What is PHP memcache?

In my previous article, I showed you how to install Memcached, the service daemon. Now, if you would like your PHP software to interface with that daemon, you will want to install a PHP extension for it.

There are actually two separate implementations of a PHP Client that wraps the memcached (daemon); both are provided via the PECL library. One is called ‘memcache’ and the other is called ‘memcached’. I know that it is a little confusing that ‘memcached’ shares the same name as the daemon itself, but it IS a separate PHP wrapper.

This article will focus on installing ‘memcache’ as it is the most commonly used. You can use the information to install ‘memcached’ as well; the installation steps are the same. The main difference is that ‘memcached’ requires the libMemcached library. You can see a comparison of the two different PHP clients here: http://code.google.com/p/memcached/wiki/PHPClientComparison

Installation, the quick method

The easiest method is to simply use PECL’s ‘install’ command. This will grab the latest stable release, configure it with the default options, and add it to the server’s php.ini:

pecl install memcache

*Note: Un-installation is just as easy:

pecl uninstall memcache

Installation, the manual method

The quick ‘install’ method uses the default configuration options and should serve most peoples’ purposes. However, if you need more control over the installation options, you can manually install from source and add it flags as you need.

Download the source package via PECL:

cd /usr/local/src/
pecl download memcache

Unpack the tar and enter into the newly extracted directory (be sure to replace the X’s with your downloaded version):

tar -xvzf memcache-X.X.X.tgz
cd memcache-X.X.X

Configure and install:

phpize
./configure && make && make install

Verify the install

Verify the installation by displaying all the installed PHP modules. See if ‘memcache’ is listed:

php -m
memcache

Problems with manual installation

The ‘make install’ should load the module into your server’s extension directory automatically. However, if you do not see memcache listed in a ‘php -m’, you will need to add the module manually

First, you’ll want to very the location of your server’s extensions directory:

grep extension_dir /usr/local/lib/php.ini

It should return something similar to the following:

extension_dir = "/usr/local/lib/php/extensions/no-debug-non-zts-20060613"

Next, copy the memcache module into that directory (be sure to replace the path with the one found on your server):

cp modules/memcache.so /usr/local/lib/php/extensions/no-debug-non-zts-20060613

Finally, add the module to your php.ini:

echo 'extension=memcache.so' >> /usr/local/lib/php.ini

Thoughts

It used to be a common issue that the quick ‘install’ method could not be used for servers where the /tmp partition was mounted ‘noexec’. The problem was that the ‘configure’ process could not execute because the PECL client downloaded the module into in /tmp. When /tmp is mounted ‘noexec’, servers cannot execute scripts from /tmp.

However, PECL now downloads and executes the script from /root/tmp. No need to worry about compiler errors with /tmp. You can use the ‘install’ method even with a secured /tmp.

Note about this article

This article is one I had written for the ServInt blog as part of the ‘Tech bench’ series. You can view it on the ServInt blog here. They are using my article with my permission.

This guide will help you setup Memcached on a CentOS server.

What is caching

Before diving into Memcache specifically, let’s take a step back. What is caching? Why should you care and why should you use it? Caching is used for two very important reasons: to speed up the delivery of the pages and to alleviate system resources. Caching is used to speed up dynamic sites; database driven sites will benefit most form caching. Think about a WordPress site. Each page you visit is not an actually file, but rather an amalgamation of the theme, widgets, posts, footers, headers, etc… Each time a page is accessed, PHP will generate the page requested on the fly from the database. It takes time to query the database to create the page. These database queries put a strain on the resources of your server.

However, what if instead of continually generating a new page, the same page, for every visitor, you were to turn those pages into static HTML files? No database querying is needed for the new visitors. A static file can be served up much faster and with significantly less resource consumption. Your visitors see their requested page sooner, and you save on CPU cycles. Everyone is happy. This is what caching does.

What is Memcached

Memcached is a general-purpose distributed memory caching system. It is one of the most popular caching tools and is used in such popular sites as: YouTube, Reddit, Zynga, Facebook, and Twitter.

According to Memcached’s official site, Memcached is defined as: Free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

In simpler terms, it decreases database load by storing objects in memory.

Installing Memcached (daemon)

The quickest and easiest method would be to install via Yum. First, you must grab the RPM that matches your OS:

CentOS 6 (64 bit):

su -c 'rpm -Uvh http://mirrors.kernel.org/fedora-epel/6/x86_64/epel-release-6-8.noarch.rpm'

CentOS 6 (32 bit):

su -c 'rpm -Uvh http://mirrors.kernel.org/fedora-epel/6/i386/epel-release-6-8.noarch.rpm'

CentOS 5 (64 bit):

su -c 'rpm -Uvh http://mirrors.kernel.org/fedora-epel/5/x86_64/epel-release-5-4.noarch.rpm'

CentOS 5 (32 bit):

su -c 'rpm -Uvh http://mirrors.kernel.org/fedora-epel/5/i386/epel-release-5-4.noarch.rpm'

CentOS 4 (32 bit):

su -c 'rpm -Uvh http://mirrors.kernel.org/fedora-epel/4/i386/epel-release-4-10.noarch.rpm'

Now, to install it with Yum:

yum install memcached

Start the memcached service:

/etc/init.d/memcached start

Configure the memcached service to start when the server boots:

chkconfig memcached on

Finally, disable the RPM so that it is not used for future Yum functions:

perl -pi -e "s/enabled=1/enabled=0/g;" /etc/yum.repos.d/epel.repo

Testing

It’s always a good idea to check your work. Make sure that memcached is running:

ps auwx | grep memcache

PHP memcache

For information on how to install the PHP extension so that your PHP software can interface with memcached (daemon), see my article here: How to install PHP memcache

Note about this article

This article is one I had written for the ServInt blog as part of the ‘Tech bench’ series. You can view it on the ServInt blog here. They are using my article with my permission.

*Note – This does NOT work on 64 bit CentOS (x86_64); it will only install for 32 bit (i386). If you need to install on 64 bit, use the guide found here: http://support.cast-control.net/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=69. Once you got it installed, you can start from my Step #3 – Configuration. I tested their guide on my personal server and it worked perfectly.

Icecast Installation Guide for CentOS 5

I ran across a request from a customer recently asking me to install Icecast. I didn’t find any easy guides out there that had the entire process laid out. So, here is my contribution to the Internet. I hope one of you find this useful. With this guide, you can set it up in a mere 10 minutes.

#1 – First off, What is Icecast?

Per the official website (http://www.icecast.org): Icecast is free server software for streaming multimedia. In particular, icecast streams audio to listeners over the Internet, and is compatible with Nullsoft’s Shoutcast.

#2 – Installation

The first thing to do is install the dependencies that are needed run icecast:

yum install curl-devel libtheora-devel libvorbis-devel libxslt-devel speex-devel

Next, grab the SRPM:

rpm -ivh http://downloads.xiph.org/releases/icecast/icecast-2.3.2-0.src.rpm

****If you get the following error:

Retrieving http://downloads.xiph.org/releases/icecast/icecast-2.3.2-0.src.rpm
error: cannot create %sourcedir /usr/src/redhat/SOURCES

You will need to install the development dependencies:

yum groupinstall 'Development Tools'

Now build the binary package using the newly acquired specs:

rpmbuild -bb /usr/src/redhat/SPECS/icecast.spec

And then install the RPM:

rpm -ivh /usr/src/redhat/RPMS/i386/icecast-2.3.2-0.i386.rpm

#3 – Configuration

You need to modify the /etc/icecast.xml file and change the default passwords for the users: source, relay,  admin. The Icecast developers definitely have a sense of humor; The default passwords are ‘hackme’.

         
              
              NEW-PASSWORD
              
              NEW-PASSWORD
     
              
              admin
              NEW-PASSWORD
         

You will have to change the user that the icecast service runs as. It cannot be initiated as root. It’s very picky and will give an error message:

[root ~]# ERROR: You should not run icecast2 as root

So simply change it to something else. The most intuitive solution would be to use ‘icecast’:

         
             icecast
             nogroup
         

And the last modification is to change the log directory from /usr/var/log/icecast to –> /var/log/icecast:

         <logdir>/var/log/icecast</logdir>

#4 – Add user and log folder

Almost done. Now add the icecast user and create the log path we specified above:

mkdir /var/log/icecast
useradd icecast
chown icecast:icecast /var/log/icecast/

#5 – Run Icecast

This is it, the moment you’ve been waiting for:

su icecast -c 'icecast -c /etc/icecast.xml -b'

Make sure port 8000 is opened in your firewall. Now you can test it by accessing: http://yourdomain.com:8000. You will see a black screen:

The front page for Icecast server

#6 – Add to system start up

You will want icecast to start when the server boots. Take the command to run the service (listed above) and place it in your:

/etc/rc.local