Load Balancing on DreamCompute with HAProxy


Load balancers are designed to host multiple applications behind the same IP address to save cost and to allow applications to horizontally scale out instances running on multiple virtual machines. One of the most popular open source load balancers is HAProxy. It is well supported, featureful, high performing, and widely available.

In this tutorial, we will be creating a virtual machine inside of DreamCompute that acts as a load balancer with HAProxy. We’ll be using Ubuntu 14.04 as the base operating system image for our load balancer.

Prepping Your Virtual Machine

Create a virtual machine in DreamCompute using your favorite method, a subsonic flavor should be enough. Make sure to assign an SSH key and allow access to HTTP (port 80) and SSH (port 22) in the Access & Security group. Associate a public IPv4 “floating” IP address to this machine.

  1. Click the More dropdown tab on in the Actions column of your instance list.
  1. Click Associate Floating IP.


    This is only necessary if you have private networking enabled

    The following dialog box appears:

  1. Allocate a floating IP with the port associated with the private IP address of your load balancer virtual machine, and then click the Associate button.

    • Once you’ve associated the IP address, give DreamCompute a few seconds to complete the association, and then you should be able to SSH into your instance via its IPv4 address.


    This is only necessary if you have private networking enabled


4. SSH into your instance via its IPv4 address (the default user is ubuntu, you can’t login as root).

Now, we’re ready to get HAProxy installed and configured.

Install HAProxy

Updating Packages

Before installing HAProxy, its important to be sure that your operating system is up to date with the latest security fixes and packages available from Ubuntu. While logged in as ubuntu, simply run:

[user@server]$ sudo apt-get upgrade

Follow the prompts, and allow apt to update your system.

Installing HAProxy

[user@server]$ sudo apt-get install haproxy

Configure HAProxy

For the purposes of our tutorial, we’re going to assume that you have two applications that you would like to deploy behind HAProxy. The first application will be on a single virtual machine and the second application will be horizontally scaled across two virtual machines.

When we are complete with our configuration, our deployment will look something like this:

    |          +-------------+   +---------------+
    +--------->|             |--------------->|      app1     |
               |   HAProxy   |                +---------------+
    +--------->|             |---+
    |          +-------------+   | +---------------+
app2.domain.io                   +----------->|    app2-a     |
                                 |            +---------------+
                                 | +---------------+
                                 +----------->|    app2-b     |

To support this deployment, edit your /etc/haproxy/haproxy.cfg:

log /dev/log    local0
log /dev/log    local1 notice
chroot /var/lib/haproxy
maxconn 4096
user haproxy
group haproxy

log    global
mode    http
option    httplog
option    dontlognull
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

option forwardfor
option http-server-close
stats enable
stats auth admin:stats
stats uri /haproxyStats

frontend http-in
bind \*:80
option forwardfor

# Define hosts
acl host_app_one hdr(host) -i app1.domain.io
acl host_app_two hdr(host) -i app2.domain.io

# Figure out which one to use
use_backend app_one_cluster if host_app_one
use_backend app_two_cluster if host_app_two

backend app_one_cluster
balance leastconn
option httpclose
server node1 cookie A check

backend app_two_cluster
balance leastconn
option httpclose
server node1 cookie A check
server node2 cookie A check

Next, you’ll need to activate HAProxy by setting ENABLED to 1 in /etc/default/haproxy. Finally, you can run HAProxy:

[user@server]$ sudo service haproxy restart

Assuming that you have configured your DNS to point app1.domain.io and app2.domain.io to your public IP address, you should be able to access your applications via HAProxy. Congratulations!

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Article last updated PST.