Video and slides synchronized, mp3 and slide download available at http://bit.ly/YKORol. Tim Stokes discusses various URI caching strategies providing real life examples relying on some of the natural behaviors that are built into the HTTP 1.1 protocol. Filmed at qconsf.com. Tim Stokes is the Applications Architect at FamilySearch.org, a not for profit organization that provides free resources for people to research their family tree. Prior to FamilySearch, Tim worked in London and Sydney with a number of companies including BT, Citigroup, Royal and SunAlliance, Press Co, Prudential, GM Vauxhall, The London Stock Exchange, Qantas, AMP and Intuit Australia.

1. Caching
Hypermedia
APIs
By Tim Stokes

2. Watch the video with slide
synchronization on InfoQ.com!
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/Caching-Hypermedia-API
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4. A very brief history
of Hypermedia
The Big Bang, 13.75 Billion Years Ago

5. Various Events…

6. Hypermedia
Ted Nelson, 1963

7. HTML
HTTP
Tim Berners-Lee (and friends), 1991

8. REST
(HTTP 1.1)
Roy Fielding (and his posse), 1999

9. By Paul Downey, http://www.flickr.com/photos/psd/
The Hypermedia Dark Ages, 2000-2005

10. POST /query HTTP/1.1
table=stick&status=thrown
The RESTful years, 2005-2009

11. Affordances
Mike Amundsen, circa 2010…

12. HTTP with
Hypermedia
+cachability
2012…

13. Choosing a
Caching Strategy
Theoretical
Natural
Managed
TTL
ETags
Other
Practical

14. Natural Caching Behavior 1
Transfer state in the
body not the URI

15. POST /box/open
GET /box

16. POST /box
state=open
GET /box

17. Natural Caching Behavior 2
Un-Safe Requests
Invalidate Cache

19. /car8
/mycar

20. /car8

21. /car8

22. Natural Caching Behavior 3
Related resources can
be Invalidated.

23. POST
1. /container is
invalidated
2. 303 + Location:
/container
/container/item8
or
2.
Content-Location:
/container/item8

24. DELETE 1. /container/item8
/container/item8
is invalidated
2. 303 + Location:
/container
or
2.
Content-Location:
/container

25. Natural Caching Behavior 4
Beware of Summaries
and Bundles

26. GET /lamp/1
1
POST /lamp/1 1
power=on
GET /lamps
links… /lamp/1, /lamp/2, /lamp/3, /lamp/4,
/lamp/5, /lamp/6, etc…
GET /all-on-lamps
5
1
3

27. RESOURCE DESIGN NOTES:
• The URI should not carry state
• Symmetry between state in and out
• One way to get each piece
of state
• Beware of Summaries
and Bundles

28. Natural Caching Behavior 5
Cached responses can
be bound to specific
contexts beyond the
URI.

29. GET /box
Accept-Language: EN
SYSTEM
box
Cache-Control: max-age=3600
Vary: Accept-Language
GET /box
Accept-Language: FR
boîte
Cache-Control: max-age=3600
Vary: Accept-Language

30. Natural Caching Behavior 6
There is no guarantee
you will see the latest
representation

31. Relativity

32. PUT /lamp
ON
OR
GET /lamp

33. Managed Caching Behavior 1
Use Etags with
conditional GETs

34. GET /dog
6
ETag: 6
SYSTEM
GET /dog If-None-Match: 6
✓ 304

35. GET /dog
6
ETag: 6
SYSTEM
GET /dog If-None-Match: 6
3
200 ETag: 3

36. Managed Caching Behavior 2
Let Caches know
about all resources
that are invalid in the
response to a state
change.

37. Mark Nottingham’s
Linked Cache Invalidation Draft
http://tools.ietf.org/html/draft-nottingham-linked-cache-inv-03

38. Relying on these Caching
Behaviors in Practice
• Compliance to HTTP 1.1
• Interpretation of HTTP 1.1
• Implementation variance
• Intermediaries

39. Approach
and granularity
• Design the shape
of your resources carefully.
• Target TTL in the Agent first for
best natural caching invalidation.
• Use, per request, Agent other
request header to trigger caching
strategies.
• ETags as second level after TTL.

40. What’s Next?
HTTP 2.0
http://tools.ietf.org/wg/httpbis/charters

41. The
End