1 graap: why do we need slas? omer rana [email protected]
TRANSCRIPT
2OGF21, October 2007
GRAAP WG Current focus:
WS-Agreement specification Support for negotiation being investigated
Investigating: Interoperability (and conformance) issues Use cases
Longer term: Aspects of “dynamic” SLAs Investigation of penalty/reward clauses
3OGF21, October 2007
What is a Service Level Agreement (SLA)?
Client Provider
Can youdo X for mefor Y in return?
Yes
SLASLA
Distinguish between: Discovery of suitable provider Establishment of an SLA
P2P Search,Directory Service
SLA-Offer
SLA-AcceptSLA-Reject
A relationship between a client and provider in the context of a particularcapability (service) provision
4OGF21, October 2007
What is an SLA?
Client Provider
Can youdo X for mefor Y in return?
No, but Ican do Zfor Y
SLASLA
Accept
SLA-CounterOffer
SLA-Offer
SLA-AcceptSLA-Reject
5OGF21, October 2007
What is an SLA?
Client Provider
Can youdo X for mefor Y in return?
No
SLASLA
Can youdo Z for mefor Y in return?
NegotiationPhase(Single orMulti-Round)
SLA-Offer
SLA-CounterOffer
SLA-OfferDependency
6OGF21, October 2007
Variations
Client
Providers
SLA
Client
Providers
SLA SLA
Multi-provider SLA
Single SLA is dividedacross multiple providers(e.g. workflow composition)
SLA dependencies
For an SLA to be valid, anotherSLA has to be agreed(e.g. co-allocation)
7OGF21, October 2007
Dynamically established and managed relationship between two parties
Objective is “delivery of a service” by one of the parties in the context of the agreement
Delivery involves: Functional and non-functional properties of service
Management of delivery: Roles, rights and obligations of parties involved
What is an SLA?
8OGF21, October 2007
Forming the Agreement Distinguish between:
Agreement itself Mechanisms that lead to the formation of the
agreement
Mechanisms that lead to agreement:Negotiation (single or multi-shot)One-shot creationPolicy-based creation of agreements, etc.
9OGF21, October 2007
SLA Life Cycle Identify Provider
On completion of a discovery phase Define SLA
Define what is being requested Agree on SLA terms
Agree on Service Level Objectives Monitor SLA Violation
Confirm whether SLO’s are being violated Destroy SLA
Expire SLA Penalty for SLA Violation
10OGF21, October 2007
Why do we need SLAs? Provide some basis for:
Judging “Quality” of provisioning QoS can be provider or user related
If “Violations” have occurred Types of penalties
Choosing providers/clients Capacity planning Scheduling Establishing trust/reputation
OGF19 BoF: Difficulty in differentiating between QoS and SLAs
OGF20: Dynamic SLA workshop Grid 2007 (Sept. 07): SLA Management for Grids (with
CoreGrid – book from workshop will appear shortly)
11OGF21, October 2007
WS-Agreement Framework for SLA creation – interface
conforming to Web Services standards Service Client/Provider does not need to
be a Web Service Provides a two layered model:
Agreement layer: Web Service-based interface to create, represent and monitor agreements
Service layer: Application specific-layer of service being provided
12OGF21, October 2007
WS-Agreement
Agreement Initiator may be Service Consumer or Service Provider
ServiceLayer
AgreementLayer
13OGF21, October 2007
WS-Agreement
Name/ID
Context
Terms Composition
Guarantee Terms
Service Terms
AgreementInformation about AgreementInitiatorResponderExpiration Time
Information about ServiceService Description Terms(generally, these are domaindependent)
Information about ServiceLevelService Level Objectives,Qualifying Conditions for the agreement to be valid,Penalty Terms, etc
14OGF21, October 2007
WS-Agreement Terms
From: Viktor Yarmolenko (U Manchester)
15OGF21, October 2007
Usage A number of projects utilizing this
Implementations vary – two key implementations currently being developed
Others utilizing part of the spec: Various European projects (CATNETs, SORMA,
OntoGrid) National projects (VIOLA)
16OGF21, October 2007
CATNETS Scenario
Service ConsumerResource Provider
Service Provider
Service Market
Resource Market
ComplexService
ComplexService
ComplexService
Resource Service
Resource Service
ResourceService
BasicService
BasicService
BasicService
Resource Consumer
17OGF21, October 2007
Orderbook Complex Service
Container 1 (40€)Container 2 (50€)Container 3 (70€)
QueryService
Demand:Complex Database Query< 200 €
QueryService
QueryService
(1)
(2)
(3)
Basic Service
Demand:(8CPUs,1GB,30GB)< 40 €
Service Market
Total Cost <Cost of service +Cost of resource
18OGF21, October 2007
Orderbook Basic Service 1
Buy-Order 1 (10€)Buy-Order 2 (18€)Buy-Order 3 (35€)
(4CPU,1GB,
15GB)
Demand:(8CPUs,1GB,30GB)< 40 €
(4CPU,1GB,
15GB)
(8CPU,1GB,
30GB)
[1,3] bundles allowed
Sum = 28 €
(1)
(2)
(3)
Ranking buy-orders Build bundle
Resource Market
19OGF21, October 2007
CATNETs: Metrics “Pyramid”
Client Application Service Builder
Master Grid Service
ServiceFactory (GT4/JavaWS)
ComplexServiceAgent
Application
CATNETS Middleware
Resource (GT4/WSRF/.NETWS/JWS)
BasicServiceAgent
ResourceAgent
Base Platform
ServiceInstance (GT4/JavaWS)
1. Request
2. Requirements
7. Service Reference
8. Invocation
3. Service negotiation
4. Resource negotiation
5. Service instantiation
6. Service Reference
Catallactic Access Point
WSAG
WS
Use of WS-Agreement
CATNETS: U Bayreuth, U Karlsruhe, UPC/Barcelona, U Ancona, ITC/IRST (Trento), U CardiffEU FP6 “Future and Emerging Technologies”
21OGF21, October 2007
Dynamic SLA Limitations of a single agreement
Modifications since agreement was in place Cost of doing re-establishment
Not fully aware of operating environment Flexibility in describing Service Level
ObjectivesNot sure what to ask for (not fully aware of the
environment in which operating)Too many violations
22OGF21, October 2007
Dynamic WS-Agreement Case 1: Static Agreement
Identify Service Description Terms,Guarantee Terms, and Service Level Objectives (SLOs)
Case 2: Dynamic Agreement Identify Service Description Terms,Guarantee Terms: defined as ranges or as
functionsService Level Objectives: defined as ranges
or as functions
23OGF21, October 2007
Conclusion WS-Agreement provides a useful basis for SLA Still restricted to “static” SLAs
Does not support negotiation mechanisms
Negotiation should not be part of SLA SLA should result as a consequence of negotiation
Mechanisms for dynamic SLAs Function-based or Category based (adaptation
between categories)
Dynamic SLA networks Means to support dynamic SLA exchange networks