Hands on With Ansible

Hands on With Ansible

Playbook

Design plan to orchestrate an ordered series of plays against a particular inventory of hosts

Play

Playbook execution:

ansible-playbook

An ordered set of tasks for a set of hosts

ansible-playbook -i preprod -f 20 deploy-website.yaml

ansible-playbook -i prod -f 100 deploy-website.yaml

• connects plays to an inventory
• sets global variables
• sets number of forks
• controls output (verbosity, logging)
• applies limits to available inventory
• etc...

Play Details

Play Purpose

• Tasks within a play are executed in parallel across the hosts in order of the tasks
• Hosts with errors are removed from the list, execution moves on until all tasks complete, or all hosts have failed
• plays are executed in order to form a playbook

• define what hosts a set of tasks should run on
• define which communication medium to use
• define variable values used in the tasks
• additional controls over the tasks

- name: Set up nginx

hosts: webservers

connection: ssh

vars:

- cachedir: /opt/cache

tasks:

- name: add cache dir

file: path={{ cachedir }} state=directory

- name: install nginx

yum: name=nginx state=present

An Introduction to Ansible

A task execution orchestration engine.

Written in python, fed with yaml

Inventory and Hosts

Inventory is a list of and information about the hosts available to run plays on.

Like....

Requires

Task

Inventory Details

Hosts Details

Pssh -- without having to scour output for errors or script in idempotence

Fabric -- without having to write python

Chef -- without having to bootstrap or write ruby

Salt -- without minions and masters

Puppet -- without master, manifests, certs...

Mcollective -- without pre-established command conifguration or infrastructure

• SSH
• Python
• (well not really python)
• (well not really even a machine)

• Sub-selection of machines available in the inventory
• Can select by group, or specific name
• Supports patterns

• Can create groups of hosts
• Can create groups of groups
• Can define variable data
• per host
• per group
• per inventory
• Can be a file, directory, or executable

A task is a discrete action that is a declaration about the state of a system

Bits of code copied to remote system and executed with arguments

Task Details

• Code comes from:
• existing modules
• custom modules
• user defined commands / shell scripts
• raw ssh commands
• Idempotent capable
• Can use variable data
• Are executed in order to form a play

- name: add cache dir

file: path=/opt/cache state=directory

- name: install nginx

yum: name=nginx state=present

- name: start nginx

service: name=nginx enabled=yes state=started

Example tasks

• Directory should exist
• Package should be installed
• Service should be running
• Instance should exist