HAProxy is a free, open source high availability proxy server and load balancer that is used with popular web servers such as Apache, NGINX, etc. It allows you to easily distribute workload among multiple web servers, database servers, etc. as per your requirement. HAProxy is available for almost all Linux distributions. In this article, we will look at how to install & configure HAProxy as a high availability load balancer that distributes requests across multiple web servers.
HAProxy Load Balancer Configuration in Linux
Here are the steps to install HAProxy load balancer configuration in Linux. For our example, we will setup load balancer at IP address 188.8.131.52 and domain www.example.com. We will use HAProxy to distribute load among 2 web servers with IP addresses 184.108.40.206, 220.127.116.11 each running Apache server.
1. Install Apache Server
First, we need to install Apache web server on all the 2 web servers. Open terminals on the four web servers at 18.104.22.168, 22.214.171.124 and run the following commands.
# yum install httpd [On RedHat based Systems] # apt-get install apache2 [On Debian based Systems]
After you install Apache on these 2 web servers, just open your web browser and visit their ip addresses as http://ip_address. You should be able to see the default Apache screen.
2. Install HAProxy
Open terminal on the server with IP address 126.96.36.199 where we want to install HAProxy and run the following commands to install HAProxy.
# yum install haproxy openssl-devel [On RedHat based Systems] # apt-get install haproxy [On Debian based Systems]
3. Configure HAProxy Logs
Next we need to enable logging in HAProxy. Run the following command to open its configuration file in a text editor.
# vi /etc/haproxy/haproxy.cfg
Next, based on your distribution enable the following lines in this document by removing # at its beginning.
Under #Global settings
log 127.0.0.1 local2
Under #Global settings, replace the following lines
log /dev/log local0 log /dev/log local1 notice
log 127.0.0.1 local2
4. Configure Syslog
Next, we configure syslog to create separate logs for HAProxy. For this, open rsyslog.conf file in text editor.
# vi /etc/rsyslog.conf
Uncomment the following lines by removing # at their beginning. Our server listens to port 514 for logging.
# Provides UDP syslog reception $ModLoad imudp $UDPServerRun 514
We create a separate HAProxy.conf file for separate logging.
# vi /etc/rsyslog.d/haproxy.conf
Add the following line to this file.
Restart Rsyslog service.
# service rsyslog restart
5. Configure HAProxy Global Settings
Next we need to configure HAProxy to communicate with out 2 web servers running Apache server. Open its configuration file in text editor.
# vi /etc/haproxy/haproxy.cfg
Update the configuration file as shown below. You just need to update the parts in bold below.
frontend LB bind 188.8.131.52:80 reqadd X-Forwarded-Proto:\ http default_backend LB backend LB 184.108.40.206:80 mode http stats enable stats hide-version stats uri /stats stats realm Haproxy\ Statistics stats auth haproxy:redhat # Username:Password for HAProxy Statistic report page. balance roundrobin # Load balancing will work in round-robin process. option httpchk option httpclose option forwardfor cookie LB insert server web1-srv 220.127.116.11:80 cookie web1-srv check # backend server. server web2-srv 18.104.22.168:80 cookie web2-srv check # backend server.
The first line above specifies the label LB for this front end section. The next line mentions the ip address and port number HAProxy is listening to. The third line specified the protocol to be followed. In the above example, we are binding HAProxy to port 80. The next line refers to the label LB of back end section where the request needs to be forwarded.
Similarly, add the corresponding back end section (line starting with backend) to serve requests received from this front end section. Just like front-end section, you can have multiple back end sections, for different websites, each labelled differently.
Let us say we want HAProxy to forward incoming requests to 2 web servers running on port 80 at ip_address1 (22.214.171.124) and ip_address2 (126.96.36.199). In such case, add the following backend section.
Replace ip_address1 and ip_address2 with ip addresses of your 2 servers. Also specify server1 & server 2 names to differentiate both of them.
backend backendnodes balance roundrobin server <server1 name> <ip_address1>:80 check server <server2 name> <ip_address2>:80 check
In our case, we have used the following values.
server web1-srv 188.8.131.52:80 cookie web1-srv check server web2-srv 184.108.40.206:80 cookie web2-srv check
Save and close the file. Restart HAProxy to apply changes.
# service haproxy restart # chkconfig haproxy on # chkconfig --list haproxy
Please note, you will be able to access HAProxy stats at http://220.127.116.11/stats URL by specifying the username haproxy and password redhat that you have mentioned in config file. In some Ubuntu/Debian systems you may need to add the following line to /etc/default/haproxy.
6. Verify HAProxy installation
Add the following HTML file index.html in both the web servers running Apache server.
<html> <head> <title>HAProxy Test Page</title> </head> <body> <!-- Main content --> <h1>My HAProxy Test Page</h1> <p>Welcome to HA Proxy test page! </body> </html>
Open browser and visit http://18.104.22.168 and you should be able to view the above html page indicating that HAProxy has fetched the page from one of the web servers.
You can view HAProxy stats by opening browser and visiting http://22.214.171.124/stats URL. You will be prompted for username & password. Enter them as haproxy & redhat respectively, as specified in your HAProxy configuration file.
That’s it. In this article, we have learnt how to install and configure HAProxy load balancer and proxy.
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