How to use Ansible to configure a reverse proxy 

What is a load balancer? A load balancer is an efficient way to distribute the network traffic among various backend servers. It is also known as a server farm or server pool. It distributes client requests or network load to target web servers. Load balancers work on the round-robin concept, which ensures high reliability and availability.

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One scenario

You have a web server that can manage 100 clients at a time. Suddenly the requests to that particular server increase by 100 percent. It's likely that the website will crash or be terminated. To avoid this situation, set up a target web server. In this scenario, the client never goes to the target web server. Instead, their request goes to the master server, and the master server sends the request to the target web server. When the target web server replies to the master web server, which is known as a reverse proxy.

[ You might also like: Turn a Kubernetes deployment into a Knative service ]

Using HAProxy as a proxy

The port on the main web server is called the frontend port. HAProxy is an HTTP load balancer that can be configured as a reverse proxy. Here we'll look at how I configured HAProxy by using an Ansible playbook.

Check the system where you need to configure HAProxy

HAProxy is not installed on this system. You can confirm that with the following command:

rpm -q haproxy

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Steps to configure HAProxy

Step 1 - Install HAProxy

To install HAProxy, you have to use a package module where you give the name of the service you want to install:

    - name: "Configure Load balancer"
      package:
        name: haproxy

Step 2 - Copy the configuration file for the reverse proxy

Copy the configuration file so that you can modify it:

cp /etc/haproxy/haproxy.cfg  /root/ws1/haproxy.cfg

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Step 3 - Change frontend port and assign backend IPs

By default, the frontend is bound to port 5000. I changed the port number to 8080. I also applied a for loop to configure the backend IP. Now you can launch as many web servers as you need, and there is no need to manually configure the IP inside the /etc/httpd/httpd.conf. It will automatically fetch the IP from inventory.

backend app
   balance     roundrobin
{%  for i in groups ["web"] %}
   server  app1{{ loop.index }} {{ i}}:80 check
{% endfor %}

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Step 4 - Copy haproxy.cfg to the managed node

Using template mode, copy the config file for HAProxy from the controller node to the managed node:

    - template:
        dest: "/etc/haproxy/haproxy.cfg"
        src: "/root/ws1/haproxy.cfg"

Step 5 - Start the service

Use the service module to start the HAProxy service:

    - service:
        name: "haproxy"
        state: restarted

Check the system where you need to install httpd webserver

For testing the HAProxy configuration, you will also configure httpd on your target node with the help of Ansible. To check that you don't already have httpd on your system, use the following command:

 rpm -q httpd

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Step 1 - Install httpd

The package module is used to install httpd on the managed node:

    - name: "HTTPD CONFIGURE"
      package:
        name: httpd

Step 2 - Copy the webpage

The template module is used to copy your webpage from the source to the destination:

    - template:
        dest: "/var/www/html/index.html"
        src: "/root/ws1/haproxy.html"

Step 3 - Start the service

The service module is used to start the httpd service:

    - service:
        name: "haproxy"
        state: restarted

Complete the playbook to configure the reverse proxy

In this playbook, you have two different hosts with two different groups. One group is for the web server, and another is for the load balancer:

---
- hosts: web
  tasks:
    - name: "HTTPD CONFIGURE"
      package:
        name: httpd
    - template:
        dest: "/var/www/html/index.html"
        src: "/root/ws1/haproxy.html"
    - service:
        name: "httpd"
        state: restarted
- hosts: lb
  tasks:
    - name: "Configure Load balancer"
      package:
        name: haproxy
    - template:
        dest: "/etc/haproxy/haproxy.cfg"
        src: "/root/ws1/haproxy.cfg"
    - service:
        name: "haproxy"
        state: restarted

Run the playbook

ansible-playbook haproxy.yml

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Output

The playbook runs successfully, and the two target web servers can be accessed by the main web server using a load balancer.

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Conclusion

The load balancer and reverse proxy have now been configured by Ansible. You can add a layer of protection and availability to your web services by adding HAProxy to your infrastructure. Be sure to check out the documentation for your specific target to learn more.