ansible best practices: the essentials best...ansible best practices: the essentials 2 the ansible...

Jake JacksonPartner Engineer

@thedoubl3j everywhere (twitter, freenode, github etc)

ANSIBLE BEST PRACTICES: THE ESSENTIALS

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THE ANSIBLE WAY

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COMPLEXITY KILLS PRODUCTIVITY

That's not just a marketing slogan. We really mean it and believe that. We strive to reduce complexity in how we've designed Ansible tools and encourage you to do the same. Strive for simplification in what you automate.

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OPTIMIZE FOR READABILITY

If done properly, it can be the documentation of your workflow automation.

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THINK DECLARATIVELY

Ansible is a desired state engine by design. If you're trying to "write code" in your plays and roles, you're setting yourself up for failure. Our YAML-based playbooks were never meant to be for programming.

Treat your Ansible content like code

● Version control your Ansible content● Start as simple as possible and iterate

○ Start with a basic playbook and static inventory○ Refactor and modularize later

WORKFLOW

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Do It with Style

● Create a style guide for developers● Consistency in:

○ Tagging○ Whitespace○ Naming of Tasks, Plays, Variables, and Roles○ Directory Layouts

● Enforce the style● Use ansible-lint, a command-line static analysis tool that checks

for behaviour that could be improved.

WORKFLOW

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basic-project

├── inventory│ ├── group_vars│ │ └── web.yml│ ├── host_vars│ │ └── db1.yml│ └── hosts└── site.yml

PROJECT LAYOUTS: BASIC

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myapp

├── roles│ ├── myapp│ │ ├── tasks│ │ │ └── main.yml│ │ └── ...│ ├── nginx│ │ └── ...│ └── proxy│ └── ...└── site.yml

PROJECT LAYOUTS: ORGANIZATIONAL ROLES

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myapp

├── config.yml├── provision.yml├── roles│ └── requirements.yml└── site.yml

PROJECT LAYOUTS: SHARED ROLES

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Give inventory nodes human-meaningful

10.1.2.75

10.1.5.45

10.1.4.5

10.1.0.40

w14301.example.com

w17802.example.com

w19203.example.com

w19304.example.com

INVENTORY

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db1 ansible_host=10.1.2.75




web1 ansible_host=w14301.example.com




Group hosts for easier inventory selection and less conditional tasks -- the more groups the better.

WHAT

[db]db[1:4]

[web]web[1:4]

db1 = db, east, dev

INVENTORY

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WHEN

[dev]db1web1

[test]db3web3

[prod]db2web2db4web4

WHERE

[east]db1web1db3web3

[west]db2web2db4web4

Use a single source of truth if you have it -- even if you have multiple sources, Ansible can unify them.

● Stay in sync automatically● Reduce human error

INVENTORY

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PUBLIC / PRIVATECLOUD

CMDB

Proper variable naming can make plays more readable and avoid variable name conflicts

● Use descriptive, unique human-meaningful variable names● Prefix role variables with its “owner” such as a role name or

package

apache_max_keepalive: 25apache_port: 80tomcat_port: 8080

VARIABLES

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Make the most of variables

● Find the appropriate place for your variables based on what, where and when they are set or modified

● Separate logic (tasks) from variables to reduce repetitive patterns and provided added flexibility.

VARIABLES

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- name: Clone student lesson app for a user host: nodes tasks: - name: Create ssh dir file: state: directory path: /home/{{ username }}/.ssh

- name: Set Deployment Key copy: src: files/deploy_key dest: /home/{{ username }}/.ssh/id_rsa

- name: Clone repo git: accept_hostkey: yes clone: yes dest: /home/{{ username }}/exampleapp key_file: /home/{{ username }}/.ssh/id_rsa repo: [email protected]:example/apprepo.git

SEPARATE LOGIC FROM VARIABLES

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EXHIBIT A

● Embedded parameter values and repetitive home directory value pattern in multiple places

● Works but could be more clearer and setup to be more flexible and maintainable

- name: Clone student lesson app for a user host: nodes vars: user_home_dir: /home/{{ username }} user_ssh_dir: "{{ user_home_dir }}/.ssh" deploy_key: "{{ user_ssh_dir }}/id_rsa" app_dir: "{{ user_home_dir }}/exampleapp" tasks: - name: Create ssh dir file: state: directory path: "{{ user_ssh_dir }}"

- name: Set Deployment Key copy: src: files/deploy_key dest: "{{ deploy_key }}"

- name: Clone repo git: dest: "{{ app_dir }}" key_file: "{{ deploy_key }}" repo: [email protected]:example/exampleapp.git accept_hostkey: yes clone: yes

SEPARATE LOGIC FROM VARIABLES

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EXHIBIT B

● Parameters values are set thru values away from the task and can be overridden.

● Human meaningful variables “document” what’s getting plugged into a task parameter

● More easily refactored into a role

Use native YAML syntax to maximize the readability of your plays

● Vertical reading is easier● Supports complex parameter values● Works better with editor syntax highlighting in editors

PLAYS & TASKS

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- name: install telegraf

yum: name=telegraf-{{ telegraf_version }} state=present update_cache=yes disable_gpg_check=yes enablerepo=telegraf

notify: restart telegraf

- name: configure telegraf

template: src=telegraf.conf.j2 dest=/etc/telegraf/telegraf.conf

- name: start telegraf

service: name=telegraf state=started enabled=yes

NO!

USE NATIVE YAML SYNTAX

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- name: install telegraf yum: > name=telegraf-{{ telegraf_version }} state=present update_cache=yes disable_gpg_check=yes enablerepo=telegraf notify: restart telegraf

- name: configure telegraf template: src=telegraf.conf.j2 dest=/etc/telegraf/telegraf.conf

- name: start telegraf service: name=telegraf state=started enabled=yes

Better, but no


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Yes!

- name: install telegraf yum: name: telegraf-{{ telegraf_version }} state: present update_cache: yes disable_gpg_check: yes enablerepo: telegraf notify: restart telegraf

- name: configure telegraf template: src: telegraf.conf.j2 dest: /etc/telegraf/telegraf.conf notify: restart telegraf

- name: start telegraf service: name: telegraf state: started enabled: yes


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Names improve readability and user feedback

● Give all your playbooks, tasks and blocks brief, reasonably unique and human-meaningful names

PLAYS & TASKS

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- hosts: web tasks: - yum: name: httpd state: latest

- service: name: httpd state: started enabled: yes

PLAYS & TASKS

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PLAY [web] ********************************

TASK [setup] ********************************ok: [web1]

TASK [yum] ********************************ok: [web1]

TASK [service] ********************************ok: [web1]

EXHIBIT A

- hosts: web name: install and start apache tasks: - name: install apache packages yum: name: httpd state: latest

- name: start apache service service: name: httpd state: started enabled: yes

PLAYS & TASKS

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PLAY [install and start apache] ********************************

TASK [setup] ********************************ok: [web1]

TASK [install apache packages] ********************************ok: [web1]

TASK [start apache service] ********************************ok: [web1]

EXHIBIT B

Focus avoids complexity

● Keep plays and playbooks focused. Multiple simple ones are better than having a huge single playbook full of conditionals

● Follow Linux principle of do one thing, and one thing well

PLAYS & TASKS

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Clean up your debugging tasks

● Make them optional with the verbosity parameter so they’re only displayed when they are wanted.

- debug: msg: "This always displays"

- debug: msg: "This only displays with ansible-playbook -vv+" verbosity: 2

PLAYS & TASKS

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Don’t just start services -- use smoke tests

- name: check for proper response

uri:

url: http://localhost/myapp

return_content: yes

register: result

until: '"Hello World" in result.content'

retries: 10

delay: 1

PLAYS & TASKS

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Use command modules sparingly

● Use the run command modules like shell and command as a last resort

● The command module is generally safer● The shell module should only be used for I/O redirect

PLAYS & TASKS

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Always seek out a module first

- name: add user command: useradd appuser

- name: install apache command: yum install httpd

- name: start apache shell: | service httpd start && chkconfig httpd on

PLAYS & TASKS

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- name: add user user: name: appuser state: present - name: install apache yum: name: httpd state: latest

- name: start apache service: name: httpd state: started enabled: yes

Still using command modules a lot?

- hosts: all vars: cert_store: /etc/mycerts cert_name: my cert tasks: - name: check cert shell: certify --list --name={{ cert_name }} --cert_store={{ cert_store }} | grep "{{ cert_name }}" register: output

- name: create cert command: certify --create --user=chris --name={{ cert_name }} --cert_store={{ cert_store }} when: output.stdout.find(cert_name)" != -1 register: output

- name: sign cert command: certify --sign --name={{ cert_name }} --cert_store={{ cert_store }} when: output.stdout.find("created")" != -1

PLAYS & TASKS

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Develop your own module

- hosts: all

vars:

cert_store: /etc/mycerts

cert_name: my cert

tasks:

- name: create and sign cert

certify:

state: present

sign: yes

user: copia

name: "{{ cert_name }}"

cert_store: "{{ cert_store }}"

PLAYS & TASKS

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● Better readability and more understandable by non-technical people

● Abstracts the logic and complexity from the user

Separate provisioning from deployment and configuration tasks

acme_corp/├── configure.yml├── provision.yml└── site.yml

$ cat site.yml---- import_playbook: provision.yml- import_playbook: configure.yml

PLAYS & TASKS

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Jinja2 is powerful but you needn't use all of it

● Templates should be simple:○ Variable substitution○ Conditionals○ Simple control structures/iterations○ Design your templates for your use case, not the world's

● Things to avoid:○ Anything that can be done directly in Ansible○ Managing variables in a template○ Extensive and intricate conditionals○ Conditional logic based on embedded hostnames○ Complex nested iterations

TEMPLATES

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Careful when mixing manual and automated configuration

● Label template output files as being generated by Ansible

{{ ansible_managed | comment }}

TEMPLATES

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Use the right tool for the job

ROLES• Self-contained portable units

of Ansible automation• Expressed in YAML and

bundled with associated assets

• Decoupled from assumptions made by plays

ROLES + MODULES

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MODULES• Small “programs” that

perform actions on remote hosts or on their behalf

• Expressed as code– i.e. Python, PowerShell

• Called by an Ansible task• Modules do all of the heavy

lifting in Ansible


ROLES• Reuse and collaboration of

common automation workflows & configurations

• Provide full life-cycle management of a service, microservice or container

• “De-facto” enforcement of standards and policies

ROLES + MODULES

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MODULES• Sophisticated interactions

and logic of a unit of work usually with a command line tool or APIs

• Abstract complexity away from users to make powerful automation simple


ROLES

ROLES + MODULES

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MODULES

Keep the purpose and function of a role self-contained and focused to do one thing well

• Think about the full life-cycle of a service, microservice or container — not a whole stack or environment

• Keep provisioning separate from configuration and app deployment

• Roles are not classes or object or libraries – those are programming constructs

• Keep roles loosely-coupled — limit hard dependencies on other roles or external variables

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ROLE DESIGN

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EXHIBIT A

# blackbox_role_playbook.yml---- hosts: all roles: - umbrella_corp_stack

EXHIBIT B

# componentized_roles_playbook.yml---- hosts: localhost roles: - azure_provisioner- hosts: all roles: - system_security- hosts: webservers roles: - python_common - python_django - nginx_uwsgi - racoon_app- hosts: databases roles: - pgsql-replication

Roles should run with as few, if any, parameter variables as possible

• Practice convention over configuration• Provide sane defaults• Use variable parameters to modify default behaviour • Easier to develop, test and use quickly & securely• A role should always be more than a single task file

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ROLE USABILITY

https://en.wikipedia.org/wiki/Convention_over_configuration

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EXHIBIT A

# defaults_no_playbook.yml---- hosts: webservers roles: - role: apache_simple apache_http_port: 80 apache_doc_root: /var/www/html apache_user: apache apache_group: apache - role: apache_simple apache_http_port: 8080 apache_doc_root: /www/example.com apache_user: apache apache_group: apache

EXHIBIT B

# defaults_yes_playbook.yml---- hosts: webservers roles: - role: apache_simple - role: apache_simple apache_http_port: 8080 apache_doc_root: /www/example.com

# default/main.yml---apache_http_port: 80apache_doc_root: /var/www/htmlapache_user: apacheapache_group: apache

Automate the testing of your roles

Use molecule, a testing framework designed to aid in the development and testing of Ansible Roles.

https://molecule.readthedocs.io/en/latest/

HINT: ansible-lint can be run as part of your Molecule test runs.

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ROLE USABILITY

https://molecule.readthedocs.io/en/latest/

Good modules are user-centric

• Modules are how Ansible balances simple and powerful• They implement common automation tasks for a user• They make easy tasks easier and complicated tasks possible• They abstract users from having to know the details to get things done• They are not one-to-one mapping of an API or command line tool interface

– This is why you should not auto-generate your modules• They are not monolithic “does everything” modules that are hard to

understand and complicated to use correctly

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BONUS: MODULE DESIGN

● Coordination across a distributed teams & organization…● Controlling access to credentials...● Track, audit and report automation and management activity...● Provide self-service or delegation…● Integrate automation with enterprise systems...

SCALING YOUR ANSIBLE WORKFLOW

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Command line tools have their limitations

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Thank you

ansible best practices: the essentials best...ansible best practices: the essentials 2 the ansible...

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