Memcached is a general-purpose distributed memory caching system that was originally developed by Danga Interactive for LiveJournal, but is now used by many other sites. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read. Memcached runs on Unix, Linux, Windows and Mac OS X and is distributed under a permissive free software license.
Memcached’s APIs provide a giant hash table distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in least recently used (LRU) order. Applications using Memcached typically layer requests and additions into RAM before falling back on a slower backing store, such as a database.
The system is used by sites including YouTube, Reddit, Zynga, Facebook, Orange, Twitter and Wikipedia. Engine Yard is using Memcached as the part of their platform as a service technology stack and Heroku offers a managed Memcached service built on Couchbase Server as part of their platform as a service. Google App Engine, AppScale, Windows Azure and Amazon Web Services also offer a Memcached service through an API.
Install Memcached daemon:
The Memcached software doesn’t exist in the standard CentOS repository. You can download from EPEL repository.
Update the repositories:
yum update -y
Start the installation:
yum install memcached
Configure Memcached:
vi  /etc/sysconfig/memcached
PORT="11211" USER="memcached" MAXCONN="1024" CACHESIZE="2048" OPTIONS=""
Start Memcached:
chkconfig --levels 235 memcached on /etc/init.d/memcached start
Check and verify Memcached
root@ns5001089 [~]# netstat -an | grep 11211 tcp 0 0 0.0.0.0:11211 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:51555 127.0.0.1:11211 TIME_WAIT tcp 0 0 :::11211 :::* LISTEN udp 0 0 0.0.0.0:11211 0.0.0.0:* udp 0 0 :::11211 :::* root@ns5001089 [~]# memcached-tool localhost:11211 stats #localhost:11211 Field Value accepting_conns 1 auth_cmds 0 auth_errors 0 bytes 44808145 bytes_read 45373990 bytes_written 71278002 cas_badval 0 cas_hits 0 cas_misses 0 cmd_flush 0 cmd_get 4073 cmd_set 546 conn_yields 0 connection_structures 16 curr_connections 10 curr_items 531 decr_hits 0 decr_misses 0 delete_hits 0 delete_misses 0 evictions 0 get_hits 744 get_misses 3329 incr_hits 0 incr_misses 0 limit_maxbytes 2147483648 listen_disabled_num 0 pid 14356 pointer_size 64 rusage_system 2.628164 rusage_user 2.664166 threads 4 time 1366212222 total_connections 3004 total_items 546 uptime 237459 version 1.4.4 root@ns5001089 [~]#
Memcached PHP Extension
Install Pecl too:
yum install php-pear yum install php-pecl-memcache
Then Start using pecl to fetch PHP Extensions:
pecl install memcache downloading memcache-2.2.7.tgz ... Starting to download memcache-2.2.7.tgz (36,459 bytes) ..........done: 36,459 bytes 11 source files, building running: phpize Configuring for: PHP Api Version: 20090626 Zend Module Api No: 20090626 Zend Extension Api No: 220090626 Enable memcache session handler support? [yes] : building in /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7 running: /root/tmp/pear/memcache/configure --enable-memcache-session=yes checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for a sed that does not truncate output... /bin/sed checking for cc... cc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether cc accepts -g... yes checking for cc option to accept ISO C89... none needed checking how to run the C preprocessor... cc -E checking for icc... no checking for suncc... no checking whether cc understands -c and -o together... yes checking for system library directory... lib checking if compiler supports -R... no checking if compiler supports -Wl,-rpath,... yes checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking target system type... x86_64-unknown-linux-gnu checking for PHP prefix... /usr/local checking for PHP includes... -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib checking for PHP extension directory... /usr/local/lib/php/extensions/no-debug-non-zts-20090626 checking for PHP installed headers prefix... /usr/local/include/php checking if debug is enabled... no checking if zts is enabled... no checking for re2c... re2c checking for re2c version... 0.13.5 (ok) checking for gawk... gawk checking whether to enable memcache support... yes, shared checking whether to enable memcache session handler support... yes checking for the location of ZLIB... no checking for the location of zlib... /usr checking for session includes... /usr/local/include/php checking for memcache session support... enabled checking for ld used by cc... /usr/bin/ld checking if the linker (/usr/bin/ld) is GNU ld... yes checking for /usr/bin/ld option to reload object files... -r checking for BSD-compatible nm... /usr/bin/nm -B checking whether ln -s works... yes checking how to recognize dependent libraries... pass_all checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking dlfcn.h usability... yes checking dlfcn.h presence... yes checking for dlfcn.h... yes checking the maximum length of command line arguments... 1572864 checking command to parse /usr/bin/nm -B output from cc object... ok checking for objdir... .libs checking for ar... ar checking for ranlib... ranlib checking for strip... strip checking if cc supports -fno-rtti -fno-exceptions... no checking for cc option to produce PIC... -fPIC checking if cc PIC flag -fPIC works... yes checking if cc static flag -static works... yes checking if cc supports -c -o file.o... yes checking whether the cc linker (/usr/bin/ld -m elf_x86_64) supports shared libraries... yes checking whether -lc should be explicitly linked in... no checking dynamic linker characteristics... GNU/Linux ld.so checking how to hardcode library paths into programs... immediate checking whether stripping libraries is possible... yes checking if libtool supports shared libraries... yes checking whether to build shared libraries... yes checking whether to build static libraries... no
creating libtool appending configuration tag "CXX" to libtool configure: creating ./config.status config.status: creating config.h running: make
...........................
cc -shared .libs/memcache.o .libs/memcache_queue.o .libs/memcache_standard_hash.o .libs/memcache_consistent_hash.o .libs/memcache_session.o -Wl,-soname -Wl,memcache.so -o .libs/memcache.so creating memcache.la (cd .libs && rm -f memcache.la && ln -s ../memcache.la memcache.la) /bin/sh /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/libtool --mode=install cp ./memcache.la /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/modules cp ./.libs/memcache.so /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/modules/memcache.so cp ./.libs/memcache.lai /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/modules/memcache.la PATH="$PATH:/sbin" ldconfig -n /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/modules ---------------------------------------------------------------------- Libraries have been installed in: /root/tmp/pear/pear-build-rootkFeKkf/memcache-2.2.7/modules
If you ever happen to want to link against installed libraries in a given directory, LIBDIR, you must either use libtool, and specify the full pathname of the library, or use the `-LLIBDIR' flag during linking and do at least one of the following: - add LIBDIR to the `LD_LIBRARY_PATH' environment variable during execution - add LIBDIR to the `LD_RUN_PATH' environment variable during linking - use the `-Wl,--rpath -Wl,LIBDIR' linker flag - have your system administrator add LIBDIR to `/etc/ld.so.conf'
See any operating system documentation about shared libraries for more information, such as the ld(1) and ld.so(8) manual pages. ----------------------------------------------------------------------
Build complete. Don't forget to run 'make test'.
running: make INSTALL_ROOT="/root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7" install Installing shared extensions: /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib/php/extensions/no-debug-non-zts-20090626/ running: find "/root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7" | xargs ls -dils 1199741 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7 1199770 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr 1199771 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local 1199772 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib 1199773 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib/php 1199774 4 drwxr-xr-x 3 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib/php/extensions 1199775 4 drwxr-xr-x 2 root root 4096 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib/php/extensions/no-debug-non-zts-20090626 1199769 248 -rwxr-xr-x 1 root root 246440 Apr 17 10:32 /root/tmp/pear/pear-build-rootkFeKkf/install-memcache-2.2.7/usr/local/lib/php/extensions/no-debug-non-zts-20090626/memcache.so Build process completed successfully Installing '/usr/local/lib/php/extensions/no-debug-non-zts-20090626/memcache.so' install ok: channel://pecl.php.net/memcache-2.2.7 Extension memcache enabled in php.ini
Restart Apache:
/etc/init.d/httpd  restart
Check Memcached plugin in PHP:
php -i | grep memcach memcache memcache support => enabled memcache.allow_failover => 1 => 1 memcache.chunk_size => 8192 => 8192 memcache.default_port => 11211 => 11211 memcache.default_timeout_ms => 1000 => 1000 memcache.hash_function => crc32 => crc32 memcache.hash_strategy => standard => standard memcache.max_failover_attempts => 20 => 20 Registered save handlers => files user sqlite memcache
Enjoy!
