The Challenges of Managing Big Data

Amr El AbbadiComputer Science, UC Santa Barbara

amr@cs.ucsb.edu

Coined by Jeannette Wing (CMU, NSF, Microsoft). Essential for the productive citizenry of the

21 century. Computer Science is the critical component

in Science, Commerce, Finance, Engineering, Social Science, and even Humanity.

Our role as educators is challenging but very rewarding. Need to understand and teach the foundations and essence of computation.

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Computational Thinking

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 Accurate and effective public health emergency response demands deep understanding of the context and the details of chaotic situations.

How Big Data Analysis Guides Hurricane Sandy Response

http://www.directrelief.org/2012/11/how-big-data-analysis-guides-our-hurricane-sandy-response/

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Evaluate more candidates, amass more data and peer more deeply into applicants' personal lives and interests.

Allows employers to predict specific outcomes, such as whether a prospective hire will quit too soon, file disability claims, or steal.

Meet the New Boss: Big Data

• For example after a half-year trial that cut attrition by a fifth, Xerox now leaves all hiring for its 48,700 call-center jobs to software.

• The model for the ideal call-center worker  is a person who lives near the job, has reliable transportation and uses one or more social networks, but not more than four.

• Note that practices that even unintentionally filter out older or minority applicants can be illegal.

• Wall Street Journal, Sept 20, 2012.

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The Big Data Eco-System in the Cloud

inter-data center

Inter-data center

Analysis & Quality

Infrastructure

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The 3 V’s of Big Data

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Big Data in Numbers

Facebook:◦ 1.5 Billion users◦ 140.3 Billion friendships

Twitter in a day:◦ 500 million tweets sent

Youtube in a day:◦ 3 billion videos viewed

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104+ Hours of video uploaded on youtube 42,408+ App Downloads 153,804+ New photos uploaded on Facebook $263,947+ money spent on web shopping 298,013+ New Tweets 1,881,737+ youtube video views 2,521,244+ search queries on Google 2,692,323+ New Facebook Likes 20,234,009+ flickr photos views 204,709,030+ emails sent over the Internet

Source: http://whathappensontheinternetin60seconds.com/

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Reality Check: Inside a Data Center

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App Server

App Server

App Server

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Scaling in the Cloud

Load Balancer (Proxy)

App Server

DATABASE

Client Site

App Server

Client Site Client Site

Database becomes the Scalability Bottleneck

Cannot leverage elasticity

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App Server

App Server

App Server

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Scaling in the Cloud

Load Balancer (Proxy)

App Server

DATABASE

Client Site

App Server

Client Site Client Site

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Key Value Stores

App Server

App Server

App Server

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Scaling for Big Data

Load Balancer (Proxy)

App Server

Client Site

App Server

Client Site Client Site

Scalable and Elastic,but limited consistency

and operational flexibility

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Every read or write of a single row is atomic.

Objective: make all operations single-sited.

Key Value Stores

Scale-up◦ Classical enterprise setting

(RDBMS)◦ Flexible ACID transactions◦ Transactions in a single node

Scale-out◦ Cloud friendly (Key value

stores)◦ Execution at a single server

Limited functionality & guarantees

◦ No multi-row or multi-step transactions

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Two approaches to scalability

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Why Consistency Matters On-line Social Media needs to be consistent!

◦ New unanticipated applications

The host’s dilemma◦ Remove “unpopular” friend X as friend◦ Post Party Next Friday at YYY”

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What about the Application Programmer?

Key-value StoresTransactions and SQL

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SQL and Scale-outS

cale

Ou

t

SQL Transactions

Key Value Stores

RDBMSs

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Cloud Elasticity

Challenge: Elasticity in Database tier

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Database tier

Load Balancer

Application/Web/Caching tier

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What the user wants…

What the service provider wants…

The need for Live Migration: If the database platform was a phone booth…

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Catastrophic Failures: Geo-Replication

“As a result they had no access to email,

calendars, or - most importantly - their

documents and Office

Online applications”

“most of digital communication - email, Lync, Sharepoint -

was out”

“Most of the other high-profile companies, including the

likes of Amazon, have had substantial outages … cloud services are still in their infancy, and glitches

like this are going to happen”

Geo Replication Promises: Low latency reads Tolerate Failures & data centers outages

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Geo Replication

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Geo Replication

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Geo Replication

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Communication Overhead

21101 99

169

341

173

260

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Latency lower-bound [SIGMOD 2015]

Replica1

Replica 2

Wide-area link

Datacenter A Datacenter B

Transaction T1

Round Trip Latency Delay

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Commit latency of T1 + Commit latency of T2 must be greater than or equal the Round-Trip Time between

them

Transaction T2

Then we have the challenge of VARIETY! Diverse access methods OLTP OLAP Graph

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Fall of ‘One Size Fits all’

Replication Driven Solution Leverage Replication by storing replicas in

different representations

Execution Engine

Column Row

Graph

OLTP Client

OLAP Client

Graph Client

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BIG Data Analytics Needs

Large scale data processing is difficult!◦ Managing hundreds or thousands of processors◦ Managing parallelization and distribution◦ I/O Scheduling◦ Status and monitoring◦ Fault/crash tolerance

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MapReduce to the Rescue?

Overview:◦ Data-parallel programming model ◦ An associated parallel and distributed

implementation for commodity clusters Pioneered by Google

◦ Processes 20 PB of data per day Popularized by open-source Hadoop project

◦ Used by Yahoo!, Facebook, Amazon, and the list is growing …

and now there is SPARK…….

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MapReduce (Hadoop) Model

Raw Input: <key, value>

MAP

<K2,V2><K1, V1> <K3,V3>

REDUCE

Execution Model: Data splits Map phase Intermediate data sort, partition and shuffling Reduce phase

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How Target Figured Out A Teen Girl Was Pregnant Before Her Dad Did

Stores everything customers bought + demographic information.

Crawl through the data, assign each shopper a “pregnancy prediction” score + estimate due date

Send coupons timed to specific stages of pregnancy.

 Jenny is 23, lives in Atlanta, in March bought cocoa-butter lotion, a large purse, zinc and magnesium supplements and a bright blue rug

87% chance that Jenny’s pregnant and her delivery date is sometime in late August.

http://www.forbes.com/sites/kashmirhill/2012/02/16/how-target-figured-out-a-teen-girl-was-pregnant-

before-her-father-did/

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Privacy in the Cloud Data confidentiality

◦ Attacks Unauthorized accesses,

side channel attacks◦ Solutions

Encryption, querying encrypted data

Trusted computing

User

Cloud Servers

DataQuery

Answer

• Access privacy– Attacks

• Inferences on access patterns or query results

– Solutions• Private information

retrieval• Query obfuscation

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The Internet and how we use it

“Nearly two-thirds of Internet users worldwide use some type of social media” (McCafferty, CACM 2012)

• “The internet's largest impact comes in connecting people to other people for advice or sharing valuable experiences. For about one-third (34%) of those who used the … social networks was part of the decision-making dynamic. ” (Horrigan et al. 2006)

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Diffusion of Information

Diffusion (a.k.a. cascade, spread) in social networks: Does it happen?

• Mass Convergence and Emergency Events (Hughes et al. 2009, Sakaki et al. 2010)

• Education through Social Networks (Cheong et al. 2010)

• Collective Action

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Time Critical Social MobilizationThe 10 red balloons DARPA Challenge. MIT winning team found the 10 balloons

in 8 hours and 52 minutes using incentivized diffusion in a social network (Twitter). Science Vol 334, 28 Oct 2011.

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Are we missing something?Morocco is the Best!

Morocco is the Best!Morocco is

the Best!

Morocco is the Best!

Morocco is the Best!

Morocco is the Best!

Traditional trend detection fails to capture the difference between the two scenarios

Dispersed interest in the

topic

Interest from structural subgroup

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Coordinated vs Uncoordinated Trends

Consider two traditionally similar hashtags #pawpawty and #mafiawars (using Prefuse)

#pawpawty: Traditional rank: 289Significant as a coordinated trend: rank 24

#mafiawars: Traditional rank: 212Insignificant as a coordinated trend (rank 25812th )

Disconnectednodes

#pawpawty is a hashtag used by animal rights defenders while #mafiawars is used by

gamers. One might entail more of a community formation…

Next question: Are topics of certain categorical nature more (or less) important as structural

trends? Yes, political hashtags tend to be more significant as structural trends while hashtags

relating to gaming, music etc. are more significant as uncoordinated trend

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GeoScope Reporting diffusion: Geo-correlated trend

detection:◦ Provides high level information about topics and

locations:◦ Detects important location-topic pairs in a sliding

window What is the popularity of #ff

in Morocco?Which topics are of

interest particularly to Ifran

today?

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Cities

Users of certain cities like Jakarta have diverse interestsWhile other cities like Cairo are interested in more local topics

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Computational Thinking Data Cross-disciplinary Globalization

Privacy and Societal issues. Energy Efficiency

Conclusions