Dog Pile Effect - QCon Sao Paulo

1. Dog-pile effect como evitar que sua aplicação desmorone
2. 1 Hugo Baraúna
4. Por que eu devo ouvir isso?
5. Porque somos bons desenvolvedores!
7. “There are only two hard problems in Computer Science: cache invalidation and naming things.” — Phil Karlton
11. Cache
12. Cache TTL de 5 minutos
13. 0 5 10 cache
14. 0 5 10 cache
15. 0 5 10 cache HIT
16. 0 5 10 cache HIT
17. 0 5 10 cache cache HIT
18. 0 5 10 cache HIT
19. 0 5 10 cache HIT
20. 0 5 10 cache HIT MISS
21. 0 5 10 cache HIT MISS
22. 0 5 10 cache HIT MISS
23. 0 5 10 cache HIT MISS
24. 0 5 10 cache HIT MISS dog-pile effect
25. Soluções?
27. 1 1 request ativa geração de cache. As outras esperam o cache ser gerado.
28. 2 1 request ativa geração de cache. As outras requests são servidas com o cache antigo. http://blog.plataformatec.com.br/2009/09/how-to-avoid-dog-pile-effect-rails-app/
29. 3 Asynchronous HTTP Cache Validations http://igvita.com/2008/10/07/asynchronous-http-cache-validations/
31. Como fazer no Rails?
32. # Read value = Rails.cache.read("my_key")
33. # Read value = Rails.cache.read("my_key") # Write Rails.cache.write("my_key", "my_value")
34. module ActiveSupport module Cache class Store end end end
35. module ActiveSupport module Cache class Store end end end
36. module ActiveSupport module Cache class MemCacheStore < Store end end end
37. module ActiveSupport module Cache class MemCacheStore < Store end end end
38. module ActiveSupport module Cache class SmartMemCacheStore < MemCacheStore end end end
39. module ActiveSupport module Cache class SmartMemCacheStore < MemCacheStore end end end
40. module ActiveSupport module Cache class SmartMemCacheStore < MemCacheStore alias_method :orig_read, :read alias_method :orig_write, :write def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end end end end
41. Como funciona?
42. module ActiveSupport module Cache class SmartMemCacheStore < MemCacheStore alias_method :orig_read, :read alias_method :orig_write, :write def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end end end end
43. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end
44. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end
45. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end Agora são: 12:00 expires_at: 12:05
46. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end
47. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end
48. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end Todas requests antes de 12:05 recebem cache hit do cache válido
49. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end
50. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end Ao 12:06 o cache vai estar stale
51. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end request salva um lock no cache
52. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end
53. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end novas requests percebem que tem um lock criado
54. def read(key, options = nil) lock_expires_in = options.delete(:lock_expires_in) if !options.nil? lock_expires_in ||= 30 response = orig_read(key, options) return nil if response.nil? data, expires_at = response if Time.now > expires_at && !orig_read("lock_#{key}").present? orig_write("lock_#{key}", true, :expires_in => lock_expires_in) return nil else data end end elas serão servidas com o cache antigo novas requests percebem que tem um lock criado
55. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end
56. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end cria o novo cache
57. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end
58. def write(key, value, options = nil) expires_delta = options.delete(:expires_delta) if !options.nil? expires_delta ||= 300 expires_at = Time.now + expires_delta package = [value, expires_at] orig_write(key, package, options) delete("lock_#{key}") end deleta o lock
59. SmartMemCache
60. @hugobarauna blog.plataformatec.com .br
61. http://www.guru-sp.org