What is Memcached?
Memcached is an open source distributed memory
object caching program that allows us to improve and speeding up
performance of dynamic web applications by caching data and objects in
Memory.
Memcached is also used to cache entire database
tables and queries to improve performance of database. It is the only
one caching system available freely and used by many big sites like
YouTube,
Facebook,
Twitter,
Reddit,
Drupal,
Zynga etc.
Enable EPEL repository under RHEL/CentOS 6.3/5.8
The fastest and easiest way to install and enable
EPEL repository using
YUM. First, select the
RPM that matches your
Linux OS architecture from the provided links and install it using method shown in below. The
EPEL repo will install all the required dependency packages for memcached. (
Note : Fedora doesn’t required EPEL repo, because it is part of fedora project).
For RHEL/CentOS 6 ( 32-Bit )
# wget http://mirrors.kernel.org/fedora-epel/6/i386/epel-release-6-7.noarch.rpm
# rpm -Uvh epel-release-6-7.noarch.rpm
For RHEL/CentOS 6 ( 64-Bit )
# wget http://mirrors.kernel.org/fedora-epel/6/x86_64/epel-release-6-7.noarch.rpm
# rpm -Uvh epel-release-6-7.noarch.rpm
For RHEL/CentOS 5 ( 32-Bit )
# wget http://mirrors.kernel.org/fedora-epel/5/i386/epel-release-5-4.noarch.rpm
# rpm -Uvh epel-release-5-4.noarch.rpm
For RHEL/CentOS 5 ( 64-Bit )
# wget http://mirrors.kernel.org/fedora-epel/5/x86_64/epel-release-5-4.noarch.rpm
# rpm -Uvh epel-release-5-4.noarch.rpm
Install Memcached
Install
Memcached program by using following command with
YUM tool.
# yum install memcached
Sample Output
Loaded plugins: fastestmirror
Determining fastest mirrors
epel: kartolo.sby.datautama.net.id
Dependencies Resolved
=====================================================================================================
Package Arch Version Repository Size
=====================================================================================================
Installing:
memcached i386 1.4.5-1.el5 epel 71 k
Transaction Summary
=====================================================================================================
Install 1 Package(s)
Upgrade 0 Package(s)
Total download size: 71 k
Is this ok [y/N]: y
Downloading Packages:
memcached-1.4.5-1.el5.i386.rpm | 71 kB 00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : memcached 1/1
Installed:
memcached.i386 0:1.4.5-1.el5
Complete!
Configure Memcached
Open the file called
/etc/sysconfig/memcached with
VI editor.
# vi /etc/sysconfig/memcached
Set or update parameters as follows, save the file and exit.
# Running on Port 11211
PORT="11211"
# Start as memcached daemon
USER="memcached"
# Set max simultaneous connections to 1024
MAXCONN="1024"
# Set Memory size to 2048 - 4GB(4096)
CACHESIZE="2048"
#Set server IP address
OPTIONS="-l 127.0.0.1"
Let’s discuss each of the above parameters in details.
- PORT : The port used by memcached to run.
- USER : The start-up daemon for memcached service.
- MAXCONN : The value used to set max simultaneous connections to 1024. For busy web servers you can increase to any number based on your requirements.
- CACHESIZE : Set cache size memory to 2048. For busy servers you can increase upto 4GB.
- OPTIONS : Set IP address of server, so that Apache or Nginx web servers can connect to it.
Start Memcached
Type the following commands to start and restart the
Memcached daemon.
# chkconfig --levels 235 memcached on
# /etc/init.d/memcached start
# /etc/init.d/memcached restart
To stop and check status, use the following commands.
# /etc/init.d/memcached stop
# /etc/init.d/memcached status
Verify Memcached
Use
netstat command to verify
Memcached is running.
# netstat -tulpn | grep :11211
tcp 0 0 127.0.0.1:11211 0.0.0.0:* LISTEN 20775/memcached
udp 0 0 127.0.0.1:11211 0.0.0.0:* 20775/memcached
Check the stats of the server using memcached-tool.
# memcached-tool 127.0.0.1 stats
Install Memcached PHP extension
Now, install PHP extension to work with
Memcached daemon.
# yum install php-pecl-memcache
Install Memcached Perl Library
Install perl library for
Memcached.
# yum install perl-Cache-Memcached
Install Memcached Python Library
Install python library for
Memcached.
# yum install python-memcached
Restart Apache
Restart the
Apache service to reflect changes.
# /etc/init.d/httpd restart
OR
# service httpd restart
Configure Firewall to Secure Memcached Server
Make sure you only have access to
memcached server, to enable access to your own servers open file called
/etc/sysconfig/iptables.
# vi /etc/sysconfig/iptables
Append the following
iptables rules to allow access to your own servers.
## Enable access on IP ranges from 172.16.1.1 to 172.16.1.10 for Port 11211 ##
# iptables -A INPUT -p tcp --destination-port 11211 -m state --state NEW -m iprange --src-range 172.16.1.1-172.16.1.10 -j ACCEPT
# iptables -A INPUT -p udp --destination-port 11211 -m state --state NEW -m iprange --src-range 172.16.1.1-172.16.1.10 -j ACCEPT
Restart the iptables service to reflect changes.
# service iptables restart
OR
# /etc/init.d/iptables restart
Cache MySQL Queries with Memcached
It isn’t an easy task for all, you need to use
API’s to modify your
PHP codes to enable
MySQL caching. You can find the examples codes at
Memcache with MySQL and PHP.
Enable Memcached on WordPress Sites
For
WordPress based sites, there is a plugin called
Memcached Object Cache that you need to install it on your
WordPress CMS.
