HAproxy is an open-source and lightweight package that offers high availability and load balancing for TCP and HTTP based programs. It distributes the load among the web and application servers. HAproxy is available for nearly all Linux distributions. It is a widely used load balancer that is popular for its efficiency, reliability, and low memory and CPU footprint. In this post, we will explain how to install and configure HAproxy on a Ubuntu system.

We have setup three machines. We will install HAproxy on one server and the Apache web servers on two servers. Our HAproxy server will then act as a load balancer and will distribute the load among Apache web servers.

Note: The procedure and commands mentioned in this post has been tested on Ubuntu 20.04 LTS (Focal Fossa). The same procedure is also valid for Debian and Mint distributions.

Network Details

We will be using three Ubuntu servers; all on the same network. The details of our servers are as follows:

Note: You must have sudo privileges on all the servers.

We will configure one machine as a load balancer and the other two as web servers. The HAproxy server will be our front-end server that will receive the requests from the users and forward them to the two web servers. The web servers will be our Backend servers that will receive those forwarded requests.

This is how our setup looks like:

Setting up web servers-Backend servers

In this section, we will setup two web servers (web-server1 and web-server2) as our backend servers.

On web-server1(192.168.72.158)

Perform the below steps in your web server. Make sure to replace the hostnames and IP addresses with the relevant IP addresses and hostnames of your web servers.

1. Configure hosts file

On web-server1, edit the /etc/hosts file:

Then add the hostname entry for HAproxy server as follows:

In our scenario, it would be:

2. Setup Apache webserver

Now install Apache web server using the below command in Terminal. You can also visit our post on How to install the Apache web server on Linux.

Then enable and start the Apache service using the below commands in Terminal:

Create an index file for web-server1 using the below command in Terminal:

If a firewall is running on your system, you will need to allow Apache traffic through it:

Then reload the firewall configurations:

Now try accessing the site in your web browser by typing http:// followed by either the IP address or the hostname of your web server.

Alternatively, you can also use the curl command to test the webpage.

On web server-2 192.168.72.159)

Perform the below steps in your second web server. Make sure to replace the hostnames and IP addresses with the relevant IP addresses and hostnames of your web servers.

1. Configure hosts file

In web-server2, edit the /etc/hosts file:

Then add the hostname entry for HAproxy server as follows:

2. Install Apache webserver

Now install Apache web server using the below command in Terminal.

Then enable and start the Apache service using the below commands in Terminal:

Create an index file for web-server2 using the below command in Terminal:

Allow Apache in the firewall:

and then reload firewall configurations:

Now try accessing the site in your web browser by typing http:// followed by either the IP address or the hostname.

Alternatively, you can use the curl command to test the webpage.

Now our Apache web servers are ready.

Setting up HAproxy load balancer-Frontend server

In this section, we will set up an HAproxy load balancer for our web servers. This HAproxy server will act as a frontend server and accepts incoming requests from clients.

On the HAproxy server (192.168.72.157), perform the below steps to setup load balancer.

1. Configure hosts file

Edit the /etc/hosts file using the below command in Terminal:

Add the following hostname entries for both Apache web servers along with its own hostname:

Now save and close the /etc/hosts file.

Installing HAproxy load balancer

Now in this step, we will be installing the HAproxy on one of our Ubuntu server (192.168.72.157). To do so, update apt using the following command in Terminal:

Then update packages using the below command:

Now install HAproxy using the following command in Terminal:

Once the installation of the HAproxy server is finished, you can confirm it using the below command in Terminal:

It will show you the installed version of HAproxy on your system which verifies that the HAproxy has been successfully installed.

Configuring HAproxy as a load balancer

In the following section, we will configure HAproxy as a load balancer. To do so, edit the /etc/haproxy/haproxy.cfg file:

Append the following lines in the haproxy.cfg file replacing the IP addresses with your own IP addresses.

The frontend web-frontend in the above configuration lines tells HAproxy to listen to incoming requests on port 80 of 192.168.72.157 and then forward them to backend servers configured under the backend web-backend. While configuring, replace the IP addresses with the relevant IP addresses of your web servers.

Configuring HAproxy Monitoring

With HAproxy monitoring, you can view a lot of information including server status, data transferred, uptime, session rate, etc. To configure HAproxy monitoring, append the following lines in the configuration file located at /etc/haproxy/haproxy.cfg:

The above configuration enables the HAproxy “stats” page using the stats directive and secures it with http basic authentication using the username and password defined by the stats auth directive.

Once you are done with the configurations, save and close the haproxy.cfg file.

Now verify the configuration file using the below command in Terminal:

The following output shows that the configurations are correct.

Now to apply the configurations, restart the HAproxy service:

It will stop and then start the HAproxy service.

To check the status of the HAproxy service, the command would be:

The active (running) status in the following output shows that the HAproxy server is enabled and running fine.

Here are some other commands for managing the HAproxy server:

In order to start the HAproxy server, the command would be:

In order to stop the HAproxy server, the command would be:

In case you want to temporarily disable the HAproxy server, the command would be:

To re-enable the HAproxy server, the command would be:

Test HAproxy

Before testing the HAproxy setup, make sure you have connectivity to web servers. From your HAproxy server, ping both web servers either by their IP addresses or hostnames.

The following output shows that the HAproxy server can reach both web servers.

Test HA Proxy using a web browser

Now in your HAproxy server, open any web browser and type http:// followed by the HAproxy server IP address which in our case is 192.168.72.157.

The HAproxy server will alternatively send the request to both web servers in a round-robin method. You can test this by reloading the webpage a few times.

This is the response we received when we visited the http://192.168.72.157 for the first time:

This is the response we received when we reloaded the webpage:

You can also use the hostname in place of the HAproxy server IP address.

Test HA Proxy using curl

You can also use the curl command in Linux to test the HAproxy setup. Open the Terminal and type curl followed by the IP address or the hostname of the HAproxy server.

or

Run the curl command a few times and you will see the response alternating between both web servers.

Instead of running the commands several times, you can also run the following one-line script to test the HAproxy server:

Testing HAproxy Monitoring

To access the HAproxy monitoring page, type http:// followed by the IP address/hostname of HAproxy server and port 8080/stats:

or

The following authentication box will appear. Enter the username and password you have configured earlier in the configurations and then press OK.

This is the statistics report for our HAproxy server.

There you have the installation and configuration of HAproxy load balancer on the Linux system. We have just discussed the basic setup and configuration of HAproxy as a load balancer for Apache web servers. We also looked at some commands for managing the HAproxy server. In the end, we tested the load balancing through the browser and the curl command. For more information, visit HAproxy official documentation