Example we have 3 server, we install HAProxy on a server (51.15.94.246), and nginx on two other servers (212.47.238.225 and 51.15.132.220 running Nginx on port 80)
Install on main server
Step 1:
yum install haproxy -y
Result:
[root@load-balancer-1 ~]# yum install haproxy -y Loaded plugins: fastestmirror, ovl Loading mirror speeds from cached hostfile * base: mirror.alpha-labs.net * epel: epel.mirror.wearetriple.com * extras: mirror.plusserver.com * updates: mirror.plusserver.com Resolving Dependencies --> Running transaction check ---> Package haproxy.x86_64 0:1.5.18-8.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: haproxy x86_64 1.5.18-8.el7 base 834 k Transaction Summary ================================================================================ Install 1 Package Total download size: 834 k Installed size: 2.6 M Downloading packages: haproxy-1.5.18-8.el7.x86_64.rpm | 834 kB 00:00 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : haproxy-1.5.18-8.el7.x86_64 1/1 Verifying : haproxy-1.5.18-8.el7.x86_64 1/1 Installed: haproxy.x86_64 0:1.5.18-8.el7 Complete!
Step 2:
Default HAProxy Configuration:
[root@load-balancer-1 ~]# cat /etc/haproxy/haproxy.cfg
#---------------------------------------------------------------------
# Example configuration for a possible web application. See the
# full configuration options online.
#
# http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------
#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
# to have these messages end up in /var/log/haproxy.log you will
# need to:
#
# 1) configure syslog to accept network log events. This is done
# by adding the '-r' option to the SYSLOGD_OPTIONS in
# /etc/sysconfig/syslog
#
# 2) configure local2 events to go to the /var/log/haproxy.log
# file. A line like the following can be added to
# /etc/sysconfig/syslog
#
# local2.* /var/log/haproxy.log
#
log 127.0.0.1 local2
chroot /var/lib/haproxy
pidfile /var/run/haproxy.pid
maxconn 4000
user haproxy
group haproxy
daemon
# turn on stats unix socket
stats socket /var/lib/haproxy/stats
#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaults
mode http
log global
option httplog
option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
retries 3
timeout http-request 10s
timeout queue 1m
timeout connect 10s
timeout client 1m
timeout server 1m
timeout http-keep-alive 10s
timeout check 10s
maxconn 3000
#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
frontend main *:5000
acl url_static path_beg -i /static /images /javascript /stylesheets
acl url_static path_end -i .jpg .gif .png .css .js
use_backend static if url_static
default_backend app
#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
backend static
balance roundrobin
server static 127.0.0.1:4331 check
#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
backend app
balance roundrobin
server app1 127.0.0.1:5001 check
server app2 127.0.0.1:5002 check
server app3 127.0.0.1:5003 check
server app4 127.0.0.1:5004 check
Load Balancing Configuration
To get started balancing traffic between our two HTTP listeners, we need to set some options within HAProxy:
frontend – where HAProxy listens to connections
backend – Where HAPoxy sends incoming connections
stats – Optionally, setup HAProxy web tool for monitoring the load balancer and its nodes
Here’s an example frontend:
frontend localnginx
bind *:80
mode http
default_backend nginx
Explain:
bind *:80 – I’ve bound this frontend to all network interfaces on port 80. HAProxy will listen on port 80 on each available network for new HTTP connections
mode http – This is listening for HTTP connections. HAProxy can handle lower-level TCP connections as well, which is useful for load balancing things like MySQL read databases, if you setup database replication
default_backend nginx – This frontend should use the backend named nginx, which we’ll see next.
Example backend configuration:
backend nginx
mode http
balance roundrobin
option forwardfor
http-request set-header X-Forwarded-Port %[dst_port]
http-request add-header X-Forwarded-Proto https if { ssl_fc }
option httpchk HEAD / HTTP/1.1\r\nHost:localhost
server web01 212.47.238.225:80 check
server web02 51.15.132.220:80 check
Explain:
mode http – This will pass HTTP requests to the servers listed
balance roundrobin – Use the roundrobin strategy for distributing load amongst the servers
Some other example:
balance url_param userid balance url_param session_id check_post 64 balance hdr(User-Agent) balance hdr(host) balance hdr(Host) use_domain_only
option forwardfor – Adds the X-Forwarded-For header so our applications can get the clients actually IP address. Without this, our application would instead see every incoming request as coming from the load balancer’s IP address
http-request set-header X-Forwarded-Port %[dst_port] – We manually add the X-Forwarded-Port header so that our applications knows what port to use when redirecting/generating URLs.
* Note that we use the dst_port “destination port” variable, which is the destination port of the client HTTP request.
option httpchk HEAD / HTTP/1.1\r\nHost:localhost – Set the health check HAProxy uses to test if the web servers are still responding. If these fail to respond without error, the server is removed from HAProxy as one to load balance between. This sends a HEAD request with the HTTP/1.1 and Host header set, which might be needed if your web server uses virtualhosts to detect which site to send traffic to
http-request add-header X-Forwarded-Proto https if { ssl_fc } – We add the X-Forwarded-Proto header and set it to “https” if the “https” scheme is used over “http” (via ssl_fc). Similar to the forwarded-port header, this can help our web applications determine which scheme to use when building URL’s and sending redirects (Location headers).
server web01-2 xx.xx.xx.xx:80 check – These two lines add the web servers for HAProxy to balance traffic between. It arbitrarily names each one web01-web02, set’s their IP address and port, and adds the directive check to tell HAProxy to health check the server
Other example backend configuration:
backend nodes
# Other options above omitted for brevity
cookie SRV_ID prefix
server web01 212.47.238.225:80 cookie 01 check
server web02 51.15.132.220:80 cookie 02 check
Means if your server send a cookie with name SRV_ID like:
setcookie('SRV_ID',$_SERVER["SERVER_ADDR"]);
You will receive a response header:
Set-Cookie: SRV_ID=02~10.5.78.75
you can use:
cookie SRV_ID rewrite
You will receive a response header:
Set-Cookie: SRV_ID=01
If you use with insert, your server doesn’t need to send a cookie with name SRV_ID
cookie SRV_ID insert
You will receive a response header:
Set-Cookie: SRV_ID=02; path=/
Step 3:
service haproxy restart
Done! now you can access http://51.15.132.220/
See more example: How to configure HAProxy to include host headers
