HTTP's Best-Kept Secret: Caching

Caching HTTP’s Best Kept Secret

Ryan Tomayko http://tomayko.com/

Sinatra http://www.sinatrarb.com

Rack http://rack.rubyforge.org

Rack::Cache http://tomayko.com/src/rack-cache

Heroku http://heroku.com

HTTP Caching?

NOT Rails Caching

GET /foo HTTP/1.1 Host: www.foo.com User-Agent: FooBrowser/1.0 Cache-Control: max-age=0 If-Modified-Since: Mon, 01 Jan 1979 ... If-None-Match: abcdef0123456789 Accept: * HTTP/1.1 200 OK Content-Type: text/html Content-Length: 24 Cache-Control: max-age=300 Last-Modified: Mon, 02 Jan 1979 ... ETag: abcdef0123456789 Vary: Accept

GET /foo HTTP/1.1 Host: www.foo.com User-Agent: FooBrowser/1.0 Cache-Control: max-age=0 If-Modified-Since: Mon, 01 Jan 1979 ... If-None-Match: abcdef0123456789 Accept: * HTTP/1.1 200 OK Content-Type: text/html Content-Length: 24 Cache-Control: public, max-age=300 Last-Modified: Mon, 02 Jan 1979 ... ETag: abcdef0123456789 Vary: Accept

Types of Caches

Client Cache Client Client Client Cache Cache Cache foo.com

Shared Proxy Cache Shared Proxy Cache foo.com

Shared Proxy Cache Cache Cache foo.com

Shared Proxy Cache

Gateway Cache foo.com Gateway Cache Backend

Caches Everywhere Client Client Cache Cache Shared Cache foo.com Gateway Cache Backend

Why Cache?

November 1990

November 1990 Web Population: 1

February 1996 Web Population: 20M

February 1996 Modem Speed: 28.8kbps

February 1996

Bandwidth.

February 1996 RFC 1945 - HTTP/1.0

March 1999 RFC 2616 - HTTP/1.1

Expiration

Gateway Cache Alice Backend

Gateway Cache Alice Backend GET /foo Host: foo.com

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK Cache-Control:public,max-age=60

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK 200OK Cache-Control:public,max-age=60 Cache-Control:public,max-age=60

Gateway Cache Bob (30 seconds later) Backend

Gateway Cache Bob (30 seconds later) Backend GET /foo Host: foo.com

Gateway Cache Bob (30 seconds later) Backend GET /foo Host: foo.com 200OK Cache-Control:public,max-age=60 Age:30

Gateway Cache Carol (60 seconds later) Backend

Gateway Cache Carol (60 seconds later) Backend GET /foo Host: foo.com

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK Cache-Control:public,max-age=60

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK 200OK Cache-Control:public,max-age=60 Cache-Control:public,max-age=60

expires_in class FooController < Application def show expires_in 60.seconds, :public => true @foo = Foo.ﬁnd(params[:id]) render :action => 'show' end end

Sinatra get '/foo' do headers['Cache-Control'] = 'public, max-age=60' @foo = Foo.ﬁnd_and_stu erb :foo end

Validation (Conditional GET)

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK ETag:quot;abcdef012345quot;

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK 200OK ETag:quot;abcdef012345quot; ETag:quot;abcdef012345quot;

Gateway Cache Bob Backend

Gateway Cache Bob Backend GET /foo Host: foo.com

Gateway Cache Bob Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345

Gateway Cache Bob Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345 304NotModified

Gateway Cache Bob Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345 304NotModified 200OK ETag:abcdef012345

Rails: fresh_when class FooController < Application def show @foo = Foo.find(params[:id]) fresh_when :etag => @foo, :last_modified => @foo.updated_at.utc end end

Rails: stale? class FooController < Application def show @foo = Foo.find(params[:id]) modified = @foo.updated_at.utc if stale?(:etag => @foo, :last_modified => modified) respond_to do |wants| # ... normal response processing end end end end

Sinatra: etag get '/foo' do @foo = Foo.ﬁnd(params[:id]) etag @foo.etag erb :foo end

Expiration + Validation

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK Cache-Control:public,max-age=60 ETag:abcdef012345

Gateway Cache Alice Backend GET /foo GET /foo Host: foo.com Host: foo.com 200OK 200OK Cache-Control:public,max-age=60 Cache-Control:public,max-age=60 ETag:abcdef012345 ETag:abcdef012345

Gateway Cache Bob (30 seconds later) Backend

Gateway Cache Bob (30 seconds later) Backend GET /foo Host: foo.com

Gateway Cache Bob (30 seconds later) Backend GET /foo Host: foo.com 200OK Cache-Control:public,max-age=60 ETag:abcdef012345 Age:30

Gateway Cache Carol (60 seconds later) Backend

Gateway Cache Carol (60 seconds later) Backend GET /foo Host: foo.com

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345 304NotModified Cache-Control:public,max-age=60

Gateway Cache Carol (60 seconds later) Backend GET /foo GET /foo Host: foo.com Host: foo.com If-None-Match: abcdef012345 200OK 304NotModified Cache-Control:public,max-age=60 Cache-Control:public,max-age=60 ETag:abcdef012345

Never Generate The Same Response Twice

use Rack::Cache $ gem install rack-cache config.middleware.use Rack::Cache, :verbose => true, :metastore => quot;file:/var/cache/rack/metaquot;, :entitystore => quot;file:/var/cache/rack/bodyquot;, :allow_reload => false, :allow_revalidate => false

High Performance Caches/Accelerators •Squid http://www.squid-cache.org/ • Varnish http://varnish.projects.linpro.no/

Heroku

Thanks!

http://en.oreilly.com	756
http://www.bsdmap.com	446
http://www.slideshare.net	82
http://cache.baidu.com	9
http://dancroak.com	6
http://207.46.192.232	4
http://httpwww.bsdmap.com	4
http://wew.bsdmap.com	4
http://web.mail.bsdmap.com	3
http://w3ww.bsdmap.com	2
http://translate.googleusercontent.com	2
http://yaoge123blogwww.bsdmap.com	2
http://static.slidesharecdn.com	1
http://www.bsdmap.com.	1
http://ww.bsdmap.com	1
http://http.bsdmap.com	1
http://webcache.googleusercontent.com	1
http://awww.bsdmap.com	1
http://www.zhuaxia.com	1

HTTP's Best-Kept Secret: Caching

by rtomayko on May 10, 2009

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