COMPUTING ON JETSTREAM:STREAMING ANALYTICS IN THE WIDE-AREA

Matvey Arye

Joint work with: Ari Rabkin, Sid Sen, Mike Freedman and Vivek Pai

THE RISE OF GLOBAL DISTRIBUTED SYSTEMS

Image shows CDN

TRADITIONAL ANALYTICS

Image shows CDN

Centralized

Database

BANDWIDTH IS EXPENSIVE

Series1

CPU(16x)Storage(10x)Bandwidth(2.7x)

Price Trends 2005-2008

[Above the Clouds, Armbrust et. al.]

BANDWIDTH TRENDS

[TeleGeography's Global Bandwidth Research Service]

BANDWIDTH TRENDS

[TeleGeography's Global Bandwidth Research Service]

20% 20%

BANDWIDTH COSTS• Amazon EC2 bandwidth: $0.05 per GB

• Wireless broadband: $2 per GB

• Cell phone broadband (ATT/Verizon): $6 per GB

– (Other providers are similar)

• Satellite Bandwidth $200 - $460 per GB

–May drop to ~$20

THIS APPROACH IS NOT SCALABLE

Image shows CDN

Centralized

Database

THE COMING FUTURE: DISPERSED DATA

Dispersed

Databases

Dispersed

Databases

Dispersed

Databases Disperse

d Database

s

WIDE-AREA COMPUTER SYSTEMS

• Web Services– CDNs– Ad Services– IaaS– Social Media

• Infrastructure– Energy Grid

• Military– Global Network– Drones– UAVs– Surveillance

NEED QUERIES ON A GLOBAL VIEW

• CDNs: – Popularity of websites globally– Tracking security threats

• Military– Threat “chatter” correlation– Big picture view of battlefield

• Energy Grid– Wide-area view of energy production and

expenditure

SOME QUERIES ARE EASY

Alert me when servers crash

Server Crashed

OTHERS ARE HARD

How popular are all of my domains? Urls?

RequestsRequestsRequestsCDN

Requests

RequestsRequestsRequestsCDN

Requests

BEFORE JETSTREAM

Time [two days]

Bandw

idt

h95% Level

Analyst’s remorse: not enough datawasted bandwidth

Buyers’s remorse: system overload or overprovisioning

Needed for backhaul

? ? ? ? ? ?

WHAT HAPPENS DURING OVERLOAD?

Time [one day]

Bandw

idth Needed for backhaulAvailable

Time

Late

ncy

Queue size grows without bound!

THE JETSTREAM VISION

Time [two days]

Bandw

idt

hAvailable

Needed for backhaul

JetStream lets programs adapt to shortages and backfill later.

Need new abstractions for programmers

Used by JetStream

SYSTEM ARCHITECTURE

compute resources (several sites)

Control plane

Data plane

…

Query graph

CoordinatorDaemon

Optimized query

JetS

tream

API

…

…

Planner Library

…

worker node

stream source

AN EXAMPLE QUERY

File Read Operator

Parse Log File

Local Storag

e

File Read Operator

Parse Log File

LocalStorag

e

QueryEvery 10 s

Central

Storage

QueryEvery 10 s

Site A

Site B

Site C

Feedback control

ADAPTIVE DEGRADATION

Local Data

DataflowOperator

s

Summarized or

Approximated

Data

Feedback control to decide when to degradeUser-defined policies for how to degrade

data

NetworkDataflowOperator

s

MONITORING AVAILABLE BANDWIDTH

Data Data Data Time

Marker Data

• Sources insert time markers into the data stream every k seconds

• Network monitor records time it took to process interval – t

=> k/t estimates available capacity

WAYS TO DEGRADE DATA

Can drop low-rank values

Can coarsen a dimension

AN INTERFACE FOR DEGRADATION (I)

• First attempt: policy specified by choosing an operator.

• Operators read the congestion sensor and respond.

Coarsening Operator

Incoming data

SampledData Network

Sending 4x too much

COARSENING REDUCES DATA VOLUMES

01:01:01 foo.com/a 1

01:01:01 foo.com/b 10

01:01:01 foo.com/c 5

01:01:02 foo.com/a 2

01:01:02 foo.com/b 15

01:01:02 foo.com/c 20

01:01:* foo.com/a 3

01:01:* foo.com/b 25

01:01:* foo.com/c 25

BUT NOT ALWAYS

01:01:01 foo.com/a 1

01:01:01 foo.com/b 10

01:01:01 foo.com/c 5

01:01:02 bar.com/a 2

01:01:02 bar.com/b 15

01:01:02 bar.com/c 20

01:01:* foo.com/a 1

01:01:* foo.com/b 10

01:01:* foo.com/c 5

01:01:* bar.com/a 2

01:01:* bar.com/b 15

01:01:* bar.com/c 20

DEPENDS ON LEVEL OF COARSENING

Data from CoralCDN logs

GETTING THE MOST DATA QUALITY FOR THE LEAST BW

IssueSome degradation techniques result in good quality but have unpredictable savings.

SolutionUse multiple techniques– Start off with technique that gives best quality– Supplement with other techniques when BW

scarce=> Keeps latency bounded; minimize analyst’s remorse

ALLOWING COMPOSITE POLICIES

• Chaos if two operators are simultaneously responding to the same sensor

• Operator placement constrained in ways that don’t match degradation policy.

Coarsening Operator

Incoming data Network

Sampling Operator

Sending 4x too much

INTRODUCING A CONTROLLER

• Introduce a controller for each network connection that determines which degradations to apply

• Degradation policies for each controller• Policy no longer constrained by operator topology

Coarsening Operator

Incoming data Network

Sampling Operator

Controller

Drop 75% of data! Sending 4x too much

DEGRADATIONType Mergeabili

ty Errors Predictable

Size Savings

Dimension Coarsening

Yes* Resolution No

Consistent Sampling

Yes Sampling Yes

Local Filtering

No Sampling Yes

Multi-round Filtering

No None No

Aggregate Approx.

Depends Depends Depends

MERGEABILITY IS NONTRIVIAL

• Can’t cleanly unify data at arbitrary degradation• Degradation operators need to have fixed levels

01 - 05

06 - 10

11 - 15

16 - 20

21 - 25Every 5

01 - 10 11 - 20Every 10 21 - 30

01 - 30Every 30??

26 - 30

01 - 06 07 - 12 13 - 18 19 - 24Every 6 25 - 30

??????

INTERFACING WITH THE CONTROLLER

Coarsening Operator

Incoming data Network

Sampling Operator

Controller

Operator

Shrinking data by 50%Possible levels:

[0%, 50%, 75%, 95%, …]

Controller

Go to level 75%

Sending 4x too much

A PLANNER FOR POLICY

Query planners:Query + Data Distribution => Execution Plan

Why not do this for degradation policy?What is the Query?

For us the policy affects the data ingestion=> Effects all subsequent Queries

Planning All Potential Queries + Data Distribution => Policy

EXPERIMENTAL SETUP

80 nodes on VICCI testbed in US and Germany

Princeton

Policy: Drop data if insufficient BW

WITHOUT ADAPTATIONBandwidt

h Shaping

WITH ADAPTATIONBandwidth Shaping

COMPOSITE POLICIES

OPERATING ON DISPERSED DATA

Dispersed

Databases

Dispersed

Databases

Dispersed

Databases Disperse

d Database

s

CUBE DIMENSIONS

01:01:00

foo.c

om

/rfo

o.c

om

/qbar.

com

/nbar.

com

/m

01:01:01

Tim

e

URL

CUBE AGGREGATES

Count Requests

Max Latency

bar.

com

/m

01:01:01

CUBE ROLLUP

01:01:00

foo.c

om

/rfo

o.c

om

/qbar.

com

/nbar.

com

/m

Tim

e

URL

bar.com/

*

foo.com/*

FULL HIERARCHY

(5,90) (3,75) (8,199) (21,40) 01:01:00

foo.c

om

/rfo

o.c

om

/qbar.

com

/nbar.

com

/m

Tim

e

URL

(8,90)(29,19

9)

(37,199)

URL: *Time: 01:01:01

RICH STRUCTURE

(5,90)(3,75)

(8,199)(21,40)

D

A

C

01:01:59

01:01:00

fo

o.

co

m/

r

fo

o.

co

m/

q

ba

r.

co

m/

n

bar.c

om/m

01:01:01

01:01:58

B

…

E

Cell URL Time

A bar.com/* 01:01:01

B * 01:01:01

C foo.com/* 01:01:01

D foo.com/r 01:01:*

E foo.com/* 01:01:*

TWO KINDS OF AGGREGATION

1. Rollups – Across Dimensions2. Inserts – Across Sources

The data cube model constrains the system to use the same aggregate function for both.

Constraint: no queries on tuple arrival order

Makes reasoning easier!

AN EXAMPLE QUERY

File Read Operator

Parse Log File

Local Storag

e

File Read Operator

Parse Log File

LocalStorag

e

QueryEvery 10 s

Central

Storage

QueryEvery 10 s

Site A

Site B

Site C

SUBSCRIBERS

• Extract data from cubes to send downstream

• Control latency vs completeness traeoff

File Read Operator

Parse Log File Local

Storage

QueryEvery 10 sFile Read

OperatorParse

Log File

Site A

SUBSCRIBER API

• Notified of every tuple inserted into cube

• Can slice and rollup cubes

Possible policies:• Wait for all upstream nodes to

contribute• Wait for a timer to go off

FUTURE WORK

• Reliability

• Individual queries– Statistical methods– Multi-round protocols

• Currently working on improving top-k

• Fairness that gives best data quality

Thanks for listening!