HAProxy or High Availability Proxy is an open source TCP and HTTP load balancer and proxy server software. HAProxy is a fast and lightweight proxy server and load balancer with a small memory footprint and low CPU usage. It is used by large sites like Github, StackOverflow, Reddit, Tumblr, Twitter and others. It has become the most popular software load balancer and proxy server in the past years.
Balance Algorithm : This is the algorithm that is used by HAProxy to select the server when doing the load balancing.
Roundrobin : This is the most simple balance algorithm. For each new connection, it will be handled by the next backend server. If the last backend server in the list is reached, it will start again from the top of backend list.
Lastconn : The new connection will be handled by the backend server with least amount of connections. This is useful when the time and load of the requests vary a lot.
Source: This is for sticky sessions, the client IP will be hashed to determine the backend server that received the last request from this IP. So an IP A will always be handled by backend1, and IP B will always be handled by banckend2 to not interrupt sessions
There are other algorithm - check the official HAProxy site for details.
Basic Concept of HAProxy
HAProxy can run in two modes: TCP mode Layer 4 and HTTP Mode Layer 7. In Layer 4 TCP mode, HAProxy forwards the RAW TCP packets from the client to the application servers. In the Layer 7 HTTP mode, HAProxy is parsing the HTTP header before forwarding them to the application servers. In this tutorial, we will use Apache as the web server that only supports the Layer 7 HTTP mode.
The following modes are available:Balance Algorithm : This is the algorithm that is used by HAProxy to select the server when doing the load balancing.
Roundrobin : This is the most simple balance algorithm. For each new connection, it will be handled by the next backend server. If the last backend server in the list is reached, it will start again from the top of backend list.
Lastconn : The new connection will be handled by the backend server with least amount of connections. This is useful when the time and load of the requests vary a lot.
Source: This is for sticky sessions, the client IP will be hashed to determine the backend server that received the last request from this IP. So an IP A will always be handled by backend1, and IP B will always be handled by banckend2 to not interrupt sessions
There are other algorithm - check the official HAProxy site for details.
Prerequisites
4 CentOS 7 pre-install servers.- Load Balancer (192.168.2.110)
- Web Server1 (192.168.2.101)
- Web Server2 (192.168.2.102)
- Web Server3 (192.168.2.103)
Step 1 – Install HAProxy
HAProxy package is available under default
yum repository for CentOS & Red Hat systems. Use the following yum package
manager command to install HAProxy on your system.
#yum install haproxy
#yum install haproxy
Step 2 – Configure HAProxy
Update your HAProxy configuration file /etc/haproxy/haproxy.cfg as
per your requirement, You may also use below given configuration file as an
example of setup and modify it.
#cd /etc/haproxy/
#mv haproxy.cfg haproxy.cfg.orig #### Take the backup file before doing modification.
# vi haproxy.cfg
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 1m
timeout connect 10s
timeout client 1m
timeout queue 1m
# [HTTP Site Configuration]
listen http_web 192.168.2.110:80
mode http
balance roundrobin # Load Balancing algorithm
option httpchk
option forwardfor
server server1 192.168.2.101:80 weight 1 maxconn 512 check
server server2 192.168.2.102:80 weight 1 maxconn 512 check
server server2 192.168.2.103:80 weight 1 maxconn 512 check
Save configuration file
Change the ips in configuration file as per your network setup. In HTTP Site Configuration section if any request on ip 192.168.2.110 on port 80, this will be redirected to port 80 of 192.168.2.100 or 192.168.2.101 or 192.168.2.102 servers.
You also need to make few changes in
configuration file as per your system configuration.
nbproc <value> # Number of
processing cores in your system.
mode <value> # ‘http’ for
http site and ‘tcp’ for https site
balance <value> # Type of
load balancing like ‘source’, ’roundrobin’ etc.
Configure
We will configure the rsyslog daemon to log the HAProxy statistics. Edit the rsyslog.conf file to enable the UDP port 514 to be used by rsyslog
Configure
We will configure the rsyslog daemon to log the HAProxy statistics. Edit the rsyslog.conf file to enable the UDP port 514 to be used by rsyslog
Uncomment this line to enable the UDP connection:
If you want to use a specific IP, you can add a new line like the one below:
#vi /etc/rsyslog.conf
$ModLoad imudp
$UDPServerRun 514
$UDPServerAddress 192.168.2.110
Save configuration file
Then create new haproxy configuration file for rsyslog:
#cd /etc/rsyslog.d/
#vi haproxy.conf
local2.=info /var/log/haproxy-access.log #For Access Log
local2.notice /var/log/haproxy-info.log #For Service Info - Backend, loadbalancer
Save configuration file
Now restart rsyslog and then start the haproxy & Add haproxy to start at boot time.
#systemctl restart rsyslog
#systemctl start haproxy
If you want to use a specific IP, you can add a new line like the one below:
#vi /etc/rsyslog.conf
$ModLoad imudp
$UDPServerRun 514
$UDPServerAddress 192.168.2.110
Save configuration file
Then create new haproxy configuration file for rsyslog:
#cd /etc/rsyslog.d/
#vi haproxy.conf
local2.=info /var/log/haproxy-access.log #For Access Log
local2.notice /var/log/haproxy-info.log #For Service Info - Backend, loadbalancer
Save configuration file
Now restart rsyslog and then start the haproxy & Add haproxy to start at boot time.
#systemctl restart rsyslog
#systemctl start haproxy
#systemctl enable haproxy
Step 3 - Install and Configure Apache
In this section, we will install Apache on web01,web02 and web03 server.Log in to the web servers using ssh:
#ssh web01
Now you can install Apache on all Servers:
#yum -y install httpd
Apache is installed. Go to the web directory and change the index file so that we can see which of the 3 servers delivered the html file:
#cd /var/www/html/
#echo "<h1>Welcome to `hostname`</h1>" > index.html
Next, add Apache to start at boot time and then start it:
#systemctl enable httpd
#systemctl start httpd
Make sure you're doing this step on web01,web02 and web03 server.
Step 4 Testing
Testing from browser by accessing the loadbalancer IP: 192.168.2.110
How to Enable HAProxy Stats
Step 1: Enable Stats in HAProxy
To enable stats edit your haproxy configuration file and add below entry after defaults section.
# vi haproxy.cfg
listen stats 192.168.2.110:1936
mode http
log global
stats enable
stats hide-version
stats refresh 30s
stats show-node
stats auth admin:password
stats uri /haproxy/stats
Save configuration file
Step 2: Access HAProxy Stats
Your can access HAProxy stats using following url. Change ip with your haproxy server ip address.
URL:http://192.168.2.110:1936/haproxy/stats
Login user: admin
Login password: password
Step 3: Change Login Details
If you want to changed login details of HAProxy stats, edit your configuration and update “stats auth” value like below
stats auth username:password
Save configuration file and restart HAProxy to update service.
Step 4: Change HAProxy Stats URL
To change url of haproxy stats edit configuration file and update following value.
stats uri /ha-stats
or
stats uri /stats
Save configuration file and restart HAProxy to update service.
Now you can access url like http://192.168.10.10:1936/ha-stats or http://192.168.10.10:1936/stats.
Haproxy stats configuration has been completed successfully.
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