Ruby, the language of devops

Who am I?
● Rob Kinyon
o @rkinyon
o rob.kinyon@gmail.com
● Devops lead for many years

What is Devops?
● The Cloud?
● Jenkins Automation?
● Continuous integration & deployment?
● A new title?
o with no extra pay . . .
● Developers doing Operations??
o And fire all the sysadmins? (NO-OPS!)
● Automating away your coworkers??!

The Programming of Operations
● Operations is:
o Build servers
o Packaging
o Monitoring
o Provisioning
o Virtualization
o Environment/Stack Management
o Many many many more things

● Lots of helpers
o Build this
o Package that
o Move things from here to there

● Lots of helpers
o Build this
o Package that
● Templating
o Homegrown templates for Nagios

● Lots of helpers
o Build this
o Package that
● Templating
o Homegrown templates for Nagios
● Lots of manual activities

Manual
===
Broken

TARGET=${1:-"monitor-prod"}
for rule in /nagios/rules/*.tmpl; do
process_template.pl $rule $TARGET
mv ${rule##tmpl#cfg} /nagios/final
done
scp /nagios/final/*.cfg $TARGET.company.com:/var/nagios/
ssh $TARGET.company.com -c "sudo service nagios3 restart”

● As a single script, it's okay.
o Concise, clear - what else do you need?

● Problems:
o No tests (untestable!)
o No reusability or extensibility
o Inscrutable code

● Problems:
o No tests (untestable!)
o No reusability or extensibility
o Inscrutable code
● Bugs:
o Assumes the contents of $PWD and $PATH
o Assumes a human will know if it worked

● Operations staff are not developers

● Operational focus is about maintenance
o Keep it on
o Keep it up
o Keep it responding

● Operational focus is about maintenance
o Keep it on
o Keep it up
o Keep it responding
● Operations has to manage changes by those
pesky developers
o Right now. While something is on fire. (Really!)

What is the perfect language?
● Multi-system
● Quick to boot
● Easy to learn
● Easy to maintain
● Large community / Lots of modules
● Easy to find good staff

Languages we won't discuss
● C/C++
● .NET (C#, F#, etc)
● JVM languages
● Functional languages
o Especially Erlang
● Node.JS

Bash/Shell scripts (Good and Bad)
● Easy to write
● Everyone has written Bash scripts
● Horrible control structures
● Horrible variable structures
● Non-existent code structuring
● “Libraries” don’t exist
● Only really works on *nix
o Git-Bash doesn't count

Perl (the Good)
● What most sysadmins use other than Bash
● Great variable structures
● Great control structures
● Excellent reusability
o CPAN is the largest single-language repository
● Works everywhere (literally)
● Good programmers can manage 500kLOC

Perl (the Bad)
● Everyone thinks they know Perl
o Bad Perl is really really bad.

Perl (the Bad)
● Standard language facilities require
libraries
o Exceptions, objects, case statements

Perl (the Bad)
libraries
● CPAN is 80%+ useless

Perl (the Bad)
libraries
● CPAN is 80%+ useless
● Really old Perls are installed everywhere
o 5.005_003 (March, 1998)

Perl (the Ugly)
● Solving a problem with regular expressions
means you have two problems.

Perl (the Ugly)
● Sigils ($, @, %, etc) make code hard to read
o Ironically, the idea was to make code easier to
read

Perl (the Ugly)
● Sigils ($, @, %, etc) make code hard to read
o Ironically, the idea was to make code easier to
read
● Too many places where hidden globals
make you cry.
o E.g., namespaces aren't namespaced.

Python (Strengths)

Python (Strengths)
● All the advanced features
o Exceptions
o Objects
o Case statements

Python (Strengths)
o Exceptions
o Objects
o Case statements
● Runs everywhere that we care about

Python (Weaknesses)
● Significant whitespace is difficult for non-
developers.

Python (Weaknesses)
developers.
● System programming libraries aren't mature

Python (Weaknesses)
developers.
● System programming libraries aren't mature
● Writing libraries isn't self-evident
o Tutorials and scaffolding also immature

Ruby (Strengths)

Ruby (Strengths)
o Exceptions
o Objects
o Case statements

Ruby (Strengths)
o Exceptions
o Objects
o Case statements
● Already used as a sysadmin language

Ruby (Weaknesses)
● Minor versions changing syntax
o 1.8.7 vs. 1.9.3 vs 2.x

Ruby (Weaknesses)
● Minor versions changing syntax
o 1.8.7 vs. 1.9.3 vs 2.x
● Ruby is not Rails
o Really!

Ruby (Superpowers)
1. Install multiple versions of same library
2. Newbies are a way of life
3. Blocks

Multiple library versions
● Sysadmins are pessimistic
o Foo-bar 1.3.9 works, so don't change it!!

● Not everyone can use the same version
o Something needs a feature in Foo-bar 2.1.5

● Not everyone can use the same version
o Something needs a feature in Foo-bar 2.1.5
● So install both and specify at runtime
gem 'Foo-bar', '=1.3.9'
require 'foobar'

Newbie friendly
● Rails is how many new web-developers start

Newbie friendly
● Rails is Ruby (plus, but still)

Newbie friendly
● Thousands of great tutorials, skeletons, and
communities.
o Google "ruby tutorial XYZ" for all values of XYZ)

Newbie friendly
● Thousands of great tutorials, skeletons, and
communities.
o Google "ruby tutorial XYZ" for all values of XYZ
● Syntax is very easy to read and write
o Reading code is very hard
o Anything that makes it easier is a "Good Thing"(tm)

Blocks (Temporary File)
require 'tempfile'
Tempfile.open('some-prefix') do |tmp|
tmp.write "Some text"
# Do something with tmp here
end

Blocks (Reading from a file)
File.foreach('/some/file') do |line|
puts “Line read: #{line}”
do_something(line)
end

Blocks (Writing to a file)
File.open('/some/file') do |file|
file.puts 'first line'
file.puts 'second line'
end

Blocks (Writing to a file)
File.open '/some/file' { |file|
file.puts 'first line'
file.puts 'second line'
}

Blocks (Changing Directory)
Dir.chdir('/some/place') do |dir|
do_something_in_some_place(dir)
end
do_something_in_original_dir()

Blocks (Nested blocks)
Dir.chdir('/some/dir') do
%w{sub1 sub2}.each do |subdir|
Dir.chdir(subdir) do
# In /some/dir/sub[12]
end
end
end

Why blocks?
● Same construct for iteration and closures
o A logical new lexical scope

Why blocks?
● Automatic cleanup
o (Not necessarily guaranteed in all cases)

Why blocks?
● Automatic cleanup
o (Not necessarily guaranteed in all cases)
● Clean delination of concerns
o Relevant code is in one place

Why blocks? (as a sysadmin)
Because my job isn't where I can faff about
until everything is perfectly just-so and my
HammerFactoryFactoryFactory has 103% test
coverage in Jenkins.
I need to be done yesterday and I need to be
sure it works by looking at it.

Why blocks? (as a devops)
Because it's the easiest way to convert a
sysadmin into a developer.

Tooling
● Vagrant
● Chef / Puppet
● Logstash
● fpm
● Cucumber
● AWS / Rackspace clients
● Rake / Capistrano

Tooling (why do I care it's in Ruby?)
Three reasons:
1. Plugins

Three reasons:
1. Plugins
2. Plugins

Three reasons:
1. Plugins
2. Plugins
3. Plugins

Three reasons:
1. Plugins
2. Plugins
3. Plugins
4. Some of them require Ruby (Vagrant)

Ruby, the language of devops

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