We live in a time when the high availability and speed of network services are critical parts of every infrastructure. By using the HAProxy Reverse Proxy Server, and its capacityto balance both load and high availability, we ensure that such systems are immune to infrastructure malfunctions.
HAProxy is a free, powerful, flexible and straightforward reverse proxy that provides the option of Load Balancing. The program was written by Willy Tarreau, and also supports SSL, compression, keep-alive, configurable log prints, and header changes in the application. Since it is not demanding and needs a small amount of resources to run, web pages such as StackOverflow and Github use it. We will describe below how to set up a HAProxy proxy server, with a task to balance the load on two Nginx web servers.
The basics of HAProxy
HAProxy supports two modes of operation, TCP layer 4 mode, in which HAProxy passes packages on a particular IP address and tcp port to configured backend servers, and HTTP layer 7 mode, in which HAProxy parses HTTP requests and forwards them to web servers. We will use HTTP layer 7 mode.
Load Balancing Types
Roundrobin
This is the simplest algorithm for load balancing and forwards each new request to the next configured backend web server.
Lastconn
The HAProxy server submits the request to the backend web server with the smallest number of requests and is very good in scenarios that involve large loads.
Source
In this case, the HAProxy server forwards the request to the backend servers based on the user’s IP address.
Logical display
System Requirements and Network Configuration
3 CentOS 7 servers:
HAProxy 192.168.0.101
nginx1 192.168.0.201
nginx2 192.168.0.202
HAProxy server
We install HAProxy
yum install haproxy
We copy the default configuration file
cd /etc/haproxy cp haproxy.cfg haproxy.cfg.back
In /etc/haproxy/haproxy.cfg we replace all frontend and backend parts of the configuration
frontend haproxy *:80 ### we set a frontend called haproxy to listen on the port 80 default_backend websrv ### we set the name of the backend to which the requests will be directed backend websrv ### We define the backend that we have previously set balance roundrobin ### We define the HAProxy server operation mode server nginx1 192.168.0.201 check ### We define backend servers, in this case nginx1 and nginx2 server nginx2 192.168.0.202 check
We configure firewalld firewall to admit tcp port 80
firewall-cmd --zone=public --add-port=80/tcp --permanent firewall-cmd --reload
We enable auto start and launch the HAProxy service
systemctl enable haproxy systemctl start haproxy
Nginx1 and Nginx2 web servers
We enable EPEL repository and install Nginx service
yum install epel-release yum install nginx
We create test index.html files
cd /usr/share/nginx/html echo “<h1>nginx1</h1> > index.html ### na nginx2 echo “<h1>nginx2</h1> > index.html
We configure firewalld firewall to admit tcp port 80
firewall-cmd --zone=public --add-port=80/tcp --permanent firewall-cmd --reload
We enable auto start and launch Nginx service
systemctl enable nginx systemctl start nginx
Testing
We open the address in the web browser:
http://192.168.0.101
Pressing the F5 key on the keyboard to refresh the page, should open a new index.html file depending on which server the request was redirected to, in this case either nginx1 or nginx2. In this way, we have successfully balanced the load between two Nginx web servers, using the HAProxy server.