Configure Memcached Distributed Memory Caching System

Memcached can speed up database driven dynamic web site. It must be deployed within trusted network where vm01 and vm02 clients may freely connect to our server. You need to type the following commands on vm03 having an IP address 192.168.1.12.

Install memcached server on vm03

Type the following yum command to install memcached server on RHEL based system:
# yum install -y memcached

Install memcached client on vm01 and vm02

You may need to install any one of the following package on vm01 and vm02 (server running php5+apache/Lighttpd):

1. perl-Cache-Memcached : Perl client (library) to work with memcached server.
2. python-memcached : Python client (library) to work with memcached server.
3. php-pecl-memcache : PHP extension to work with the Memcached server.

Configure memcached

Edit /etc/sysconfig/memcached file, enter:
# vi /etc/sysconfig/memcached
Sample outputs:

PORT="11211"
USER="memcached"
MAXCONN="1024"
CACHESIZE="512"
## make sure we accept connection from vm01 and vm02 on 192.168.1.12:11211
OPTIONS="-l 192.168.1.12 -L"

Save and close the file. Start the memcached server:
# chkconfig memcached on
# /sbin/service memcached start
Edit /etc/sysconfig/iptables and make sure only vm01 and vm02 are allowed to connect to the our server:

## open vm01 and vm02 tcp/udp port for memcached server ##
-A INPUT -m state --state NEW -s 192.168.1.10 -m tcp -p tcp --dport 11211 -j ACCEPT
-A INPUT -m state --state NEW -s 192.168.1.11 -m udp -p udp --dport 11211 -j ACCEPT
-A INPUT -m state --state NEW -s 192.168.1.10 -m udp -p udp --dport 11211 -j ACCEPT
-A INPUT -m state --state NEW -s 192.168.1.11 -m tcp -p tcp --dport 11211 -j ACCEPT

Save and close the file. Restart the iptables service, enter:
# /sbin/service iptables restart
# /sbin/iptables -L -v -n

Increase file system and ports limits on vm03

For busy memcached server you need to increase system file descriptor and IP port limits:

# Increase system file descriptor limit to
fs.file-max = 50000
# Increase system IP port limits
net.ipv4.ip_local_port_range = 2000 65000

Load the changes by typing the following sysctl command to modify Linux kernel parameters at runtime:
# sysctl -p

See also

• WordPress Install Memcached Object Cache Plugin To Speed Up Blog
• Memcached source installation for RHEL 5.x and older systems.

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