1. Caching
HTTP’s Best Kept Secret

2. Ryan Tomayko
http://tomayko.com/

3. Sinatra
http://www.sinatrarb.com

4. Rack
http://rack.rubyforge.org

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

6. Heroku
http://heroku.com

7. HTTP Caching?

8. NOT Rails Caching

9. 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

10. 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

11. Types of Caches

12. Client Cache
Client Client Client
Cache Cache Cache
foo.com

13. Shared Proxy Cache
Shared Proxy
Cache
foo.com

14. Shared Proxy Cache
Cache Cache
foo.com

15. Shared Proxy Cache

16. Gateway Cache
foo.com
Gateway
Cache
Backend

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

18. Why Cache?

19. November 1990

20. November 1990
Web Population: 1

22. February 1996
Web Population: 20M

23. February 1996
Modem Speed: 28.8kbps

24. February 1996

25. February 1996

26. Bandwidth.

27. February 1996
RFC 1945 - HTTP/1.0

28. March 1999
RFC 2616 - HTTP/1.1

29. Today

30. Expiration

31. Gateway Cache
Alice Backend

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

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

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

35. 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

36. Gateway Cache
Bob (30 seconds later) Backend

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

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

39. Gateway Cache
Carol (60 seconds later) Backend

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

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

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

43. 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

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

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

46. Validation
(Conditional GET)

47. Gateway Cache
Alice Backend

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

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

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

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

52. Gateway Cache
Bob Backend

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

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

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

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

57. 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

58. 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

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

60. Expiration
+
Validation

61. Gateway Cache
Alice Backend

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

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

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

65. 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

66. Gateway Cache
Bob (30 seconds later) Backend

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

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

69. Gateway Cache
Carol (60 seconds later) Backend

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

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

72. 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

73. 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

74. Never Generate The
Same Response Twice

75. 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

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

77. Heroku

78. Thanks!