Memcached is a general-purpose distributed memory caching system. It is usually used to speed up dynamic database-driven webapps or websites by caching objects in RAM. It is often result into reducing database load. You need to install the following packages:
- memcached - A high-performance memory object caching server
- php5-memcache - Memcache extension module for PHP5
- php5-memcached - Memcached extension module for PHP5, uses libmemcached
- python-memcache - Pure python memcached client
How to install memcached on Ubuntu 14.04
Type the following apt-get command:
sudo apt-get update sudo apt-get install memcached
Sample outputs:
Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: libevent-2.0-5 libsasl2-2 libsasl2-modules libsasl2-modules-db Suggested packages: libsasl2-modules-otp libsasl2-modules-ldap libsasl2-modules-sql libsasl2-modules-gssapi-mit libsasl2-modules-gssapi-heimdal libcache-memcached-perl libmemcached The following NEW packages will be installed: libevent-2.0-5 libsasl2-2 libsasl2-modules libsasl2-modules-db memcached 0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded. Need to get 328 kB of archives. After this operation, 1,036 kB of additional disk space will be used. Do you want to continue? [Y/n] y Get:1 http://archive.ubuntu.com/ubuntu/ trusty/main libsasl2-modules-db amd64 2.1.25.dfsg1-17build1 [14.9 kB] Get:2 http://archive.ubuntu.com/ubuntu/ trusty/main libsasl2-2 amd64 2.1.25.dfsg1-17build1 [56.5 kB] Get:3 http://archive.ubuntu.com/ubuntu/ trusty-updates/main libevent-2.0-5 amd64 2.0.21-stable-1ubuntu1.14.04.1 [126 kB] Get:4 http://archive.ubuntu.com/ubuntu/ trusty/main libsasl2-modules amd64 2.1.25.dfsg1-17build1 [64.3 kB] Get:5 http://archive.ubuntu.com/ubuntu/ trusty/main memcached amd64 1.4.14-0ubuntu9 [66.7 kB] Fetched 328 kB in 1s (220 kB/s) Selecting previously unselected package libsasl2-modules-db:amd64. (Reading database ... 14575 files and directories currently installed.) Preparing to unpack .../libsasl2-modules-db_2.1.25.dfsg1-17build1_amd64.deb ... Unpacking libsasl2-modules-db:amd64 (2.1.25.dfsg1-17build1) ... Selecting previously unselected package libsasl2-2:amd64. Preparing to unpack .../libsasl2-2_2.1.25.dfsg1-17build1_amd64.deb ... Unpacking libsasl2-2:amd64 (2.1.25.dfsg1-17build1) ... Selecting previously unselected package libevent-2.0-5:amd64. Preparing to unpack .../libevent-2.0-5_2.0.21-stable-1ubuntu1.14.04.1_amd64.deb ... Unpacking libevent-2.0-5:amd64 (2.0.21-stable-1ubuntu1.14.04.1) ... Selecting previously unselected package libsasl2-modules:amd64. Preparing to unpack .../libsasl2-modules_2.1.25.dfsg1-17build1_amd64.deb ... Unpacking libsasl2-modules:amd64 (2.1.25.dfsg1-17build1) ... Selecting previously unselected package memcached. Preparing to unpack .../memcached_1.4.14-0ubuntu9_amd64.deb ... Unpacking memcached (1.4.14-0ubuntu9) ... Processing triggers for ureadahead (0.100.0-16) ... Setting up libsasl2-modules-db:amd64 (2.1.25.dfsg1-17build1) ... Setting up libsasl2-2:amd64 (2.1.25.dfsg1-17build1) ... Setting up libevent-2.0-5:amd64 (2.0.21-stable-1ubuntu1.14.04.1) ... Setting up libsasl2-modules:amd64 (2.1.25.dfsg1-17build1) ... Setting up memcached (1.4.14-0ubuntu9) ... Starting memcached: memcached. Processing triggers for libc-bin (2.19-0ubuntu6.6) ... Processing triggers for ureadahead (0.100.0-16) ...
How do I start / stop / restart memcached server?
The syntax is as follows:
/etc/init.d/memcached start /etc/init.d/memcached stop /etc/init.d/memcached restart /etc/init.d/memcached force-reload /etc/init.d/memcached status
Verify that memcached is install and functioning on your server
Use the pgrep command or ps command as follows to find out if memcached is running or not:
pgrep memcached ## or ## ps aux | grep '[m]emcached' ## or ## sudo /etc/init.d/memcached status
Sample outputs:
Fig.01: Ubuntu Linux find out if memcached running or not on a server
Memcached server configuration
You need to edit the file called /etc/memcached.conf, enter:
sudo vi /etc/memcached.confSetting up a memory limits
By default memcached will start with a cap of 64 MB of memory. The daemon will grow to this size, but does not start out holding this much memory. In this example, I'm setting up to 2048 MB (2GB):
-m 2048
Set an IP address to listen on
By default memcached will listen on 127.0.0.1 only. You can specify which IP address to listen on. This parameter is one of the only security measures that memcached has, so make sure it's listening on a firewalled interface. I'm going to use 127.0.0.1 only:
-l 127.0.0.1
Limit the number of simultaneous incoming connections
The daemon default is 1024 and can be increased for high trafficked websites:
-c 1024
Save and close the file. Make sure you restart the server:
sudo /etc/init.d/memcached restart
Sample outputs:
Restarting memcached: memcached.
Testing memcached server
Type the following command:
echo stats | nc 127.0.0.1 11211 echo "stats settings" | nc localhost 11211
Sample outputs:
STAT maxbytes 1073741824 STAT maxconns 1024 STAT tcpport 11211 STAT udpport 11211 STAT inter 127.0.0.1 STAT verbosity 0 STAT oldest 0 STAT evictions on STAT domain_socket NULL STAT umask 700 STAT growth_factor 1.25 STAT chunk_size 48 STAT num_threads 4 STAT num_threads_per_udp 4 STAT stat_key_prefix : STAT detail_enabled no STAT reqs_per_event 20 STAT cas_enabled yes STAT tcp_backlog 1024 STAT binding_protocol auto-negotiate STAT auth_enabled_sasl no STAT item_size_max 1048576 STAT maxconns_fast no STAT hashpower_init 0 STAT slab_reassign no STAT slab_automove 0 END
You can use memcached storage/caching command as follows from bash shell. The syntax is:
command [key] [flags] [exptime] [bytes] [noreply]\r\n[value]\r | | \./ set add get gets replace append prepend cas delete
Let us add a key called foo with value BAR, enter:
echo -e 'add foo 0 300 3\r\nBAR\r' | nc localhost 11211
Sample outputs:
STORED
Where,
- add : Add/store data to memcached server
- foo : Key name
- 0 : 32-bit unsigned integer
- 300 : Expiration time in seconds
- 3 : Number of bytes in the data block (e.g. BAR == 3, nixCraft == 8 and so on)
- \r\nBAR\r : Value
To see key (i.e. get foo value), enter:
echo -e 'get foo\r' | nc localhost 11211
Sample outputs:
VALUE foo 0 3 BAR END
To delete key, enter:
echo -e 'delete foo\r' | nc localhost 11211
Sample outputs:
DELETED
Install memcached PHP support
Type the following apt-get command:
sudo apt-get install php5-memcached php5-fpm php5
You may also install mysql server and php support:
sudo apt-get install mysql-server php5-mysql php5
Finally, make sure you restart the web-server/php-fam:
## restart php5-fpm if installed ## sudo service php5-fpm restart ## restart Nginx if installed ## sudo service nginx restart ## restart Apache 2 if installed ## sudo service apache2 restart
Finally, verify that php5 memcache support is enabled, by typing the following command:
php5 -i | grep memcache
Sample outputs:
/etc/php5/cli/conf.d/20-memcache.ini,
memcache
memcache support => enabled
memcache.allow_failover => 1 => 1
memcache.chunk_size => 32768 => 32768
memcache.compress_threshold => 20000 => 20000
memcache.default_port => 11211 => 11211
memcache.hash_function => crc32 => crc32
memcache.hash_strategy => consistent => consistent
memcache.lock_timeout => 15 => 15
memcache.max_failover_attempts => 20 => 20
memcache.protocol => ascii => ascii
memcache.redundancy => 1 => 1
memcache.session_redundancy => 2 => 2
Registered save handlers => files user memcache
You can also create a PHP test page with the following code to verify that memcached+php5 is working on the server:
sudo vi /var/www/html/test.php
Append the following code:
<?php phpinfo(INFO_MODULES); ?>
Fire a browser and type the following url:
http://your-server-name-or-ip-here/test.php
Sample outputs:
Fig.02: PHP Memcached Check the Installation Test Script
Install memcached Python support
Type the following apt-get command:
sudo apt-get install python-memcache
How do I see memcached memory slabs and stats from CLI?
The syntax is as follows:
/usr/share/memcached/scripts/memcached-tool <host[:port] | /path/to/socket> [mode]
See memcached slabs
/usr/share/memcached/scripts/memcached-tool 127.0.0.1:11211 display
Sample outputs:
# Item_Size Max_age Pages Count Full? Evicted Evict_Time OOM 1 96B 25s 1 5 yes 0 0 0 2 120B 344s 1 2 yes 0 0 0 3 152B 774542s 3 13945 yes 0 0 0 4 192B 774003s 26 140491 yes 0 0 0 5 240B 500480s 1 102 yes 0 0 0 6 304B 483401s 1 24 yes 0 0 0 7 384B 596752s 2 3261 yes 0 0 0 8 480B 761228s 11 22058 yes 0 0 0 9 600B 488482s 1 391 yes 0 0 0 10 752B 492207s 1 720 yes 0 0 0 11 944B 488482s 2 1135 yes 0 0 0 12 1.2K 774542s 3 2352 yes 0 0 0 13 1.4K 560606s 2 1277 yes 0 0 0 14 1.8K 487974s 5 2672 yes 0 0 0 15 2.3K 487974s 10 4384 yes 0 0 0 16 2.8K 407204s 15 5048 yes 0 0 0 17 3.5K 347351s 12 3175 yes 0 0 0 18 4.4K 633802s 36 8104 yes 0 0 0 19 5.5K 351573s 39 7101 yes 0 0 0 20 6.9K 293697s 46 6695 yes 0 0 0 21 8.7K 667676s 56 6597 yes 0 0 0 22 10.8K 653196s 29 2714 yes 0 0 0 23 13.6K 75620s 19 1138 yes 0 0 0 24 16.9K 2580s 39 385 yes 0 0 0 25 21.2K 3824s 92 415 yes 0 0 0 26 26.5K 763s 2 39 yes 0 0 0 27 33.1K 653s 1 17 yes 0 0 0 28 41.4K 501s 1 11 yes 0 0 0 29 51.7K 962s 1 5 yes 0 0 0 30 64.7K 226s 1 5 yes 0 0 0 31 80.9K 199s 1 4 yes 0 0 0 32 101.1K 6s 1 1 yes 0 0 0 33 126.3K 522s 1 1 yes 0 0 0 35 197.4K 339s 1 1 yes 0 0 0
See memcached general stats
/usr/share/memcached/scripts/memcached-tool 127.0.0.1:11211 stats
Sample outputs:
#127.0.0.1:11211 Field Value
accepting_conns 1
auth_cmds 0
auth_errors 0
bytes 302290901
bytes_read 34590998647
bytes_written 348047507143
cas_badval 0
cas_hits 0
cas_misses 0
cmd_flush 0
cmd_get 167116484
cmd_set 5551928
cmd_touch 0
conn_yields 0
connection_structures 72
curr_connections 56
curr_items 234265
decr_hits 0
decr_misses 0
delete_hits 299319
delete_misses 1582752
evicted_unfetched 0
evictions 0
expired_unfetched 167287
get_hits 159501058
get_misses 7615426
hash_bytes 2097152
hash_is_expanding 0
hash_power_level 18
incr_hits 2087299
incr_misses 0
libevent 2.0.21-stable
limit_maxbytes 2147483648
listen_disabled_num 0
pid 801
pointer_size 64
reclaimed 194549
reserved_fds 20
rusage_system 5567.638938
rusage_user 1467.841043
threads 4
time 1425157331
total_connections 31733
total_items 4255143
touch_hits 0
touch_misses 0
uptime 774819
version 1.4.14 (Ubuntu)
Dumps memcached keys and values (not recommended)
/usr/share/memcached/scripts/memcached-tool 127.0.0.1:11211 dump
How do I flush contents of a Memcached server using CLI?
Type the following command:
nc 192.168.1.10 11211<<<"flush_all"
For more info, see our faq "HowTo: Flush Contents Of a Memcached Server Using Command Line".
Optional: Graphic stand-alone administration for memcached to monitor and debug purpose
phpMemcachedAdmin allows to see in real-time (top-like) or from the start of the server, stats for get, set, delete, increment, decrement, evictions, reclaimed, cas command, as well as server stats (network, items, server version) with googlecharts and server internal configuration.
Install phpMemcachedAdmin
Type the following commands:
cd /var/www/html/ sudo mkdir pmadm sudo wget http://phpmemcacheadmin.googlecode.com/files/phpMemcachedAdmin-1.2.2-r262.tar.gz sudo tar xvf phpMemcachedAdmin* -C pmadm cd pmadm chmod 0777 Config/Memcache.php chmod 0777 Temp/
Finally, password protect /var/www/html/pmadm/ on a Nginx server:
sudo mkdir /etc/nginx/.htpasswd/ sudo htpasswd -c /etc/nginx/.htpasswd/passwd vivek
Edit nginx.conf file and update your server { ..... } block/context as follows:
location /pmadm/ { auth_basic "Restricted"; auth_basic_user_file /etc/nginx/.htpasswd/passwd; }
Restart/reload the nginx server, enter:
sudo service nginx reload
Fire a browser and type the following url:
http://your-server-name-or-ip-here/pmadm/
Sample outputs:
Fig.03: phpMemcachedAdmin in action (click to enlarge)
References:
- Install LEMP (Linux, Nginx, MySQL and PHP) Stack on Ubuntu Linux 14.04 LTS
- RHEL / CentOS 6 Linux Install Memcached High Performance Distributed Memory Object Cache Server
- Memcached project
- phpMemcachedAdmin
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