Browser Caching and You - A Love Story

Over time, Web developers have feared, hated and loved Web caching, at times trying to kill it, at others professing undying love. Mark Nottingham (chair of the IETF HTTPbis Working Group and author of its revised Web Caching specification) will examine how browsers (mis)-treat your content today, as well as where your relationship with browser caching might go in the future.

Transcript

1. Browser Caching & You
   (a love story) Mark Nottingham / mnot.net
2. At First Sight:
   The Honeymoon
3. EMPTY FULL http://www.yuiblog.com/blog/2007/01/04/performance-research-part-2/
5. Relationship Trouble
6. http://www.websiteoptimization.com/speed/tweak/average-web-page/
7. Mozilla: 50MB
   IE: 10% (max 1G)
   Safari: ??
   Chrome: 8-250M?
8. Mozilla: 100 pages
9. Mozilla: 16384 entries 89 // Min and max values for the number of records in the DiskCachemap 90 #define kMinRecordCount 512 91 92 #define kSeparateFile 0 93 // #define must always be <= 65535KB, or overflow. See bug 443067 Comment 8 94 #define kMaxDataFileSize 5 * 1024 * 1024 // 5 MB (in bytes) 95 #define kBuckets (1 << 5) // must be a power of 2! (~230 pages)
10. Cache-Control: max-age=0,
    no-cache, no-store,
    private, pre-check=0,
    post-check=0
11. “Maybe we should start seeing other people...”
12. HTML5 AppCache
14. • privacy concerns (“EverCookie”) • relationship with HTTP caching is poorly de^ined • designed for of^line use
15. Getting to know
    each other
17. max-age / expires Chrome 6 IE7
18. max-age / expires Safari 5.0.2 Take-away: Cache timing is OK, but not exact
19. no-cache no-store Take-away: no-store is enough
20. Age IE8
21. Date Safari 5.0.2 IE (any)
22. pre-check, post-check Take-away: max-age=0, pre-check=0, post-check=0 is a really bad idea. IE (most)
23. Where is this thing going?
    (“the talk”)
24. • Fixing Bugs • Sizing Caches Appropriately • Replacement Algorithms
25. stale-while-revalidate cache
26. stale-if-error
27. Cache Invalidation
28. RFC 2616:
    the internets Cache origin server POST/PUT/DELETE/etc. Invalidations after Updates or Deletions Request-URI Content-Location Location
29. Problem: Related Responses POST /articles/123/new_comment /newest_comments /articles/123/comments /comment_feed
30. Link: rel=invalidated-by POST /articles/123/new_comment /newest_comments /articles/123/comments /comment_feed Link: </articles/123/new_comment>; rel=”invalidate Link: </articles/123/new_comment>; rel=”invalidated-by” Link: </articles/123/new_comment>; rel=”invalidated-by”
31. Problem 3: Dynamic Relations POST /articles/123/new_comment /newest_comments /articles/123/comments /comment_feed Link: </articles/123/new_comment>; rel=”invalidate Link: </articles/123/new_comment>; rel=”invalidated-by” Link: </articles/123/new_comment>; rel=”invalidated-by” /bob/comments /cat/vuvuzela
32. Link: rel=invalidates POST /articles/123/new_comment /newest_comments /articles/123/comments /comment_feed Link: </articles/123/new_comment>; rel=”invalidate Link: </articles/123/new_comment>; rel=”invalidated-by” Link: </articles/123/new_comment>; rel=”invalidated-by” /bob/comments /cat/vuvuzela Link: </cat/vuvuzela>; rel=”invalidates” Link: </bob/comments>; rel=”invalidates”
33. Linked
    Cache
    Invalidation “side effect” invalidation + link relations =
34. Further Out
    (“there’s still life in this thing”) • Cache API for invalidation • Revisiting of^line caching • Forward Cache Digests • Explicit Cache Key