社会网络服务影响的性能和可伸缩性Web服务器Infrastractures

ImpactofSocialNetworkingServicesonthePerformanceandScalabilityofWebServerInfrastracturesClaudiaCanali∗,JoseDanielGarcia†,RiccardoLancellotti∗∗UniversityofModenaandReggioEmilia{claudia.canali,riccardo.lancellotti}@unimore.it†[e-mail]Internetisheadingtowardsanewgen-erationofsocialnetworkingservicesthatarecharacterizedbynovelaccesspatternsdeterminedbysocialinteractionsamongtheusersandbyagrowingamountofmultimediacontentinvolvedineachuserinteraction.TheimpactofthesenovelservicesontheunderlyingWebinfrastructuresissignificantlydifferentfromtraditionalWeb-basedservicesandhasnotyetbeenwidelystudied.ThispaperpresentsascalabilityandbottleneckanalysisofaWebsystemsup-portingsocialnetworkingservicesfordifferentscenariosofuserinteractionpatterns,amountofmultimediacontentandnetworkcharacteristics.Ourstudydemonstratesthatforsomesocialnetworkingservicestheuserinteractionpat-ternsmayplayafundamentalroleinthedefinitionofthebottleneckresourceandmustbeconsideredinthedesignofsystemssupportingnovelapplications.1IntroductionTheWebevolutionisheadingtowardsaradicalchangeintheuserbehavior,withagrowingamountofusersthatcreate,share,anddistributecontentontheWeb.Theshifttowardsa“Read-write”paradigmisoneofthebiggestchangesintheWebsinceitsbeginning.Thisparadigmchangeisdrivenbythepopularitysurgeofthesocalledsocialnetworkingservices[18]thatenableuserstobuildsocialnetworksandsharetheirowngeneratedcontent.To-day,themostpopularexampleofWebsitesofferingsocialnetworkingservicesareWeblogs(blogs)[7],whereuserexchangemostlytextualinformation,sitesthatallowuserstosharephotossuchasFlickr[10,17]andFacebook[9],andsiteswheretheinteractionamongusersisbasedonex-changingvideoclips(e.g.,YouTube[11]).Thesuccessofthesesocialnetworkingservicesisdemonstratedbythehighnumberandheterogeneityofpar-ticipatingusers.AccordingtoNielsen/NetRatings,socialnetworkingsiteshaveseentheirtrafficgrowing47%inthelastyear,reaching45%ofallactiveWebusers[3].Thisconfluenceofparticipantsispossiblebecauseofthelowbarriertoentryintoon-linecommunities.Manysocialnet-workingservicesaredesignedsuchthatsigningup,view-ing,anduploadingcontentsarerelativelyeasy.Thisen-ablesuserswhomaynotbetechnicallyskilledtoparticipatealongsidemoreexperiencedusers.Thenovelcharacteristicsofsocialnetworkingservicesconcernaccesspatternsandresourceworkingset.Theaccesspatternsarecharacterizedbyvariabilityandunpre-dictabilityduetosocialinteractions(e.g.,slashdoteffects).Furthermore,theread-writenatureoftheservicesleadstoasignificantlyhigheramountofuploadoperationswithre-specttotraditionalWeb-basedservices.Ontheworkloadside,weobservethatsocialnetworkingservicespresentawiderangeofmultimediacontents:frommostly-textualblogs,tositeswheretheuserinteractionisbasedonim-agesandvideoclips,determiningaradicalshiftinthetypeofdatatransferred.Thecombinationofthenovelfeaturesofhighuserin-teractivityandmultimediarichcontentsintroducesnewrequirementsontheunderlyingserverinfrastructuresthataresignificantlydifferentfromtheseoftraditionalWeb-basedservices.Whilethereareseveralstudiesonperfor-manceandbottleneckanalysisfortraditionalWebapplica-tions[20,4],therehavebeennosubstantivestudiesregard-ingnovelsocialnetworkingservices.Themaincontributionofthispaperistoinvestigatehowcurrentlyavailableinfrastructurescancopewiththere-quirementsofnovelsocialnetworkingservices.Ouranaly-sisaimstoidentifythebottlenecksthathinderperformanceintheserverinfrastructuresasafunctionofthetypeofsup-portedsocialnetworkingservice,becauseweclaimthatun-derstandingtheimpactofnovelservicesisafundamental1stepthatwillaidinnetworkmanagement,capacityplan-ning,anddesignofnewsystems.Inthispaperweconsiderthreesignificantexamplesofsocialnetworkingservices,namelyBlogging,Photoshar-ingandVideosharing.Theservicesarecharacterizedbydifferentamountsofmultimediacontents,andforeachser-viceweconsiderdifferentlevelsofuserinteractivity(thatis,thereadvs.writeratio).Furthermore,weconsiderhowtheclient-sideconnectionmayimpactontheinternalbottle-necksoftheserverinfrastructure.Throughsimulationweshowthatthepresenceofmultimedia-richcontentinsocialnetworkingserviceswillcauseamajorshiftintheinfras-tructurebottlenecks.Furthermore,weshowthatthelevelofuserinteractivityandthenetworkcharacteristicscanplayafundamentalroleindeterminingthesystembottleneck.Theremainingofthepaperisorganizedasfollows:Sec-tion2describesthemainfeaturesofsocialnetworkingser-vices.Section3describesthesystemandworkloadmodelusedforouranalysis.Section4presentstheresultsofourexperiments,providinganinsightontheimpactoftheser-viceevolutionontheunderlyinginfrastructure.Section5discussestherelatedwork.Finally,Section6providessomeconcludingremarks.2SocialnetworkingservicesSocialnetworkingservicesarecharacterizedbytwomainfeatures:theinteractivityoftheusersthataccesstheservicesandthehighdegreeofmultimediacontentpro-videdthroughtheseservices.Bothfeaturesarebecomingmoreandmoreprominentasthesocialnetworkingservicesunleashtheirpotentialofsupportingnewuserinteractionmodels.Akeyrequiremen