Quality Ruby Code Techniques for Maintainable Applications

Quality Ruby Code
Michael Durrant
m2@snap2web.com
June 2019

Thanks to all the bostonrb organizers!

Thank you EzCater, a good sponsor makes a huge difference!

Thank you to all my friends in Indianapolis for teaching me so
much! Thank you Stacey, Aldrin, Ben, Bella, Joe, Adam,
Adrian, Orando!

Thank you to all my friends in Indianapolis for teaching me so
much! Thank you Stacey, Aldrin, Ben, Bella, Joe, Adam,
Adrian, Orando!
Thank YOU for coming tonight and supporting the community!

My talks are intended to be interactive so

- Ask questions (wave hand, call out ‘Michael’)

- Hearing your opinions and experiences is very welcome

- Prefer questions, answers, conversations during not after

- Expect polls and use them to learn about your community

- Cell phone and laptop use during main talk is discouraged

- Cell phone airplane mode is encouraged

- Cell phone airplane mode is encouraged
- Public Video is being recorded for most of my talks, !smile

17
But first… Docker...
git clone --recursive https://github.com/bretfisher/container.training
cd ~/container.training/stacks
docker-compose up
docker-compose down
docker node ls # (err)docker
docker swarm init # (ONE node only!) Err? next line
docker swarm init --advertise-addr eth0
docker swarm join
--token SWMTKN-1-59fl4ak4nqjmao1ofttrc4eprhrola2l87...
172.31.4.182:2377
Docker node ls
See https://dockercon19.bretfisher.com/#1

18
And… about deploying code...

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25

27

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- IAC Infrastructure As Code. Recipies (chef), Playbooks (Ansible), etc.

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- Programming configuration via a DSL (e.g. Chef count attribute)

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- Idempotent. Immutable Infrastructure. Set it. And forget it! (bow to Ronco BBQ)

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- Set the State, let the tool manage it

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- Know the key factors – docker has a daemon, ansible doesn’t and uses ssh
(port 22) to do things, etc.

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- Know the key factors – docker has a daemon, ansible doesn’t and uses ssh
(port 22) to do things, etc.
- Use checklists (for developing IAS is a very good idea)

34
Why we use Terraform and not Chef, Puppet, Ansible, SaltStack, or CloudFormation
https://blog.gruntwork.io/why-we-use-terraform-and-not-chef-puppet-ansible-saltstack-or-cloudformation-
7989dad2865c
Infrastructure as Code: Chef, Ansible, Puppet, or Terraform?
https://www.ibm.com/cloud/blog/chef-ansible-puppet-terraform
Puppet vs. Chef vs. Ansible vs. SaltStack
https://www.intigua.com/blog/puppet-vs.-chef-vs.-ansible-vs.-saltstack
Comparing top DevOps tools: Docker vs Kubernetes vs Puppet vs Chef vs Ansible
https://www.znetlive.com/blog/compare-top-devops-tools-docker-kubernetes-puppet-chef-ansible/
Choosing a deployment tool - ansible vs puppet vs chef vs salt
https://gist.github.com/jaceklaskowski/bd3d06489ec004af6ed9
Puppet vs Salt vs Chef vs Ansible, which to choose?
https://www.reddit.com/r/linuxadmin/comments/9ljveg/puppet_vs_salt_vs_chef_vs_ansible_which_to_choose/

36
As a Quality Engineer..
● I’m always thinking about more tests

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● I’m always thinking about more tests better tests

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so we can have less bugs

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so we can have less bugs higher quality

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so we can have less bugs higher quality
● Or we can end up solving the wrong problems !

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We have a codebase with bugs...

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Now we have two codebases for bugs

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And our overall code may now be

45
● Twice as hard to maintain

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● Twice as hard to fix

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● Twice as hard to fix
● Twice as hard to change

49
Tests can reveal issues with Quality
However just having them does not
improve application quality

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We need to address quality issues
in the code itself (both automation
and application code)

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We need (in all code)
● Quality Code Approaches (todays topic)
● KPIs ! Not # tests/bugs, but code level
● Automated Linting, e.g. Rubocop
● Code Grading, Code Climate
● Robust exception handling (also covered today)
● Open minded Code Review mentality
● Easy to use Code Review tools
● IAC

53
● Has Tests
● Is molded
● Good names
● Low wtf Ratio
● Handles Exceptions
● KISS Mr Meta gently
● Uses few parameters
● Uses Linting and Grading
● Allows a Little Duplication
Quality (Ruby) Code
● Is a choice
● Is easy to read
● Is not optimized
● Is easy to change
● Uses standards that evolve
● Uses the right rules guidelines
● Has small classes and methods
● Values comments as they are so rare
● Has less bugs

54
Is Molded
Through a healthy code review process that features:
- Code is owned by all
- PR Comments are the norm
- Quality is not generally time-boxed
- Humbleness leads with pride in code not ego
- Refactoring is nearly always done in-cycle. Now

55
Uses Good Names
Bad
i
j
k
n
flag
type
max_limit
final_size
num_items
all_items
last_entry
Better
index
auto_payment_on_flag
payment_method_type
max_dollar_amount
final_room_sq_ft
number_current_order_items
all_current_order_items
last_order_entry
last_payment_received_date
payment_final_due_date
student_time_at_last_address

57
Handles Exceptions
# Not so good
begin
...
some code
...
rescue
end

58
Handles Exceptions
# Better (scoped)
begin
...
some code
...
Rescue StandardError
end

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Handles Exceptions
# Even better (scoped with re-raise)
begin
...
some code
...
rescue StandardError => e
some code
If condition still an issue can do `raise e`
end
Rescue the most specific exception possible

60
Handles Exceptions
# Even Even better (scoped more with re-raise)
begin
...
some code
...
rescue StandardError::ArgumentError, ZeroDivisionError => e
some code
If condition still an issue can do `raise e`
end
Rescue the most specific exception(s) possible

61
Handles Exceptions
# Sometimes (code with dependencies) you just want to retry
Example1: An API error for get prices which can be retried:

62
def get_api_prices
tries = 0
begin
tries += 1
prices = api_get_buy_sell
sleep 2
rescue SocketError => e
p e.message
if (tries < 5)
p "but retrying... try: #{tries}"
sleep(2 ** tries)
retry
else
p 'giving up...'
raise e # Do not remove, we need a current price to be set
end
end
end
Handles Exceptions – Retry
Example 1

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visit_with_retry sell_url
def visit_with_retry(url, tries = 5)
begin
@s.visit(url)
sleep 2
find_link(‘login’)
rescue Capybara::ElementNotFound, Net::ReadTimeout => e
p e.message
if (tries < 1)
p "but retrying... try: #{tries}"
sleep(2 ** tries)
tries -= 1
retry
else
p 'giving up...'
raise e # Do not remove, we need a current price to be set
end
end
end
Handles Exceptions – Retry
Example 2

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Handles Exceptions – Raise them well

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raise “just the text and not the best”

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raise RuntimeError, “stop executing please”

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Create custom errors (“help your fellow / future programmer):
class PaymentError < StandardError
end
raise PaymentError, “zero amount in payment field pmt-001”

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Create custom errors (“help your fellow / future programmer):
class PaymentError < StandardError
end
raise PaymentError, “zero amount in payment field pmt-001”
Pass information to exceptions
raise TemperatureError.new(180)
Then add attribute and set in initialize

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Handles Exceptions – method missing

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- Saves the day

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- Saves the day
- Lets you code carelessly

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- Saves the day
- Makes everything feel better

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- Saves the day
- Is a swiss Army knife that can tear your code apart

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- Saves the day
- Is a swiss Army knife that can tear your code apart
- Can lead to highly opinionated programmer talking at you

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Handles Exceptions – Learn More...

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Handles Exceptions – avoids them

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- Treat all objects as if they could be nil

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- Pays attention to warnings

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- Prefer Set and Struct to Array and Hash for some structured data
- unique data (Set)
- attribute names (getters, setters)
- instance and class methods

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- unique data (Set)
- Use module (scope) to avoid reopening classes, e.g. “class” or “initialize”

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- unique data (Set)
- Prefer Class Instance (self.thing) over class (@@) variables – hierarchy

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- unique data (Set)
- Always pass a parameter to reduce / inject, e.g. 0, {}, etc. due to empty issue

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- unique data (Set)
- Manages Resources with Blocks and ensure* (db connections, file locks, etc)

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- unique data (Set)
- Prefer throw-catch (last value) to raise-rescue (pass in exception)

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- unique data (Set)
- Prefer define_method to method_missing

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- unique data (Set)
- Simulate determinism with Mock Objects, e.g. make http fail

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- unique data (Set)
- Memoize ||= expensive operations

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- unique data (Set)
- Memoize ||= expensive operations - prefer local over instance

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KISS Mr Meta gently
Metaprogramming is the
answer to all programming
problems !!!

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Use few parameters
1 is ok.

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Use few parameters
1 is ok.
2 is a lot

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Use few parameters
1 is ok.
2 is a lot
0 is best

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Use few parameters
1 is ok.
2 is a lot
0 is best
However don’t play the “object
trick” without thinking it through

99
Allow a little duplication
“A little duplication is better
than the wrong abstraction”

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Avoid extremes

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Avoid extremes

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Avoid extremes

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Is easy to read
Use english

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Is not optimized
Very little code in 2019 needs
to be highly performant.
Usually not in anticipation of
performance issues

107
Uses standards that evolve (!)

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Uses standards that evolve (!)
Over longer time periods new
structures and needs will
become apparent and should
be discussed

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Uses the right rules guidelines

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Uses the right rules guidelines
Quality code is code that strikes
a balance between the rules, not
just code that follows all the rules

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Has small classes and methods

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SRP

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SRP
Sandy Metz

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SRP
Sandy Metz
Duh

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Value comments - they are so rare

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Exceptions to avoiding comments:

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# Module Support to expire 12/1/2019

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# Dependent library randomly fails here, cause unknown

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# Dependent library randomly fails here, cause unknown
# More efficient approach here in order to save memory

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Has less bugs
See previous 30 slides ;)

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A number of voluntary activities and
approaches that Application and
Automation Engineers use to create
better quality code today
Quality Code Is

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Quality Code is Iike Tests because

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It is optional

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It is optional
*** IT IS UP TO YOU **

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Quality Code is
Level II thinking

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Recursion, Linked lists (single, double,
circular), trees, binary tree searches, maps,
design patterns, etc. are all useful tools at the
right time.
However, as you’ve seen, there is a lot more
to quality than algorithms for highly
performant code </rant>

131
Quality Code is also
more of a pleasure and
less of a pain in the *

133
Comments ?
Questions ?
Discussion ?
Experiences ?
Advice ?

Quality Ruby Code Techniques for Maintainable Applications

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