Session 7: Implementation of HA and CRM

OVERVIEW

The High-Availability cluster and the Cluster Resource Manager are responsible for the recovery of nodes in case of failure in the network occurs. The concept of Active and Passive Cluster will be discussed in this activity.

Active/Passive Cluster

The Active/Passive Cluster works when a node (active node) fails, the passive node will assume the role of the failed node, and the service will continue. 

Two computers (servers) are needed in this cluster. One computer will serve as the active node, while the other is the passive node. Once the process execution of the active node fails, the passive node will take over of the execution, so that the failure will never occur.

Active/Passive Cluster

[Reference: http://opentodo.net/2012/04/configuring-a-failover-cluster-with-heartbeat-pacemaker/]

PROBLEM STATEMENT

The activity needs to be performed by at least two people. Two to three computers are needed to execute the activity. The concept of IP configuration will be of help because assigning IP addresses and names to each computer is needed, and a virtual IP address to a computer that will act as a server. The Active/Passive Cluster will be use.

GUIDES IN SOLVING THE PROBLEM

Configuring the needed configuration files

To be able to configure two servers using Apache and Heartbeat to communicate with a client or browser, we need to edit several configuration files. And these configuration files are as follows:

- ha.cf

The ha.cf configuration file can be found at /etc/ha.d directory. Just type $ sudo gedit /etc/ha.d/ha.cf to edit the file. The basis of the contents of ha.cf is from this site http://www.zivtech.com/blog/setting-ip-failover-heartbeat-and-pacemaker-ubuntu-lucid. This file should contain the name of the two servers needed.

Edit ha.cf configuration file

- authkeys

The authkeys configuration file can be found at the /etc/ha.d directory. To edit this file, type $ sudo gedit /etc/ha.d/authkeys on the terminal. The basis of the contents of this file is from this site http://opentodo.net/2012/04/configuring-a-failover-cluster-with-heartbeat-pacemaker/

Edit authkeys file

-haresources

The haresources file can be found at /etc/ha.d directory. It contains the name of the server assigned to be the active node, and the virtual IP address needed.

Edit haresources file

- /etc/hosts

The /etc/hosts file should contain the name of the two computers which will act as the two server with its distinct IP address. Also, the virtual IP address or alias of another server holding the said two servers should be specified along with its name. To edit this file, type $ sudo gedit /etc/hosts.

Edit /etc/hosts file

- /etc/hostname

The /etc/hostname file should contain the name of the computer you are using. It is neccessary for the ha.cf and /etc/hosts files.To edit this file, type $ sudo gedit /etc/hostname.

Edit /etc/hostname file

Test the Active/Passive Cluster

Try the following commands to test your set-up:

- Check if Apache is running.

   Command: $ sudo /etc/init.d/apache2 start

Start Apache

- Check if Heartbeat is running.

  Command: $ sudo /etc/init.d/heartbeat restart

Restart Heartbeat

- Try to access the virutal IP address (10.0.5.66) in the browser using another computer. It should display the web page of the active node (server1).

Web Page of server1 (Active Node)

- Disconnect the LAN cable of the active node (server1). Refresh the web page. It should display the web page of the passive node (server2). 

Web Page of server2 (Passive Node)

LEARNING AND INSIGHTS

Configuring the configuration files is a bit challenging because we didn't know how to do it. Thanks to the power of the Internet, we were able to do it (barely). 

Through patience, we were able to start heartbeat successfully. Also, we were able to access the active server via the virtual IP address. And if we disconnect the LAN cable of the active server, the browser can display the page of the passive server. We were so overwhelmed that we were able to do this after two lab meetings. T__T

***Lesson learned (for me): In order to avoid problems, the server should be regularly restarted so that changes can be made on the server.

CONCLUSION
The activity, for me is so difficult. It is difficult to accomplish because once you have made mistakes on the configuration files, you need to check all those files and trace what was wrong. Though it is kinda confusing, we were able to fulfill the tasks needed in this activity. We barely surpass the trial and error on all the computers in the laboratory to have a better access on our virtual server.