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Caching the Uncacheable: Leveraging Your CDN to Cache Dynamic Content
The document discusses caching dynamic content using CDNs, highlighting the importance of instant purging and real-time analytics for improved performance and user experience. It emphasizes that dynamic content can be cached more effectively than traditionally thought and advocates for the use of programmable APIs for better control and visibility. The conclusion urges careful management of caching rules to optimize web traffic and content delivery.
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Caching the Uncacheable: Leveraging Your CDN to Cache Dynamic Content
- 1. Caching The Uncacheable: Leveraging Your CDN to Cache Dynamic Content Hooman Behesh+, VP Technology
- 2. Dynamic Content Is Really Interes=ng!
- 3. What Is Dynamic Content? • Stuff that’s not sta+c! • With web traffic, generally the base HTML – Big deal because it’s blocking – And some+mes the largest object à longer download • Could be other things too – AJAX calls – API calls • More…
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- 8. Classically, with dynamic content… Caching
- 9. Dynamic Content Caching Problems • Serving stale pages – Lack of good invalida+on framework
- 10. Caching vs. Invalida=on
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- 15. Dynamic Content Caching Problems • Serving stale pages – Lack of good invalida+on framework
- 16. Dynamic Content Caching Problems • Serving stale pages – Lack of good invalida+on framework • Real-‐+me visibility – Real-‐+me analy+cs/stats – Real-‐+me logging
- 17. CDNs and Dynamic Content • Generally, handling dynamic content has been a maRer of transport – Op+mize from-‐origin delivery – “DSA” (Dynamic Site Accelera+on) – Middle mile op+miza+ons – TCP tweaks
- 18. Dynamic Content, Tradi=onally CDN Node Client Origin Some TCP Tweaks
- 19. Dynamic Content, Tradi=onally CDN Node CDN Node Client Origin Lots of TCP Tweaks
- 20. Dynamic Content, Tradi=onally • We some+mes do micro caching of HTML – Short TTL for HTML content – Not full proof • Ex: news stories faux-‐pas! • ESI (Edge Side Includes) – Par+al caching – Hard and onerous
- 21. Actually… • Dynamic content is more cacheable than we think • Sta+c for short periods of +me • Unpredictable invalida+on – Standard HTTP caching rules aren’t good enough
- 22. A Lot BeMer! CDN Node CDN Node Client Origin
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- 27. So Many Benefits! • Performance – Faster +me to first byte – Faster start render – Happy users! • Offload – Less work for our servers – Less bandwidth at origin
- 28. What would make it beMer?
- 29. Programma=c Invalida=on • Invalida+on API • Granular • Instantaneous – Big problem with classic CDNs (mul+-‐minute purges)
- 30. Power of the Purge! • Instant purging: – As a page gets published, a purge command also gets published – Instant means: predictable and determinis+c behavior
- 31. Power of the Purge! • Purge dependencies – Surrogate Keys – Using tags to purge en+re chunks of content at once
- 32. More than just Invalida=on…
- 33. The Influence of Clouds • The CDN is an extension of the app • No longer a black box • Real-‐+me integra+on with the app • Infrastructure as code – Your content => You need control
- 34. Control • Programmability – Configura+on API – Invalida+on API – Instantaneous and real +me – Granular caching • Ex: Geo-‐based caching
- 35. Control at the Edge • Moving app logic to the edge • VCL – Varnish Configura+on Language – Script-‐like configura+on for func+onality at the edge
- 36. Visibility • Real +me analy+cs – Network stats – HTTP stats (status codes , etc) – Caching stats (hits, misses, etc) – Stats API • Logging – Real +me logs – Streaming to various log des+na+ons
- 37. Example: CMS + Purge
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- 42. WordPress: Before CDN Node Cache
- 44. WordPress: AWer CDN Node
- 45. WordPress: AWer CDN Node HTTP/1.1 200 OK Content-Type: text/html Content-Length: 55,666 Cache-Control: Long Time, totally!
- 46. WordPress: AWer CDN Node
- 47. WordPress: AWer CDN Node
- 48. WordPress: AWer CDN Node PURGE
- 49. WordPress: AWer CDN Node PURGE
- 50. WordPress: AWer CDN Node PURGE (Has to be instantaneous!)
- 51. WordPress: AWer CDN Node HTTP/1.1 200 OK Content-Type: text/html Content-Length: 55,666 Cache-Control: Long Time, totally!
- 52. Example: Beacon Termina=on at the Edge
- 53. Before CDN Node Origin Log Analysis http://collector.site.com/beacon.img?a=1&b=2&c=3
- 54. Before CDN Node Origin Log Analysis http://collector.site.com/beacon.img?a=1&b=2&c=3
- 55. Before CDN Node Origin Log Analysis HTTP/1.1 200 OK Pragma: no-cache Expires: Wed, 19 Apr 2000 11:43:00 GMT Cache-Control: no-cache, no-store Last-Modified: Wed, 21 Jan 2004 19:51:30 GMT Content-Type: image/gif Date: Fri, 20 Jun 2014 12:22:20 GMT Server: Apache Content-Length: 35 http://collector.site.com/beacon.img?a=1&b=2&c=3
- 56. Before CDN Node Origin Log Analysis HTTP/1.1 200 OK Pragma: no-cache Expires: Wed, 19 Apr 2000 11:43:00 GMT Cache-Control: no-cache, no-store Last-Modified: Wed, 21 Jan 2004 19:51:30 GMT Content-Type: image/gif Date: Fri, 20 Jun 2014 12:22:20 GMT Server: Apache Content-Length: 35 http://collector.site.com/beacon.img?a=1&b=2&c=3
- 57. AWer CDN Node Origin http://collector.site.com/beacon.img?a=1&b=2&c=3
- 58. AWer CDN Node Origin HTTP/1.1 200 OK Pragma: no-cache Expires: Wed, 19 Apr 2000 11:43:00 GMT Cache-Control: no-cache, no-store Last-Modified: Wed, 21 Jan 2004 19:51:30 GMT Content-Type: image/gif Date: Fri, 20 Jun 2014 12:22:20 GMT Server: Apache Content-Length: 35 http://collector.site.com/beacon.img?a=1&b=2&c=3
- 59. AWer CDN Node Origin HTTP/1.1 204 No Content Date: Sat, 21 Jun 2014 23:21:12 GMT Server: Awesome Server Content-Length: 0 http://collector.site.com/beacon.img?a=1&b=2&c=3
- 60. AWer CDN Node Origin Syslog / S3 / FTP/etc http://collector.site.com/beacon.img?a=1&b=2&c=3
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- 62. JSON Data Center ID CDN Node Origin http://www.site.com/which_datacenter.js
- 63. JSON Data Center ID CDN Node Origin { ‘datacenter’ : ‘SJC’ } http://www.site.com/which_datacenter.js
- 64.
- 65. More Examples • Caching with tracking cookies: – hRp://www.fastly.com/blog/how-‐to-‐cache-‐with-‐ tracking-‐cookies • API Caching: – hRp://www.fastly.com/blog/api-‐caching-‐part-‐iii (part 3, with links to previous two parts) • Log Streaming: – hRp://www.fastly.com/blog/+ps-‐for-‐streaming-‐logs
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- 67. Summary • Dynamic content can be cached – We need instant purging – We need real-‐+me logs and stats • Real-‐+me integra+on of our CDN with our app is cool! – Extensive/granular API to control the CDN – Control and visibility at the edge lets us be really crea+ve • Never use “Long Time, totally!” in a Cache-Control header!
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