Memcached is very fast caching system for MySQL. It uses libevent or epoll (Linux runtime) to scale to any number of open connections and uses non-blocking network I/O.
Required Packages
1. memcached : High Performance, Distributed Memory Object Cache.
2. memcached-selinux : SELinux policy module supporting memcached.
3. perl-Cache-Memcached : Perl client for memcached.
4. php-pecl-memcache : Php client / extension to work with the Memcached caching daemon.
5. python-memcached : A Python memcached client library.
Step # 1: Turn on EPEL Repo
Type the following command to enable EPEL repo which carries required memcache packages.
rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
See this FAQ for further details.
Step # 2: Install memcached
Type the following command to install memcached with php extension:
yum install memcached php-pecl-memcache memcached-selinux
Sample outputs:
Loaded plugins: downloadonly, rhnplugin, security, verify
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package memcached.x86_64 0:1.2.8-1.el5 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
==============================================================================================================================================================
Package Arch Version Repository Size
==============================================================================================================================================================
Installing:
memcached x86_64 1.2.8-1.el5 epel 60 k
Transaction Summary
==============================================================================================================================================================
Install 1 Package(s)
Update 0 Package(s)
Remove 0 Package(s)
Total download size: 60 k
Is this ok [y/N]: y
Downloading Packages:
memcached-1.2.8-1.el5.x86_64.rpm | 60 kB 00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : memcached 1/1
Installed:
memcached.x86_64 0:1.2.8-1.el5
Complete!
Step # 3: Configure memcached
Edit using vim or nano /etc/sysconfig/memcached, and enter:
vi /etc/sysconfig/memcached
Update it as follows:
PORT="11211"
USER="memcached"
# max connection 2048
MAXCONN="2048"
# set ram size to 2048 - 2GiB
CACHESIZE="4096"
# 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"
The above options will starts memcached up as a daemon, using 4GB of memory, and listening on IP 127.0.0.1, port 11211. Save and close the file.
Step # 4: Run memcached
Type the following command to start memcached, enter:
chkconfig memcached on
service memcached start
To stop / restart use the following commands:
service memcached stop
service memcached restart
How Do I See Memory Memcached Slabs?
Type the following command:
memcached-tool IP_ADDRESS:Port
memcached-tool IP_ADDRESS:Port display
memcached-tool 127.0.0.1:11211
Sample outputs:
Item_Size Max_age 1MB_pages Count Full?
1 104 B 5134 s 1 10 no
2 136 B 5135 s 1 40 no
3 176 B 0 s 1 0 no
4 224 B 2648 s 1 7 no
8 552 B 1810 s 1 12 no
9 696 B 1810 s 1 6 no
10 872 B 2935 s 1 8 no
11 1.1 kB 4262 s 1 18 no
12 1.3 kB 2990 s 1 23 no
13 1.7 kB 2434 s 1 22 no
14 2.1 kB 3489 s 1 11 no
15 2.6 kB 2964 s 1 16 no
16 3.3 kB 2861 s 1 14 no
17 4.1 kB 2076 s 1 5 no
18 5.2 kB 2981 s 1 5 no
20 8.1 kB 64 s 1 1 no
21 10.1 kB 1865 s 1 3 no
29 60.2 kB 1550 s 1 2 no
How Do I See Memory Memcached Stats?
Type the following command:
memcached-tool IP_Address:Port stats
memcached-tool 127.0.0.1:11211 stats
Sample outputs:
127.0.0.1:11211 Field Value
accepting_conns 1
bytes 399395
bytes_read 504797
bytes_written 17313658
cmd_flush 0
cmd_get 1141
cmd_set 248
connection_structures 9
curr_connections 5
curr_items 205
evictions 0
get_hits 898
get_misses 243
limit_maxbytes 1073741824
listen_disabled_num 0
pid 40159
pointer_size 64
rusage_system 0.227965
rusage_user 0.034994
threads 5
time 1255803547
total_connections 344
total_items 259
uptime 5829
version 1.2.8
