{"id":2365,"date":"2015-12-18T18:17:13","date_gmt":"2015-12-18T16:17:13","guid":{"rendered":"https:\/\/upcloud.com\/global\/us\/resources\/tutorials\/haproxy-load-balancer-debian\/"},"modified":"2015-12-18T18:17:13","modified_gmt":"2015-12-18T16:17:13","slug":"haproxy-load-balancer-debian","status":"publish","type":"tutorial","link":"https:\/\/upcloud.com\/global\/resources\/tutorials\/haproxy-load-balancer-debian\/","title":{"rendered":"How to install HAProxy load balancer on Debian"},"content":{"rendered":"\n

Try this guide out on UpCloud with our free trial!\u00a0Get started<\/a><\/h3>\n\n\n\n

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

HAProxy aims to optimise resource usage, maximise throughput, minimise response time, and avoid overloading any single resource. It is available for installation on many Linux distributions like Debian 8 in this guide, but also on Ubuntu 16<\/a> and CentOS 7<\/a> systems.<\/p>\n\n\n\n

\"HAproxy<\/figure>\n\n\n\n

HAProxy is particularly suited for very high-traffic websites and is, therefore, often used to improve web service reliability and performance for multi-server configurations. This guide lays out the steps for setting up HAProxy as a load balancer on Debian 8 to its own cloud host, which then directs the traffic to your web servers.<\/p>\n\n\n\n

As a pre-requirement for the best results, you should have a minimum of two web servers and a server for the load balancer. The web servers must be running at least the basic web service such as Apache2 or nginx to test the load balancing between them.<\/p>\n\n\n\n

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Test hosting on UpCloud!<\/a><\/div>\n<\/div>\n\n\n\n

Installing HAProxy 1.7<\/h2>\n\n\n\n

As a fast-developing open-source application, HAProxy available for installation in the Debian default repositories might not be the latest release. To find out what version number is offered through the official channels, enter the following command.<\/p>\n\n\n\n

sudo aptitude show haproxy<\/pre>\n\n\n\n
HAProxy always has three active stable versions of the releases, two of the latest versions in development plus a third older version still receiving critical updates. You can always check the currently newest stable version listed on the HAProxy website and then decide which version you wish to go with.<\/p>\n\n\n\n
While the latest stable version, 1.7, of HAProxy is not yet available on the packet manager by default, it can be found in a backported repository. To install HAProxy from a backport repo, you will need to add the source using the following command.<\/p>\n\n\n\n
echo \"deb http:\/\/httpredir.debian.org\/debian jessie-backports main\" | \n      sudo tee \/etc\/apt\/sources.list.d\/backports.list<\/pre>\n\n\n\n
Next, update your sources list.<\/p>\n\n\n\n
sudo aptitude update<\/pre>\n\n\n\n
Then, install HAProxy from the backport using the command below.<\/p>\n\n\n\n
sudo aptitude install -t jessie-backports haproxy<\/pre>\n\n\n\n
Afterwards, you can double-check the installed version number with the following command.<\/p>\n\n\n\n
haproxy -v<\/pre>\n\n\n\n
HA-Proxy version 1.7.5-2~bpo8+1 2017\/05\/27\nCopyright 2000-2017 Willy Tarreau <willy@haproxy.org><\/pre>\n\n\n\n
<\/a>The installation is then complete. Continue below with instructions on configuring the load balancer to redirect requests to your web servers.<\/p>\n\n\n\n
Configuring the load balancer<\/h2>\n\n\n\n
Setting up HAProxy for load balancing is quite straightforward. All you need to do is tell HAProxy what kind of connections it should be listening for and where the connections should be relayed.<\/p>\n\n\n\n
<\/a>This is done by creating a configuration file \/etc\/haproxy\/haproxy.cfg<\/tt> with the defining settings. You can read about the configuration options on the HAProxy documentation page<\/a> if you wish to find out more.<\/p>\n\n\n\n
Load balancing on layer 4<\/h2>\n\n\n\n
Once installed, HAProxy should have a template for configuring the load balancer. Open the configuration file, for example, using nano<\/tt> with the command underneath.<\/p>\n\n\n\n
sudo nano \/etc\/haproxy\/haproxy.cfg<\/pre>\n\n\n\n
Add the following sections to the end of the file. Replace the <server name><\/tt> with whatever you want to call your servers on the statistics page and the <private IP><\/tt> with the private IPs for the servers you wish to direct the web traffic. You can check the private IPs in your UpCloud Control Panel and the Private Network tab under the Network<\/em> menu.<\/p>\n\n\n\n
frontend http_front\n   bind *:80\n   stats uri \/haproxy?stats\n   default_backend http_back\n\nbackend http_back\n   balance roundrobin\n   server <server1 name> <private IP 1>:80 check\n   server <server2 name> <private IP 2>:80 check<\/pre>\n\n\n\n
<\/a>This defines a layer 4 load balancer with a front-end name http_front<\/tt> listening to port number 80<\/tt>, which then directs the traffic to the default backend named http_back<\/tt>. The additional stats URI \/haproxy?stats<\/tt> enable the statistics page at that specified address.<\/p>\n\n\n\n
Different load-balancing algorithms<\/h2>\n\n\n\n
Configuring the servers in the backend section allows HAProxy to use these servers for load balancing according to the roundrobin<\/tt> algorithm whenever available.<\/p>\n\n\n\n
The balancing algorithms are used to decide which server each connection is transferred to at the backend. Some of the useful options include the following:<\/p>\n\n\n\n