Chained Negotiation for Distributed Notification Services Richard Lawley, Michael Luck and Luc Moreau Intelligence, Agents, Multimedia Group School of Electronics & Computer Science University of Southampton ral01r@ecs.soton.ac.uk

Chained Negotiation for Distributed Notification Services Outline Introduction Notification Services Negotiation Chained Negotiation Evaluation of Negotiation Engine Future Work & Conclusion 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Introduction Notification services (NSs) provide asynchronous communication between services in distributed environment Consumers and providers may conflict over delivery preferences (QoS) Negotiation enables mutually acceptable QoS levels to be found 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Introduction Previous work introduced automated service-oriented negotiation engine suitable for use with notification service Distributed notification services require different kind of negotiation Chained negotiation supports reselling or redistribution of existing services 05/05/2019 Chained Negotiation for Distributed Notification Services

Notification Services (1) Message-oriented middleware layer using publish-subscribe model Publishers publish information on a topic Consumers subscribe to that topic Notifications are delivered by NS to consumer Can process notifications before sending Filtered notifications Notifications combined into a digest 05/05/2019 Chained Negotiation for Distributed Notification Services

Notification Services (2) Example notification topics: Changes in database content Release of new tools or services Change in workflow execution state Many existing notification services MSMQ, MQSeries, Grid Monitoring Architecture, NaradaBrokering Negotiation not supported 05/05/2019 Chained Negotiation for Distributed Notification Services

Distributed Notification Services Centralised NSs leads to scaling problem Overloaded with many consumers Single point of failure Distributed NS allows loads to be spread and effect of failure to be reduced 05/05/2019 Chained Negotiation for Distributed Notification Services

Distributed Notification Services Consumers & publishers connect to different NS Enables notifications to be redistributed Less bandwidth used Consumers use local NS instead of remote NS1 NS2 P2 C1 Publisher Notification Service C2 P1 NS3 Consumer NS4 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services myGrid e-Science project aimed at Bioinformatics Allows workflow-based in-silico experiments Automated workflow management through personalisation, notification of change and publication of experiments Increasing focus on data-intensive bioinformatics 05/05/2019 Chained Negotiation for Distributed Notification Services

myGrid Notification Service JMS-based notification service Persistent message delivery model Push/Pull subscribers Supports federated topics Topics at each NS are part of a virtual topic Consumer subscribing to virtual topic receives notifications from all member topics Uses service directory for virtual topic data 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services QoS in Distributed NS Consumers still want to request QoS levels in a distributed NS If QoS requests are simply granted, can’t redistribute notifications Some form of negotiation needed to find acceptable levels of QoS 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services “The process by which two or more parties exchange proposals in order to reach a mutually acceptable agreement on a particular matter” Components of negotiation Item – the object under negotiation Terms – attributes of item under negotiation Proposals – set of values suggested by one party Preferences – values acceptable to a party Utility functions – a method of evaluating the utility of a particular proposal 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Negotiation formally described as: Negotiation Protocols – Rules governing a negotiation Types of participants Valid negotiation states & actions Negotiation Strategies – How participants behave within protocol Proposal Generation When to accept a proposal Specification of negotiation enables automated negotiation to take place 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Conventional negotiation (direct) involves negotiation between client and supplier Chained negotiation involves middlemen between supplier and client Enables reselling or redistribution Made up of multiple subnegotiations Item can be supplied by supplier or middlemen 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Middlemen choose which sub-negotiation to proceed with at each step Upstream = away from client Downstream = towards client 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation Protocol Rule: “Proposals may be sent upstream only if there is time for the reply to get back to the client” Messages contain distance of sender from client Rule: “NC cannot confirm downstream without having a commitment in place upstream” Prevents consumers committing to something unavailable Propose, Accept, Confirm-Accept messages Enables getting everyone “prepared to accept” 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Proximity function determines whether one proposal is satisfiable by another Used to find suitable existing commitments Actions created each time proposal received Selecting existing commitments Passing across proposal Scoring functions choose best action 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Scoring functions used Proximity – how close is the proposal in each action to the last received proposal? Acceptable? – would this action directly lead to an acceptable state? Favour least used – if the previous few rounds have resulted in upstream negotiation, this favours downstream more 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation Evaluation Evaluate different types of negotiation Direct (client – supplier) Forwarded (middleman forwards proposals) Chained (middlemen uses existing commitments) Experiment setup similar to evaluation of previous negotiation engine Common interval-based time model Only time-dependent tactics used Single tactics used for proposal generation Only client utility considered 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Variable Deadline “What effect does varying the deadline have on utility and success rate?” Vary deadline (1-100 messages). Measure utility and success rate for different types of negotiation 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Variable Deadline Problem with “spikes” Client doesn’t know distance from supplier Final concession not reaching destination Failed negotiation Predictable troughs 2n(m + 1) – 1 05/05/2019 Chained Negotiation for Distributed Notification Services

Variable Negotiation Terms Easy to match to existing commitment when using a single term All terms in a proposal need to match commitment in order to reuse it Increase number of terms and measure success rate for each type of negotiation 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Supplier Capacity Multiple connected middlemen Clients spread between them Compared to negotiating with publisher’s NS M M M M M S S C S C S C S C S C 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Supplier Capacity Most chained negotiations satisfied by existing commitment (<5% direct) Load on supplier greatly reduced Negotiations more successful and better utility when using chained negotiation 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Future Work Reduce impact of deadline problem Integrate with myGrid Notification Service Use myGrid Notification Service to provide better performance in some test cases Alternate interaction patterns between NSs? 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Conclusion Distributed negotiation services need a new type of negotiation to select QoS levels Better success rate & client utility can be obtained by reusing existing commitments Benefits of chained negotiation decrease with larger numbers of terms Chained negotiation suffers from a periodic poor result with certain values for the deadline 05/05/2019 Chained Negotiation for Distributed Notification Services

Chained Negotiation for Distributed Notification Services Questions? E-mail: ral01r@ecs.soton.ac.uk 05/05/2019 Chained Negotiation for Distributed Notification Services