The Basics of HAProxy

4 min readMar 8, 2022

A brief about HAProxy:

HAProxy is a free, open source load balancer and proxy server. It can be used to distribute TCP and HTTP traffic to multiple servers and to cache static content.

HAProxy is very dynamic and can handle a high volume of traffic. It can also act as a reverse proxy, caching HTTP responses from the backend servers to improve performance.It can optimize the resource usage and improve performance.

Installing and Configuring HAProxy :

The process of installation and configuring HAProxy can be done very easily by following the below steps.

Installing HAProxy:

HAProxy package is available under the default yum repository for the linux systems. The followig command needs to be used to install HAProxy in our system.

Install HAProxy

> Configuring HAProxy:

The HAProxy configuration file is present in the following path: /etc/haproxy/haproxy.cfg

Upon execution of the following command the configuration file opens .

Open Configuration file

Once the configuration file is opened it needs to be modified according to our requirement . The configuration file looks like the following

global
        log 127.0.0.1   local0
        log 127.0.0.1   local1 debug
        maxconn   45000 # Total Max Connections.
        daemon
        nbproc      1 # Number of processing cores.
defaults
        timeout server 86400000
        timeout connect 86400000
        timeout client 86400000
        timeout queue   1000s

# [HTTP Site Configuration]
listen  http_web 192.168.10.10:80
        mode http
        balance roundrobin  # Load Balancing algorithm
        option httpchk
        option forwardfor
        server server1 192.168.10.100:80 weight 1 maxconn 512 check
        server server2 192.168.10.101:80 weight 1 maxconn 512 check

# [HTTPS Site Configuration]
listen  https_web 192.168.10.10:443
        mode tcp
        balance source# Load Balancing algorithm
        reqadd X-Forwarded-Proto: http
        server server1 192.168.10.100:443 weight 1 maxconn 512 check
        server server2 192.168.10.101:443 weight 1 maxconn 512 check#Update values marked in BOLD corresponding to setup

Now we have to change the IPs in configuration file as per our network setup. In HTTP Site Configuration section if any request comes on IP 192.168.10.10 on port 80, this will be redirected to port 80 of 192.168.10.100 or 192.168.10.101 servers. Similarly in HTTPS Site Configuration if any request on ip 192.168.10.10 on port 443, this will be redirected to port 443 of 192.168.10.100 or 192.168.10.101 servers.

We also need to make a few changes in the configuration file as per your system configuration.

nbproc <value> # Number of processing cores in our system.
mode <value> # ‘http’ for http site and ‘tcp’ for https site
balance <value> # Type of load balancing like ‘source’, ’roundrobin’ etc.

HAProxy Load Balancng based on URL:

But in case the application is a REST api or incase if we need to do the load balancing based on URL , then the above configuration would be a limitation , hence we need to add the following configuration .

Lets imagine the network setup as follows:

HAProxy Server: 192.168.1.90
WEB1 : 192.168.1.103
WEB2 : 192.168.1.105
Domain: testHAproxy.com

So here HAProxy ACL comes nto action .The below example includes ACL for url_beg. url_beg matches the string used in url submitted. Using the url all requests starting with /path1 ( testHAproxy.com/path1 ) will redirect to WEB2 ( 192.168.1.105 ) Server. All other requests will redirect to one of two server ( WEB1, WEB2 ), depending on load balancing algorithm used.

The configuration would be as follows:-

global
    log 127.0.0.1 local0 notice
    maxconn 50000
    daemon
defaults
    log global
    mode http
    option httplog
    option dontlognull
    contimeout 120000
    clitimeout 120000
    srvtimeout 120000
    option forwardfor
    option http-server-close

# Configuration for HTTP site
frontend http-in
    bind 192.168.1.90:80
    acl is_path1 url_beg  /path1
    use_backend testHAProxy_path1 if is_path1
    default_backend HAProxy_website

backend testHAProxy_path1
    mode http
    balance roundrobin  # Load Balancing algorithm
    option httpchk
    option forwardfor
    server WEB2 192.168.1.105:80 weight 1 maxconn 512 check

backend HAProxy_website
    mode http
    balance roundrobin  # Load Balancing algorithm
    option httpchk
    option forwardfor
    server WEB1 192.168.1.103:80 weight 1 maxconn 512 check
    server WEB2 192.168.1.105:80 weight 1 maxconn 512 check

Starting HAProxy:

Now the following command needs to be used for starting HAProxy.

Enabling HAProxy Stats:

A lot of information regarding data transfer, total connection, server state etc can be found using the HAProxy statistics. For enabling stats we should edit our HAProxy configuration file and add below entries in the defaults section.

listen  stats   192.168.10.10:1936
        mode            http
        log             global

        maxconn 10

        clitimeout      100s
        srvtimeout      100s
        contimeout      100s
        timeout queue   100s

        stats enable
        stats hide-version
        stats refresh 30s
        stats show-node
        stats auth admin:password
        stats uri  /haproxy?stats

Accessing the stats:

We can access the stats using the following URL. We should use our server ip address followed by stats uri in above configuration. Use login details configured with stats auth in configuration file.

So now according to the above added configuration , the stats can be viewed by accessing the following url with the credentials mentioned .

URL: http://192.168.10.10:1936/haproxy?stats
 Login user: admin
 Login password: password

Conclusion:

So now by following all the above steps we can install, configure and setup HAProxy load balancing for our applications and improve the performance in a reliable way.

References:

The Basics of HAProxy

Written by Satya Sai