Installing memcached And The PHP5 memcache Module On Debian Etch (Apache2)

Installing memcached And The PHP5 memcache Module On Debian Etch (Apache2)

Version 1.0
Author: Falko Timme

This guide explains how to install memcached and the PHP5 memcache module on a Debian Etch system with Apache2. memcached is a daemon that can store objects in the system's memory (e.g. results of database queries) which can speed up your web site tremendously. You can use memcached over a network (i.e., install your web application on one server and memcached on another server), but usually you install both on one server to avoid the networking overhead.

It should be noted the memcached is no out-of-the-box solution for speeding up your web applications. Typically you have to adjust your scripts (PHP, Perl, etc.) to work with memcached, so this requires a little bit of work.

This document comes without warranty of any kind! I do not issue any guarantee that this will work for you!

 

1 Preliminary Note

I have tested this on a Debian Etch server with the IP address 192.168.0.100 where Apache2 and PHP5 are already installed and working. I'll use Apache's default document root /var/www in this tutorial for demonstration purposes. Of course, you can use any other vhost as well, but you might have to adjust the path to the info.php file that I'm using in this tutorial.

 

2 Checking PHP5's Current State

First, before we install memcached, let's find out about our PHP5 installation. To do this, we create the file info.php in our document root /var/www:

vi /var/www/info.php

<?php
phpinfo();
?>

Afterwards, we call that file in a browser: http://192.168.0.100/info.php

As you see, we have PHP 5.2.0 installed...

... but the PHP5 memcache module isn't mentioned anywhere on the page:

 

3 Installing memcached And The PHP5 memcache Module

memcached and the PHP5 memcache module are available as packages for Debian Etch, so we can install them as follows:

apt-get install memcached php5-memcache

After the installation, memcached should already be running. You can check that by typing

netstat -tap | grep memcached

server1:~# netstat -tap | grep memcached
tcp        0      0 *:11211                 *:*                     LISTEN     3053/memcached
server1:~#

As you see, memcached is running on port 11211 (the default memcached port), and it's listening on all interfaces on the system. As memcached has no built-in authentication mechanisms (in order to not give up on speed), this means that anyone can connect to it from outside and use it. To avoid this, you can either close port 11211 in your firewall, or you configure memcached to listen on localhost only. I will use the latter method here.

To do this, open the memcached configuration which is stored in /etc/memcached.conf:

vi /etc/memcached.conf

Add -l 127.0.0.1 to the configuration (you can also adjust the other settings if you like - the file contains explanations for each setting):

[...]
# Specify which IP address to listen on. The default is to listen on all IP addresses
# This parameter is one of the only security measures that memcached has, so make sure
# it's listening on a firewalled interface.
# -l 12.34.56.78
-l 127.0.0.1
[...]

Restart memcached...

/etc/init.d/memcached restart

... and run

netstat -tap | grep memcached

again. As you see, memcached is now listening on localhost only:

server1:~# netstat -tap | grep memcached
tcp        0      0 localhost.localdo:11211 *:*                     LISTEN     3092/memcached
server1:~#

Afterwards, we restart Apache so that our new PHP configuration takes effect:

/etc/init.d/apache2 restart

Afterwards, open info.php again in a browser: http://192.168.0.100/info.php

You should now see memcache mentioned on the page which means it has successfully been integrated and is working as expected:

To use the PHP memcache module with your PHP applications, you should check out the memcache examples and the memcache function reference.

I will use the example script from http://dk.php.net/manual/en/memcache.examples.php and save it in the file /var/www/memcachetest.php:

vi /var/www/memcachetest.php

<?php

$memcache = new Memcache;
$memcache->connect('localhost', 11211) or die ("Could not connect");

$version = $memcache->getVersion();
echo "Server's version: ".$version."<br/>\n";

$tmp_object = new stdClass;
$tmp_object->str_attr = 'test';
$tmp_object->int_attr = 123;

$memcache->set('key', $tmp_object, false, 10) or die ("Failed to save data at the server");
echo "Store data in the cache (data will expire in 10 seconds)<br/>\n";

$get_result = $memcache->get('key');
echo "Data from the cache:<br/>\n";

var_dump($get_result);

?>

Then I call that file in a browser (http://192.168.0.100/memcachetest.php). If all goes well, the output should look as follows:

 

4 Links

• memcached: http://www.danga.com/memcached
• PHP: http://www.php.net
• Apache: http://httpd.apache.org
• Debian: http://www.debian.org