Load Balancing web servers using POUND Load Balancer
Load balancing for a web server refers to evenly distribution of incoming traffic across two or more backend servers. Load balancing leads to increased server functionality, decreased traffic congestion leading to faster page load times & also provide redundancy. Load balancing is what you need when you have a website with lots of traffic.
In this tutorial, we are going to discuss Pound Load balancer. Pound load balancer acts as a front end for all the http/https request, it can be used as a reverse proxy & will evenly distribute request to the backend servers.
When configured, pound will be the public facing server which will accept the incoming request form port 80 & 443. Then it will evenly distribute the request to the available backend servers. For example, if we have 2 backend servers first request will go to server1 & then to server2. & then pound server will deliver the content back to clients as per the request (reverse proxy).
(Recommended Read: How to use Apache reverse proxy as Load Balancer )
(Also Read: How to use Apache as Reverse Proxy on CentOS & RHEL)
In order to test the working of Pound load-balancer, we will need
- A server with pound load balancer installed (epel repository needed). Install EPEL repository using the following steps,
$ sudo rpm -Uvh https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-11.noarch.rpm
RHEL/CentOS 6 (64 Bit)
$ sudo rpm -Uvh http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
RHEL/CentOS 6 (32 Bit)
$ sudo rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
- Two backend servers with apache installed (for detailed installation & configuration, read our tutorials HERE & HERE)
Hostname- pound.ltechlab.com IP address- 192.168.1.100
Hostname- server1.ltechlab.com IP address- 192.168.1.111
Hostname- server2.ltechlab.com IP address- 192.168.1.112
So now let’s move onto creating a Pound Load balancer,
We will now prepare apache server on our backend machines. To install apache, run following command on both the machines,
$ yum install httpd
After installation has been done on both machines, we will move onto configuration part.
Now we need to create an index.html to identify both web servers. Go to /var/www/html & create an index.html page with following content,
$ cd /var/www/html
$ echo “This is web server 1” > index.html
Similarly create index.html page on server 2 as well but change “This is web server 1” to “This is web server 2”
Restart apache service on both machines to implement the changes,
$ systemctl restart httpd
You can check the pages by entering the IP address or FQDN of the machine into your internet browser.
To install Pound server, we first have to enable EPEL repository as Pound Load balancer is not available with default repositories. To enable EPEL repository, run
$ rpm -Uvh https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-11.noarch.rpm
Once the repo has been installed, we will install pound by running,
$ yum install pound
Main configuration file for Pound load balancer is /etc/pound.cfg. We will edit this file to configure load balancing for our backend servers.
$ vi /etc/pound.cfg
Now edit the file as done below,
Save & exit the file.
NOTE:- Remove the section with ListenHTTPS if not using HTTPS, which in our case is true.
Now restart the pound services to implement changes to the configuration file,
$ systemctl restart pound
Testing the load balancer
To test the load balancer, open you browser & enter the Pound server’s IP address i.e. 192.168.1.100. It will open the web page saying “This is web server 1 ”, refresh the page & you will then be redirected to web server 2, keep refreshing & you will see that one request goes to server 1 & then to server 2.
This concludes our tutorial, feel free to mention any queries/questions in the comment box below.