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LAMP Stack + HAProxy: Example Playbooks
This example is an extension of the simple LAMP deployment. Here we'll deploy a web server with an HAProxy load balancer in front. This set of playbooks also have the capability to dynamically add and remove web server nodes from the deployment. It also includes examples to do a rolling update of a stack without affecting the service.
###Setup Entire Site. First we configure the entire stack by listing our hosts in the 'hosts' inventory file, grouped by their purpose:
[webservers]
web3
web2
[dbservers]
web3
[lbservers]
lbserver
After which we execute the following command to deploy the site:
ansible-playbook -i hosts site.yml
The deployment can be verified by accessing the IP address of your load balnacer host in a web browser: http://:8888. Reloading the page should have you hit different webservers.
###Remove a Node
Removal of a node from the cluster is as simple as executing the following command:
ansible-playbook -i hosts playbooks/remove_webservers.yml --limit=web2
###Add a Node
Adding a node to the cluster can be done by executing the following command:
ansible-playbook -i hosts playbooks/add_webservers.yml --limit=web2
###Rolling Update
Rolling updates are the preferred way to update the web server software or deployed application, since the load balancer can be dynamically configured to take the hosts to be updated out of the pool. This will keep the service running on other servers so that the users are not interrupted.
In this example the hosts are updated in serial fashion, which means that only one server will be updated at one time. If you have a lot of web server hosts, this behaviour can be changed by setting the 'serial' keyword in webservers.yml file.
Once the code has been updated in the source repository for your application which can be defined in the group_vars/all file, execute the following command:
ansible-playbook -i hosts playbooks/rolling_update.yml