A simulation process and tool used to test and evaluate the algorithms necessary to optimally arrange a peer-to-peer distributed awareness system for Software Engineering

Nutter, David

English

University of Lincoln Institutional Repository

Simulated Self-Organization of a Peer To Peer Awareness NetworkDavid NutterUniversity Of Lincolndnutter@hemswell.lincoln.ac.ukIntroductionSoftware engineers working in distributed teamsare deprived of much “out of band”communication with their colleagues, withconsequent effects on the coherence of teamwork [3]. Distribution itself has deleteriouseffects on team work due to problems rarelysuffered by colocated teams including a languagebarrier, time differences and cultural differences.Consequently, to help alleviate these problems,software tools instead of colocation must providecontext awareness for software engineersworking in distributed teams.Many awareness systems are real time(synchronous awareness), facilitating tasks suchas collaborative editing of documents [4, 1] byhighlighting changes made by other users. Whileuseful at times they do not provide adevelopmental history of the collaborative objectIn distributed software engineering domains,particularly Libre software, this knowledge isoften incompletely contained in mailing listarchives and the log files of configurationmanagement repositories.Therefore the concept of historical awareness hasbeen defined[5]:The complete context of an artefact’s creation,derived from a collection of heterogenousartefacts (source code, design etc) rather thana contextless view of a single artefact’sevolution.Certain elements of such information should bepresented to the user for a specific artefact orcollection of artefacts.•Details of previous conflicts• “Proximity” of current user activities•Artefacts related to current artefactTool In UseAwareness Distribution ModelIn order to provide ad-hoc context awarenesscapabilities for distributed teams withoutcomplex setup the Peer To Peer model ofdistribution has been selected. Rather than allawareness information passing through a centralreflector, with attendant scalability androbustness problems, users’ clients exchangeawareness information with a limited number ofpeers.As an additional benefit, given a suitablyorganised network, peers will be “close enough”to all other peers working on artefacts relevant tothem that awareness information may be given aTime To Live (TTL) in hops from the originatingpeer. Once information has travelled this“distance” it will no longer be relevant and maybe discarded, keeping network load down.Therefore, the remaining problem is theorganisation of the network. Much research hasbeen carried out in the area of Semantic OverlayNetworks[2] though most implementations relyon the concept of a Super Peer or EdgeRendezvous Peer to incorporate new nodes intothe network. Whilst appropriate for largenetworks (such as filesharing or messaging)Super Peers are not required for small, ad hocawareness networks.The simulation toolPrior to deployment of the awareness toolset in acontrolled experiment, the algorithms used toorganise the network will be tested in asimulation environment. This environment willallow:•Algorithms to be refined without costly,complex experiments•Algorithm performance evaluation in multiplenetwork environments that would be difficultor disruptive to simulate for real.•Reproducible experiments and test cases, withtotal parameter control. Other activities on a“real” network may disrupt experimentsunpredictably.• Simple demonstration of the self-organizationconcept.Architecture & algorithmsThe tool is based on an Open Source graphframework (JGraph) and associated layoutalgorithms. Consequently, operations on thenetwork (connection/disconnection of peers,routing of information) may be expressed asoperations on the graph.The simulation packages offers the experimentervarious parameters including:•The Message Time To Live (MsgTTL)•Max and Min connections permitted per node.•Event frequency (tick)•Automatic content generation, within bounds•Length of the simulation run•Number of seed nodes to generateAt simulation launch, nodes will be randomlyconnected to one other node. No guarantee ismade that the network will be fully connected.Subsequently, algorithms are applied by each nodeto organise the network into an optimum state.An example of the current algorithm operatingon four distinct peers may be shown as follows:Peer Aconnect−−−−→ Peer BPeer Asend details of A−−−−−−−−−→ Peer BPeer Bsend details of A−−−−−−−−−→ Peer CPeer Bsend details of A−−−−−−−−−→ Peer DPeer Breconnect D−−−−−−→ Peer APeer Adisconnect←−−−−− Peer BPeer Aconnect−−−−→ Peer DThe tool architecture is as follows:Org AlgorithmTimer ThreadNodeSimulationOrgAlgorithm ConnectionGraphical ViewAnnotation ViewEvaluation TestbedBy using the simulation, a refined algorithm fornetwork organisation will be developed.Subsequently, the algorithm will be ported to theSun JXTA framework and the awareness timelineview implemented as an Eclipse plugin. Theeclipse plugin will also start the JXTA back end toconnect to other clients and exchange awarenessinformation.The items being edited in Eclipse will indicate tothe awareness system what items are currently“relevant” to the user and consequently whatnodes the network organisation algorithmdecides to connect to.The current experimental plan[5] is to validatethe testbed by deploying it with existing Eclipseusers in the research group. Once successfullyvalidated, a controlled experiment based onsimple collaborative programming exercises isplanned, with awareness and without.Awareness project goalsThis loose requirement for historical awarenessmay be decomposed into some high-level projectgoals for implementing historical awareness fordistributed teams:•Contextual view of an artefact’s development,displayed using the timeline visualisation•Reflector-free distribution model, for ad-hocconstruction of awareness networks. Bycontrast, the most common method of CSCWapplication development relies on a centralisedreflector to distribute information• Integration with existing developmentenvironment for evaluation purposes.•Evaluation driven development of theprototype implementaiton.References[1] P. Dourish and V. Belotti. Awareness and coordination in sharedworkspaces. In ACM Conference on Computer Supported CooperativeWork (CSCW’92), pages 107–114, Toronto, Ontario, November 1992.ACM Press, New York City.[2] D. Doval and D. O’Mahony. Overlay networks: A scalabalealternative for P2P. IEEE Internet Computing, August 2003.[3] J. A. Espinosa, R. E. Kraut, S. A. Slaughter, J. F. Lerch, J. D.Herbsleb, and A. Mockus. Shared mental models, familiarity, andcoordination: A multi-method study of distributed software teams.In Proceedings of the 23rd International Conference in InformationSystems (ICIS), pages 425–433, Barcelona, Spain, 2002.[4] C. Gutwin, S. Greenberg, and M. Roseman. Workspace awarenesssupport with radar views. In CHI Conference Companion, pages210–211, 1996.[5] D. Nutter and C. Boldyreff. Historical awareness support and itsevaluation in collaborative software engineering. In Proceedings ofWETICE 2003, pages 171–176. IEEE Computer Society, June 2003.

Awareness and coordination in shared workspaces.

Simulated self-organization of a peer to peer awareness network

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