Download as PDF, PPTX
![Ordering[T]
Slightly chronological.
!
By no means is it “worst to best”.](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-9-2048.jpg)
![2 Generals translated to Akka:
!
!
class General(general: Option[ActorRef]) extends Actor {!
!
! val WhenIWantToAttack: Date = ???!
!
general foreach { _ ! AttackAt(WhenIWantToAttack) }!
!
def receive = {!
case AttackAt(when) =>!
println(s”General ${otherGeneralName} attacks at $when”)!
! ! ! println(s”I must confirm this!")!
!
sender() ! AttackAt(when)!
}!
!
def otherGeneralName = !
! ! ! if(self.path.name == “blue")!“yellow" else "blue"!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-42-2048.jpg)
![2 Generals translated to Akka:
!
!
class General(general: Option[ActorRef]) extends Actor {!
!
! val WhenIWantToAttack: Date = ???!
!
general foreach { _ ! AttackAt(WhenIWantToAttack) }!
!
def receive = {!
case AttackAt(when) =>!
println(s”General ${otherGeneralName} attacks at $when”)!
! ! ! println(s”I must confirm this!")!
!
sender() ! AttackAt(when)!
}!
!
def otherGeneralName = !
! ! ! if(self.path.name == “blue")!“yellow" else "blue"!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-43-2048.jpg)
![2 Generals translated to Akka:
!
!
class General(general: Option[ActorRef]) extends Actor {!
!
! val WhenIWantToAttack: Date = ???!
!
general foreach { _ ! AttackAt(WhenIWantToAttack) }!
!
def receive = {!
case AttackAt(when) =>!
println(s”General ${otherGeneralName} attacks at $when”)!
! ! ! println(s”I must confirm this!")!
!
sender() ! AttackAt(when)!
}!
!
def otherGeneralName = !
! ! ! if(self.path.name == “blue")!“yellow" else "blue"!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-44-2048.jpg)
![2 Generals translated to Akka:
!
!
class General(general: Option[ActorRef]) extends Actor {!
!
! val WhenIWantToAttack: Date = ???!
!
general foreach { _ ! AttackAt(WhenIWantToAttack) }!
!
def receive = {!
case AttackAt(when) =>!
println(s”General ${otherGeneralName} attacks at $when”)!
! ! ! println(s”I must confirm this!")!
!
sender() ! AttackAt(when)!
}!
!
def otherGeneralName = !
! ! ! if (self.path.name == “blue")!"yellow" else "blue"!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-45-2048.jpg)
![2PC translated to Akka
class Proposer(acceptors: List[ActorRef]) extends Actor {!
var transactionId = 0!
var preparedAcceptors = 0!
!
def receive = {!
case value: String =>!
transactionId += 1!
acceptors foreach { _ ! Prepare(transactionId, value) }!
!
case Prepared =>!
preparedAcceptors += 1!
!
if (preparedAcceptors == acceptors.size)!
acceptors foreach { _ ! Commit }!
!
case Conflict =>!
! ! ! ! ! context stop self!
}!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-73-2048.jpg)
![2PC translated to Akka
class Proposer(acceptors: List[ActorRef]) extends Actor {!
var transactionId = 0!
var preparedAcceptors = 0!
!
def receive = {!
case value: String =>!
transactionId += 1!
acceptors foreach { _ ! Prepare(transactionId, value) }!
!
case Prepared =>!
preparedAcceptors += 1!
!
if (preparedAcceptors == acceptors.size)!
acceptors foreach { _ ! Commit }!
!
case Conflict =>!
! ! ! ! ! context stop self!
}!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-74-2048.jpg)
![2PC translated to Akka
class Proposer(acceptors: List[ActorRef]) extends Actor {!
var transactionId = 0!
var preparedAcceptors = 0!
!
def receive = {!
case value: String =>!
transactionId += 1!
acceptors foreach { _ ! Prepare(transactionId, value) }!
!
case Prepared =>!
preparedAcceptors += 1!
!
if (preparedAcceptors == acceptors.size)!
acceptors foreach { _ ! Commit }!
!
case Conflict =>!
! ! ! ! ! context stop self!
}!
}!
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-75-2048.jpg)
![2PC with ResumeProposer in Akka
!
class ResumeProposer(!
proposer: ActorRef, !
acceptors: List[ActorRef]) extends Actor {!
!
context watch proposer!
!
var anyAcceptorCommitted = false!
!
def receive = {!
case Terminated(`proposer`) =>!
println("Proposer died! Try to finish the transaction...")!
acceptors map { _ ! StatusPlz }!
!
case _: AcceptorStatus =>!
// impl of recovery here!
}!
}
Presentation–sized–snippet = does not cover all cases](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-77-2048.jpg)
![Paxos: Proposals
ProposalNr must:
• be greaterThan any prev proposalNr
used by this Proposer
• example: [roundNr|serverId]](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-113-2048.jpg)
![Raft translated to Akka
abstract class RaftActor !
! extends Actor !
! with FSM[RaftState, Metadata]](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-155-2048.jpg)
![Raft translated to Akka
abstract class RaftActor !
! extends Actor !
! with FSM[RaftState, Metadata]](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-156-2048.jpg)
![Akka-Raft in User-Land //alpha!!!
class WordConcatRaftActor extends RaftActor {!
!
type Command = Cmnd!
!
var words = Vector[String]()!
!
/** Applied when command committed by Raft consensus */!
def apply = {!
case AppendWord(word) =>!
words = words :+ word!
word!
!
case GetWords =>!
log.info("Replying with {}", words.toList)!
words.toList!
}!
}!
akka-raft is a work in progress community project – it may change a lot](https://image.slidesharecdn.com/2014-distibuted-consensus-140911092329-phpapp01/75/Distributed-Consensus-A-K-A-What-do-we-eat-for-lunch-164-2048.jpg)
Uploaded byKonrad Malawski
Distributed Consensus A.K.A. "What do we eat for lunch?"
The document presents a talk by Konrad Malawski on distributed consensus, exploring its definitions, challenges, and techniques involved in distributed systems, such as the Two Generals Problem and algorithm implementations like Paxos and Raft. It discusses the fundamentals of consensus, failure detection, and notable models and fallacies in distributed computing, along with code snippets demonstrating concepts using Akka actors. The talk emphasizes the importance of agreement and reliability within distributed systems and provides an overview of various consensus protocols.
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Distributed Consensus A.K.A. "What do we eat for lunch?"
- 1. Konrad 'ktoso' Malawski Distributed Consensus “What do we eat for lunch?” GeeCON 2014 @ Kraków, PL A.K.A. Konrad `@ktosopl` Malawski
- 2. Konrad 'ktoso' Malawski Distributed Consensus GeeCON 2014 @ Kraków, PL A.K.A. “What do we eat for lunch?” real world edition Konrad `@ktosopl` Malawski
- 3. hAkker @ Konrad`@ktosopl` Malawski
- 4. hAkker @ Konrad`@ktosopl` Malawski typesafe.com geecon.org Java.pl / KrakowScala.pl sckrk.com / meetup.com/Paper-Cup @ London GDGKrakow.pl meetup.com/Lambda-Lounge-Krakow
- 5.
- 6.
- 7.
- 8. What is thistalk about? The network. ! How to think about distributed systems. ! Some healthy madness. Code in slides covers only “simplest possible case”.
- 9. Ordering[T] Slightly chronological. ! By no means is it “worst to best”.
- 10.
- 11. Consensus - informal “we all agree on something”
- 12. Consensus - formal Termination Every correct process decides some value. ! Validity If all correct processes propose the same value v, then all correct processes decide v. ! Integrity If a correct process decides v, then v must have been proposed by some correct process. ! Agreement Every correct process must agree on the same value.
- 13.
- 14.
- 15.
- 16. Distributed Consensus Whatis a distributed system anyway?
- 17. Distributed system definition A distributed system is one in which the failure of a computer you didn't even know existed can render your own computer unusable. — Leslie Lamport http://research.microsoft.com/en-us/um/people/lamport/pubs/distributed-system.txt
- 18. Distributed system definition A system in which participants communicate asynchronously using messages. http://research.microsoft.com/en-us/um/people/lamport/pubs/distributed-system.txt
- 19. Distributed Systems -failure detection
- 20. Distributed Systems -failure detection
- 21. Distributed Systems -failure detection Jim had quit CorpSoft a while ago, but no-one ever told Bob…
- 22. Distributed Systems -failure detection
- 23. Distributed Systems -failure detection Failure detection: • can only rely on external knowledge • but what if there’s no-one to tell you? • thus: must be in-some-way time based
- 24.
- 25. Two Generals Problem Yellow and Blue armies must attack Pink City. They must attack together, otherwise they’ll die in vain. Now they must agree on the exact time of the attack. ! They can only send messengers, which Pink may intercept and kill.
- 26.
- 27. Two Generals Problem- happy case I need to inform blue about my attack plan. I don’t know when yellow will attack…
- 28. Two Generals Problem- happy case
- 29. 1) Initial messagenot lost
- 30. Two Generals Problem- happy case I don’t know if Blue will also attack at 13:37… I’ll wait until I hear back from him.
- 31. Two Generals Problem- happy case I don’t know if Blue will also attack at 13:37… I’ll wait until I hear back from him. Why?
- 32. 2) Message mighthave not reached blue
- 33. Blue must confirmthe reception of the command
- 34. 1) Yellow isnow sure, but Blue isn’t!
- 35. 1) Yellow isnow sure, but Blue isn’t! Why?
- 36. 2) Blue’s confirmationmight have been lost!
- 37. This is exactlymirrors the initial situation!
- 38. 2 Generals Problem Translated to Akka
- 39. 2 Generals translatedto Akka: Akka Actors implement the Actor Model: ! Actors: • communicate via messages • create other actors • change their behaviour on receiving a msg !
- 40. 2 Generals translatedto Akka: Akka Actors implement the Actor Model: ! Actors: • communicate via messages • create other actors • change their behaviour on receiving a msg ! Gains? Distribution / separation / modelling abstraction
- 41. 2 Generals translatedto Akka: case class AttackAt(when: Date) Presentation–sized–snippet = does not cover all cases
- 42. 2 Generals translatedto Akka: ! ! class General(general: Option[ActorRef]) extends Actor {! ! ! val WhenIWantToAttack: Date = ???! ! general foreach { _ ! AttackAt(WhenIWantToAttack) }! ! def receive = {! case AttackAt(when) =>! println(s”General ${otherGeneralName} attacks at $when”)! ! ! ! println(s”I must confirm this!")! ! sender() ! AttackAt(when)! }! ! def otherGeneralName = ! ! ! ! if(self.path.name == “blue")!“yellow" else "blue"! }! Presentation–sized–snippet = does not cover all cases
- 43. 2 Generals translatedto Akka: ! ! class General(general: Option[ActorRef]) extends Actor {! ! ! val WhenIWantToAttack: Date = ???! ! general foreach { _ ! AttackAt(WhenIWantToAttack) }! ! def receive = {! case AttackAt(when) =>! println(s”General ${otherGeneralName} attacks at $when”)! ! ! ! println(s”I must confirm this!")! ! sender() ! AttackAt(when)! }! ! def otherGeneralName = ! ! ! ! if(self.path.name == “blue")!“yellow" else "blue"! }! Presentation–sized–snippet = does not cover all cases
- 44. 2 Generals translatedto Akka: ! ! class General(general: Option[ActorRef]) extends Actor {! ! ! val WhenIWantToAttack: Date = ???! ! general foreach { _ ! AttackAt(WhenIWantToAttack) }! ! def receive = {! case AttackAt(when) =>! println(s”General ${otherGeneralName} attacks at $when”)! ! ! ! println(s”I must confirm this!")! ! sender() ! AttackAt(when)! }! ! def otherGeneralName = ! ! ! ! if(self.path.name == “blue")!“yellow" else "blue"! }! Presentation–sized–snippet = does not cover all cases
- 45. 2 Generals translatedto Akka: ! ! class General(general: Option[ActorRef]) extends Actor {! ! ! val WhenIWantToAttack: Date = ???! ! general foreach { _ ! AttackAt(WhenIWantToAttack) }! ! def receive = {! case AttackAt(when) =>! println(s”General ${otherGeneralName} attacks at $when”)! ! ! ! println(s”I must confirm this!")! ! sender() ! AttackAt(when)! }! ! def otherGeneralName = ! ! ! ! if (self.path.name == “blue")!"yellow" else "blue"! }! Presentation–sized–snippet = does not cover all cases
- 46. 2 Generals translatedto Akka: val system = ActorSystem("two-generals")! ! val blue = ! system.actorOf(Props(new General(general = None)), name = "blue")! ! val yellow = ! system.actorOf(Props(new General(Some(blue))), name = "yellow")! The blue general attacks at 13:37, I must confirm this!! The yellow general attacks at 13:37, I must confirm this!! The blue general attacks at 13:37, I must confirm this!! ... Presentation–sized–snippet = does not cover all cases
- 47. 8 Fallacies ofDistributed Computing
- 48. 8 Fallacies ofDistributed Computing 1. The network is reliable. 2. Latency is zero. 3. Bandwidth is infinite. 4. The network is secure. 5. Topology doesn’t change. 6. There is one administrator. 7. Transport cost is zero. 8. The network is homogeneous. Peter Deutsch “The Eight Fallacies of Distributed Computing” https://blogs.oracle.com/jag/resource/Fallacies.html
- 49.
- 50. Failure models: Fail– Stop Fail – Recover Byzantine
- 51. Failure models: Fail– Stop Fail – Recover Byzantine
- 52. Failure models: Fail– Stop Fail – Recover Byzantine
- 53. Failure models: Fail– Stop Fail – Recover Byzantine
- 54.
- 55. 2PC - step1: Propose value
- 56. 2PC - step1: Propose value
- 57. 2PC - step1: Promise to agree on write
- 58. 2PC - step2: Commit the write
- 59. 2PC - step1: Propose value, and die
- 60. 2PC - step1: Propose value to 1 node, and die
- 61. 2PC: Prepare needstimeouts
- 62. 2PC: Timeouts +recovery committer
- 63. 2PC: Timeouts +recovery committer
- 64. 2PC: Timeouts +recovery committer
- 65. 2PC: Timeouts +recovery committer
- 66. 2PC: Timeouts +recovery committer
- 67. Still can’t tolerateif the “accepted value” Actor dies
- 68. 2PC: Timeouts +recovery committer
- 69. 2PC: Timeouts +recovery committer
- 70. 2 Phase Commit translated to Akka
- 71. 2PC translated toAkka case class Prepare(value: Any)! case object Commit! ! sealed class AcceptorStatus! case object Prepared extends AcceptorStatus! case object Conflict extends AcceptorStatus! ! Presentation–sized–snippet = does not cover all cases
- 72. 2PC translated toAkka case class Prepare(value: Any)! case object Commit! ! sealed class AcceptorStatus! case object Prepared extends AcceptorStatus! case object Conflict extends AcceptorStatus! ! Presentation–sized–snippet = does not cover all cases
- 73. 2PC translated toAkka class Proposer(acceptors: List[ActorRef]) extends Actor {! var transactionId = 0! var preparedAcceptors = 0! ! def receive = {! case value: String =>! transactionId += 1! acceptors foreach { _ ! Prepare(transactionId, value) }! ! case Prepared =>! preparedAcceptors += 1! ! if (preparedAcceptors == acceptors.size)! acceptors foreach { _ ! Commit }! ! case Conflict =>! ! ! ! ! ! context stop self! }! }! Presentation–sized–snippet = does not cover all cases
- 74. 2PC translated toAkka class Proposer(acceptors: List[ActorRef]) extends Actor {! var transactionId = 0! var preparedAcceptors = 0! ! def receive = {! case value: String =>! transactionId += 1! acceptors foreach { _ ! Prepare(transactionId, value) }! ! case Prepared =>! preparedAcceptors += 1! ! if (preparedAcceptors == acceptors.size)! acceptors foreach { _ ! Commit }! ! case Conflict =>! ! ! ! ! ! context stop self! }! }! Presentation–sized–snippet = does not cover all cases
- 75. 2PC translated toAkka class Proposer(acceptors: List[ActorRef]) extends Actor {! var transactionId = 0! var preparedAcceptors = 0! ! def receive = {! case value: String =>! transactionId += 1! acceptors foreach { _ ! Prepare(transactionId, value) }! ! case Prepared =>! preparedAcceptors += 1! ! if (preparedAcceptors == acceptors.size)! acceptors foreach { _ ! Commit }! ! case Conflict =>! ! ! ! ! ! context stop self! }! }! Presentation–sized–snippet = does not cover all cases
- 76. 2PC with ResumeProposerin Akka case class Prepare(value: Any)! case object Commit! ! sealed class AcceptorStatus! case object Prepared extends AcceptorStatus! case object Conflict extends AcceptorStatus! case class Committed(value: Any) extends AcceptorStatus! Presentation–sized–snippet = does not cover all cases
- 77. 2PC with ResumeProposerin Akka ! class ResumeProposer(! proposer: ActorRef, ! acceptors: List[ActorRef]) extends Actor {! ! context watch proposer! ! var anyAcceptorCommitted = false! ! def receive = {! case Terminated(`proposer`) =>! println("Proposer died! Try to finish the transaction...")! acceptors map { _ ! StatusPlz }! ! case _: AcceptorStatus =>! // impl of recovery here! }! } Presentation–sized–snippet = does not cover all cases
- 78. 2PC with ResumeProposerin Akka Presentation–sized–snippet = does not cover all cases
- 79.
- 80. Quorum voting Fromthe perspective of the Omnipotent Observer *
- 81. Quorum voting Fromthe perspective of the Omnipotent Observer * * does not exist in a running system
- 82.
- 83.
- 84.
- 85.
- 86.
- 87.
- 88. Quorum voting –split votes
- 89. Quorum voting –split votes
- 90. Quorum voting –split votes
- 91. Quorum voting –split votes
- 92. Quorum voting –split votes
- 93. James Mickens “TheSaddest Moment” http://research.microsoft.com/en-us/people/mickens/thesaddestmoment.pdf
- 94.
- 95. Basic Paxos = “choose exactly one value”
- 96. Paxos - photoby Luigi Piazzi
- 97. Paxos: a high-leveloverview It’s the distributed systems algorithm
- 98. Paxos: a high-leveloverview JavaZone had a full session on Paxos already today…
- 99. A few Paxoswhitepapers "Reaching Agreement in the Presence of Faults” – Lamport, 1980 … “FLP Impossibility Result” – Fisher et al, 1985 “The Part Time Parliament” – Lamport, 1998 … “Paxos made Simple” – Lamport, 2001 “Fast Paxos” – Lamport, 2005 … “Paxos made Live” – Chandra et al, 2007 … “Paxos made Moderately Complex” – Rennesse, 2011 ;-)
- 100. Lamport’s “Replicated StateMachine”
- 101.
- 102.
- 103.
- 104.
- 105.
- 106.
- 107. ! Consensus time! Chose a value (raise your hand)
- 108. Consensus time! Chosea value (raise your hand): v1 = Basic Paxos + Raft v2 = Just Raft
- 109. Consensus time! Chosea value (raise your hand): v1 = Basic Paxos + Raft v2 = Just Raft
- 110. Consensus time! Chosea value (raise your hand): v1 = Basic Paxos + Raft v2 = Just Raft
- 111. Consensus time! Chosea value (raise your hand): v1 = Basic Paxos + Raft v2 = Just Raft (if enough time, Paxos)
- 112. Basic Paxos simpleexample
- 113. Paxos: Proposals ProposalNrmust: • be greaterThan any prev proposalNr used by this Proposer • example: [roundNr|serverId]
- 114. Paxos: 2 phases Phase 1: Prepare Phase 2: Accept
- 115. Paxos, Prepare Phase n = nextSeqNr()
- 116. Paxos, Prepare Phase acceptors ! Prepare(n, value)
- 117. Paxos, Prepare Phase case Prepare(n, value) =>! if (n > minProposal) {! minProposal = n! accVal = value! }! ! sender() ! Accepted(minProposal, accVal)
- 118. Paxos, Prepare Phase case Prepare(n, value) =>! if (n > minProposal) {! minProposal = n! accVal = value! }! ! sender() ! Accepted(minProposal, accVal)
- 119. Paxos, Prepare Phase value = highestN(responses).accVal ! // replace my value, with accepted value!
- 120. Paxos, Accept Phase acceptors ! Accept(n, value)
- 121. Paxos, Accept Phase case Accept(n, value) =>! if (n >= minProposal) {! acceptedProposal = minProposal = n! acceptedValue = value! }! ! learners ! Learn(value)! sender() ! minProposal
- 122.
- 123.
- 124. Paxos, Accept Phase if (acceptedN > n) restartPaxos()! else println(n + “ was chosen!”)
- 125. Basic Paxos BasicPaxos, needs extensions for the “real world”. Additions: • “stable leader” • performance (basic = 2 * broadcast roundtrip) • ensure full replication • configuration changes
- 126.
- 127. Multi Paxos “Basicallyeveryone does it, but everyone does it differently.”
- 128. Multi Paxos •Keeps the Leader • Clients find and talk to the Leader • Skips Phase 1, in stable state • 2 delays instead of 4, until learning a value
- 129.
- 130. Raft – inspiredby Paxos Paxos is great. Multi-Paxos is great, but no “common understanding”. ! ! Raft wants to be understandable and just as solid. "In search of an understandable consensus protocol" (2013)
- 131. Raft – inspiredby Paxos ! ! • Leader based • Less processes than Paxos • It’s goal is simplicity • “Basic” includes snapshotting / membership
- 132. Raft - summarisedon one page Diego Ongaro & John Ouserhout – In search of an understandable consensus protocol
- 133.
- 134.
- 135. Raft - startingthe cluster
- 136. Raft - Electiontimeout
- 137. Raft - 1stelection
- 138. Raft - 1stelection
- 139. Raft - ElectionTimeout
- 140. Raft - ElectionPhase
- 141.
- 142.
- 143.
- 144.
- 145.
- 146.
- 147.
- 148.
- 149.
- 150.
- 151. Raft – heartbeat= empty entries
- 152. Raft – heartbeat= empty entries
- 153. Akka–Raft ! (communityproject) (work in progress)
- 154.
- 155. Raft translated toAkka abstract class RaftActor ! ! extends Actor ! ! with FSM[RaftState, Metadata]
- 156. Raft translated toAkka abstract class RaftActor ! ! extends Actor ! ! with FSM[RaftState, Metadata]
- 157. Raft translated toAkka onTransition {! ! case Follower -> Candidate =>! self ! BeginElection! resetElectionDeadline()! ! // ...! }
- 158. Raft translated toAkka onTransition {! ! case Follower -> Candidate =>! self ! BeginElection! resetElectionDeadline()! ! // ...! }
- 159. Raft translated toAkka ! case Event(BeginElection, m: ElectionMeta) =>! log.info("Init election (among {} nodes) for {}”,! m.config.members.size, m.currentTerm)! ! val request = RequestVote(m.currentTerm, m.clusterSelf, replicatedLog.lastTerm, replicatedLog.lastIndex)! ! m.membersExceptSelf foreach { _ ! request }! ! val includingThisVote = m.incVote! stay() using includingThisVote.withVoteFor(m.currentTerm, m.clusterSelf)! }!
- 160.
- 161. Raft Heartbeat usingAkka sendHeartbeat(m)! log.info("Starting hearbeat, with interval: {}", heartbeatInterval)! setTimer(HeartbeatName, SendHeartbeat, heartInterval, repeat = true)! akka-raft is a work in progress community project – it may change a lot
- 162. Raft Heartbeat usingAkka sendHeartbeat(m)! log.info("Starting hearbeat, with interval: {}", heartbeatInterval)! setTimer(HeartbeatName, SendHeartbeat, heartInterval, repeat = true)! akka-raft is a work in progress community project – it may change a lot
- 163. Raft Heartbeat usingAkka sendHeartbeat(m)! log.info("Starting hearbeat, with interval: {}", heartbeatInterval)! setTimer(HeartbeatName, SendHeartbeat, heartInterval, repeat = true)! val leaderBehaviour = {! // ...! case Event(SendHeartbeat, m: LeaderMeta) =>! sendHeartbeat(m)! stay()! akka-raft is a work in progress community project – it may change a lot }
- 164. Akka-Raft in User-Land//alpha!!! class WordConcatRaftActor extends RaftActor {! ! type Command = Cmnd! ! var words = Vector[String]()! ! /** Applied when command committed by Raft consensus */! def apply = {! case AppendWord(word) =>! words = words :+ word! word! ! case GetWords =>! log.info("Replying with {}", words.toList)! words.toList! }! }! akka-raft is a work in progress community project – it may change a lot
- 165.
- 166. FLP Impossibility Proof(19 Impossibility of Distributed Consensus with One Faulty Process 1985 by Fisher, Lynch, Paterson
- 167. FLP Impossibility Result Impossibility of Distributed Consensus with One Faulty Process 1985 by Fisher, Lynch, Paterson
- 168. FLP Impossibility Result Impossibility of Distributed Consensus with One Faulty Process 1985 by Fisher, Lynch, Paterson
- 169. ktoso @ typesafe.com twitter: ktosopl github: ktoso blog: project13.pl team blog: letitcrash.com JavaZone @ Oslo 2014 ! ! Takk! Dzięki! Thanks! ありがとう！ akka.io
- 170. Happy Byzantine Lunch-time! Konrad 'ktoso' Malawski GeeCON 2014 @ Kraków, PL
- 171. ©Typesafe 2014 –All Rights Reserved
- 172. Links 1. http://cs-www.cs.yale.edu/homes/arvind/cs425/doc/fischer.pdf 2. http://hydra.infosys.tuwien.ac.at/teaching/courses/AdvancedDistributedSystems/download/ 1975_Akkoyunlu,%20Ekanadham,%20Huber_Some%20constraints%20and%20tradeoffs %20in%20the%20design%20of%20network%20communications.pdf 3. http://research.microsoft.com/en-us/people/mickens/thesaddestmoment.pdf 4. http://research.microsoft.com/en-us/um/people/lamport/pubs/lamport-paxos.pdf 5. http://research.microsoft.com/en-us/um/people/lamport/pubs/paxos-simple.pdf 6. http://the-paper-trail.org/blog/consensus-protocols-paxos/ 7. http://static.googleusercontent.com/media/research.google.com/en//archive/ paxos_made_live.pdf 8. http://static.googleusercontent.com/media/research.google.com/en//archive/chubby-osdi06. pdf 9. https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf 10. Recent Leslie Lamport interview: http://www.se-radio.net/2014/04/episode-203-leslie-lamport- on-distributed-systems/ 11. http://book.mixu.net/distsys/ 12. http://codahale.com/you-cant-sacrifice-partition-tolerance/ Peter Deutsch “The Eight Fallacies of Distributed Computing” https://blogs.oracle.com/jag/resource/Fallacies.html
- 173. Links 1. ExcellentPaxos lecture by Diego Ongaro https://www.youtube.com/watch?v=JEpsBg0AO6o 2. Fallacies, actual paper: http://www.rgoarchitects.com/Files/fallacies.pdf 3. Diego Ongaro & John Ouserhout – In search of an understandable consensus protocol 4. http://macs.citadel.edu/rudolphg/csci604/ImpossibilityofConsensus.pdf Peter Deutsch “The Eight Fallacies of Distributed Computing” https://blogs.oracle.com/jag/resource/Fallacies.html
- 174. Images / drawings 1. Paxos Island Photo – Luigi Piazzi (CC license) https://www.flickr.com/photos/photolupi/ 3686769346/in/photolist-6BME5J-orKHL2-58qmez-58uz7s-7bRwTj-7bRvHY-6DdRC2- fBqFFU-35KTg7-8vbe23-bsBGL7-58qq6z-58uAjG-8vbeCd-d1Sqqw-d1Smsj-d1Sqi5- d1SoMA-d1SmBE-d1SpVo-d1Sk2U-d1SoBQ-d1SoXu-d1SoqN-d1Spqu-d1Sq4w-d1SpLU-d1SKDG- d1Skcu-d1Sp8f-d1Sqaq-d1SpCw-75YaVN-d1SLs1-d1SK15-d1SJiC-d1Suiu-d1SKtS-d1SjQS- d1StyU-d1SKi1-d1SxGS-d1Sm6j-d1Sxdh-d1SKMN-d1SxAq-d1SwgC-d1Smgj-d1SvhJ- d1SjC7 2. Drawings – myself (use-them-at-will-unless-mocking-my-horrible-drawing-skills-license) Peter Deutsch “The Eight Fallacies of Distributed Computing” https://blogs.oracle.com/jag/resource/Fallacies.html