Ansible

IT Automation Tool

Configure - Deploy - Orchestrate

Ad-hoc Commands

Given an inventory defining 'webservers'

ansible webservers -m user -a "name=marsel state=present"

hosts

module

arguments

ansible webservers -m user -a "name=moriarty state=absent"

Playbook

Describe a policy or set of steps to apply to

groups of hosts

---
- hosts: webservers
   remote_user: config
   sudo: true
   tasks:
     - name: Add Pythonista
       user: name=marsel state=present
     - name: Remove bad guy
       user: name=moriarty state=absent

Nginx

Install Nginx

- name: Install nginx

apt: pkg=nginx state=present update-cache=yes

NGINX

Add repo for latest stable nginx package

- name: Install nginx key

apt_key: url=http://nginx.org/keys/nginx_signing.key state=present

- name: Add repo for nginx

apt_repository: repo='deb http://nginx.org/packages/debian/ wheezy nginx'

- name: Add src repo for nginx

apt_repository: repo='deb-src http://nginx.org/packages/debian/ wheezy nginx'

Nginx Role

Reusable container for related actions

In roles/nginx/tasks/main.yml:

---
- name: Install nginx key
  apt_key: url=http://nginx.org/keys/nginx_signing.key state=present

- name: Add repo for nginx
  apt_repository: repo='deb http://nginx.org/packages/debian/ wheezy nginx'

- name: Add src repo for nginx
  apt_repository: repo='deb-src http://nginx.org/packages/debian/ wheezy nginx'

- name: Install nginx
  apt: pkg=nginx state=present update-cache=yes

NGINX ROLE (cont)

Apply the role in a playbook

---
- hosts: webservers
  sudo: true
  roles:
    - nginx

Nginx Config File

In roles/nginx/tasks/main.yml

<snip>...- name: Install main config file
  copy: src=nginx.conf dest=/etc/nginx/nginx.conf
    owner=root group=root mode=0644  notify:    - Restart nginx # define handler in roles/nginx/handlers/main.yml or below

In roles/nginx/templates/nginx.conf

server {
    listen 80;
    server_name example.com;

    location /static/ {
        alias {{ website_static_dir }};
    }
    # ...
}

In roles/nginx/defaults/main.yml

---
website_static_dir: /whatever/path/you/like

Variables

In inventory file (we'll see these in a moment)
In group/host var files
In playbooks
In roles (defaults)
In roles (vars)
On command line (-e)

Inventory File

production

[dbservers]
db.mydomain.com

[app1-servers]
app1-[1-4].mydomain.com

[app2-servers]
wizard.mydomain.com

[redis-servers:children]
dbservers

[appservers:children]
app1-serversapp2-servers

[all:vars]
env=production

[appservers:vars]
git_branch=master

Runtime!

Run myapp playbook against the production inventory

ansible-playbook -i production myapp.yml

limited to a group (-l)

ansible-playbook -i production -l appservers myapp.yml

Execution model:

separate ssh connection for each module invocation
parallelized across machines

Environments (RYO)

In inventory file:

[all:vars]
env=production

In playbook:

---
- hosts: all
  remote_user: config
  vars_files:
    - "vars/common.yml"
    - "vars/{{ env }}.yml"
  roles:
    - webserver
    - node

Ansible - Key Benefits

Shallow learning curve

Minimal number of abstractions

Data, not code

Predictable execution model

Good documentation

Few moments of hair-tearing frustration