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by Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original paper and presentation

By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

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Page 1: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

by Huang et al., SOSP 2013

An Analysis ofFacebook Photo Caching

Presented by Phuong Nguyen

Some animations and figures are borrowed from the original paper and presentation

Page 2: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Photos on Facebook: Overview

Profile

Feed

Album

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250 billion photos, as of Sep 2013

Page 3: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Photos on Facebook: Overview

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StorageBackend

FBCacheLayers Full-stack

Study

AkamaiCDN

Page 4: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

FACEBOOK PHOTO CACHING: HOW IT WORKS?

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Page 5: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Client-based Browser CacheClient

Browser Cache

Client

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LocalFetch

Page 6: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Geo-distributed Edge Cache (FIFO)

Edge Cache

(Tens)

Browser Cache

Client PoP

(Millions)

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Page 7: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Single Global Origin Cache (FIFO)

Browser Cache

Edge Cache

OriginCache

PoPClient Data Center

(Tens)(Millions) (Four)

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Hash(url)

Page 8: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Haystack Backend

Backend (Haystack)

Browser Cache

Edge Cache

OriginCache

PoPClient Data Center

(Tens)(Millions) (Four)

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Page 9: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

FULL-STACK CACHE STUDY: DATA COLLECTION

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Page 10: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

• Objective: collecting a representative sample that could permits correlation of events related to the same request

Trace Collection

Instrumentation Scope

Backend (Haystack)

Browser Cache

Edge Cache

OriginCache

PoPClient Data Center

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Page 11: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Sampling Strategies

• Request-based: sampling requests randomly• Bias on popular content

• Objected-based: focused on some subset of photos selected by a deterministic test on photoId• Fair coverage of unpopular photos• Cross stack analysis

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Page 12: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

WORKLOAD ANALYSIS

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Page 13: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Analysis Objectives

• Traffic sheltering effects of caches

• Photo popularity distribution

• Geographic traffic distribution & collaborative caching

• Can we make the cache better?

• Impact of sizes & algorithm

• Could we know which photos to cache?

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Page 14: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

ANALYSIS:TRAFFIC SHELTERING

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Page 15: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Traffic Sheltering

77.2M

26.6M11.2M

7.6M

Backend (Haystack)

Browser Cache

Edge Cache

OriginCache

PoPClient Data Center

65.5%58.0%

31.8%

R

Traffic Share

65.5% 20.0% 4.6% 9.9%

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Page 16: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

ANALYSIS:PHOTO POPULARITY IMPACT

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Page 17: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Popularity Distribution

Skewness is reduced after layers of cache17

Page 18: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Popularity Impact on Caches

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Page 19: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

ANALYSIS:GEOGRAPHIC TRAFFIC DISTRIBUTION & COLLABORATIVE CACHING

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Page 20: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Substantial Remote Traffic at Edge

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Atlanta 20% local

Miami 35% localDallas 50% local

Chicago 60% local

LA 18% local

NYC 35% local

Page 21: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Substantial Remote Traffic at Edge

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Atlanta 20% local

5% Dallas

35% D.C.

5% NYC

20% Miami

5% California

10% Chicago

• Atlanta has 80% requests served by remote Edges

Page 22: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Collaborative Edge

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Page 23: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Impact of Using Collaborative Edge

Collaborative Edge increases hit ratio by 18%

18%

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Collaborative

Page 24: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

ANALYSIS:IMPACTS OF CACHE SIZE & ALGORITHM

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Page 25: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Potential Improvement Study

• Methodology: cache simulation• Replay the trace (25% warm up)• Evaluate using remaining 75%

• Improvement factors:• Cache size• Caching algorithm

• Evaluation metric: hit ratio

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Page 26: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Edge Cache with Different Sizes & Algorithms

Infinite Cache

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The same hit ratio can be achieved with a smaller cache and higher-performing algorithms

Page 27: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Edge Cache with Different Sizes & Algorithms

Infinite Cache

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Sophisticated algorithm can achieve better hit ratio with the same cache size

Page 28: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

ANALYSIS:WHICH PHOTOS TO CACHE?

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Page 29: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Intuitions

• Properties that intuitively associated with photo traffic: • The age of photos • The number of Facebook followers

associated with the owner

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Page 30: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Content Age Affect

• Age-based cache replacement algorithm could be effective

• Fresh content is popular and tends to be effectively cached throughout the hierarchy

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Page 31: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Social Affect

• The more popular photo owner is, the more likely the photo is to be accessed

• Browser caches tend to have lower hit ratios for popular users (“viral” effect)

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Page 32: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

DISCUSSIONS

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Page 33: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Discussions

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• Evaluation method:• Only consider desktop clients, excluding mobile

clients• Trends by mobility of users

• Sampling: object-based sampling might not represent realistic workload

• Impact of caching done by Akamai CDN• Correlating requests method is not perfect

• Latency issue• Evaluation mainly focuses on hit ratio & traffic

sheltering, not latency• Latency of collaborative caching is note evaluated

Page 34: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

Discussions (cont.)

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• Other potential improvements:• Improved caching algorithm taking into account

metadata of photos• Optimal placement of resizing functionality along

the stack• The use of Clairvoyant caching might be possible

based on predicting future accesses• E.g., photos from the same album, photos

appear on news feed, etc.• Solve geographical diversity by improving routing

policy (e.g., put more weight into locality aspect)

Page 35: By Huang et al., SOSP 2013 An Analysis of Facebook Photo Caching Presented by Phuong Nguyen Some animations and figures are borrowed from the original

THANK YOU!

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