stats, enter:
# memcached-tool 10.10.1.5:11211 stats
Sample outputs:

#10.10.1.5:11211   Field       Value
         accepting_conns           1
               auth_cmds           0
             auth_errors           0
                   bytes    14945401
              bytes_read  1320187573
           bytes_written  3180772729
              cas_badval           0
                cas_hits           0
              cas_misses           0
               cmd_flush           0
                 cmd_get     1280549
                 cmd_set     1262345
             conn_yields           0
   connection_structures          73
        curr_connections          72
              curr_items       15724
               decr_hits           0
             decr_misses           0
             delete_hits       11296
           delete_misses       24284
               evictions           0
                get_hits     1156788
              get_misses      123761
               incr_hits           0
             incr_misses           0
          limit_maxbytes   536870912
     listen_disabled_num           0
                     pid       42690
            pointer_size          64
               reclaimed           2
           rusage_system   51.550163
             rusage_user   20.861828
                 threads           4
                    time  1284368953
       total_connections         558
             total_items       75121
                  uptime       43527
                 version       1.4.5

To dumps keys and values, enter:
# memcached-tool 10.10.1.5:11211 dump | less

More Tips: To Increase Your WordPress Based Blog Speed

  1. Turn on MySQL query cache.
  2. Use xcache opcode cacher to accelerates the performance of PHP on servers.
  3. Use CDN (Content Delivery Network) for WordPress to speed up your blog.

Conclusion

The end result was pretty good. The database request are completed faster and loads on database servers are decreased. The above setup can be used with other php or webapps too.

Recommended readings:

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{ 3 comments… read them below or add one }

1 Scott September 28, 2010 at 4:35 am

Hi great post. I followed your tutorial but get alot of segfaults after:
[Thu Sep 30 09:36:05 2010] [notice] child pid 23839 exit signal Segmentation fault (11)
[Thu Sep 30 09:36:06 2010] [notice] child pid 23840 exit signal Segmentation fault (11)
[Thu Sep 30 09:36:06 2010] [notice] child pid 23841 exit signal Segmentation fault (11)

Have you seen this as well. Using php 5.1.6 and Apache/2.2.3

Reply

2 Minh January 19, 2013 at 10:15 am

Make changes as per your setup and requirements. Save and close the file. <<<

Could you tell me how to save and close the file ??

Reply

3 Abhishek January 6, 2014 at 11:25 am

Does wordpress’s memcached module support nginx ?

Reply

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