{"id":89711,"date":"2020-07-25T13:42:31","date_gmt":"2020-07-25T11:42:31","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/ustanavlivaem-balansirovshhik-nagruzki-haproxy-na-centos"},"modified":"2020-07-25T13:42:31","modified_gmt":"2020-07-25T11:42:31","slug":"ustanavlivaem-balansirovshhik-nagruzki-haproxy-na-centos","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/administrirovanie\/ustanavlivaem-balansirovshhik-nagruzki-haproxy-na-centos","title":{"rendered":"Installing the HAProxy load balancer on CentOS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

This article's translation was prepared in anticipation of the course launch Linux Administrator: Virtualization and Clustering<\/a><\/noindex><\/em><\/strong><\/p>\n

\"Installing<\/p>\n

<\/p>\n

Load balancing is a common solution for horizontally scaling web applications across multiple hosts while providing users with a single access point to the service. HAProxy<\/a><\/noindex> is one of the most popular open-source load balancing programs, which also ensures high availability and proxying functionality.<\/p>\n

<\/p>\n

HAProxy aims to optimize resource utilization, maximize throughput, minimize response times, and avoid overloading any individual resource. It can be installed on a variety of Linux distributions, such as CentOS 8, which we will focus on in this guide, as well as on systems Debian 8<\/a><\/noindex> and Ubuntu 16<\/a><\/noindex>.<\/a><\/noindex><\/p>\n

<\/p>\n

\"Installing<\/p>\n

<\/p>\n

HAProxy is particularly suitable for websites with very high traffic and is often used to enhance the reliability and performance of web service configurations with multiple servers. This guide outlines the steps to set up HAProxy as a load balancer on a CentOS 8 cloud host, which then directs traffic to your web servers.<\/p>\n

<\/p>\n

As a prerequisite for achieving the best results, you should have at least two web servers and a load balancing server. The web servers should have at least a basic web service running, such as nginx or httpd, to verify load balancing between them.<\/p>\n

<\/p>\n

Installing HAProxy on CentOS 8<\/h2>\n

<\/p>\n

Due to HAProxy being a rapidly evolving open-source application, the version available in the standard CentOS repositories may not be the latest. To check the current version, run the following command:<\/p>\n

<\/p>\n

sudo yum info haproxy<\/code><\/pre>\n
<\/p>\n
HAProxy always offers three stable versions to choose from: the two most recent supported versions and a third, older one that still receives critical updates. You can always check the latest stable version listed on the HAProxy website and then decide which version you want to work with.<\/p>\n
<\/p>\n
In this guide, we will install the latest stable version 2.0, which was not available in the standard repositories at the time of writing this guide. You will need to install it from the source. But first, ensure that you meet the necessary prerequisites for downloading and compiling the program.<\/p>\n
<\/p>\n
sudo yum install gcc pcre-devel tar make -y<\/code><\/pre>\n
<\/p>\n
Download the source code using the command below. You can check if a newer version is available at the HAProxy download page<\/a><\/noindex>.<\/p>\n
<\/p>\n
wget http:\/\/www.haproxy.org\/download\/2.0\/src\/haproxy-2.0.7.tar.gz -O ~\/haproxy.tar.gz<\/code><\/pre>\n
<\/p>\n
Once the download is complete, extract the files using the command below:<\/p>\n
<\/p>\n
tar xzvf ~\/haproxy.tar.gz -C ~\/<\/code><\/pre>\n
<\/p>\n
Navigate to the extracted source directory:<\/p>\n
<\/p>\n
cd ~\/haproxy-2.0.7<\/code><\/pre>\n
<\/p>\n
Then compile the program for your system:<\/p>\n
<\/p>\n
make TARGET=linux-glibc<\/code><\/pre>\n
<\/p>\n
And finally, install HAProxy itself:<\/p>\n
<\/p>\n
sudo make install<\/code><\/pre>\n
<\/p>\n
HAProxy is now installed, but it requires some additional configurations to work. Let\u2019s continue setting up the software and services below.<\/p>\n
<\/p>\n
Configuring HAProxy for your server<\/h2>\n
<\/p>\n
Now add the following directories and statistics file for HAProxy records:<\/p>\n
<\/p>\n
sudo mkdir -p \/etc\/haproxy\nsudo mkdir -p \/var\/lib\/haproxy \nsudo touch \/var\/lib\/haproxy\/stats<\/code><\/pre>\n
<\/p>\n
Create a symbolic link for the binary files, so you can run HAProxy commands as a regular user:<\/p>\n
<\/p>\n
sudo ln -s \/usr\/local\/sbin\/haproxy \/usr\/sbin\/haproxy<\/code><\/pre>\n
<\/p>\n
If you want to add the proxy server to the system as a service, copy the haproxy.init file from examples to your \/etc\/init.d directory. Edit the file permissions so that the script is executable, and then reload the systemd daemon:<\/p>\n
<\/p>\n
sudo cp ~\/haproxy-2.0.7\/examples\/haproxy.init \/etc\/init.d\/haproxy\nsudo chmod 755 \/etc\/init.d\/haproxy\nsudo systemctl daemon-reload<\/code><\/pre>\n
<\/p>\n
You also need to enable the service to start automatically on system startup:<\/p>\n
<\/p>\n
sudo chkconfig haproxy on<\/code><\/pre>\n
<\/p>\n
For convenience, it is also recommended to add a new user to run HAProxy:<\/p>\n
<\/p>\n
sudo useradd -r haproxy<\/code><\/pre>\n
<\/p>\n
After this, you can check the installed version number again with the following command:<\/p>\n
<\/p>\n
haproxy -v\nHA-Proxy version 2.0.7 2019\/09\/27 - https:\/\/haproxy.org\/<\/code><\/pre>\n
<\/p>\n
In our case, the version should be 2.0.7, as shown in the output example above.<\/p>\n
<\/p>\n
Finally, the firewall in CentOS 8 is quite restrictive by default for this project. Use the following commands to allow the necessary services and reload the firewall:<\/p>\n
<\/p>\n
sudo firewall-cmd --permanent --zone=public --add-service=http\nsudo firewall-cmd --permanent --zone=public --add-port=8181\/tcp\nsudo firewall-cmd --reload<\/code><\/pre>\n
<\/p>\n
Load Balancer Configuration<\/h2>\n
<\/p>\n
Configuring HAProxy is a relatively straightforward process. Essentially, all you need to do is tell HAProxy which connections it should listen to and where to route them.<\/p>\n
<\/p>\n
This is done by creating a configuration file at \/etc\/haproxy\/haproxy.cfg with the defining settings. You can read about the HAProxy configuration options on the documentation page<\/a><\/noindex>, if you want to learn more about it.<\/p>\n
<\/p>\n
Layer 4 Load Balancing<\/h2>\n
<\/p>\n
Let\u2019s start with a basic setup. Create a new configuration file, for example, using vi<\/strong> with the command below:<\/p>\n
<\/p>\n
sudo vi \/etc\/haproxy\/haproxy.cfg<\/code><\/pre>\n
<\/p>\n
Add the following sections to the file. Replace server_name<\/strong> with what should be calling your servers on the stats page, and private_ip<\/strong> with the private IP addresses of the servers to which you want to direct web traffic. You can check the private IP addresses in the UpCloud control panel<\/a><\/noindex> and on the tab Private Network<\/em> in the menu. Network<\/em>.<\/p>\n
<\/p>\n
global\n   log \/dev\/log local0\n   log \/dev\/log local1 notice\n   chroot \/var\/lib\/haproxy\n   stats timeout 30s\n   user haproxy\n   group haproxy\n   daemon\n\ndefaults\n   log global\n   mode http\n   option httplog\n   option dontlognull\n   timeout connect 5000\n   timeout client 50000\n   timeout server 50000\n\nfrontend http_front\n   bind *:80\n   stats uri \/haproxy?stats\n   default_backend http_back\n\nbackend http_back\n   balance roundrobin\n   server server_name1 private_ip1:80 check\n   server server_name2 private_ip2:80 check<\/code><\/pre>\n
<\/p>\n
This defines a layer 4 load balancer with the external name http_front listening on port 80, which then directs traffic to the default backend named http_back. The additional stats \/haproxy?stats connects the stats page at the specified address.<\/p>\n
<\/p>\n
Various Load Balancing Algorithms.<\/h2>\n
<\/p>\n
Specifying servers in the backend section allows HAProxy to use these servers for load balancing based on the round-robin algorithm when possible.<\/p>\n
<\/p>\n
Load balancing algorithms are used to determine which backend server each connection is sent to. Here are some useful options:<\/p>\n
<\/p>\n