1.
Performance Optimization 101
for Ruby developers

2.
whoami
Nihad Abbasov
github.com/narkoz
nihad@42na.in

3.
AGENDA
- Ruby
- Rails
- Front-end

4.
What is
application performance
indication of the time
it takes application to
respond

5.
What is
performance optimization
process of modifying a
software system to make
some aspect of it work more
efficiently or use fewer
resources

6.
Why is
performance important
if your application loads and
runs slowly, it is more likely to
be abandoned by your users

7.
1.
Optimizing Ruby
Tips and techniques for optimizing your Ruby code

8.
Measure code
execution time
Use benchmark-ips
gem

9.
Benchmark with
benchmark-ips
require 'benchmark/ips'
Benchmark.ips do |x|
x.report('addition') { 1 + 1 }
x.report('addition with send') { 1.send(:+, 1) }
x.compare!
end

10.
Use #sample instead
of #shuffle.first
# slow
[*1..100].shuffle.first
# fast
[*1..100].sample

11.
Use #map instead of
#each + push
# slow
array = []
[*1..100].each { |e|
array.push e }
# fast
array = [*1..100].map {
|e| e }

12.
Use #flat_map instead of
#map + flatten
# slow
[*1..100].map { |e|
[e, e] }.flatten
# fast
[*1..100].flat_map { |e|
[e, e] }

13.
Use #reverse_each
instead of #reverse + each
# slow
[*1..100].reverse.each {
|e| e }
# fast
[*1..100].reverse_each {
|e| e }

14.
Use #min_by instead of
#sort_by + first
# slow
[*1..100].sort_by { |e|
e.next }.first
# fast
[*1..100].min_by { |e|
e.next }

15.
Use #min/max instead of
#sort + first/last
# slow
[*1..100].sort_by { |e| e.next
}.last
[*1..100].sort { |e| e.next
}.first
[*1..100].sort { |e| e.next
}.last
# fast
[*1..100].max_by { |e| e.next
}
[*1..100].min { |e| e.next }
[*1..100].max { |e| e.next }

16.
Use #detect instead of
#select + first
# slow
[*1..100].select { |e| e
== 20 }.first
# fast
[*1..100].detect { |e| e
== 20 }

17.
Use #reverse.detect
instead of #select.last
# slow
[*1..100].select { |e|
(e % 10).zero? }.last
# fast
[*1..100].reverse.detect
{ |e| (e % 10).zero? }

18.
Use #each_key instead of
#keys + each
# slow
HASH.keys.each { |k| k }
# fast
HASH.each_key { |k| k }
HASH = Hash[*('aa'..'zz')]

19.
Use #key? instead of
#keys + include?
# slow
HASH.keys.include? 'zz'
# fast
HASH.key? 'zz'
HASH = Hash[*('aa'..'zz')]

20.
Use #value? instead of
#values + include?
# slow
HASH.values.include? 'zz'
# fast
HASH.value? 'zz'
HASH = Hash[*('aa'..'zz')]

21.
Make objects immutable
with #freeze
# slow
string = 'Hello'.freeze
10.times { puts string }
# slow
string = 'Hello'
10.times { puts string }

22.
Use magic comment #
frozen_string_literal: true
# frozen_string_literal: true

23.
Use Date.iso8601
instead of Date.parse
# slow
Date.parse('2018-03-19')
# fast
Date.iso8601('2018-03-19')

24.
Use Time.iso8601
instead of Time.parse
# slow
Time.parse('2018-03-21T1
1:26:50Z')
# fast
Time.iso8601('2018-03-21T1
1:26:50Z')

25.
Use Hash
instead of OpenStruct
# slow
require 'ostruct'
person = OpenStruct.new
person.name = 'John'
person.name
# fast
person = {}
person[:name] = 'John'
person[:name]

26.
Additional resources
and tools
▪ github.com/JuanitoFatas/fast-ruby
▪ github.com/DamirSvrtan/fasterer
▪ github.com/rubocop-hq/rubocop-performance

27.
2.
Optimizing Rails
Tips and techniques for optimizing your Rails application

28.
Benchmark
your application
- wrk
- h2load
- ab
- siege

29.
Use application
monitoring metrics
- scout_apm
- skylight
- newrelic

30.
Check application
performance profile
REQUESTS PER-MINUTE CLASSIFICATION
< 50 ms Fast
< 300 ms Normal
> 300 ms Slow

31.
Use database queries
to deal with records
# DO:
Item.order(created_at: :desc).limit(20)
# DONT:
Item.all.sort_by(&:created_at).reverse.first(20)

32.
Use database queries
to deal with records
Don't be afraid to use raw SQL

33.
Use select to get only
the necessary data
@users = User.select(:name, :email).limit(20)
<% @users.each do |user| %>
<%= user.name %><br>
<%= user.email %>
<% end %>

34.
Use size on relation
instead of count
@messages = current_user.messages.unread
<% @messages.each do |message| %>
<%= message.body %>
<% end %>
<h2>Unread Messages: <%= @messages.size %></h2>

35.
Use database indexes
correctly
User.where(email: 'user@example.org')
# migration:
add_index :users, :email, unique: true

36.
Indexes for
polymorphic associations
class Comment
belongs_to :commentable, polymorphic: true
belongs_to :user
end
class Post
has_many :comments, as: :commentable
has_one :user
end

37.
Indexes for
polymorphic associations
add_index :comments, :user_id
add_index :comments, %i[commentable_type commentable_id]

38.
Order records
by ID
User.order(id: :desc)
# faster alternative to
User.order(created_at: :desc)

39.
Use subqueries
with ActiveRecord
# 2 separate queries
Ad.where(id: current_user.bookmarks.pluck(:ad_id))
# 1 query with subquery
Ad.where(id: current_user.bookmarks.select(:ad_id))

40.
Eliminate
N+1 queries
@user = User.first
<% @user.comments.each %>
<%= comment.body %>
<% end %>

41.
Eliminate
N+1 queries
Use AR#includes
@user = User.includes(:comments).first

42.
Use
materialized database views
*PostgreSQL only.
use scenic gem

43.
Use limit
in queries
User.limit(10)
Use pagination:
@pagy, @records = pagy(Post.published)

44.
Use explain
when in doubt
User.where(id: [1, 2]).comments.explain

45.
Use
background processing
UserMailer.welcome(@user).deliver_later
VideoImportJob.perform_later(current_user)

46.
Avoid
rendering with loops
<% @users.each do |user| %>
<%= render 'users/profile_card', user: user %>
<% end %>

47.
Use
collection rendering
<%= render partial: 'users/profile_card',
collection: @users %>

48.
Use
collection caching
<%= render @post.comments, cached: true %>

49.
Minimize or suppress
HTTP redirects
Use HTTP Strict
Transport Security
(HSTS)

50.
Enable
HSTS preload
config.force_ssl = true
config.ssl_options = { hsts: { preload: true } }

51.
Use libvips
for image processing
config.active_storage.variant_processor = :vips

52.
Reduce
log writes
Use gems:
▪ rails_semantic_logger
▪ lograge

53.
Use
faster gems
▪ github.com/SamSaffron/fast_blank
▪ github.com/ohler55/oj
▪ github.com/ohler55/ox
▪ github.com/redis/hiredis-rb
▪ github.com/ddnexus/pagy

54.
Use
a faster language
▪ Go
▪ Elixir
▪ C 👀

55.
Additional resources
and tools
▪ github.com/MiniProfiler/rack-mini-profiler
▪ github.com/gregnavis/active_record_doctor
▪ github.com/tmm1/stackprof
▪ github.com/schneems/derailed_benchmarks
▪ github.com/plentz/lol_dba
▪ github.com/flyerhzm/bullet

56.
3.
Optimizing Front-end
Tips and techniques for optimizing front-end of your application

57.
Serve
compressed assets
Nginx example with gzip:
location ~ ^/(assets|packs)/ {
...
gzip_static on;
}

58.
Use
better compression
Use Brotli compression format:
location ~ ^/(assets|packs)/ {
...
gzip_static on;
brotli_static on;
}

59.
Use
modern cache control
Add immutable to Cache-Control headers:
location ~ ^/(assets|packs)/ {
...
add_header Cache-Control public,immutable;
}

60.
Use
resource hints
<link rel="dns-prefetch"
href="https://assets.example.com">

61.
Use WEBP
for images
Supported by:
▪ Google Chrome (desktop) 17+
▪ Google Chrome for Android version 25+
▪ Microsoft Edge 18+
▪ Firefox 65+
▪ Opera 11.10+
▪ Native web browser, Android 4.0+ (ICS)

62.
Use
Turbolinks
Or:
▪ Vuejs
▪ React
▪ Stimulus

63.
Use with caution
HTTP/2 Push
path = view_context.asset_path('application.css', host: '',
protocol: :relative)
response.set_header('Link', "<#{path}>; rel=preload; as=style")

64.
Questions?
github.com/narkoz
nihad@42na.in