Configuring A High Availability Cluster (Heartbeat) On CentOS

Configuring A High Availability Cluster (Heartbeat) On CentOS

This Post shows how you can set up a two node, high-availability HTTP cluster with heartbeat on CentOS. Both nodes use the Apache web server to serve the same content.

Pre-Configuration Requirements :

Ø      Assign hostname as nodeA  to primary node with IP address 192.168.1.1 to eth0.

Ø      Assign hostname as nodeB  to slave node with IP address 192.168.1.2.

Please Verify the Hostnames on both nodes.

192.168.1.3 is the virtual IP address that will be used for our Apache webserver (i.e., Apache will listen on that address).

Configuration Steps:

1. Download and install the heartbeat package. We are using CentOS so we will install heartbeat with yum:

#yum install heartbeat

or download these packages:

heartbeat-2.08

heartbeat-pils-2.08

heartbeat-stonith-2.08

2. Now we have to configure heartbeat on our two node cluster. Here we will deal with three files.

They are:

authkeys

ha.cf

haresources

3. Now moving to our configuration. But there is one more thing to do, that is to copy these files to the /etc/ha.d directory. In our case we copy these files as given below:

cp /usr/share/doc/heartbeat-2.1.2/authkeys     /etc/ha.d/

cp /usr/share/doc/heartbeat-2.1.2/ha.cf    /etc/ha.d/

cp /usr/share/doc/heartbeat-2.1.2/haresources    /etc/ha.d/

4. Now let's start configuring heartbeat. First we will deal with the authkeys file, we will use authentication method 2 (sha1). For this we will make changes in the authkeys file as below.

vi /etc/ha.d/authkeys

Then add the following lines:

auth 2

2 sha1 test-ha

Change the permission of the authkeys file:

chmod 600 /etc/ha.d/authkeys

5. Moving to our second file (ha.cf) which is the most important. So edit the ha.cf file with vi:

vi /etc/ha.d/ha.cf

Add the following lines in the ha.cf file:

logfile /var/log/ha-log

logfacility local0

keepalive 2

deadtime 30

initdead 120

bcast eth0

udpport 694

auto_failback on

node nodeA

node nodeB

Note: nodeA and nodeB is the output generated by

uname -n

6. The final piece of work in our configuration is to edit the haresources file. This file contains the information about resources which we want to highly enable. In our case we want the webserver (httpd) highly available:

vi /etc/ha.d/haresources

Add the following line:

nodeA 192.168.1.1 httpd

7. Copy the /etc/ha.d/ directory from nodeA to nodeB:

scp -r /etc/ha.d/ root@nodeB:/etc/

8. As we want httpd highly enabled let's start configuring httpd:

vi /etc/httpd/conf/httpd.conf

Add this line in httpd.conf:

Listen 192.168.1.3:80

9. Copy the /etc/httpd/conf/httpd.conf file to nodeB:

scp /etc/httpd/conf/httpd.conf root@nodeB:/etc/httpd/conf/

10. Create the file index.html on both nodes (nodeA & nodeB):

On nodeA:

echo "node1 apache test server" > /var/www/html/index.html

On nodeB:

echo "node2 apache test server" > /var/www/html/index.html

11. Now start heartbeat on the primary node1 and slave node2:

/etc/init.d/heartbeat start

12. Open web-browser and type in the URL:

http://192.168.0.3

It will show node1 apache test server.

13. Now stop the hearbeat daemon on node1:

/etc/init.d/heartbeat stop

In your browser type in the URL http://192.168.0.3 and press enter.

It will show nodeB apache test server.

14. We don't need to create a virtual network interface and assign an IP address (192.168.0.3) to it. Heartbeat will do this for you, and start the service (httpd) itself. So don't worry about this.

Note : Don't use the IP addresses 192.168.1.1 and 192.168.1.2 for services. These addresses are used by heartbeat for communication between nodeA and nodeB.

When any of them will be used for services/resources, it will disturb hearbeat will not work.