qos-based web service selection and agreement marco comuzzi dipartimento di elettronica e...

QoS-Based Web service Selection and Agreement

Marco ComuzziDipartimento di Elettronica e Informazione

Politecnico di Milano

[email protected]

2

Outline

QoS in SOA

Modelling QoS and

negotiation

QoS-Based WS selection

and agreement

Data QoS syndication

Network QoS negotiation

Conclusion and future

work

QoS negotiation in SOA: goals

Introducing negotiation of QoS profile Goals:

Improve matchmaking and service ranking Dynamic generation of contracts on QoS

How: Consider partial overlap of service offer and requirements Automated Negotiation for contract Generation

Contract Registry

Providers’Pricing Models


Requestors’Negotiation Strategies


Web Service QoS-enabled

registry


registry

WS-BPEL Engine

Auction WS

Recaller WS

Configuration WSContract

Generator WS

Management interface

Publishing interface

Management interface

Request interface

PROVIDER WEB INTERFACE

NEGOTIATION BROKER

REQUESTOR WEB INTERFACE

Negotiation Process

3

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

QoS-Based service selection: Quality model

Scenario: 1 requestor, M (functionally equivalent) Web services j

Quality model N (independent) QoS dimensions qi

Ki ordered discrete QoS levels for each qi (ranges or single values) Si=(si1,…,siKi)

Response time Ki=3 Sresptime={(0s,2s],(2s,3s], (3s,10s]} Availability Ki=2 Savailability={0.99,0.9999}

Service publication PUBj=<offer,price_mod> Service offer offeri Si, i Additive pricing model price(sik)=sik

(exploited in service ranking)

Service request REQR=<reqs,priority,strategy,B> QoS requirements reqsi Si, i Importance of QoS dimensions priority={w1,…,wN} Strategy to be used in the negotiation Available budget B

WS WS QoSQoSWS WS QoSQoS

Web service Web service QoSQoS

ServicesServices

ProviderProvider RequestorRequestor

Network Network QoSQoSNetwork Network QoSQoS

Data Data QoSQoSData Data QoSQoS

……

4

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

Requestor Requestor reqsreqs

LLiiCase 1Case 1

Case 2Case 2

Case 3Case 3



Provider Provider jjOfferOffer



maxijik

lminijik

l

maxiRik

lminiRik

l0ijpen

ijiRijiR Mkmk maxmin

1l iKl

maxijik

lminijik

l

maxiRik

lminiRik

l

maxmax , ijijijiR kMMk

maxmaxmax

iRikijijiRij lckkpen

maxijik

lminijik

l

maxiRik

lminiRik

l

minmin , ijijijiR kmmk

minminmin

ijikijiRijij lckkpen

Service ranking

Matchmaking Considering also Partial overlap of service offers

and reqs Intersection of service offer and reqs Iij

Service ranking Scoring function:

Minimize price while maximizing overlap penalize partial overlap offers (when Iij reqsi) with penij

Scoring mechanism equivalent to a multiattribute, reverse, sealed-bid auction

The lowest scoring WS provider sp is selected for service provisioning

Pricing models are adaptive: sik=(selj(t))sik

t: counts the number of time a service is requested selj(t)

Provider j is selected (wins the auction). sel j(t)++ Provider j is not selected: selj(t)--

Adaptation (at time t) Increase applied price if selected in previous

rounds Decrease applied price when not selected

Objective: avoid winner’s curse and create market equilibrium



ServicesServices




……

i Is

ijikj

ijik

pensscore

0

5

10

15

20

25

30

35

-20 -10 0 10 20

sel j (t)

αij(t

)

(1+k)α ij (0)

(1-k)α ij (0)

5

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

Exp. Results: Selection and Adaptive pricing

D is experiencing the winner’s curse (t<4)

A,B,D converge to the actual market valuation of the offered service

C starts from a too high initial evaluation (330% higher than A)

0

2000

4000

6000

8000

10000

12000

14000

1 2 3 4 5 6 7 8 9 10

Time t (number of times service is requested)

Sc

ore

j(X

)

Provider A Provider B Provider C Provider D

160D

180C

1100B

1200A

Provider

160D

180C

1100B

1200A

Provider 0ij iij ,

D’s winner curse



ServicesServices




……

6

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

0

5

10

15

20

25

30

Extra Budget EB

Qo

S L

evel

In

crea

se

QoS i=1

QoS i=2

QoS i=3

QoS i=4

5 10 15 20 15 20 25 30 35 40 45 50 55 60 65 70

QoS profile Negotiation and Agreement

Negotiation with the selected provider sp

Extra budget EB = B – pricesp(Xmin)

Two strategies to allocate EB (in the service request) Horizontal: split EB proportionally to the service requestor’s priorities wi

Vertical: improve the QoS dimension of the highest priority until saturation, than try with the second highest priority QoS dimension….

The outcome is written in an electronic contract (WS-Agreement)

0

5

10

15

20

25

30

Extra Budget EB

Qo

S L

evel

In

crea

se

QoS i=1

QoS i=2

QoS i=3

QoS i=4

5 10 15 20 15 20 25 30 35 40 45 50 55 60 65 70

Requestor’s priorities wi (5,1,1,3)Providers cost functions:QoS i=1 =1 β=1QoS i=2 =1 β=1QoS i=3 =0.1 β=1QoS i=4 =0.1 β=1

HORIZONTAL VERTICAL



ServicesServices




……

7

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

Exp. Results: Contract Efficiency

Only for the Horizontal strategy Contracts remain close to the Pareto Frontier Higher utility for increased extra budget and Quadratic pricing models “Leaving money on the table” in case of Quadratic pricing models

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

0.4 0.5 0.6 0.7 0.8 0.9 1

Utility Provider

Uti

lity

Req

ues

tor

Pareto fontier

Radical Config.

Linear Config.

Mixed Linear/Quadratic Config.

Quadratic config.

EB=20

EB=60EB=20

EB=60



ServicesServices




……

8

Outline

QoS in SOA

Modelling QoS and

negotiation


and agreement




work

Technological Overview

JBOSS (Servlet Container, WS deployment)

OraBPEL (Oracle WS-BPEL Process Engine)

MySQL (storing the service categorization)



ServicesServices




……

Contract Registry




registry

PROVIDER WEB INTERFACE

NEGOTIATION BROKER

REQUESTOR WEB INTERFACE

Negotiation ProcessNegotiation Process

Negotiation Strategy Policies

(WS-Policy)

Pricing model Policies

(WS-Policy)

Service Offers and Contract template(WS-Agreement

Template)

Contracts(WS-Agreement)

QoS Description(XML-Schema)

qos-based web service selection and agreement marco comuzzi dipartimento di elettronica e...

Documents