分布式非关系数据库的设计模式

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1、DesignPatternsforDistributedNon-RelationalDatabasesakaJustEnoughDistributedSystemsToBeDangerous(in40minutes)ToddLipcon(Otlipcon)ClouderaIntroductionCommonUnderlyingAssumptionsDesignPatternsConsistentHashingConsistencyModelsDataModelsStorageLayoutsLog-StructuredMergeTreesClusterManageme

2、ntOmniscientMasterGossipQuestionstoAskPresentersWhyWe'reAllHere►Scalingupdoesn'twork►ScalingoutwithtraditionalRDBMSsisn*tsohoteither►Shardingscales,butyouloseallthefeaturesthatmakeRDBMSsuseful!►Shardingisoperationallyobnoxious.►Ifwedon'tneedrelationalfeatures,wewantadistributedNRDBMS.C

3、losed-sourceNRDBMSsuTheInspiration11►GoogleBigTable►Applications:webtable,Reader,Maps,Blogger,etc.►AmazonDynamo►ShoppingCart,?►Yahoo!PNUTS►Applications:?DataInterfaces"ThisistheNOSQLmeetup,right?H►Everyrowhasakey(PK)►Key/valueget/put►multiget/multiput►Rangescan?Withpredicatepushdown?►M

4、apReduce?►SQL?UnderlyingAssumptions?douderaAssumptions-DataSize►Thedatadoesnotfitononenode.►Thedatamaynotfitononerack.►SANsaretooexpensive.Conclusion:Thesystemmustpartitionitsdataacrossmanynodes.Assumptions-Reliability►Thesystemmustbehighlyavailabletoserveweb(andother)applications.►Sin

5、cethesystemrunsonmanynodes,nodeswillcrashduringnormaloperation.►Datamustbesafeeventhoughdisksandnodeswillfail.Conclusion:Thesystemmustreplicateeachrowtomultiplenodesandremainavailabledespitecertainnodeanddiskfailure・Assumptions-Performance…andpricethereof►Allsystemswe'retalkingabouttod

6、ayaremeantforreal-timeuse.►95thor99thpercentileismoreimportantthanaveragelatency►Commodityhardwareandslowdisks.Conclusion:Thesystemneedstoperformwelloncommodityhardware,andmaintainlowlatencyevenduringrecoveryoperations.Design?douderaPatternsPartitioningSchemes“Wheredoesakeylive?"►Given

7、akey,weneedtodeterminewhichnode(s)itbelongson.►Ifthatnodeisdown,weneedtofindanothercopyelsewhere.►Difficulties:►Unboundednumberofkeys.►Dynamicclustermembership.►Nodefailures.Maintaininghashinginadynamiccluster00000■nodeA■nodeBf6ac9■nodeCnodeD00402v^^^3283c45a89?douderaKeyPlacement■no