ConcurrentProgramming withRubyandTupleSpaces

LucCastera Founder/messagepub.com

AFundamentalTurnTowardConcurrencyinSoftware Themajorprocessormanufacturersandarchitectures haverunoutofroomwithmostoftheirtraditional approachestoboostingCPUperformance.Insteadof drivingclockspeedsandsstraightlineinstruction throughputeverhigher,theyareinsteadturningenmasse tohyperthreadingandmulticorearchitectures.[]And thatputsusatafundamentalturningpointinsoftware development,atleastforthenextfewyears... HerbSutterMarch2005Source:http://www.gotw.ca/publications/concurrencyddj.htm

TheFreeLunchisOver:

Outline1.TheproblemwithRubyThreads 2.MultipleRubyProcesses 3.InterprocessCommunication withTupleSpaces

PART1

TheProblemWithThreadsAcloserlookattheRubythreadingmodel

3TypesofThreadingModels:

1:N 1:1 M:N

3TypesofThreadingModels:

1:N 1:1 M:NKernelThreads UserSpaceThreads

1:NGreenThreadsOnekernelthreadforNuserthreads akalightweightthreads

10 ms

10 ms

10 ms

10 ms

10 ms

10 ms

10 ms

10 ms

RU BY 1. 8

ProsandConsPros:Threadcreation,execution,andcleanuparecheap Lotsofthreadscanbecreated

Cons:Notreallyparallelbecausekernelschedulerdoesn't knowaboutthreadsandcan'tschedulethemacross CPUsortakeadvantageofSMP BlockingI/OoperationcanblockallgreenthreadsExample:CExtension Example:mysqlgem(solution:NeverBlockmysqlplus)

blocking

1:1NativeThreads1kernelthreadforeachuserthread

ProsandConsPros:ThreadscanexecuteondifferentCPUs(trulyparallel) Threadsdonotblockeachother

Cons:SetupOverhead Lowlimitonnumberofthreads Linuxkernelbugwithlotsofthreads

RU BY 1 . 9

Ilied.

GlobalInterpreterLockAGlobalInterpreterLock(GIL)isamutual exclusionlockheldbyaprogramminglanguage interpreterthreadtoavoidsharingcodethatis notthreadsafewithotherthreads.Thereis alwaysoneGILforoneinterpreterprocess. UsageofaGlobalInterpreterLockinalanguage effectivelylimitsconcurrencyofasingle interpreterprocesswithmultiplethreadsthereis noorverylittleincreaseinspeedwhenrunning

Aperson(maleorfemale)whointentionallyor unintentionallystopstheprogressoftwoothers gettingtheirgameon.

Concurrencyisa mythinRubyIlyaGrigorik

Unlessyouare usingJRuby.

AnoteonFibersRuby1.9introducesfibers. Fibersaregreenthreads,butscheduling mustbedonebytheprogrammerandnot theVM. Fasterandcheaperthennativethreads. ImplementedforRuby1.8byAmanGupta. LearnMore:http://tinyurl.com/rubyfibers http://allthing.net/fibers

M:NHybridModelM kernel threads for N user threads best of both worlds

ProsandConsPros: TakeadvantageofmultipleCPUs Notallthreadsareblockedbyblocking systemcalls Cheapcreation,execution,andcleanup Cons: Needschedulerinuserlandandkernelto

TheOtherProblemwithThreads

Writingmultithreadedcodeisreally, reallyhard.Anditishardbecauseof SharedMemory.JimWeirich

http://rubyconf2008.confreaks.com/what-all-rubyist-should-know-about-threads.html

MultiThreaded CodeisHard

+Concurrencyisa myth

= FAIL!

Stopthinkinginthreads Designyourapplication tousemultipleprocesses

PART2

Multiple Ruby Processes

ProsandConsPros: Nolongersharingmemory TakeadvantageofmultipleCPUs (Performance) Notallthreadsareblockedbyblocking systemcalls. Scalability FaultTolerance Cons:

Monitoring FaultTolerance Starting/Stopping Latency

butwewillfocuson...

Howdotheprocessescommunicate?

OptionsDRB Sockets Queues RabbitMQ ActiveMQ KeyValueDatabases Redis

Examples

Rails+Mongrel/ThinClusterofapplicationservers(Mongrel,Thin...) Communicationbetweenprocessesisdoneviathe database.

NaniteAselfassemblingfabricofRubydaemons http://github.com/ezmobius/nanite UsesRabbitMQ/AMQPforIPC

RevactorUsestheactormodel Actorsarekindalikethreads,withmessaging bakedin. EachActorhasamailbox. It'slikecodingerlanginRuby. MessagesarepassedbetweenactorsusingTCP sockets. GoodDocumentation

JournetaJournetaisadirtsimplelibraryforpeer discoveryandmessagepassingbetweenRuby applicationsonaLAN UsesUDPSocketsforIPC UsesthefuckedupRubysocketAPIfromtheirRDOC

Demo(?)

PART3

TupleSpacesInterprocessCommunicationwithTupleSpaces

Atuplespaceprovidesa repositoryoftuples thatcanbeaccessed concurrently.

TheBlackboardMetaphor[:a dd, 1, 2] [:a dd, 60 , 5] [:resu lt, 79]

[:s ubtra ct, 10, 2 ] [:s ear ch, linda ] [:tok en] [:s ave, 78 64 ] [:wh ere_ is, :wa ldo

TheBlackboardMetaphor[:a dd, ni l, ni l] [:a dd, 1, 2] [:a dd, 60 , 5] [:resu lt, 79]

[:s ubtra ct, 10, 2 ] [:s ear ch, linda ] [:tok en] [:s ave, 78 64 ] [:wh ere_ is, :wa ldo

TheBlackboardMetaphor[:a dd, 1, 2] [:a dd, 60 , 5] [:resu lt, 79]

[:s ubtra ct, 10, 2 ] [:s ear ch, linda ] [:tok en] [ni l] [:s ave, 78 64 ] [:wh ere_ is, :wa ldo

TheBlackboardMetaphor[:a dd, 1, 2] [:a dd, 60 , 5] [:resu lt, 79]

[:s ubtra ct, 10, 2 ] [:s ear ch, linda ] [:tok en] [:s ave, 78 64 ] [:wh er e_i s, :waldo] [:wh ere_ is, :wa ldo

AboutTupleSpacesFirstimplementationwasLinda. LindawasdevelopedbyDavidGelernterand NicholasCarrieroatYaleUniversity. Implementationsexistsformostlanguages. TheRubyimplementationisRinda. Rindaisabuiltinlibrary,sononeedtoinstall.

5BasicOperationsread read_all write take notify

5BasicOperationsread read_all write take notify

Readstuple,butdoesnotremoveit. Blocking,bydefault,buttakesan additionaltimeoutargument.

5BasicOperationsread read_all write take notify

Returnsalltuplesmatchingtuple. Doesnotremovethefoundtuples.

5BasicOperationsread read_all write take notify

AddsTuple Takesanoptionaltimeoutparameter

5BasicOperationsread read_all write take notify

AtomicRead+Delete Blocking,bydefault,buttakesan additionaltimeoutargument.

5BasicOperationsread read_all write take notify

Registersfornotificationsofevents: Write Take Delete

KeyFeaturesSpacesaresharedSpacehandlesdetailsofconcurrentaccess

SpacesarepersistentIfagentprocessdies,dataisstillinspace However,ifspaceprocessdies,dataislost(?)

SpacesareassociativeAssociativelookupsratherthanmemorylocationor identifier

Spacesaretransactionallysecure

ARindatuplecanbean arrayorahash

ARindatuplecanbean arrayorahash

( But let's stick with the array, I like that better! )

StartaTupleSpaceonport1234

Clients/Agents

DEMORinda

RingServer

ThisisalsoaTupleSpace

SPOF

Rindaisnotpersistent...Ifitcrasheswhileyouhavetuplesin thespace,youlosethemall.

OnlyRuby

IntroducingBlackboardTupleSpaceimplementationontopofRedis Persistent Redisisareallyfastkeyvaluedatabase. Likememcachedbutdataisnotvolatile. SameAPIPlug&Play Fornow,onlysupports:take,read,andwrite http://github.com/dambalah/blackboard

Server

Juststarttheredisserver: $ redis-server

Client/Agents

Blackboard

DEMO

BlackboardBenchmarksWrite (1000) Take (500) Read (500) Rinda 0.042749 0.082744 0.020098 Blackboard 0.253068 15.844250 20.098478

Blackboard:FutureMovefromRedistoacustombasedErlang blackboardimplementation. IwouldlikethatErlangimplementationtobe easilyusedfromotherprogramminglanguages also. Soit'sreallytwoprojects:Blackboardinerlang Rubylibrarytotalktoblackboardinerlang

Thankyou!

LucCastera Founder/messagepub.com

Questions?Feedback? luc.castera@gmail.com www.speakerrate.com

LucCastera Founder/messagepub.com

Resources/ReferencesPart1:ThreadingModels http://timetobleed.com/threadingmodelssomany differentwaystogetstuffdone/ http://envycasts.com/products/scalingruby http://www.infoq.com/news/2007/05/rubythreading futures http://thebogles.com/blog/2006/11/rubythreading/ http://spec.rubydoc.org/wiki/Ruby_Threading http://www.bitwiese.de/2007/09/onprocessesand threads.html http://www.igvita.com/2008/11/13/concurrencyisa

Resources/ReferencesPart2:MultipleProcesses http://github.com/ezmobius/nanite http://erlang.org/ http://www.rabbitmq.com/ http://code.google.com/p/redis/ http://revactor.org/ http://journeta.rubyforge.org/http://home.mindspring.com/~eric_rollins/ParallelRuby.html

Resources/ReferencesPart3:TupleSpaces http://c2.com/cgi/wiki?TupleSpace http://en.wikipedia.org/wiki/Tuplespace http://www.julianbrowne.com/article/viewer/spacebased architectureexample http://www.rubyagent.com/ http://segment7.net/projects/ruby/drb/ http://segment7.net/projects/ruby/drb/rinda/ringserver.html JavaSpacesPrinciples,Patterns,andPracticeFreeman,Hupfer,et.al. http://www.rubydoc.org/stdlib/libdoc/rinda/rdoc/index.html

ThingsIwishIhadtimetospendonMPIandRubyMPI http://github.com/abedra/mpiruby/tree/master Rubyforkoff: http://tinyurl.com/forkoff