DevOps: What is it and why is it important?

Mark Stillwell

September 28, 2014

Traditional Development/Deployment best practices

I source code only in vcs

I static release as versioned archive

I unit testing of code in development environment

I final product not installed on developer machine

I deployment instructions via howto or interactive application

I time consumingI difficult to replicate

Similar Workflows

I Collaborating on a paper by emailing Word .doc filesI Developing software without vcs, periodically creating

versioned/dated zip file in a backup/ directory

Issues With These Approaches

I Coordination, Communication, Documentation:

I “I’ll edit the document and email you when I’m done.”I “I had to tinker with /etc/foo to get things working.”

I Handling of conflicts

I No automating of merges

I Lack of one true authoritative “latest version”.I Culture of Fear

I “I know generally what needs to be done, but I’m afraid to trybecause I might break it and not be able to get things workingagain.”

Software Specific Issues

I Difficulty verifying complicated interaction between multipleparts.

I “Brittle” deployment: It works, mostly, but don’t touch it!I Experts-Only install discourages end-users, results in lower

adoption/mindshare.

DevOps

I deployment as code in vcsI continuously testedI test environment similar to deployment environment

I enabled by virtual machines and containers

I regular deployments to productionI industry standard practice!

I NetFlix, Etsy, Twitter, etc tear down infrastructure andredeploy multiple times per day. . .

I culture of fearless development

Enabling Technologies

I ansibleI vagrantI docker

Ansible

I tool for managing distributed software deploymentsI similar tools: puppet, chef, salt, cfengineI free software (for command line, commercial web-based

management interface)I written in pythonI configuration as list of “idempotent” tasks in yaml based

configuration

I really only pseudo-idempotent

I push model that only requires administrator’s computer haveansible software and client machines have sshd and python

I all other require some kind of bootstrapping process on clientsI some (e.g., puppet) require server setup

Example Playbook

- hosts: all

sudo: True

tasks:

- name: ensure sysctl is configured

sysctl:

name: vm.swappiness

value: 10

state: present

- name: ensure latest version is installed

apt:

pkg: etckeeper

state: latest

Vagrant

I command line wrapper to virtualisation tools likevirtualbox/kvm

I sets up disks / networking etc.I all configuration in text VagrantfileI can bring up and network multiple vms with different

operating systemsI can invoke provisioning tools like ansible, or shell scriptsI user just needs to cd to right directory, type “vagrant up”

Example Vagrantfile

Vagrant.configure(2) do |config|

config.vm.box = "ubuntu/trusty"

config.vm.network "forwarded_port", guest: 80, host: 80

config.vm.provider "virtualbox" do |v|

v.memory = 1280

end

config.vm.provision "ansible" do |ansible|

ansible.playbook = "site.yml"

end

end

Docker

I interface for managing “container” based deployments

I light-weight environment virtualisation that makes use oflinux-kernel features

I “like chroot on steroids”I currently uses lxc, but this may change in the future

I also manages “layered” file sytems using aufs copy-on-write

I disk-space efficientI docker.io has a repository of of layers, e.g. “docker pull

ubuntu”

I can be used to provide “lightweight linux virtual machines”,but this isn’t the most efficient approach

I no need to run multiple copies of system servicesI preference is one process per container, “single responsibility

principle”I inter-process communication enabled by mapping directories /

ports between containers and/or host

Websites

I http://ansible.comI http://vagrantup.comI http://docker.io