Investigation on Webserver (Apache) and High Availability

Research on the following topics:

1. Apache
A web server application that is developed and maintained by an open community of developers under the supervision of the Apache Software Foundation. Apache became became the dominant web Server by 2009

In order to install Apache on Ubuntu open a terminal then use the following command

sudo apt-get install apache2

Some notable Apache files used for configuration are:

• apache2.conf: the main Apache2 configuration file. Contains settings that are global to Apache2.
• conf.d: contains configuration files which apply globally to Apache2. Other packages that use Apache2 to serve content may add files, or symlinks, to this directory.
• httpd.conf: historically the main Apache2 configuration file, named after the httpd daemon. The file can be used for user specific configuration options that globally effect Apache2.

To test if Apache is installed and running correctly, open a browser and enter the URL http://localhost
which should show the following

2. High availability
high availability refers to a system that is continuously operational for a desirably long length of time or a system that can be continuously be used over a long period of time.

One example is the service provided by websites needs to have high availability for clients to continuously use the services offered from the website they are currently using. This can be achieved by multiple servers where a working server will take on the role of a failed server.

Heartbeat is a daemon that provides cluster infrastructure services to its clients. This allows clients to know whether the peer processes on other machines are working or not and easily exchange messages with them.      

Installing and Configuring Heartbeat
To install Heartbeat in Ubuntu open a terminal and type
sudo apt-get install heartbeat-2

Heartbeat config files are stored in /etc/heartbeat/

Configuration Files

• ha.cf - tells Heartbeat what types of media paths to use and how to configure them
• haresources - list of resources that moves to machine to machine as nodes and come up in the cluster. This file must be the same on both nodes.
• authkeys - contains an auth directive with an associated method ID number, and there is a line that has the authentication method and the key that go with the ID number of the auth directive. Must be owned by root and be chmod 600.

Explaining Heartbeat to a 3 year old Child:
Imagine having a set of different beverages (e.g. milk, chocolate, orange): if one drink is unavailable to use you can use the other beverages to satisfy your thirst in place of the unavailable one

References:
http://www.apache.org/
http://searchdatacenter.techtarget.com/definition/high-availability
http://i.technet.microsoft.com/dynimg/IC166357.gif
https://help.ubuntu.com/10.04/serverguide/httpd.html
http://linux-ha.org/wiki/Heartbeat