1.
EASY RAILS PERFORMANCE WINS
@mraaroncruz

2.
AARON CRUZ!!!!
@mraaroncruz

3.
AARON CRUZ!!!!
• I build bots for startups so
they can better engage with
their audience
@mraaroncruz

4.
AARON CRUZ!!!!
• I build bots for startups so
they can better engage with
their audience
• Been using Rails for ~7
years
@mraaroncruz

5.
WHERE AREYOU AT?
• Beginner
• Expert
• Somewhere in the middle?

6.
PROFILING
1st Win

7.
MEASURE ALLTHETHINGS

8.
ATTACKTHE LARGEST FIRST

9.
HOWTO PROFILE

10.
http://newrelic.com

11.
WITH NEWRELICYOU CAN
MONITOR

12.
WITH NEWRELICYOU CAN
MONITOR
• Slow controller actions

13.
WITH NEWRELICYOU CAN
MONITOR
• Slow controller actions
• Slow SQL analysis

14.
WITH NEWRELICYOU CAN
MONITOR
• Slow controller actions
• Slow SQL analysis
• Time spent in database calls

15.
WITH NEWRELICYOU CAN
MONITOR
• Slow controller actions
• Slow SQL analysis
• Time spent in database calls
• Performance of External Services

16.
WITH NEWRELICYOU CAN
MONITOR
• Slow controller actions
• Slow SQL analysis
• Time spent in database calls
• Performance of External Services
• Much more...

17.
IT’S FREE!
💵 🙏 😭

18.
METRIC FU

19.
CODE QUALITY GEMS

20.
CODE QUALITY GEMS
• Reek - finds code smells

21.
CODE QUALITY GEMS
• Reek - finds code smells
• Cane - fails your build if code quality thresholds
are not met

22.
CODE QUALITY GEMS
• Reek - finds code smells
• Cane - fails your build if code quality thresholds
are not met
• Many more…

23.
RACK MINIPROFILER

24.
THE DATABASE
2nd Win

25.
SOURCE OF MOST
PERFORMANCE ISSUES
😿

26.
MOST COMMON ISSUES

27.
MOST COMMON ISSUES
• Not using an index

28.
MOST COMMON ISSUES
• Not using an index
• Loading too many records into memory (more an
application design problem)

29.
MOST COMMON ISSUES
• Not using an index
• Loading too many records into memory (more an
application design problem)
• Not being able to fit your index into memory

30.
1. USING AN INDEX

31.
WHAT IS AN INDEX?

32.
THE DOWNSIDE OF INDEXES

33.
WHENTO ADD AN INDEX

34.
HOWTO FIND BOTTLENECKS

35.
SLOW QUERY LOG

36.
MYSQL SLOW LOG

37.
MYSQL SLOW LOG
• /etc/mysql/my.cnf

38.
MYSQL SLOW LOG
• /etc/mysql/my.cnf

39.
MYSQLDUMPSLOW

40.
A FEW OTHERTOOLS
• pt-query-digest
• mysqlsla
• Anemometer

41.
POSTGRESQL SLOW LOG
• Open the file postgresql.conf file
• log_min_duration_statement = 100
• Save the file and reload
• Watch the logs (/var/lib/pgsql/data/pg_log/)

42.
EXPLAIN

43.
users=# EXPLAIN ANALYZE SELECT username FROM users
JOIN page_views p ON users.id = p.user_id
WHERE users.friend_count = 50
LIMIT 100;

44.
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------
-
Limit (cost=0.42..4706.66 rows=100 width=11) (actual time=0.324..15.557 rows=100 loops=1)
-> Nested Loop (cost=0.42..2172491.96 rows=46162 width=11) (actual time=0.323..15.543 rows=100 loops=1)
-> Seq Scan on page_views p (cost=0.00..82430.44 rows=4496144 width=4) (actual time=0.004..0.839 rows=8179 loops=1)
-> Index Scan using users_pkey on users (cost=0.42..0.45 rows=1 width=15) (actual time=0.002..0.002 rows=0 loops=8179)
Index Cond: (id = p.user_id)
Filter: (friend_count = 50)
Rows Removed by Filter: 1
Planning time: 0.300 ms
Execution time: 15.592 ms
(9 rows)

45.
CREATE INDEX ON page_views (user_id);

46.
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------
-----------
Limit (cost=0.43..122.29 rows=100 width=11) (actual time=0.049..0.316 rows=100 loops=1)
-> Nested Loop (cost=0.43..56250.88 rows=46162 width=11) (actual time=0.048..0.303 rows=100 loops=1)
-> Seq Scan on users (cost=0.00..20834.00 rows=10267 width=15) (actual time=0.020..0.172 rows=21 loops=1)
Filter: (friend_count = 50)
Rows Removed by Filter: 1110
-> Index Only Scan using page_views_user_id_idx on page_views p (cost=0.43..3.38 rows=7 width=4) (actual time=0.004..0.005 rows=5
loops=21)
Index Cond: (user_id = users.id)
Heap Fetches: 0
Planning time: 0.314 ms
Execution time: 0.355 ms
(10 rows)

47.
44TIMES FASTER
😹

48.
2. LOADINGTOO MUCH INTO
MEMORY

49.
N+1 QUERIES
3rd Win

50.
#includes

51.
class Post < ActiveRecord::Base
belongs_to :author
scope :published, -> {
where(published: true)
.order(published_at: :desc)
}
end
class Author < ActiveRecord::Base
has_many :posts
end

52.
posts = Post.published.limit(100)
posts.each do |post|
puts "#{post.title} - by #{post.author.name}"
end
# 1 query for articles
# 100 queries for authors

53.
Post.includes(:author).published.limit(100)
# 2 queries
# 1 for posts
# 1 for authors

54.
#joins

55.
young_author_posts =
Post.joins(:author)
.where("authors.birth_year > ?", Date.today - 20.years)
.order(:title)
puts "Posts by young authors"
young_author_posts.each |post|
puts post.title
end

56.
TOOLS

57.
# In ~/.zshrc, ~/.profile or ~/bashrc
alias devlog=“tail -f log/development.log"
USE ALIASES AND BASH
FUNCTIONS

58.
VIEW RENDERING
4th Win

59.
YOU CAN SPEND A LOT OF
TIME RENDERINGVIEWS

60.
RACK MINIPROFILER

61.
https://youtu.be/txT-PM8ujLM
Miha Rekar at RubyC 2016 about flame graphs

62.
YOURVIEW SHOULD BE DUMB
😜

63.
REALLY DUMB
😜 😜 😜 😜 😜 😜 😜 😜 😜

64.
VIEW CACHING
5th Win

65.
💵 CACHE IT! 💵
If you can’t speed it up

66.
CACHING IN RAILS IS
SOOOO EASY!

67.
<% @products.each do |product| %>
<% cache product do %>
<%= render product %>
<% end %>
<% end %>

68.
MODEL CACHING
6th Win

69.
Rails.cache.fetch
ISYOUR FRIEND

70.
cache.write('today', 'Monday')
cache.fetch('today') # => "Monday"
cache.fetch('city') # => nil
cache.fetch('city') do
'Duckburgh'
end
cache.fetch('city') # => "Duckburgh"

71.
class Product < ActiveRecord::Base
def competing_price
Rails.cache.fetch([cache_key,“competing_price”], expires_in: 12.hours) do
Competitor::API.find_price(id)
end
end
end

72.
JS AND CSS
7th Win

73.
DELETE WHATYOU DON’T
NEED

74.
PROFILE NOW

75.
FIXYOUR DATABASE

76.
💵 💵 💵 💵 💵 💵 💵

77.
THANKYOU!
@mraaroncruz