以過來人的經驗分享用 Ruby 每分鐘抓取 2000+ 頁面、維護上億筆紀錄資料庫的心路歷程，從單線程到多線程再到 Auto Scaling 讓大家一步一步體會撰寫爬蟲各階段可能遇到的瓶頸，期望能在未來為從事相關工作的朋友們帶來一點幫助。 Shi-Ken Don @ RubyConf Taiwan 2016

1. Crawler from zero
shiken.don@gmail.com
RubyConf Taiwan 2016

2. About Me
• a.k.a. Shi-Ken Don
• 2009 - 2014
• Ruby Developer since 2013
• 2014 - 2015
• Web Developer at Backer-Founder since 2015

3. About Me
• a.k.a. Shi-Ken Don
• 2009 - 2014
• Ruby Developer since 2013
• 2014 - 2015
• Web Developer at Backer-Founder since 2015
200
20

4. Agenda
• What I did
• Why Ruby? Ruby
• Comparison
• Know-how

5. Crawler Architecture
Wikipedia:File:WebCrawlerArchitecture.svg

6. Crawler Architecture
Wikipedia:File:WebCrawlerArchitecture.svg

7. CrowdTrail
:D

8. CrowdTrail
• 14
• 2
•

9. DEMO
CrowdTrail
:D
>>>> https://goo.gl/sWfDBc <<<<

10. • 5000
• Web
• 0

11. • 5000
• Web
• 0
Kickstarter
2
T T

12. •
• JRuby
• Ruby

13. Ruby

14. Ruby
Ruby

15. Ruby
Ruby
Why, or Why not?

16. (Crawler) Python
Python Ruby

17. Ruby

18. Ruby
(Scrape web content)

19. Network flow
Google Chrome DeveloperTools screenshot
1.75 1.34
76%

20. Ruby Python
user system total real
Ruby Thread.new 16.090000 1.010000 17.100000 ( 17.254499)
Ruby Parallel 16.900000 1.100000 18.000000 ( 18.080813)
Python threading 0.000000 0.000000 16.360000 ( 16.532583)
1000 thread www.facebook.com
ruby_thread_tests.rb
threading_test.py
Python Ruby

21. user system total real
Thread.new (parse and create) 5.640000 0.580000 6.220000 ( 6.073333)
Thread.new (parse only) 5.060000 0.440000 5.500000 ( 5.455837)
Thread.new (create directly) 3.340000 0.520000 3.860000 ( 5.169519)
ruby_thread_sidekiq_test.rb
100 thread www.facebook.com
parse only

22. • ActiveRecord::ConnectionTimeoutError: could not
obtain a database connection within 5.000 seconds
(waited 5.009 seconds)

23. database.yml
default: &default
adapter: postgresql
encoding: unicode
pool: 25 # Increase this

24. Thread
begin
# …
ProjectLog.create!(title: title)
ensure
ActiveRecord::Base.clear_active_connections!
end

25. Sidekiq
• 200 8
• RubyThread
• Auto scaling

26. Heroku Auto Scaling
heroku.rake
task :auto_scaling, [:WORKER_NAME] => :environment do |_t, args|
args.with_defaults(WORKER_NAME: "worker")
APP_NAME = ENV["HEROKU_APP_NAME"]
WORKER_NAME = args[:WORKER_NAME]
heroku = Heroku::API.new
queues = Sidekiq::Queue.all
queues_size = queues.map { |queue| Sidekiq::Queue.new(queue.name).size }.inject(0, :+)
# 2X dyno 600 jobs
# 50 parse project_log
# jobs 45
now_minutes = Time.now.strftime("%M").to_i
# / /
left_minutes = now_minutes.between?(0, 45) ? 45 - now_minutes : 0
workers_size = queues_size / 500 / [left_minutes, 1].max
workers_size = 1 if workers_size < 1
workers_size = 10 if workers_size > 10 # 10 worker
puts "Scaling #{WORKER_NAME} dyno count to #{workers_size}"
heroku.post_ps_scale(APP_NAME, WORKER_NAME, workers_size)
end

27. Sidekiq
• PostgreSQL > Redis > Sidekiq connections
Sidekiq Redis Thread Redis
Thread

28. Heroku PostgreSQL Pricing

29. PostgreSQL Standard 2
• Rails App DB
• RakeTask DB
• Restarting
• Sidekiq MAX connections = 200

30. • File descriptor
✦ MacOS: 256 (default)
✦ Linux: 1024 (default)
✦ Windows: who cares
Linux File descriptor
1024
CPU RAM

31. Linux
• #
• cat /proc/sys/fs/file-max
• #
• sysctl -w fs.file-max=100000

32. Know-how

33. •
• Heroku dyno 500 Thread
• dynos#process-thread-limits

34. Queue (Weight)
Sidekiq Queue Job

35. Queue
Project.find_each do |project|
# Sidekiq queue
name = project.platform.name
SnapshotWorker.sidekiq_options_hash["queue"] = name
SnapshotWorker.perform_async(…)
end

36. Retry
sidekiq_options_hash["retry"] += 1
self.class.sidekiq_retry_in do |count|
Random.rand(retry_after + count)
end

37. • User-Agent
• Mozilla/5.0 (compatible; MSIE 10.0;Windows NT 6.1;Trident/6.0)
• Google Bot
• Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)

38. • User-Agent
• Mozilla/5.0 (compatible; MSIE 10.0;Windows NT 6.1;Trident/6.0)
• Google Bot
• Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
SEO
Googlebot
ψ( ∇´)ψ

39. User-Agent
DEFAULT_USER_AGENT = "Mozilla/5.0 (compatible;
CrowdTrail/1.0; +https://crowdwatch.tw/)"
def random_user_agent_string
format(
"%s Random/0.%d.%d",
DEFAULT_USER_AGENT,
Random.rand(100),
Random.rand(100)
)
end
HTTParty.get("https://www.facebook.com", headers:
{ "User-Agent" => random_user_agent_string })

40. • header IP
• X-Forward-For
• X-Real-IP
• CF-Connecting-IP

41. X-Forward-For
def random_x_forward_for
format(
"140.118.%d.%d",
Random.rand(255),
Random.rand(255)
)
end
HTTParty.get("https://www.facebook.com", headers:
{ "X-Forward-For" => random_x_forward_for })

42. Proxy
• Proxy Server
• Proxy
• http://txt.proxyspy.net/proxy.txt

43. CAPTCHA
• Ruby OCR
e.g. ruby-tesseract-ocr
• antigate.com
reCAPTCHA antigate

44. Parser Know-how

45. index
# Bad
doc.css('.tab')[2].text
# Good
doc.css('.tab').text[/ (d+) /, 1]
DOM Parser Regular Expression

46. Integer Float to_i
# Bad
doc.css('.tab .pledged').text.to_i
# Good
Integer(doc.css('.tab .pledged').text)
to_i nil 0

47. THANKYOU
Follow me on
https://github.com/shikendon
https://medium.com/@shikendon
https://www.facebook.com/zxuandon