Tips de caching

1. Caching tips
Leo Soto M.
Continuum
Lecture & Beef, Marzo 2013
Sunday, March 3, 13

2. Caching tips
(for webapps)
Leo Soto M.
Continuum
Lecture & Beef, Marzoss 2013
Sunday, March 3, 13

3. “There are only
two hard things
in computer
science...
Sunday, March 3, 13

4. ...cache
invalidation and
naming things”
- Phil Karlton
Sunday, March 3, 13

5. HTTP Caching
•Client-side!
•...or “middle-side” (proxys!)
•Conceptos claves:
•Frescura (freshness)
•Validacion/Invalidacion
Sunday, March 3, 13

6. 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

7. 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

8. CACHE INVALIDATION
•METODOS HTTP QUE INVALIDAN
CACHES FRESCAS:
POST
/resource
DELETE
/resource
PUT
/resource
Sunday, March 3, 13

9. EN RAILS
•FRESH CACHES:
expires_in
1.hour
•VALIDATED CACHES
if
stale?(etag:
@modelo)
otros_hits_a_la_bd
end
Sunday, March 3, 13

10. stale?(etag:
x)
-­‐>
Etag:
md5(expand_cache_key(x))
# File activesupport/lib/active_support/cache.rb, line 77
def 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_key
end
# File activesupport/lib/active_support/cache.rb, line 90
def 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_s
end
Sunday, March 3, 13

11. # File activerecord/lib/active_record/integration.rb, line 37
def 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}"
end
end
Sunday, March 3, 13

12. EN RAILS
•SIN ETAGGER
stale?(etag:
[current_user,
@modelo])
stale?(etag:
[current_user,
@otro])
stale?(etag:
[current_user,
@otromas])
Sunday, March 3, 13

13. EN RAILS
•CON ETAGGER
etag
{
current_user
}
stale?(etag:
modelo)
stale?(etag:
otro)
stale?(etag:
otromas)
Sunday, March 3, 13

14. EN RAILS
•EN AC PERFORACIONES
etag
{
[current_user,
ENV[‘COMMIT_HASH’]
}
stale?(etag:
modelo)
stale?(etag:
otro)
stale?(etag:
otromas)
Sunday, March 3, 13

15. 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 51
def 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

16. RUSSIAN DOLL
CACHING
-­‐
cache
[reporte,
‘perforaciones’]
do
-­‐
perforacion.each
do
|p|
-­‐
cache
perforacion
do
%h1=
perforacion.titulo
%p=
perforacion.whatever
Sunday, March 3, 13

17. TIPS FRAGMENT
CACHING
•Aplicar a cosas que no
dependan del usuario actual
•Usar cache_digests +
memcached
Sunday, March 3, 13

18. CONCLUSIONES
•HTTP CACHING:
•CACHE LOCAL AL USUARIO
•AHORRA:
•LATENCIA
•ANCHO DE BANDA,
•TIEMPO DE RESPUESTA DEL
SERVIDOR
Sunday, March 3, 13

19. CONCLUSIONES
•FRAGMENT CACHING:
•CACHE GLOBAL DE LA APP
•AHORRA:
•HITS A LA BD
•CALCULOS
•RENDERING
Sunday, March 3, 13

20. 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