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SPA2015: Hooman Beheshti – The Future of CDNs
The document discusses the evolution and complexities of Content Delivery Networks (CDNs), highlighting the need for better caching strategies and real-time control features to manage dynamic and event-driven content. It outlines various types of content—static, dynamic, and event-driven—and emphasizes the importance of programmability and visibility through real-time analytics at the edge. The future of CDNs entails enhanced security measures and more logic at the edge to improve application performance and delivery.
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SPA2015: Hooman Beheshti – The Future of CDNs
- 1. Evolution of the CDN Hooman Beheshti, VP Technology SPA2015
- 2. CDN • Globally distributed network of servers • Built primarily with caching engines (squid, nginx, varnish, etc) • Footprints vary
- 4. CDN benefits • Performance •Latency decrease due to footprint • Origin offload • Much much more…
- 5. Deployment • Originally simple: •Serve root web page (HTML) direct from origin • Point static assets on the page to a domain owned by the CDN • Everything controlled through DNS
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- 9. Transport and delivery optimization
- 10. Transport and delivery optimization
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- 12. Things have started changing…
- 13. Applications have became smarter
- 14. Caching has gotten more complicated
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- 17. Static = Cacheable All Else = Dynamic = Uncacheable
- 18. Static = Cacheable All Else = Dynamic = Uncacheable
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- 20. Static for unpredictable periods of time Event Driven Content:
- 21. Three types of content • Static • Infrequent changes, can cache for a long time • Cache-‐control headers are often good enough • Examples: images, javascript, css, etc • Dynamic • Can’t cache at all – must go to origin • DSA and transport optimization is key for performance • Examples: logins, credit card transactions, Ajax, etc • Event-‐driven: • Static, but unpredictably • Cache-‐control headers are not good enough on their own • Examples: news stories, wiki pages, user comments, sports scores, etc
- 22. Three types of content • Static • Infrequent changes, can cache for a long time • Cache-‐control headers are often good enough • Examples: images, javascript, css, etc • Dynamic • Can’t cache at all – must go to origin • DSA and transport optimization is key for performance • Examples: logins, credit card transactions, Ajax, etc • Event-‐driven: • Static, but unpredictably • Cache-‐control headers are not good enough on their own • Examples: news stories, wiki pages, user comments, sports scores, etc
- 23. Three types of content • Static • Infrequent changes, can cache for a long time • Cache-‐control headers are often good enough • Examples: images, javascript, css, etc • Dynamic • Can’t cache at all – must go to origin • DSA and transport optimization is key for performance • Examples: logins, credit card transactions, Ajax, etc • Event-‐driven: • Static, but unpredictably • Cache-‐control headers are not good enough on their own • Examples: news stories, wiki pages, user comments, sports scores, etc
- 24. Long-‐tail Content (cacheable but seldom fetched)
- 25. Usage patterns have changed
- 26. CDN problems • Services were black boxes • Lots of professional services • Caching efficiency has decreased • Not a lot of visibility • No real-‐time feedback • No real-‐time interfaces • APIs • Not enough real-‐time control • Removing content from the CDN • Configuration changes
- 27. CDNs have to evolve…
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- 29. Caching event-‐driven content •Caching predictably static content is relatively straight forward • Headers • Configuration • Caching unpredictably static content is really difficult • We don’t know lifetime in advance • Trigger-‐based invalidation
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- 36. Purging content from a CDN • Event-‐driven content can be cached if the CDN allows instantaneous programmatic purging • Cache normally • Purge when change trigger happens • Rinse and repeat! • Slow purge times unacceptable in this case • We need instant purging • Deterministic and predictable
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- 45. WordPress: Now CDN Node HTTP/1.1200 OK Content-Type: text/html Content-Length: 55,666 Cache-Control: Totally Long Time!
- 46. WordPress: Now CDN Node HTTP/1.1200 OK Content-Type: text/html Content-Length: 55,666 Cache-Control: Totally Long Time!
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- 51. WordPress: Now CDN Node (Has to be instantaneous!) PURGE
- 52. WordPress: Now CDN Node HTTP/1.1200 OK Content-Type: text/html Content-Length: 55,666 Cache-Control: Totally Long Time!
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- 54. Long tail content and cache hit ratio
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- 64. Popular Medium Tail (1hr) Long tail (6hr)
- 65. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Popular 14msec 1hr Tail 15msec 6hr Tail 16msec
- 66. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Popular 14msec 1hr Tail 15msec 6hr Tail 16msec
- 67. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Popular 14msec 1hr Tail 15msec 6hr Tail 16msec
- 68. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Popular 14msec 1hr Tail 15msec 6hr Tail 16msec
- 69. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Wait (median) Popular 14msec 19msec 1hr Tail 15msec 26msec 6hr Tail 16msec 32msec
- 70. Popular Medium Tail (1hr) Long tail (6hr) Connect (median) Wait (median) Popular 14msec 19msec 1hr Tail 15msec 26msec 6hr Tail 16msec 32msec 6,400+ measurements 77,000+ measurements 38,000+ measurements
- 71. Popular Medium Tail (1hr) Long tail (6hr) Isn’t this better?
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- 73. Caching • Cache more •Serve more from the edge • Control caching and uncaching, instantaneously
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- 75. Programmability • Granular invalidation API • Configuration API • Logic at the edge • All configuration interaction must be instantaneous
- 78. Control at the edge • Moving application logic to the edge • Example: VCL (Varnish Configuration Language) • Script-‐like configuration for functionality at the edge
- 80. Control at the edge • Moving application logic to the edge • Example: VCL (Varnish Configuration Language) • Script-‐like configuration for functionality at the edge • Not exclusive to varnish • Any mechanism offered by the CDN to allow logic to be executed at the edge is good
- 81. Logic at the edge • Generate content at the edge • HTTP header manipulation • Origin selection • Caching rules • Geo-‐IP rules • Forcing SSL • Serving stale content • Etc, etc, etc
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- 83. Control • Programmatic interfaces •Real-‐time interaction with the CDN • Running logic at the edge
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- 85. Real-‐time analytics • Statistics API • Network stats • HTTP stats (status codes, etc) • Caching stats (hits, misses, errors, etc) • Everything has to be real-‐time • Historic data is also a must
- 86. Logging • Daily or hourly logs are not good enough • Logs in real-‐time • Log streaming • To any logging destination endpoint • Syslog, S3, FTP, etc.
- 87. Visibility • We need to see what’s going on • Real-‐time stats • Stats API • Real-‐time logs
- 88. Example: Beacon Termination at the Edge
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- 96. Then CDN Node Origin Log Analysis HTTP/1.1200 OK 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
- 97. Then CDN Node Origin Log Analysis HTTP/1.1200 OK 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
- 98. Then CDN Node Origin Log Analysis HTTP/1.1200 OK 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
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- 100. Now CDN Node Origin HTTP/1.1 200OK 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
- 101. Now (204) CDN Node Origin HTTP/1.1204 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
- 102. Now CDN Node Origin Syslog / S3 / FTP/etc Stream ed W 3C Log http://collector.site.com/beacon.img?a=1&b=2&c=3
- 103. Summary: CDN is an extension of the app • Flexible caching… • …and uncaching • All tail sizes should perform comparably! • Control over functionality at the edge • Real time interfaces for programmability • Logic at the edge • Real-‐time visibility • Real-‐time analytics
- 104. The future • Security (more now than future!) • Even more at the edge • More logic • Other parts of applications • More delivery features
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