Certain investigations on performance enhancement of stub code in corba based applications

Abstract

DistributedObjectSystemsprovideanexcellentsupportforevolutionarydevelopmentofsoftwarefordistributedapplicationsthroughsoftwarereuse.RequestbrokerslikeCommonObjectBrokerArchitecture(CORBA)shieldtheapplicationdevelopersfromlow-level,tediousanderrorproneplatformdetails.Theyprovideplatform,language,network,hardware,protocolandobjectlocationtransparencybyincludinganabstractionlayerbetweentheapplicationprogramsandthenetworkingprotocols.JavaRemoteMethodInvocation(RMI)islanguagedependentandDistributedComponentObjectModel(DCOM)isplatformdependent.ButCORBAistransparenttoprogramminglanguageandplatform.CORBAusesGeneralInteroperableProtocol(GIOP)asitscommunicationprotocol.Itfitsintotheapplication,presentationandsessionlayersintheOpenSystemsInterconnection(OSI)model.Presentationconversiondealswiththeconversionofdatafromlocalmachinerepresentationtoacommonnetworkformat.ThisprocessofmarshallingiscarriedoutusingstaticstubsgeneratedbytheInterfaceDefinitionLanguage(IDL)compilerorgenericdynamicstubs.ThestubcodegeneratedfromtheIDLtakescareofmarshallingtherequeststransparentlytotheuser.MajorlimitationsofcoreCORBAincludelackofselectiveinheritance,creation/destructionoftheobjectsbytheclientandinefficientmarshalling,alignandcheck,bufferinganddatacopyingprocedures.AlsoCORBAlackssupportforgenerationoftime-efficientandcompactstubcode.OtherinefficienciesinCORBAincludeThemajorobjectiveofthisthesisistostudy,analyseandproposemethodstoenhancetheperformanceofstubcode.Theresearchworkisfocusedonthefollowingissues:•EnhancementsonCORBAstandard:1.AmethodtoachieveselectivemultipleinheritanceinCORBAstatically. VISelectivemultipleinheritancecannotbedirectlyimplementedinCORBA,becausefunctionredefinitionisnotallowedinderivedinterface.AmethodusingconditionalinterfacestoimplementselectivemultipleinheritanceinCORBAisproposed.Thisusesacontainerclassderivedfromthebaseinterfacebasedonthecondition.2.AmethodforcreationanddestructionofCORBAobjectsusingabaseinterface.DeactivationoftheCORBAobjectoccurswhentheserverterminates.Thisleadstounder-utilizationofresources.Henceabaseinterfacewithoperationsforreferencecounting,instantiationand destructionofCORBA objectsisimplemented.•IdentificationofthecommonsourcesofoverheadinmarshallinginCORBA-basedapplications.•Improvementsintheefficiencyofmarshallingusingthefollowingapproaches:1. Incorporatingchangesinthetransmissionmedium.2.Introducingnewencodingrulestotakecareofreductionofsizeofthedatapassedinthenetworkandthemarshallingtime.3.Improvingthesecurityinlinklevelcommunicationofthemarshaleddata.4.Optimisedencode/decodesoftwaretogeneratetime-efficientandcompactencoding/decodingmarshallingroutines.CommonsourcesofoverheadinmarshallinginCORBA-based applicationshavebeenidentified.Thisincludesinefficientalignandcheck, multiplexinganddatacopyingalgorithmswhichreducesthespeedofInternet InteroperableProtocol(HOP),presenceofextrapaddingbytesinCommon DataRepresentation(CDR)foralignmentandlackoftime-efficientandcompactstubcode.Basedonthisstudy,changeswereproposedinthetransmissionmedium,encodingformatandencodingproceduresinCORBA.