Ansible - A 'crowd' introduction

SOFTWARE CRAFTSMANSHIP TOLEDO
A “crowd” introduction

Software Craftsmanship Toledo
• Pasión por la ingeniería software y el desarrollo de
software en la comunidad de Castilla-La Mancha.
• Clara vocación por aprender, fomentar y compartir las
metodologías ágiles en la región.
• Grupo totalmente abierto: http://www.meetup.com/es/
Software-Craftsmanship-Toledo-ES
• Miembros profesionales y/o apasionados del desarrollo
software.
• Tenemos un canal de Slack… Apúntante!

Meet me
• Manuel de la Peña
• @mdelapenya
• Support >
Engineering >
Testing > IT … at
Liferay, Inc.
• DEVOPS?

This was my ﬁrst day
at work…

moss@itcrowd1:~$ ssh root@server1
password:
root@server1:~$ apt-get update
root@server1:~$ apt-get install apache2
root@server1:~$ apt-get install htop
root@server1:~$ vi /etc/fstab
root@server1:~$ mount /mnt/devops
root@server1:~$ exit
moss@itcrowd1:~$
server2, server3, server4, server5 … server30
buzz, scar, ariel, mickey, mulan … goofie
ares, odin, hera, atenea, loki … melkart
logan, natasha, clark, peter, bruceW … bruceB
And all these following servers too:

Why don’t you
automate THIS?
Why don’t you
automate THIS?

AUTOMATION FOR EVERYONE
Deploy apps. Manage systems. Crush complexity.
Ansible helps you build a strong foundation for DevOps.

How it works
• It uses a very simple language (YAML, in the form
of Ansible Playbooks)
• Plain English!
• By default manages machines over the SSH
protocol.
• It uses no agents and no additional custom
security infrastructure.

SSH Keys
• SSH keys with ssh-agent are
recommended.
• Root logins are not required, you can
login as any user, and then su or
sudo to any user.

Installation
• No database, and no running daemons!
• Install it on only one machine (a laptop?) as central
point.
• It does not leave software installed or running on
remote machines —> upgrades super easy :D

Control Machine
• “Any” machine with Python 2.6 or 2.7 installed.
• This includes Red Hat, Debian, CentOS, OS X, any
of the BSDs, and so on.
• Windows isn’t supported for the control machine.

Managed Nodes
• You need a way to communicate, normally ssh.
• SSH uses sftp. If not available, switch to scp.
• Python 2.4 or later. (If Python < 2.5 also need
python-simplejson)

Remote connection
• Native OpenSSH for remote communication when
possible.
• If OpenSSH is too old in control machine
(Enterprise Linux 6 OS)—> Fallback to Paramiko:
a Python implementation.
• SSH keys are encouraged but password
authentication can also be used (--ask-pass).

sudo

Inventory
• What machines/hosts you are
managing using a very simple INI ﬁle.
• Managed machines/hosts in groups of
your own choosing.
• Deﬁne variables by scope.

Inventory variables
• Host variables
• Group variables
• Advanced variables

Inventory: Host vars

Inventory: Group vars

Inventory: Advanced vars
Affects to groups
Speciﬁc group of servers
Arbitrary criterium

Host matching: Patterns
• all
• *
• 192.168.1.*, *.example.com
• OR —> webservers:dbservers
• AND —> webservers:&staging

Host matching: Patterns
• Exclusions —> webservers:!phoenix
• Combinations —>
webservers:dbservers:&staging:!phoenix
• Host selection —> webservers[0],
webservers[0:1], webservers[1:]
• Regexp —> ~(web|db).*example.com

Host matching: Limit

Ansible Modules

Ansible modules
• copy
• ﬁle
• yum
• user
• service
• git
• apache
• apt
• azure
• bower
• cron
• mysql_db
• npm
• puppet
• django
• ec2
And many more!

Modules

git module

Ad-hoc commands
Fork 10 parallel threads

Ansible Variables

Variables
• Should be letters, numbers, and
underscores.
• Variables should always start with a letter.
• YAML also supports dictionaries which
map keys to values.
• There are reserved Python-related
keywords.

Variables
• Defined in Inventory.
• Defined in Playbooks.
• Defined in includes.
• Defined in Roles.

Variables: Jinja2
• Jinja2 —> Template system
• How to use a variable? —>
{{ variable_name }}
• Safer —> “{{ variable_name }}”

Variables: register
• Run a command and save its result into a
variable.

Variables: external
• Private information?? Hide them in
variables!
• In a task list —>
vars_ﬁles: /opt/private/my_vars.yml

Variables: command
• Directly pass variables to command line:
• --extra-vars “version=1.3 my_var=foo”
• --extra-vars
‘{"pacman":"mrs","ghosts":
["inky","pinky","clyde","sue"]}'
• --extra-vars "@some_ﬁle.json"

Variables: precedence
• role defaults < inventory vars < inventory
group_vars < inventory host_vars <
playbook group_vars < playbook host_vars
< host facts < registered vars < set_facts <
play vars < play vars_prompt < play
vars_ﬁles < role and include vars < block
vars (only for tasks in block) < task vars
(only for the task) < extra vars

Ansible Playbooks

Playbooks
• Orchestrate steps/tasks of any
manual ordered process.
• Executed a/synchronously.
• YAML format.
• Minimum syntax —> not a language
but a model.

Playbooks: Tasks
• Should have a name: included in
output and readable by humans.
• Accept variables:
template: src=someﬁle.j2 dest=/etc/
httpd/conf.d/{{ vhost }}

Playbooks: Tasks lists
• Each play contains a list of tasks.
• Tasks are executed in order, one at a time,
against all machines matched by the host
pattern.
• Important! Same task directives to all hosts.
• Tasks goal? execute a module, with arguments.
• Modules are idempotent.

Playbooks:Hosts&Users
• For each play, choose machines to
target and remote user to complete
the steps/tasks as.
• Deﬁne remote users per task.
• Use sudo on a particular task
instead of the whole play.

Playbooks: Handlers
• Playbooks respond to change.
• Can notify at the end of each block of
tasks.
• Triggered only once, even if notiﬁed by
multiple tasks.
• Best used to restart services and trigger
reboots.

ansible-playbook playbook.yml

Ansible Roles

Roles
• Reuse playbooks.
• Combine ﬁles to form clean,
reusable abstractions.
• Grouping allows easy sharing of
roles with other users.
• include directive —> Include ﬁles.

Roles: structure
• Automatically loads certain
vars_files, tasks, and handlers based
on a known file structure.
• Where is the magic? Improvements
to search paths for referenced files.

‘common’ role structure
‘webservers’ role structure

Roles: main.yml
• roles/x/tasks/main.yml —> Add tasks to the
play.
• roles/x/handlers/main.yml —> Add handlers
to the play.
• roles/x/vars/main.yml —> Add variables to
the play.
• roles/x/meta/main.yml —>, Add roles as
dependency (1.3 and later).

Roles: paths
• Any copy, script, template or include
tasks (in the role) can reference ﬁles
in roles/x/{ﬁles,templates,tasks}/
without having to path them
relatively or absolutely

Roles:parameters

Roles:defaults
• Add a defaults/main.yml ﬁle in your role
directory.
• Set default variables for included or
dependent roles.
• Lowest priority of any variables
available, so they are easily overridden,
including inventory variables!

Roles:dependencies
• A list of roles and parameters to
insert and execute before the
speciﬁed role.
• Automatically pull in other roles.
• meta/main.yml within the role.
• Executed recursively.

Roles:dependencies

https://galaxy.ansible.com
Where can I ﬁnd
ready to use Roles?
Ansible Galaxy

https://github.com/ansible/ansible-
examples/tree/master/lamp_haproxy
Ansible Real Example (1)

Ansible Real Example (2):
LELK

LELK
• Liferay Portal
• Elasticsearch
• Logstash
• Kibana
• generate
• index
• process
• display

Liferay + Tomcat Liferay + Tomcat
Liferay + Tomcat Liferay + Tomcat
LELK

LELK: Roles
• Server —> ElasticSearch +
Logstash + Kibana
• Clients -> Liferay Deployment

Role: liferay-deployment
• Ansible Role: liferay-users (add liferay
user with UID=1000)
• Ansible Role: liferay-os-tools (vim, htop,
curl, rsync, tree, zip)
• Ansible Role: liferay-dev-tools (java)
• Ansible Role: liferay-logstash-forwarder

Role: logstash-forwarder
• Copy SSL certiﬁcate
• Copy init.d startup
• Copy logstash-forwarder conﬁguration
logstash-forwarder.conf.j2

Role: logstash-forwarder

Role: elastic-search-server
• Install Logstash
• Install ElasticSearch
• Install Kibana
• Install Nginx

Role: elastic-search-server
logstash-input.conf.j2
logstash-output.conf.j2

LELK Next??
• Applied logstash-forwarder role to
more machines, setting log_paths
and tags variable to the desired ﬁle.
• Add more client types —> Apache
Server, Firewall

With tests!!!

Recap
• Server are hard to maintain up-to-date
• Automation over infrastructure
• Infrastructure as code
• Ansible Inventory & Modules
• Variables & template system
• Playbooks & Roles & Galaxy

What about using GIT
to version
Inventory and Roles??

Ansible - A 'crowd' introduction

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