Development, Analysis And Research

Recently I had to install memcache on a number of servers, and I would always tend to end up with errors whilst memcache tries to locate libevent. I always seem to forgett LD_DEBUG, so I figured I would write up the process for installing memcache.

One of the dependencies of memcache is libevent, so firstly download the source files for Libevent.


tar -xvf libevent-1.3b.tar.gz
cd libevent-1.3b
./configure;make;make install;


Download the latest Memcached source code from danga.com


gunzip memcached-1.2.1.tar.gz
tar -xvf memcached-1.2.1.tar
cd memcached-1.2.1
./configure;make;make install;


Often libevent.so cannot be found when executing memcache. A useful command LD_DEBUG, is very helpful to determine where libraries are being loaded from.


LD_DEBUG=help memcached -v
 
LD_DEBUG=libs memcached -v 2>&1 > /dev/null | less
18990: find library=libevent-1.3b.so.1 [0]; searching
…
18990: trying file=/usr/lib/libevent-1.3b.so.1
18990:
memcached: error while loading shared libraries: libevent-1.3b.so.1: cannot open shared object file: No such file or directory


Simply place the library where memcached will find it and execute memcached.


ln -s /usr/local/lib/libevent-1.3b.so.1 /lib/libevent-1.3b.so.1
memcached -d -u nobody -m 512 127.0.0.1 -p 11211
 


The options for memcached are:

-l <ip_addr>  
Listen on <ip_addr>; default to INDRR_ANY. This is an important option to consider as there is no other way to secure the installation. Binding to an internal or firewalled network interface is suggested.
-d
Run memcached as a daemon.
-u <username>
Assume the identity of <username> (only when run as root).
-m <num>
Use <num> MB memory max to use for object storage; the default is 64 megabytes.
-M
Instead of throwing items from the cache when max memory is reached, throw an error
-c <num>
Use <num> max simultaneous connections; the default is 1024.
-k
Lock down all paged memory. This is a somewhat dangerous option with large caches, so consult the README and memcached homepage for configuration suggestions.
-p <num>
Listen on port <num>, the default is port 11211.
-r
Maximize core file limit
-M
Disable automatic removal of items from the cache when out of memory. Additions will not be possible until adequate space is freed up.
-r
Raise the core file size limit to the maximum allowable.
-h
Show the version of memcached and a summary of options.
-v
Be verbose during the event loop; print out errors and warnings.
-vv
Be even more verbose; same as -v but also print client commands and responses.
-i
Print memcached and libevent licenses.
-P <filename>
Print pidfile to <filename>, only used under -d option.

To install the pecl package for PHP

wget http://pecl.php.net/get/memcache-2.1.2.tgz
gzip -df memcache-2.1.2.tgz
tar -xvf memcache-2.1.2.tar
cd memcache-2.1.2
phpize
./configure;make;make install;


Add memcache.so to the php.ini file

extension=memcache.so


Then run

php -i | grep -i 'memcache'

memcache should be listed and then restart the web server.

For further information:
Distributed Caching with Memcached