sagas: distributed transactions without locks · sagas: distributed transactions without locks in...

Sagas:distributedtransactionswithoutlocksinErlangMARKALLEN- ALERTLOGIC

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@BYTEMEORG

TypesofSagas§BackwardRecovery§ForwardRecovery§“RecoveryBlocks”§ParallelSagas

SagasinErlang

TheBig IdeaFoldoveralistofclosures…

TheBig IdeaFoldoveralistofclosures…...unlessthere’sanerror.

TheBig IdeaFoldoveralistofclosures…...unlessthere’sanerror;Then,foldoveralistofclosures.

Flows

Forward1 Forward2 Forward3 Forward4 Forward5

Rollback1 Rollback2 Rollback3 Rollback4 Rollback5

Flows



BOOM

Flows

Forward1 Forward2 Forward3

Rollback1 Rollback2 Rollback3

BOOM

Terminology

§Operation§Step§Transaction

Terminology



ImplicitAssumptionsandRequirements

CompensatingClosures

CannotAbort

IdempotentRequests

Whatif??

Forward1 Forward2 Forward3


BOOM

Whatif??

Forward1 Forward2 Forward3 Forward4


FuturesinErlang

WhydoesErlangneedfutures?!

Itdoesn’t!Except…

AsynchronousSagaOperations

Implementation

Semantics?

PropertyBasedTests

Whatisit?§Writeoneormoreinvariants§Testvaluesareautomaticallygeneratedandtheinvarianttested§Failuresareshrunktothesmallestpossiblefailurecase§Modifycode(ortestcase)andrestarttest§Testsareusuallytimeboxed§Extremelyusefultobuildconfidenceincomplexscenarios

AcademichistoryQuickCheck:ALightweightToolforRandomTestingofHaskellPrograms

Implementationsfor§Go§C/C++§Clojure§Scala§Haskell(ofcourse)§… lotsofothers…§Erlang/Elixir(watchThomasArtstalkatElixirConf EU2015)

Erlang implementations§Quviq CommercialQuickCheck (http://www.quviq.com)§Free(butnotopensource)“QuickCheck mini”– doesn’tdostatem§PropEr (https://github.com/manopapad/proper)§Triq (https://github.com/triqng/triq)

Generators§Allstandardbasictypes:§ integers,§ floats,§atoms,§binaries,§strings,§ lists

§Listsofbasictypes§Userdefinedgeneratorsusing?LETand?SUCHTHAT

Propositions§?FORALL(Variable,generator_function(),test_function(Variable))

Resources§https://github.com/mrallen1/gisla

§https://github.com/mrallen1/criswell

§Sagaspaper:http://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf

§Caitie McCaffrey,PapersWeLoveonSagas:https://youtu.be/7dc4Tl5ZHRg?t=27m16s

§Caitie McCaffrey,DistributedSagas:https://speakerdeck.com/caitiem20/distributed-sagas-a-protocol-for-coordinating-microservices

§Theseslides: https://speakerdeck.com/mrallen1/sagas-distributed-transactions-without-locks

sagas: distributed transactions without locks · sagas: distributed transactions without locks in...

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