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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 being offered through the official channels enter the following command.<\/p>\n\n\n\n
sudo aptitude show haproxy<\/pre>\n\n\n\n
HAProxy has always three active stable versions of the releases, two of the latest versions in development plus a third older version that is 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 with 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 with 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 the instructions for how to configure 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 a quite straightforward process. Basically, all you need to do is tell HAProxy what kind of connections it should be listening for and where the connections should be relayed to.<\/p>\n\n\n\n
<\/a>This is done by creating a\u00a0configuration file\u00a0\/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\nOnce installed HAProxy should already 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\nsudo nano \/etc\/haproxy\/haproxy.cfg<\/pre>\n\n\n\nAdd 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 at your UpCloud Control Panel and Private network\u00a0tab under the Network<\/em>\u00a0menu.<\/p>\n\n\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 <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\u00a0http_front<\/tt> listening to port number 80<\/tt>, which then\u00a0directs the traffic to the default backend named\u00a0http_back<\/tt>. The additional stats URI \/haproxy?stats<\/tt> enables the statistics page at that specified address.<\/p>\n\n\n\n Different load balancing algorithms<\/h2>\n\n\n\nConfiguring 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 at the backend each connection is transferred to. Some of the useful options include the following:<\/p>\n\n\n\n\nRoundrobin:\u00a0Each server is used in turns according to its weights.\u00a0This is the smoothest and fairest algorithm when the server\u2019s processing time remains equally distributed. This algorithm\u00a0is dynamic, which allows\u00a0server weights to\u00a0be adjusted\u00a0on the fly.<\/li>\n\n\n\n Leastconn: The server with the lowest number of connections is chosen. Round-robin is performed between servers with the same load. Using this algorithm is recommended with long sessions, such as LDAP, SQL, TSE, etc, but it is not very well suited for short sessions such as HTTP.<\/li>\n\n\n\n First: The first server with available connection slots receives the connection. The servers are chosen from the lowest numeric identifier to the highest, which defaults to the server\u2019s position on the farm. Once a server reaches its maxconn<\/tt> value, the next server is used.<\/li>\n\n\n\n<\/a>Source: The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. This way the same client IP address will always reach the same server while the servers stay the same.<\/li>\n<\/ul>\n\n\n\nConfiguring load balancing for layer 7<\/h2>\n\n\n\nAnother possibility is to configure the load balancer to work on layer 7, which is useful when parts of your web application are located on different hosts. This can be accomplished by conditioning the connection transfer for example by the URL.<\/p>\n\n\n\n Open the HAProxy configuration file with a text editor.<\/p>\n\n\n\nsudo nano \/etc\/haproxy\/haproxy.cfg<\/pre>\n\n\n\nThen set the front and backend segments according to the example below.<\/p>\n\n\n\nfrontend http_front\n bind *:80\n stats uri \/haproxy?stats\n acl url_blog path_beg \/blog\n use_backend blog_back if url_blog\n default_backend http_back\n\nbackend http_back\n balance roundrobin\n server <server name> <private IP>:80 check\n server <server name> <private IP>:80 check\n\nbackend blog_back\n server <server name> <private IP>:80 check<\/pre>\n\n\n\nThe front end declares an ACL rule named url_blog<\/tt> that applies to all connections with paths that begin with \/blog<\/tt>. Use_backend<\/tt> defines that connections matching the url_blog<\/tt> condition should be served by the backend named blog_back<\/tt>, while all other requests are handled by the default backend.<\/p>\n\n\n\n At the backend side, the configuration sets up two server groups, http_back<\/tt> like before and the new one called blog_back<\/tt> that servers specifically connections to example.com\/blog<\/tt>.<\/p>\n\n\n\n After making the configurations, save the file and restart HAProxy with the next command.<\/p>\n\n\n\nsudo systemctl restart haproxy<\/pre>\n\n\n\n<\/a>If you get any errors or warnings at startup, check the configuration for any mistypes and then try restarting again.<\/p>\n\n\n\n Testing the setup<\/h2>\n\n\n\nWith the HAProxy configured and running, open your load balancer server\u2019s public IP in a web browser and check that you get connected to your backend correctly. The parameter stats uri<\/tt> in the configuration enables the statistics page at the defined address.<\/p>\n\n\n\nhttp:\/\/<load balancer public IP>\/haproxy?stats<\/pre>\n\n\n\nWhen you load the statistics page and all of your servers are listed in green your configuration was successful!<\/p>\n\n\n\n<\/figure>\n\n\n\nThe statistics page contains some helpful information to keep track of your web hosts including up and down times and session counts. If a server is listed in red, check that the server is powered on and that you can ping it from the load balancer machine.<\/p>\n\n\n\n<\/a>In case your load balancer does not reply, check that HTTP connections are not getting blocked by a firewall. Also, confirm that HAProxy is running with the command below.<\/p>\n\n\n\n sudo systemctl status haproxy<\/pre>\n\n\n\nPassword protecting the statistics page<\/h2>\n\n\n\nHaving the statistics page simply listed at the front end, however, is publicly open for anyone to view, which might not be such a good idea. Instead, you can set it up to its own port number by adding the example below to the end of your haproxy.cfg<\/tt> file. Replace the username<\/tt> and password<\/tt> with something secure.<\/p>\n\n\n\nlisten stats\n bind *:8181\n stats enable\n stats uri \/\n stats realm Haproxy Statistics\n stats auth username:password<\/pre>\n\n\n\nAfter adding the new listen<\/tt> group, remove the old reference to the stats uri<\/tt> from the frontend<\/tt> group. When done, save the file and restart HAProxy again.<\/p>\n\n\n\nsudo systemctl restart haproxy<\/pre>\n\n\n\nThen open the load balancer again with the new port number, and log in with the username and password you set in the configuration file.<\/p>\n\n\n\nhttp:\/\/<load balancer public IP>:8181<\/pre>\n\n\n\nCheck that your servers are still reporting all green and then open just the load balancer IP without any port numbers on your web browser.<\/p>\n\n\n\nhttp:\/\/<load balancer public IP>\/<\/pre>\n\n\n\nIf your backend servers have at least slightly different landing pages you will notice that each time you reload the page you get the reply from a different host. You can try out different balancing algorithms in the configuration section or take a look at the full documentation<\/a>.<\/p>\n\n\n\n Conclusions<\/h2>\n\n\n\nCongratulations on successfully configuring HAProxy! With a basic load balancer setup, you can considerably increase your web application performance and availability. This guide is however just an\u00a0introduction to load balancing with HAProxy, which is capable of much more than what could be covered in first-time setup instructions. We recommend experimenting with different configurations with the help of the extensive documentation<\/a> available for HAProxy and then start planning the load balancing for your production environment.<\/p>\n\n\n\n While using multiple hosts to protect your web service with redundancy, the load balancer itself can still leave a single point of failure. You can further improve the high availability by setting up a floating IP between multiple load balancers. You can find out more about this in our article for floating IPs on UpCloud<\/a>.<\/p>\n","protected":false},"featured_media":27365,"comment_status":"open","ping_status":"closed","template":"","community-category":[113,115],"class_list":["post-24609","tutorial","type-tutorial","status-publish","has-post-thumbnail","hentry","community-category-integrations","community-category-load-balancing"],"acf":[],"_links":{"self":[{"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/tutorial\/24609","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/tutorial"}],"about":[{"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/types\/tutorial"}],"replies":[{"embeddable":true,"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/comments?post=24609"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/media\/27365"}],"wp:attachment":[{"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/media?parent=24609"}],"wp:term":[{"taxonomy":"community-category","embeddable":true,"href":"https:\/\/studiogo.tech\/upcloudold\/wp-json\/wp\/v2\/community-category?post=24609"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}