On the Use of Service Level Agreements in AssessGrid Karim Djemame and Dominic Battré

Outline System Overview Scenarios Architecture Towards Dynamic SLAs End-user Broker Provider Towards Dynamic SLAs Summary

System Overview Aim Risk awareness incorporated across three layers integrate a risk-aware Service Level Agreement (SLA) model into current Grid technology Risk awareness incorporated across three layers Therefore an architecture designed to Give resource providers the capability to perform risk assessments prior to making offers Give the broker the ability to assess the reliability of providers’ risk assessments Give the end-user the ability to choose offers based on risk alongside price and penalty.

Role Description RP Broker RP End-user RP Resource Providers I offer access to resources and services through formal SLA offers I need to find suitable resource providers to take SLA I need to perform a specific task with associated requirements through an SLA RP Broker RP End-user RP Resource Providers

Architectural Overview WS-Agreement Negotiation for SLAs RMS: Resource Management System

Usage Scenarios Broker as a mediator Broker as a contractor End-user submits SLA request to broker Once end-user selects SLA offer Broker’s responsibility ends End-user interacts directly with provider Broker as a contractor Acts as a virtual provider End-user agrees SLA with broker Broker agrees SLAs with provider(s) Useful to map workflows to resources Direct SLA negotiation end-user – provider End-user submits SLA request to provider End-user can query broker’s confidence service

Scenario 1: User – Provider Negotiaion Fill Template Job description Max. PoF Min. Penalty Commit Contract SLA Request Get Template SLA Offer User requests template User defines job to be executed, max PoF and Penalty (the letter are given from the business of the user) RMS analyzes SLA request, and in case it accepts it, is defines a required price (depends on risk, resource requirements, …) User can decide whether price is acceptable and commits Contract between parties established Create Offer RMS: Resource Management System PoF: Probability of Failure

Scenario 2a: Broker = Mediator Get Templates Template Subscription Broker receives templates over WS-Notification as subscription from RMS End User asks Broker for template – most favorable situation: only one template that matches all RMS RMS: Resource Management System

Scenario 2a: Broker = Mediator SLA Request Evaluate Reliability SLA Offer User submits SLA request, broker forwards it to only those RMS that might be capable of providing the resources RMS calculate price and PoF Broker submits offers to user User asks Broker to assess the real risk of failure (incorporating that some providers might tend to underestimate the PoF) RMS: Resource Management System

Scenario 2a: Broker = Mediator Commit User agrees one offer Other offer expires RMS: Resource Management System

Scenario 2b: Broker = Contractor Broker can be a provider as well. Job submitted/negotiated with broker, who subcontracts Very interesting for work flows RMS: Resource Management System

Provider - Negotiation Manager Open source implementation of WS-Agreement specification for negotiating SLAs between end-user, broker, and provider Protocol more powerful and agile

Provider – Extending WS-Agreement Changed the original single-round acceptance model to a two-phase acceptance model Introduced the negotiation possibility, in other words the bargaining capability: Flexible SLA negotiation scheme – getQuotes method Two-phase commit negotiation protocol

Dynamic SLAs - Extending WS-Agreement Anticipate violations state for the agreement in which a warning has been issued due to the fact that one or more guarantees are likely to be violated in the near future. Negotiation Is part of its life-cycle initial negotiation before the execution of the services under SLA run-time re-negotiation: occurs in case of a recoverable violation of a term, or the monitoring system is anticipating a possible violation of a term (pessimistic scenario) the monitoring system is anticipating a better QoS to be delivered

Re-Negotiation (pessimistic scenario) Example: provider anticipating a possible violation of a term - monitoring of dynamic risk - re-negotiate the SLA instead of paying a (high) penalty fee lower price Provider Customer I can do X instead of Y for you for Z in return? SLA SLA Request to re-negotiate Accept Reject Need to ensure both parties get a better deal through the new agreement

Re-Negotiation (optimistic scenario) Example: user would like to increase the price to get a lower Penalty of Failure Provider Customer Can you do X for me for Y in return? SLA SLA Request to re-negotiate SLA-Accept SLA-Reject Need to define specific properties in the agreement: Re-negotiation needs an EPR

Re-Negotiation (optimistic scenario) Example: provider is able to provide a better service - increase the price - lower Probability of Failure Provider Customer I can do X for you for Y in return? SLA SLA Request to re-negotiate Accept Reject Need to ensure both parties get a better deal through the new agreement

Summary AssessGrid architecture provides a framework for supporting risk assessment and management throughout the Grid infrastructure Single tasks Workflows Advanced risk assessment models Provider and broker layers Interaction between components within the architecture Use as much as possible of WS-Agreement specification Preliminary work on extension of WS-Agreement Scenarios identified Current implementation of the architecture Currently deployed in three separate administrative domains