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HAProxy is a network software application that offers high availability, load balancing, and proxying for TCP and HTTP network applications. It is suited for high traffic websites, and powers many popular sites across the web. This article will show you how to install and configure HAProxy on Debian 9.1.
Although HAProxy has several prominent features, this article focuses on how to setup HAProxy to “proxy” your web application.
- At least two IT Web Services servers (for load balancing functionality) with your website or web application deployed to both of them.
Debian 9 already ships with HAProxy 1.7 (latest stable release at time of writing), and we can simply install it using
# apt-get update # apt-get install haproxy
If the previous commands were successful, then you have installed HAProxy and you can proceed to the next step.
The HAProxy configuration file is split up into two sections — “global” and “proxies”. One deals with process-wide configuration, while the latter consists of default configuration, frontend, and backend sections.
Using your favorite text editor, open
/etc/haproxy/haproxy.cfg and notice the predefined sections: “global” and “defaults”. The first thing that you may want to do is increase the
maxconn to a reasonable size, as this affects the connections that HAProxy allows. Too many connections may cause your web service to crash due to many requests. You will need to adjust the size to see what works for you. In the global section, we have chosen a
maxconn value of
global daemon maxconn 3072
In the default section, add the following line under mode
This will add
X-Forwarded-For headers to each request, which allows your backend servers to learn the original IP address of the user.
Also, add this line to enable HTTP connection-close mode on the server side while keeping the ability to support HTTP keep-alive on the client side. This reduces latency on the client side and helps conserve server resources:
If you wish to use keep-alive on both the client and server sides, then you could use
option http-keep-alive instead. This option is particularly useful when the cost of establishing a new connection to the server is significant compared to the cost of retrieving the requested resource.
Finally, the resulting config file will look something like this:
defaults mode http option forwardfor option http-server-close timeout connect 5000ms timeout client 50000ms timeout server 50000ms
To set up your proxy, you will need to add two sections to the configuration file to define the two parts of the proxy: the frontend and the backend.
The frontend will handle your HTTP connections. Add the following to the end of your
frontend http-frontend bind public_ip:80 reqadd X-Forwarded-Proto: http default_backend wwwbackend
Be sure to replace
public_ip with your server’s public IP address or domain name.
Setup your backend by adding the following lines to the end of your configuration file:
backend wwwbackend server 1-www server1_ip:80 check server 2-www server2_ip:80 check server 3-www server3_ip:80 check
The backend configuration used here creates 3 connections named
X is 1, 2 or 3.) Each one of them corresponds to a
serverX_ip:80 address. (Replace
serverX_ip with your IT Web Services instances’ IP addresses.) This will allow you to load balance between each server in the specified server set (assuming each IP address corresponds to a different server). The
check option makes the load balancer perform health checks on the server.
Save the configuration file, and then restart HAProxy:
service haproxy restart
If everything is working, then you will be able to connect to
http://public_ip/ (replacing it with your public IP or domain name as configured in the frontend step) and view your website.
If your HAProxy instance refuses to start after your modifications, chances are that you have an error somewhere in the configuration file. To get clear messages about the issue in the configuration file, you can try to start HAProxy manually using this command:
# haproxy -f /etc/haproxy/haproxy.cfg
For instance, if you see output like this:
[ALERT] 234/195612 (2561) : parsing [/etc/haproxy/haproxy.cfg:48] : server 1-www has neither service port nor check port nor tcp_check rule 'connect' with port information. Check has been disabled. [ALERT] 234/195612 (2561) : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg [ALERT] 234/195612 (2561) : Fatal errors found in configuration.
Then, you have forgotten to specify the port number for the server
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