1 / 16

Lifetime Behavior and its Impact on Web Caching

Lifetime Behavior and its Impact on Web Caching. X. Chen and P. Mohapatra, IEEE Workshop on Internet Applications (WIAPP), 1999. 김호중 , CA Lab. Site 별 , document type 별로 서로 다른 lifetime behavior 를 보인다는 논문 . Log 분석이 부실하므로 추천하지 않습니다. Introduction. Web cache consistency

hina
Download Presentation

Lifetime Behavior and its Impact on Web Caching

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lifetime Behavior and its Impact on Web Caching X. Chen and P. Mohapatra, IEEE Workshop on Internet Applications (WIAPP), 1999. 김호중, CA Lab. Site별, document type 별로 서로 다른 lifetime behavior를 보인다는 논문. Log 분석이 부실하므로 추천하지 않습니다.

  2. Introduction • Web cache consistency • If-Modified-Since (IMS) • Expires • Time-To-Live (TTL) • Fixed TTL • Adaptive TTL • Concerns only about traffic, not lifetime behavior

  3. Log Analysis (1/5) • Summary of logs from 3 classes EDU COM NEWS

  4. Log Analysis (2/5) • Document types

  5. Log Analysis (3/5) • Access pattern of different types in each class

  6. Log Analysis (4/5) • Not-modified (304) / Get retrieval (200) • Large NM/Get rate : TTL < lifetime • Change of a document can be found quickly • Waste of network resources

  7. Log Analysis (5/5) • Lifetime calculation • LTij = MTi(j+1) - MTij • How to detect modification in a log? • Change of file size • Distorting factors • Objects never changed in a log : lifetime? • Results of frequently accessed objects are more accurate

  8. Results (1/4) • Average lifetime • Documents in EDU class are much more stable

  9. Results (2/4) • EDU class • GIF files are seldom modified Documents distribution Access distribution 1.3% of HTML files 42% of access requests

  10. Results (3/4) • COM class • Similar to EDU • Popular documents are more mutable Documents distribution Access distribution 94% of HTML files : <10 modifications <50% of requests

  11. Results (4/4) • NEWS class • More popular GIF has shorter lifetime • How about JPG? Documents distribution Access distribution 2.7% of HTML files 50% of access requests

  12. Design Issues (1/3) • Document classification • Highly mutable documents • Frequent modification • Not worth caching • Stable documents • 44% of HTML and 78% of images are unchanged • 20% of HTML and 80% of images are stable • Short life documents • Accessed or existed 1~2 days • 1/3 of NEWS class, 20% of COM class • others

  13. Design Issues (2/3) • Two-state TTL algorithm • Transient state : short TTL • Stready state : long TTL • Simulation • Fixed TTL (1/4 of average lifetime) • 19.8% stale data / 10.9% Not-Modified-Since • Adaptive TTL (1/2 of elapsed time since last modification) • 7.3% stale data / 25.4% Not-Modified-Since • Two-state TTL • +0.9% stale data / -3.1 Not-Modified-Since • +2.8% cache hit rate

  14. Design Issues (3/3) • Web-adjusted caching algorithm • Stable data • Best candidate for conventional caching algorithms • Short time data • LRU with 2-state expiration time • Highly mutable data • Avoid LFU • TTL must be shorter • Pushing may be better than caching

  15. Conclusion • Lifetime-based workload characterization • Different type, different class • Different lifetime behavior • Popular files tend to be changed frequently • Cache algorithm design • Document classification • Two-state TTL algorithm

  16. Critique • How to classify sites & documents at proxy? • For popular sites & document? • Reverse proxy cache • Two-state TTL algorithm • adaptive TTL with only min. & max. • No relationship with document classification • Plenty of data, lack of analysis

More Related