Leo Soto M.ContinuumLecture & Beef, Marzo 2013

Caching tips

Sunday, March 3, 13

Leo Soto M.ContinuumLecture & Beef, Marzoss 2013

Caching tips (for webapps)

Sunday, March 3, 13

“There are only two hard things in computer science...

Sunday, March 3, 13

...cache invalidation and naming things”

- Phil Karlton

Sunday, March 3, 13

HTTP Caching

•Client-side!

•...or “middle-side” (proxys!)

•Conceptos claves:

•Frescura (freshness)

•Validacion/Invalidacion

Sunday, March 3, 13

FRESH CACHES

•HTTP/1.0:

Expires:  Fri,  01  March  2013  20:00:00  GMT

•HTTP/1.1:

Cache-­‐Control:  *pila-­‐de-­‐opciones*

Cache-­‐Control:  private,  max-­‐age=3600

Sunday, March 3, 13

VALIDATED CACHES

•HTTP/1.0:

Last-­‐Modified  /  If-­‐Modified-­‐Since

304  Not  Modified

•HTTP/1.1:

ETag  /  If-­‐None-­‐Match

304  Not  Modified

Sunday, March 3, 13

CACHE INVALIDATION

•METODOS HTTP QUE INVALIDAN CACHES FRESCAS:

POST  /resource

DELETE  /resource

PUT  /resource

Sunday, March 3, 13

EN RAILS

•FRESH CACHES:

expires_in  1.hour

•VALIDATED CACHES

if  stale?(etag:  @modelo)

   otros_hits_a_la_bd

end

Sunday, March 3, 13

stale?(etag:  x)  -­‐>  Etag:  md5(expand_cache_key(x))# File activesupport/lib/active_support/cache.rb, line 77def expand_cache_key(key, namespace = nil) expanded_cache_key = namespace ? "#{namespace}/" : ""

if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"] expanded_cache_key << "#{prefix}/" end

expanded_cache_key << retrieve_cache_key(key) expanded_cache_keyend

# File activesupport/lib/active_support/cache.rb, line 90def retrieve_cache_key(key) case when key.respond_to?(:cache_key) then key.cache_key when key.is_a?(Array) then key.map { |element| retrieve_cache_key(element) }.to_param else end.to_send

Sunday, March 3, 13

# File activerecord/lib/active_record/integration.rb, line 37def cache_key case when new_record? "#{self.class.model_name.cache_key}/new" when timestamp = self[:updated_at] timestamp = timestamp.utc.to_s(:number) "#{self.class.model_name.cache_key}/#{id}-#{timestamp}" else "#{self.class.model_name.cache_key}/#{id}" endend

Sunday, March 3, 13

EN RAILS

•SIN ETAGGER

stale?(etag:  [current_user,  @modelo])

stale?(etag:  [current_user,  @otro])

stale?(etag:  [current_user,  @otromas])

Sunday, March 3, 13

EN RAILS

•CON ETAGGERetag  {  current_user  }

stale?(etag:  modelo)

stale?(etag:  otro)

stale?(etag:  otromas)

Sunday, March 3, 13

EN RAILS

•EN AC PERFORACIONESetag  {  [current_user,  ENV[‘COMMIT_HASH’]  }

stale?(etag:  modelo)

stale?(etag:  otro)

stale?(etag:  otromas)

Sunday, March 3, 13

Rails Fragment Caching

-­‐cache  ‘foo’  do...end

-­‐cache  modelo  do...end

-­‐cache  [reporte,  ‘inbox’]  do..end

# File actionpack/lib/action_controller/caching/fragments.rb, line 51def fragment_cache_key(key) ActiveSupport::Cache.expand_cache_key( key.is_a?(Hash) ? url_for(key).split("://").last : key, :views)end

Sunday, March 3, 13

RUSSIAN DOLL CACHING

-­‐  cache  [reporte,  ‘perforaciones’]  do

   -­‐  perforacion.each  do  |p|

       -­‐  cache  perforacion  do

           %h1=  perforacion.titulo

           %p=  perforacion.whatever

Sunday, March 3, 13

TIPS FRAGMENT CACHING

•Aplicar a cosas que no dependan del usuario actual

•Usar cache_digests + memcached

Sunday, March 3, 13

CONCLUSIONES

•HTTP CACHING:

•CACHE LOCAL AL USUARIO

•AHORRA:

•LATENCIA

•ANCHO DE BANDA,

•TIEMPO DE RESPUESTA DEL SERVIDOR

Sunday, March 3, 13

CONCLUSIONES

•FRAGMENT CACHING:

•CACHE GLOBAL DE LA APP

•AHORRA:

•HITS A LA BD

•CALCULOS

•RENDERING

Sunday, March 3, 13

BONUS TRACK def prefetch(url) content_tag("script", %Q{ $("<link href='#{escape_javascript(url)}' rel='subresource'/>").appendTo('head') }.html_safe ) unless current_page?(url) end

def tab_detalle_reporte(text, opts = {}) collection = opts[:collection] || text.downcase.pluralize url = send("reporte_#{collection}_path", estado, reporte) tab_title(opts.merge!( name: text, href: url, active: tab == collection )) + prefetch(url) end

Sunday, March 3, 13