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Speed up your Ansible Playbooks


I'm always impressed with my friends of Streetlife. They built a new infrastructure based on immutable deploys. I'm surprised about how fast they are able to build this AMIs, they can start a new full configured server in only 6 min.

Three years ago I've started using Ansible. My deploys were always up to twenty minutes, so one day I decided to achieve an eight-min deploy. Eight min will be the time that I have to build a new server.

To get this eight minute build, I focused on the following tasks:

APT cache time:

When you have different roles in Ansible, usually you always set update_cache in the apt task. This is pretty useful, but painful with different roles.

Ansible provides the cache_valid_time option. If you enable it, Ansible will check the cache age. If cache age is less than your value, apt-get update will be ignored.

- name: Installing useful packages
    name: "{{ item }}"
    update_cache: yes
    cache_valid_time: 3600
    - htop
    - ngrep
    - vim

Async Tasks:

Async tasks are in Ansible from version 1.7. It works like this: while one long task is running, another short task can be executed.

For example, if you want to install pip dependencies and bower dependencies: both are needed, both can run at the same time and both take few minutes.

With async tasks, tasks can be executed and forget, but this background task can be checked later. So Ansible provides the option to get the task status in any time.

The following example show how pip and bower dependencies will run in two new coroutines. While the dependencies are being installed in the system, another task will create the users (or any other task). Before the playbook is finished, it's going to be checked if the coroutines has finished properly.

- name: bower install requirements (Coroutine #2)
    path: /my_app/frontend/
    state: latest
  async: 1000
  poll: 0
  register: bower_install

- name: Add the users in the platform
    name: "{{item.name}}"
    shell: /bin/bash
    groups: "{{item.groups}}"
    state: "{{item.status}}"
    - {name: eloy, state: present, groups: admin}
    - {name: www, state: present, groups: admin}
    - {name: ftp, state: present, groups: admin}

- name: PIP result check (Check coroutine #1)
    jid: "{{ pip_install.ansible_job_id }}"
  register: job_result
  until: job_result.finished
  retries: 30

- name: Bower result check (Check coroutine #2)
    jid: "{{ bower_install.ansible_job_id }}"
  register: job_result
  until: job_result.finished
  retries: 30

Ansible async task and loops:

When you start with Ansible, you use a lot of with_items. Loops are not supported in Async tasks, but the following workaround can be used:

# vars.yml
  - bison
  - gcc
  - git
  - make
  - mercurial
- name: Installing dependencies
    name: "{{ ','.join(dependencies) }}"
    update_cache: yes
    cache_valid_time: 3600
  async: 1000
  poll: 0

Happy deploy!


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