软件架构设计与模式高级培训

1,软件架构设计与模式薛君敖博士JunaoXuePh.Dxuejunao2009年12月9-11日,2,讲师介绍,81年赴美，美国哥伦比亚大学电脑科学硕士、物理学博士。85-87在美国芝加哥AT/TBellLaboratory工作期间，参与编写5ESS（超大型交换机）DatabaseRetrofit的数据库架构层面的设计和实施方案，包括：设计和管理安全的数据库架构，设计和管理高可用性解决方案，优化和实施数据库的数据恢复计划，设计、部署和巩固数据库架构。88-94在美国新泽西州AT/TBellLaboratory工作期间，是DACS（大型传输交换连接设备）的Architect组成员，为DACS的逻辑架构、物理架构和系统架构设计提供解决方案，并主持DACS的FSTS（工厂测试系统）系统设计，从硬件基础设施、技术平台、应用平台到应用的设计和实施。之后参与编写SDH和DWDM两大光通讯网络的网管系统（INMS）的逻辑/物理/系统架构设计方案。94-02LucentTechnologiesBellLabsInnovations在任朗讯科技贝尔实验室网管技术支持小组组长兼任原邮电部网管专家顾问期间，为北京，上海，深圳，武汉，南昌等地SDH/DWDM/光网络及网管的设计和实施提供技术解决方案03-06在任“微软-北京邮电大学软件学院-亚鸿世纪软件联合研究中心”副主任、兼任北京亚鸿世纪软件公司总经理和中科软国际部技术顾问期间，为中国电信业提供业务流程重组（BPR）、业务流程管理（BPM）的IT解决方案；领导编写为韩国电信和中国电信用的基于COBIT/ITIL/MOF的IT解决方案，指导开发基于Biztalk和SPS的OSS/BSS已部署在河南通信、威海通信。06-现在普信管理theyareusefulconceptsthatcaptureelementsofanarchiture.Eachistheoutcomeofearlydesigndecisions.,WhatIsSoftwareArchitecture?,94,SoftwareStructures,Thesethreestructurescorrespondtothethreetypesofdecisionthatarchitecturaldesigninvolves:Howisthesystemtobestructuredasasetofcodeunits(modules)?Howisthesystemtobestructuredasasetofelementsthathaveruntimebehavior(components)andinteractions(connectors)?Howisthesystemtorelatetononsoftwarestructuresinitsenvironment(i.e.,CPUs,filesystems,networks,developmentteams,etc.)?,95,ArchitecturalStructuresandViews,Architecturalstructurescanbyandlargebedividedintothreegroups,dependingonthebroadnatureoftheelementstheyshow.Modulestructures.Heretheelementsaremodules,whichareunitsofimplementation.Modulesrepresentacode-basedwayofconsideringthesystem.Theyareassignedareasoffunctionalresponsibility.Thereislessemphasisonhowtheresultingsoftwaremanifestsitselfatruntime.ModulestructuresallowustoanswerquestionssuchasWhatistheprimaryfunctionalresponsibilityassignedtoeachmodule?Whatothersoftwareelementsisamoduleallowedtouse?Whatothersoftwaredoesitactuallyuse?Whatmodulesarerelatedtoothermodulesbygeneralizationorspecialization(i.e.,inheritance)relationships?Component-and-connectorstructures.Heretheelementsareruntimecomponents(whicharetheprincipalunitsofcomputation)andconnectors(whicharethecommunicationvehiclesamongcomponents).Component-and-connectorstructureshelpanswerquestionssuchasWhatarethemajorexecutingcomponentsandhowdotheyinteract?Whatarethemajorshareddatastores?Whichpartsofthesystemarereplicated?Howdoesdataprogressthroughthesystem?Whatpartsofthesystemcanruninparallel?Howcanthesystemsstructurechangeasitexecutes?Allocationstructures.Allocationstructuresshowtherelationshipbetweenthesoftwareelementsandtheelementsinoneormoreexternalenvironmentsinwhichthesoftwareiscreatedandexecuted.TheyanswerquestionssuchasWhatprocessordoeseachsoftwareelementexecuteon?Inwhatfilesiseachelementstoredduringdevelopment,testing,andsystembuilding?Whatistheassignmentofsoftwareelementstodevelopmentteams?,96,ArchitecturalStructuresofaSystem,97,ArchitecturalStructuresofaSystem,98,CreatinganArchitecture,99,ArchitectureandQualityAttributes,Architectureiscriticaltotherealizationofmanyqualitiesofinterestinasystem,andthesequalitiesshouldbedesignedinandcanbeevaluatedatthearchitecturallevel.Architecture,byitself,isunabletoachievequalities.Itprovidesthefoundationforachievingquality,butthisfoundationwillbetonoavailifattentionisnotpaidtothedetails.Qualityattributes:Qualitiesofthesystem.Wewillfocusonavailability,modifiability,performance,security,testability,andusability.Businessqualities(suchastimetomarket)thatareaffectedbythearchitecture.Qualities,suchasconceptualintegrity,thatareaboutthearchitectureitselfalthoughtheyindirectlyaffectotherqualities,suchasmodifiability.,100,Availabilitygeneralscenarios(generation),101,Availabilitygeneralscenariosgeneration,102,(Sample)modifiabilityscenario(generation),103,(Sample)performancescenario(generation),104,(Sample)securityscenario(generation),105,Securityscenariogeneration,106,Sampletestabilityscenario,107,TestabilityGeneralScenarioGeneration,108,Sampleusabilityscenario,109,UsabilityGeneralScenarioGeneration,110,QualityAttributeStimuli,111,BusinessQualities,Timetomarket.Timetomarketisoftenreducedbyusingprebuiltelementssuchascommercialoff-the-shelf(COTS)productsorelementsre-usedfrompreviousprojects.Theabilitytoinsertordeployasubsetofthesystemdependsonthedecompositionofthesystemintoelements.Costandbenefit.Differentarchitectureswillyielddifferentdevelopmentcosts.Anarchitecturethatishighlyflexiblewilltypicallybemorecostlytobuildthanonethatisrigid(althoughitwillbelesscostlytomaintainandmodify).Projectedlifetimeofthesystem.Ifthesystemisintendedtohavealonglifetime,modifiability,scalability,andportabilitybecomeimportant.Amodifiable,extensibleproductismorelikelytosurvivelongerinthemarketplace,extendingitslifetime.Targetedmarket.Portabilityandfunctionalityarekeytomarketshare.Otherqualities,suchasperformance,reliability,andusabilityalsoplayarole.Toattackalargemarketwithacollectionofrelatedproducts,aproductlineapproachshouldbeconsideredinwhichacoreofthesystemiscommon(frequentlyincludingprovisionsforportability)andaroundwhichlayersofsoftwareofincreasingspecificityareconstructed.Rolloutschedule.Ifaproductistobeintroducedasbasefunctionalitywithmanyfeaturesreleasedlater,theflexibilityandcustomizabilityofthearchitectureareimportant.Particularly,thesystemmustbeconstructedwitheaseofexpansionandcontractioninmind.Integrationwithlegacysystems.Ifthenewsystemhastointegratewithexistingsystems,caremustbetakentodefineappropriateintegrationmechanisms.Thispropertyisclearlyofmarketingimportancebuthassubstantialarchitecturalimplications.Thearchitecturalconstraintsimpliedbythisintegrationmustbeanalyzed.,112,Availabilitytactics,113,Modifiabilitytactics,114,Performancetactics,115,Tacticsforsecurity,116,Testabilitytactics,117,Runtimeusabilitytactics,118,DesignTheArchitecture,119,EvolutionaryDeliveryLifeCycle,120,Attribute-drivendesign(ADD),SampleInputBeginningADDADDSteps1ChoosetheModuletoDecompose2.aChoosetheArchitecturalDrivers2.bChooseanArchitecturalPattern2.cInstantiateModulesandAllocateFunctionalityUsingMultipleViewsInstantiatemodulesAllocatefunctionalityRepresentthearchitecturewithviews2.dDefineInterfacesoftheChildModules2.eVerifyandRefineUseCasesandQualityScenariosasConstraintsfortheChildModulesFunctionalrequirementsConstraintsQualityscenarios,121,TheinputtoADDisasetofrequirements.ADDassumesfunctionalrequirements(typicallyexpressedasusecases)andconstraintsasinput,asdootherdesignmethods.However,inADD,wedifferfromthosemethodsinourtreatmentofqualityrequirements.ADDmandatesthatqualityrequirementsbeexpressedasasetofsystem-specificqualityscenarios.Thegeneralscenariosdiscussedinhereactasinputtotherequirementsprocessandprovideachecklisttobeusedindevelopingthesystem-specificscenarios.System-specificscenariosshouldbedefinedtothedetailnecessaryfortheapplication.,SampleInput,122,1.Choosethemoduletodecompose.Themoduletostartwithisusuallythewholesystem.Allrequiredinputsforthismoduleshouldbeavailable(constraints,functionalrequirements,qualityrequirements).2.Refinethemoduleaccordingtothesesteps:a.Choosethearchitecturaldriversfromthesetofconcretequalityscenariosandfunctionalrequirements.Thisstepdetermineswhatisimportantforthisdecomposition.b.Chooseanarchitecturalpatternthatsatisfiesthearchitecturaldrivers.Create(orselect)thepatternbasedonthetacticsthatcanbeusedtoachievethedrivers.Identifychildmodulesrequiredtoimplementthetactics.c.Instantiatemodulesandallocatefunctionalityfromtheusecasesandrepresentusingmultipleviews.d.Defineinterfacesofthechildmodules.Thedecompositionprovidesmodulesandconstraintsonthetypesofmoduleinteractions.Documentthisinformationintheinterfacedocumentforeachmodule.e.Verifyandrefineusecasesandqualityscenariosandmakethemconstraintsforthechildmodules.Thisstepverifiesthatnothingimportantwasforgottenandpreparesthechildmodulesforfurtherdecompositionorimplementation.3.Repeatthestepsaboveforeverymodulethatneedsfurtherdecomposition.,ADDSteps,123,Thefollowingareallmodules:system,subsystem,andsubmodule.Thedecompositiontypicallystartswiththesystem,whichisthendecomposedintosubsystems,whicharefurtherdecomposedintosubmodules.,1a.ChoosetheModuletoDecompose,124,Architecturaldriversarethecombinationoffunctionalandqualityrequirementsthat“shape”thearchitectureortheparticularmoduleunderconsideration.Thedriverswillbefoundamongthetop-priorityrequirementsforthemodule.Thedeterminationofarchitecturaldriversisnotalwaysatop-downprocess.Sometimesdetailedinvestigationisrequiredtounderstandtheramificationsofparticularrequirements.Forexample,todetermineifperformanceisanissueforaparticularsystemconfiguration,aprototypicalimplementationofapieceofthesystemmayberequired.Wewillbaseourdecompositionofamoduleonthearchitecturaldrivers.Otherrequirementsapplytothatmodule,but,bychoosingthedrivers,wearereducingtheproblemtosatisfyingthemostimportantones.Wedonottreatalloftherequirementsasequal;thelessimportantrequirementsaresatisfiedwithintheconstraintsofthemostimportant.ThisisasignificantdifferencebetweenADDandotherarchitecturedesignmethods.,2.aChoosetheArchitecturalDrivers,125,Thegoalofstep2bistoestablishanoverallarchitecturalpatternconsistingofmoduletypes.Thepatternsatisfiesthearchitecturaldriversandisconstructedbycomposingselectedtactics.Twomainfactorsguidetacticselection.Thefirstisthedriversthemselves.Thesecondisthesideeffectsthatapatternimplementingatactichasonotherqualities.Ifwechooseoneexampleofeach:increasecomputationalefficiencyandchooseschedulingpolicy.thenthisyieldsthefollowingtactics:Semanticcoherenceandinformationhiding.Separateresponsibilitiesdealingwiththeuserinterface,communication,andsensorsintotheirownmodules.Wecallthesemodulesvirtualmachinesandweexpectallthreetovarybecauseofthedifferingproductsthatwillbederivedfromthearchitecture.Separatetheresponsibilitiesassociatedwithdiagnosisaswell.Increasecomputationalefficiency.Theperformance-criticalcomputationsshouldbemadeasefficientaspossible.Schedulewisely.Theperformance-criticalcomputationsshouldbescheduledtoensuretheachievementofthetimingdeadline.,2.bChooseanArchitecturalPattern,126,Intheprecedingsection,wediscussedhowthequalityarchitecturaldriversdeterminethedecompositionstructureofamoduleviatheuseoftactics.Asamatteroffact,inthatstepwedefinedthemoduletypesofthedecompositionstep.Wenowshowhowthosemoduletypeswillbeinstantiated.InstantiatemodulesWeidentifiedanon-performance-criticalcomputationrunningontopofavirtualmachinethatmanagescommunicationandsensorinteractions.Thesoftwarerunningontopofthevirtualmachineistypicallyanapplication.Inaconcretesystemwewillnormallyhavemorethanonemodule.Therewillbeoneforeachgroupoffunctionality;thesewillbeinstancesofthetypesshowninthepattern.Ourcriterionforallocatingfunctionalityissimilartothatusedinfunctionality-baseddesignmethods,suchasmostobject-orienteddesignmethods.,2.cInstantiateModulesandAllocateFunctionalityUsingMultipleViews,127,Applyingusecasesthatpertaintotheparentmodulehelpsthearchitectgainamoredetailedunderstandingofthedistributionoffunctionality.Thisalsomayleadtoaddingorremovingchildmodulestofulfillallthefunctionalityrequired.Attheend,everyusecaseoftheparentmodulemustberepresentablebyasequenceofresponsibilitieswithinthechildmodules.Assigningresponsibilitiestothechildreninadecompositionalsoleadstothediscoveryofnecessaryinformationexchange.Thiscreatesaproducer/consumerrelationshipbetweenthosemodules,whichneedstoberecorded.Atthispointinthedesign,itisnotimportanttodefinehowtheinformationisexchanged.Istheinformationpushedorpulled?Isitpassedasamessageoracallparameter?Theseareallquestionsthatneedtobeansweredlaterinthedesignprocess.Atthispointonlytheinformationitselfandtheproducerandconsumerrolesareofinterest.ThisisanexampleofthetypeofinformationleftunresolvedbyADDandresolvedduringdetaileddesign.Sometacticsintroducespecificpatternsofinteractionbetweenmoduletypes.Atacticusinganintermediaryoftypepublish-subscribe,forexample,willintroduceapattern,PublishforoneofthemodulesandapatternSubscribefortheother.Thesepatternsofinteractionshouldberecordedsincetheytranslateintoresponsibilitiesfortheaffectedmodules.Thesestepsshouldbesufficienttogainconfidencethatthesystemcandeliverthedesiredfunctionality.Tocheckiftherequiredqualitiescanbemet,weneedmorethanjusttheresponsibilitiessofarallocated.Dynamicandruntimedeploymentinformationisalsorequiredtoanalyzetheachievementofqualitiessuchasperformance,security,andreliability.Therefore,weexamineadditionalviewsalongwiththemoduledecompositionview.,Allocatefunctionality,128,ADDusesthesethreecommonviews.Moduledecompositionview.Ourdiscussionaboveshowshowthemoduledecompositionviewprovidescontainersforholdingresponsibilitiesastheyarediscovered.Majordataflowrelationshipsamongthemodulesarealsoidentifiedthroughthisview.Concurrencyview.Intheconcurrencyviewdynamicaspectsofasystemsuchasparallelactivitiesandsynchronizationcanbemodeled.Thismodelinghelpstoidentifyresourcecontentionproblems,possibledeadlocksituations,dataconsistencyissues,andsoforth.Modelingtheconcurrencyinasystemlikelyleadstodiscoveryofnewresponsibilitiesofthemodules,whicharerecordedinthemoduleview.Itcanalsoleadtodiscoveryofnewmodules,suchasaresourcemanager,inordertosolveissuesofconcurrentaccesstoascarceresourceandthelike.Theconcurrencyviewisoneofthecomponent-and-connectorviews.Thecomponentsareinstancesofthemodulesinthemoduledecompositionview,andtheconnectorsarethecarriersofvirtualthreads.Avirtualthreaddescribesanexecutionpaththroughthesystemorpartsofit.Thisshouldnotbeconfusedwithoperatingsystemthreads(orprocesses),whichimpliesotherpropertieslikememory/processorallocation.Thosepropertiesarenotofinterestonthelevelatwhichwearedesigning.Nevertheless,afterthedecisionsonanoperatingsystemandonthedeploymentofmodulestoprocessingunitsaremade,virtualthreadshavetobemappedontooperatingsystemthreads.Thisisdoneduringdetaileddesign.Theconnectorsinaconcurrencyviewarethosethatdealwiththreadssuchassynchronizeswith,starts,cancels,andcommunicateswith.Aconcurrencyviewshowsinstancesofthemodulesinthemoduledecompositionviewasameansofunderstandingthemappingbetweenthosetwoviews.Itisimportanttoknowthatasynchronizationpointislocatedinaspecificmodulesothatthisresponsibilitycanbeassignedattherightplace.,Representthearchitecturewithviews,129,-Twousersdoingsimilarthingsatthesametime.Thishelpsinrecognizingresourcecontentionordataintegrityproblems.-Oneuserperformingmultipleactivitiessimultaneously.Thishelpstouncoverdataexchangeandactivitycontrolproblems.-Startingupthesystem.Thisgivesagoodoverviewofpermanentrunningactivitiesinthesystemandhowtoinitializethem.Italsohelpsindecidingonaninitializationstrategy,suchaseverythinginparalleloreverythinginsequenceoranyothermodel.-Shuttingdownthesystem.Thishelpstouncoverissuesofcleaningup,suchasachievingandsavingaconsistentsystemstate.,understandtheconcurrencyinasystem,130,Ifmultipleprocessorsorspecializedhardwareisusedinasystem,additionalresponsibilitiesmayarisefromdeploymenttothehardware.Usingadeploymentviewhelpstodetermineanddesignadeploymentthatsupportsachievingthedesiredqualities.Thedeploymentviewresultsinthevirtualthreadsoftheconcurrencyviewbeingdecomposedintovirtualthreadswithinaparticularprocessorandmessagesthattravelbetweenprocessorstoinitiatethenextentryinthesequenceofactions.Thus,itisthebasisforanalyzingthenetworktrafficandfordeterminingpotentialcongestion.Thedeploymentviewalsohelpsindecidingifmultipleinstancesofsomemodulesareneeded.Forexample,areliabilityrequirementmayforceustoduplicatecriticalfunctionalityondifferentprocessors.Adeploymentviewalsosupportsreasoningabouttheuseofspecial-purposehardware.Thederivationofthedeploymentviewisnotarbitrary.Aswiththemoduledecompositionandconcurrencyviews,thearchitecturedrivershelpdeterminetheallocationofcomponentstohardware.Tacticssuchasreplicationofferameanstoachievehighperformanceorreliabilitybydeployingreplicasondifferentprocessors.Othertacticssuchasareal-timeschedulingmechanismactuallyprohibitdeploymentondifferentprocessors.Functionalconsiderationsusuallyguidethedeploymentofthepartsthatarenotpredeterminedbytheselectedtactics.Thecrossingofavirtualthreadfromoneprocessortoanothergeneratesresponsibilitiesfordifferentmodules.Itindicatesacommunicationrequirementbetweentheprocessors.Somemodulemustberesponsibleformanagingthecommunication;thisresponsibilitymustberecordedinthemoduledecompositionview.,Deploymentview,131,Thefollowinginformationshouldbeavailableinthemodulesinterfacedocumentation:Themoduleviewdocumentsproducers/consumersofinformation.patternsofinteractionthatrequiremodulestoprovideservicesandtousethem.Theconcurrencyviewdocumentsinteractionsamongthreadsthatleadtotheinterfaceofamoduleprovidingorusingaservice.theinformationthatacomponentisactiveforexample,hasitsownthreadrunning.theinformationthatacomponentsynchronizes,sequentializes,andperhapsblockscalls.Thedeploymentviewdocumentsthehardwarerequirements,suchasspecial-purposehardware.sometimingrequirements,suchasthatthecomputationspeedofaprocessorhastobeatleast10MIPS.communicationrequirements,suchasthatinformationshouldnotbeupdatedmorethanonceeverysecond.,2.dDefineInterfacesoftheChildModules,132,2.eVerifyandRefineUseCasesandQualityScenariosasConstraintsfortheChildModules,FunctionalrequirementsConstraintsQualityscenarios,133,Userinterface.Recognizeuserrequestsandtranslatethemintotheformexpectedbytheraising/loweringdoormodule.Raising/loweringdoormodule.Controlactuatorstoraiseorlowerthedoor.Stopthedoorwhenitreacheseitherfullyopenorfullyclosed.Obstacledetection.Recognizewhenanobstacleisdetectedandeitherstopthedescentofthedoororreverseit.Communicationvirtualmachine.Manageallcommunicationwiththehomeinformationsystem.Sensor/actuatorvirtualmachine.Manageallinteractionswiththesensorsandactuators.Scheduler.Guaranteethattheobstacledetectorwillmeetitsdeadlines.Diagnosis.Managetheinteractionswiththehomeinformationsystemdevotedtodiagnosis.,Functionalrequirements,134,Constraints,Constraintsoftheparentmodulecanbesatisfiedinoneofthefollowingways:Thedecompositionsatisfiestheconstraint.Forexample,theconstraintofusingacertainoperatingsystemcanbesatisfiedbydefiningtheoperatingsystemasachildmodule.Theconstrainthasbeensatisfiedandnothingmoreneedstobedone.Theconstraintissatisfiedbyasinglechildmodul