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HAProxy load balancing Apache with LXD containers


HAProxy stands for "High Availability Proxy." This proxy can sit before any TCP application (such as web servers), but it is often used as a load balancer between many website instances.

There might be many reasons for doing this. If you have a website that is being hit hard — adding another instance of that same website and placing HAProxy in front of both — allows you to distribute traffic between instances. Another reason might be to be able to update content on a website without any down time. HAProxy can also help mitigate DOS and DDOS attacks.

This guide will explore using HAProxy with two website instances, and load balancing with round-robin rotation on the same LXD host. This might be a perfectly fine solution for ensuring that updates can be performed without downtime.

However, if your problem is website performance, you may need to distribute your multiple sites across actual bare metal or multiple LXD hosts. It is certainly possible to do all of this on bare metal without using LXD. However, LXD offers great flexibility and performance, and is also excellent for lab testing.

Prerequisites and assumptions

  • Complete comfort at the command line on a Linux machine
  • Experience with a command line editor (using vim here)
  • Experience with crontab
  • Knowledge of LXD. For more information, you may want to consult the LXD Server document. It is fine to install LXD on a notebook or workstation without doing the full-blown server install. This document is written with a lab machine running LXD, but is not set up as an entire server as the document linked above uses.
  • Some knowledge of installing, configuring, and using web servers.
  • We will assume that LXD is already installed and ready to create containers.

Installing containers

On your LXD host for this guide, you will need three containers. There can be more web server containers if you want. You will use web1 and web2 for our website containers and proxyha for our HAProxy container. To install these on your LXD host do:

lxc launch images:rockylinux/8 web1
lxc launch images:rockylinux/8 web2
lxc launch images:rockylinux/8 proxyha

Running an lxc list should return something like this:

|  NAME   |  STATE  |         IPV4         | IPV6 |   TYPE    | SNAPSHOTS |
| proxyha | RUNNING | (eth0) |      | CONTAINER | 0         |
| web1    | RUNNING | (eth0) |      | CONTAINER | 0         |
| web2    | RUNNING | (eth0)  |      | CONTAINER | 0         |

Creating and using the macvlan profile

The containers run on the default bridge interface with bridge-assigned DHCP addresses. These need to change to DHCP addresses from our local LAN. The first thing needed is to create and assign the macvlan profile.

Start by creating the profile:

lxc profile create macvlan

Ensure that your editor is set to your preferred editor, in this case vim:

export EDITOR=/usr/bin/vim

Next, change the macvlan profile. Before you do, you need to know what interface the host uses for our LAN. Run ip addr and look for the interface with the LAN IP assignment:

2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether a8:5e:45:52:f8:b6 brd ff:ff:ff:ff:ff:ff
    inet brd scope global dynamic noprefixroute eno1


In this case, the interface you are looking for is "eno1", which could be completely different on your system. Use your interface information!

Now that you know the LAN interface, you can change our macvlan profile. To do this, at the command line enter:

lxc profile edit macvlan

Edit the profile to look something like this. The author excluded the comments at the top of the file, but if you are new to LXD, examine those:

config: {}
description: ""
    name: eth0
    nictype: macvlan
    parent: eno1
    type: nic
name: macvlan

When creating the macvlan profile, the system copies the default profile. Changing the default profile is impossible.

Now that the macvlan profile exists, you need to apply it to our three containers:

lxc profile assign web1 default,macvlan
lxc profile assign web2 default,macvlan
lxc profile assign proxyha default,macvlan

Unfortunately, the default behavior of macvlan as implemented in the kernel, is inexplicably broken within an LXD container (see this document) dhclient on boot in each of the containers.

Doing this is pretty simplistic when using DHCP. Just follow this for each container:

  • lxc exec web1 bash which will put you at the command line of the web1 container
  • crontab -e which will edit root's crontab on the container
  • type I to get into insert mode.
  • add a line: @reboot /usr/sbin/dhclient
  • hit the Esc key to exit out of insert mode.
  • save your changes with Shiftcolon+w+q++
  • type exit to exit the container

Repeat steps for web2 and proxyha.

After completing these steps, restart the containers:

lxc restart web1
lxc restart web2
lxc restart proxyha

and when you do an lxc list again, you will see that the DHCP addresses are now assigned from your LAN:

|  NAME   |  STATE  |         IPV4         | IPV6 |   TYPE    | SNAPSHOTS |
| proxyha | RUNNING | (eth0) |      | CONTAINER | 0         |
| web1    | RUNNING | (eth0) |      | CONTAINER | 0         |
| web2    | RUNNING | (eth0) |      | CONTAINER | 0         |

Installing Apache and changing the welcome screen

Our environment is ready. Next, install Apache (httpd) on each web container. You can do this without physically accessing them:

lxc exec web1 dnf install httpd
lxc exec web2 dnf install httpd

You will need more than Apache for any modern web server, but this is enough to run some tests.

Next, enable httpd, start it, and change the default welcome screen. This way, you know the server is responding when attempting to access by proxy.

Enable and start httpd:

lxc exec web1 systemctl enable httpd
lxc exec web1 systemctl start httpd
lxc exec web2 systemctl enable httpd
lxc exec web2 systemctl start httpd

Change the welcome screen. This screen comes up when no website configured, essentially a default page that loads. In Rocky Linux, this page is here /usr/share/httpd/noindex/index.html. Changing that file requires no direct access to the container. Just do the following:

lxc exec web1 vi /usr/share/httpd/noindex/index.html

search for the <h1> tag, which will show this:

<h1>HTTP Server <strong>Test Page</strong></h1>

Change that line to read:

<h1>SITE1 HTTP Server <strong>Test Page</strong></h1>

Repeat the process for web2. Going to these machines by IP in a browser will now return the correct welcome page for each. There is more to do with the web servers, but leave them and go to the proxy server for now.

Installing HAProxy on proxyha and LXD proxy configuration

It is simplistic to install HAProxy on the proxy container. Again, no need to access that container directly:

lxc exec proxyha dnf install haproxy

Next you want to configure haproxy to listen on port 80 and port 443 for the web services. Do this with the configure subcommand of lxc:

lxc config device add proxyha http proxy listen=tcp: connect=tcp:
lxc config device add proxyha https proxy listen=tcp: connect=tcp:

For our testing, you are only going to use port 80, or HTTP traffic, but this shows you how you configure the container to listen on the default web ports for HTTP and HTTPS. Using this command also ensures that restarting the proxyha container will maintain those listening ports.

The HAProxy configuration

You have already installed HAProxy on the container, but you have done nothing with the configuration. Before configuring, you need to do something to resolve your hosts. Normally you would use fully qualified domain names, but in this lab environment, you use IPs. To get some names associated with the machines, you are going to add some host file records to the proxyha container.

lxc exec proxyha vi /etc/hosts

Add the following records to the bottom of the file:   site1.testdomain.com     site1   site2.testdomain.com     site2

Which allows the proxyha container to resolve those names.

Edit the haproxy.cfg file. You are not using much of the original file. You need to make a backup of the file first by moving it to a different name:

lxc exec proxyha mv /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg.orig

Create a new configuration file:

lxc exec proxyha vi /etc/haproxy/haproxy.cfg

Note, the commenting out of HTTPS protocol lines for now. In a production environment, you will want to use a wildcard certificate that covers your web servers and enable HTTPS:

log /dev/log local0
log /dev/log local1 notice
chroot /var/lib/haproxy
stats socket /run/haproxy/admin.sock mode 660 level admin expose-fd listeners
stats timeout 30s
user haproxy
group haproxy

# For now, all https is remarked out
#ssl-default-bind-options no-sslv3 no-tlsv10 no-tlsv11 no-tls-tickets
#ssl-default-bind-ciphers EECDH+AESGCM:EDH+AESGCM
#tune.ssl.default-dh-param 2048

log global
mode http
option httplog
option dontlognull
option forwardfor
option http-server-close
timeout connect 5000
timeout client 50000
timeout server 50000
errorfile 400 /etc/haproxy/errors/400.http
errorfile 403 /etc/haproxy/errors/403.http
errorfile 408 /etc/haproxy/errors/408.http
errorfile 500 /etc/haproxy/errors/500.http
errorfile 502 /etc/haproxy/errors/502.http
errorfile 503 /etc/haproxy/errors/503.http
errorfile 504 /etc/haproxy/errors/504.http

# For now, all https is remarked out
# frontend www-https
# bind *:443 ssl crt /etc/letsencrypt/live/example.com/example.com.pem
# reqadd X-Forwarded-Proto:\ https

# acl host_web1 hdr(host) -i site1.testdomain.com
# acl host_web2 hdr(host) -i site2.testdomain.com

# use_backend subdomain1 if host_web1
# use_backend subdomain2 if host_web2

frontend http_frontend
bind *:80

acl web_host1 hdr(host) -i site1.testdomain.com
acl web_host2 hdr(host) -i site2.testdomain.com

use_backend subdomain1 if web_host1
use_backend subdomain2 if web_host2

backend subdomain1
# balance leastconn
  balance roundrobin
  http-request set-header X-Client-IP %[src]
# redirect scheme https if !{ ssl_fc }
     server site1 site1.testdomain.com:80 check
     server site2 web2.testdomain.com:80 check

backend subdomain2
# balance leastconn
  balance roundrobin
  http-request set-header X-Client-IP %[src]
# redirect scheme https if !{ ssl_fc }
     server site2 site2.testdomain.com:80 check
     server site1 site1.testdomain.com:80 check

A little explanation of what is going on above. You should see this in your testing, when you get to the testing section of this guide (below):

Definitions for site1 and site2 are in the "acl" section. Each site is in each other's round-robins for their respective back ends. What happens when you go to site1.testdomain.com in the test, the URL does not change, but the page inside will switch each time you access the page from the site1 to the site2 test pages. Same goes for site2.testdomain.com.

Doing this shows you the switch is occurring, but in reality, your website content will look exactly the same regardless of which server you are hitting. Note the document is showing how you might want to distribute traffic between multiple hosts. You can also use "leastcon" in the balance line, and instead of switching based on the previous hit, it will load the site with the least number of connections.

The error files

Some versions of HAProxy come with a standard set of web error files, however the version that comes from Rocky Linux (and the upstream vendor), does not have these files. You probably do want to create them, as they may help you troubleshoot any problems. These files go in the directory /etc/haproxy/errors which does not exist.

First, create that directory:

lxc exec proxyha mkdir /etc/haproxy/errors

Create each of these files in that directory. Note that you can do this with each filename from your LXD host with the command lxc exec proxyha vi /etc/haproxy/errors/filename.http, where "filename.http" references one of the file names below. In a production environment, your company may have more specific errors that they want to use:

File name 400.http:

HTTP/1.0 400 Bad request
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>400 Bad request</h1>
Your browser sent an invalid request.

File name 403.http:

HTTP/1.0 403 Forbidden
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>403 Forbidden</h1>
Request forbidden by administrative rules.

Filename 408.http:

HTTP/1.0 408 Request Time-out
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>408 Request Time-out</h1>
Your browser didn't send a complete request in time.

Filename 500.http:

HTTP/1.0 500 Internal Server Error
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>500 Internal Server Error</h1>
An internal server error occurred.

Filename 502.http:

HTTP/1.0 502 Bad Gateway
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>502 Bad Gateway</h1>
The server returned an invalid or incomplete response.

Filename 503.http:

HTTP/1.0 503 Service Unavailable
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>503 Service Unavailable</h1>
No server is available to handle this request.

Filename 504.http:

HTTP/1.0 504 Gateway Time-out
Cache-Control: no-cache
Connection: close
Content-Type: text/html

<html><body><h1>504 Gateway Time-out</h1>
The server didn't respond in time.

Running the proxy

Create a "run" directory for haproxy before starting the service:

lxc exec proxyha mkdir /run/haproxy

Next, enable the service and start it:

lxc exec proxyha systemctl enable haproxy
lxc exec proxyha systemctl start haproxy

If you get any errors, research the reason by using:

lxc exec proxyha systemctl status haproxy

If everything starts and runs without issue, you are ready to move on to testing.

Testing the proxy

As with the hosts (/etc/hosts) setup used so that our proxyha container can resolve the web servers, and since our lab environment does not have a local DNS server running, set the IP values on our local machine for each the websites, to correspond to our haproxy container.

To do this, change your /etc/hosts file on your local machine. Consider this method of domain resolution a "poor man's DNS."

sudo vi /etc/hosts

Add these two lines:   site1.testdomain.com     site1   site2.testdomain.com     site2

If you ping either site1 or site2 on your local machine now, you will get a response from proxyha:

PING site1.testdomain.com ( 56(84) bytes of data.
64 bytes from site1.testdomain.com ( icmp_seq=1 ttl=64 time=0.427 ms
64 bytes from site1.testdomain.com ( icmp_seq=2 ttl=64 time=0.430 ms

Open your web browser and type site1.testdomain.com (or site2.testdomain.com) as the URL in the address bar. You will get a response back from one of the two test pages and if you load the page again, you will get the next server's test page. Note that the URL does not change, but the returned page will change alternately between servers.

screenshot of web1 being loaded and showing the second server test message


Even though our configuration file is set up correctly for logging, you need two things: First, a directory in /var/lib/haproxy/ called "dev":

lxc exec proxyha mkdir /var/lib/haproxy/dev

Next, create a system process for rsyslogd to grab instances from the socket (/var/lib/haproxy/dev/log in this case) and store those in /var/log/haproxy.log:

lxc exec proxyha vi /etc/rsyslog.d/99-haproxy.conf

Add the following contents to that file:

$AddUnixListenSocket /var/lib/haproxy/dev/log

# Send HAProxy messages to a dedicated logfile
:programname, startswith, "haproxy" {

Save the file and exit, and restart rsyslog:

lxc exec proxyha systemctl restart rsyslog

To populate that log file with something right away, restart haproxy again:

lxc exec proxyha systemctl restart haproxy

View the log file created:

lxc exec proxyha more /var/log/haproxy.log

Which will show you something like this:

Sep 25 23:18:02 proxyha haproxy[4602]: Proxy http_frontend started.
Sep 25 23:18:02 proxyha haproxy[4602]: Proxy http_frontend started.
Sep 25 23:18:02 proxyha haproxy[4602]: Proxy subdomain1 started.
Sep 25 23:18:02 proxyha haproxy[4602]: Proxy subdomain1 started.
Sep 25 23:18:02 proxyha haproxy[4602]: Proxy subdomain2 started.
Sep 25 23:18:02 proxyha haproxy[4602]: Proxy subdomain2 started.


HAProxy is a powerful proxy engine used for many things. It is a high-performance, open source load balancer and reverse proxy for TCP and HTTP applications. This document demonstrated how to use load balancing of two web server instances.

Using it for other applications, including databases, is also possible. It works within LXD containers, and on standalone servers.

There are plenty of uses not covered in this document. Check out the official manual for HAProxy here.

Author: Steven Spencer

Contributors: Ezequiel Bruni, Antoine Le Morvan, Ganna Zhyrnova