Automating with Ansible

Michael DeHaan (Creator)

Ansible Background

The Ansible Story...

• Red Hat: Cobbler/Func
• Other tools...
• Hosted deployments...
• Lightblub...

What does Ansible do?

• Application deployment
• Configuration management
• Cloud provisioning
• Ad-hoc task execution
• Multi-tier orchestration & continuous deployment

Philosophy

• Agentless
  • ssh used as a connection tunnel to push and execute scripts
• Automation shouldn't be your day job
• Keep things simple / auditable
• Batteries included (~235 modules in core)

Some statistics and info

• Open source
• ~2 years old
• #5 most contributions on GitHub
• Top 10 python project on GitHub for stars & forks
• New contributor added every ~1.3 days

Use case examples

• edX.org and Fedora Infrastructure have OSS'ed their Ansible content
• Gawker - continuously deploying 5-10 times an hour with rolling updates
• MapR - product installer
• Rackspace orchestrates production OpenStack upgrades with Ansible

Examples

Inventory

• define groups of hosts
• execute commands against a group

    ansible [group] [command]

Playbooks

    ansible-playbook [playbook file]

Task Files

• jinja2 for templates

Ansible Galaxy

• (galaxy.ansible.com)[galaxy.ansible.com]
• community collection of defined roles
• backed by GitHub

    ansible-galaxy install username.rolename

Ansible Vault

• allows storing encrypted data in playbooks
• encrypt secrets and put them in version control
• de-encrypt in memory when needed

Rolling Updates are simple

Extending Ansible with Python

Modules

• can implement in any language that can emit JSON
• or even return key=value and write one in bash
• core modules are all Python

Plugins

• lookup plugins / enumerations
• connection plugins
  • could implement a protocol other than ssh
• action plugins
• filter plugins (extend Jinja2)
• inventory
  • examples: OpenStack, AWS, Rackspace
  • any executable program that can emit JSON
  • core/examples plugins are all Python

API/REST API

• python API for runner -- not the main purpose of the app
• REST API is part of Tower, fully discoverable, annotated, and awesome
• based on Django-REST-Framework

Requirements

• Python 2.6+ on server, 2.4+ on nodes
• python 2 only now, for reasons

Modules used Heavily

• multiprocessing
• native OpenSSH and paramiko
• PyYAML, json
• Jinja2
• subprocess