Recently I’m playing a lot with Ansible. The goal is to deploy a large Django stack to production with all kinds of high availability stuff. The components in this stack: CentOS, Postgres, Nginx with uWSGI and Django, RabbitMQ, several celery workers with supervisord. As a subgoal it would be nice to run the complete production environment also from inside a vagrant VM; but then with all components on a single host.
Deploying a Django stack on CentOS 6.5
A small, but complete, prototype can be found here. It’s based on a fork of this
You can try this complete Django setup, when you already have Ansible, VirtualBox and Vagrant installed by running:
git clone git@github.com:acidjunk/ansible-centos-django-stack.git
cd ansible-centos-django-stack
vagrant up
open "http://192.168.33.10"
Working on your Ansible playbooks
I use Sublime for editing. Because i’m used to PyCharms autosave I installed the Sublime’s autosave plugin for that. Sublime has excellent YAML syntax highlighting out of the box.
Some handy commands
As a quick reminder for myself I list some commands here that I used a lot while working on the Ansible scripts.
Run commands on your cluster
When you have an inventory file with the group all:
ansible all -m command -a "uptime"
Show all ansible setup variabels inside your cluster
It can be quite handy to see the ansible variabeles/environment stuff on a server or VM:
ansible all -i hosts -m setup
Quircks with handlers
Keep in mind that ansible only calls the handlers upon successful completion of the completion of the playbook. When a task fails on a host, handlers which were previously notified will not be run on that host. This can lead to cases where an unrelated failure can leave a host in an unexpected state. For example, a task could update a configuration file and notify a handler to restart some service. If a task later on in the same play fails, the service will not be restarted despite the configuration change. You could circumvent that by providing --force-handlers on the command line. If it happened while working on a playbook you can trigger that tasks inside the handler clause manually by running:
ansible all -m service -a "name=nginx state=restarted"
Start clean
When you need to start clean again you can do this:
vagrant destroy --force
vagrant up
Other handy adhoc stuff
Install a package on CentOS hosts:
ansible all -i hosts -m yum "name=nginx state=present" -s
Deinstall it again:
ansible all -i hosts -m yum "name=nginx state=absent" -s
Add a firewalld rule, activate it now and after the next boot make it permanent:
- name: insert firewalld
firewalld: port=/tcp permanent=true state=enabled immediate=yes