Ians Ramblings

I didn’t find a great deal of information about how to run memcached across multiple servers and have them treated as one pool. Most of the examples just seem to show the installation and running of a single server instance or multiple instances on the same server running on different ports.

Far more useful in my opinion is running memcached on a number of servers in a web cluster. Now the install is as simple as “yum install memcached”. The following will start the server as a daemon on each of the machines in the cluster: -

memcached -d -p 11211 -u nobody -c 1024 -m 1024

This starts the service on port 11211 and is set to use 1gb of RAM.

Now in your code, when you instantiate your memcached object, you can pass an array of servers, this is the pool. The following is an example in Perl.

use Cache::Memcached;

  $memd = new Cache::Memcached {
    'servers' => [ "10.0.0.15:11211", "10.0.0.15:11212", "/var/sock/memcached",
                   "10.0.0.17:11211", [ "10.0.0.17:11211", 3 ] ],
    'debug' => 0,
    'compress_threshold' => 10_000,
  };
  $memd->set_servers($array_ref);
  $memd->set_compress_threshold(10_000);
  $memd->enable_compress(0);

Installing memcached for php on CentOS is as easy as: -

[code]

yum install memcached

yum install php-pecl-memcache

service httpd graceful

[/code]

Once installed you can start the memcached service as either a standalone service or as a daemon.

Run as any user other than root, starts as a normal process using up to 1 gig of RAM.

[code]

memcached -m1024

[/code]

Or as a daemon

[code]

memcached -d -m1024

[/code]

You can always get more info about memcached’s options with

[code]

man memcached

[/code]

PHP memcache documentation http://php.net/manual/en/book.memcache.php

Memcached’s site http://memcached.org/