WIP: Inital consensus state machine work
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Marto
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@ -7,123 +7,121 @@
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# This file may not be copied, modified, or distributed except according to
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# those terms.
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import std/tables
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import std/rlocks
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import types
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import chronicles
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import std/[times]
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type
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# Node events
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EventType* = enum
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VotingTimeout,
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ElectionTimeout,
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HeartbeatTimeout,
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AppendEntriesTimeout
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HeartbeatReceived,
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HeartbeatSent,
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AppendEntriesReceived,
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AppendEntriesSent,
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RequestVoteReceived,
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RequestVoteSent,
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ClientRequestReceived,
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ClientRequestProcessed
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RaftRpcMessageType* = enum
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Vote = 0,
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VoteReplay = 1,
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Append = 2,
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AppendReplay = 3
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# Define callback to use with transitions. It is a function that takes a node as an argument and returns nothing.
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# It is used to perform some action when a transition is triggered. For example, when a node becomes a leader,
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# it should start sending heartbeats to other nodes.
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ConsensusFsmTransitionActionType*[NodeType] = proc(node: NodeType) {.gcsafe.}
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# Define logical functions (conditions) computed from our NodeType etc. (Truth Table)
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LogicalConditionValueType* = bool
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LogicalCondition*[NodeTytpe, RaftMessageType] =
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proc(node: NodeTytpe, msg: Option[RaftMessageType]): LogicalConditionValueType
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LogicalConditionsLut*[RaftNodeState, EventType, NodeType, RaftMessageType] =
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Table[(RaftNodeState, EventType), seq[LogicalCondition[NodeType, RaftMessageType]]]
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RaftRpcAppendRequest* = object
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previousTerm: RaftNodeTerm
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# Define Terminals as a tuple of a Event and a sequence of logical functions (conditions) and their respective values computed from NodeType, NodeTytpe and RaftMessageType
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# (kind of Truth Table)
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TerminalSymbol*[EventType, NodeType, RaftMessageType] =
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(EventType, seq[LogicalConditionValueType])
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RaftRpcAppendReplay* = object
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# Define State Transition Rules LUT of the form ( NonTerminal -> Terminal ) -> NonTerminal )
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# NonTerminal is a NodeState and Terminal is a TerminalSymbol - the tuple (EventType, seq[LogicalConditionValueType])
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StateTransitionsRulesLut*[RaftNodeState, EventType, NodeType, RaftMessageType] = Table[
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(RaftNodeState, TerminalSymbol[NodeType, EventType, RaftMessageType]),
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(RaftNodeState, Option[ConsensusFsmTransitionActionType[NodeType]])
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]
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RaftRpcVoteRequest* = object
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# FSM type definition
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ConsensusFsm*[RaftNodeState, EventType, NodeType, RaftMessageType] = ref object
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mtx: RLock
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state: RaftNodeState
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logicalFunctionsLut: LogicalConditionsLut[RaftNodeState, EventType, NodeType, RaftMessageType]
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stateTransitionsLut: StateTransitionsRulesLut[RaftNodeState, EventType, NodeType, RaftMessageType]
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RaftRpcVoteReplay* = object
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# FSM type constructor
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proc new*[RaftNodeState, EventType, NodeType, RaftMessageType](
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T: type ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageType], startSymbol: RaftNodeState = rnsFollower): T =
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LeaderState* = object
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result = T(mtx: RLock(), state: startSymbol)
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initRLock(result.mtx)
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CandidateState* = object
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votes: seq[RaftNodeId]
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debug "new: ", fsm=repr(result)
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FollowerState* = object
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leader: RaftNodeId
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proc addFsmTransition*[RaftNodeState, EventType, NodeType, RaftMessageType](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageType],
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fromState: RaftNodeState,
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termSymb: TerminalSymbol[EventType, NodeType, RaftMessageType],
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toState: RaftNodeState,
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action: Option[ConsensusFsmTransitionActionType]) =
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RaftRpcMessage* = object
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currentTerm: RaftNodeTerm
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sender: RaftNodeId
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case kind: RaftRpcMessageType
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of Vote: voteRequest: RaftRpcVoteRequest
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of VoteReplay: voteReplay: RaftRpcVoteReplay
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of Append: appendRequest: RaftRpcAppendRequest
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of AppendReplay: appendReplay: RaftRpcAppendReplay
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fsm.stateTransitionsLut[(fromState.state, termSymb)] = (toState, action)
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Command* = object
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data: seq[byte]
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LogEntry* = object # Abstarct Raft Node Log entry containing opaque binary data (Blob etc.)
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term: RaftNodeTerm
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index: RaftLogIndex
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# TODO: Add configuration too
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data: Command
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proc addFsmTransitionLogicalConditions*[RaftNodeState, EventType, NodeType, RaftMessageType](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageType],
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state: RaftNodeState,
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event: EventType,
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logicalConditions: seq[LogicalCondition[NodeType, RaftMessageType]]) =
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RaftLog* = object
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logEntries: seq[LogEntry]
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fsm.logicalFunctionsLut[(state, event)] = logicalConditions
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RaftStateMachineOutput* = object
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logEntries: seq[LogEntry]
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# Entries that should be applyed to the "User" State machine
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committed: seq[LogEntry]
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messages: seq[RaftRpcMessage]
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debugLogs: seq[string]
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proc computeFsmLogicFunctionsPermutationValuе*[RaftNodeState, NodeType, EventType, RaftMessageType](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageType],
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node: NodeType,
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termSymb: TerminalSymbol,
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msg: Option[RaftMessageType]): TerminalSymbol =
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RaftStateMachine* = object
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myId*: RaftNodeId
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term: RaftNodeTerm
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commitIndex: RaftLogIndex
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log: RaftLog
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output: RaftStateMachineOutput
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electionTimeout: times.Duration
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lastUpdate: Time
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case state: RaftNodeState
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of rnsFollower: follower : FollowerState
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of rnsCandidate: candidate: CandidateState
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of rnsLeader: leader: LeaderState
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let
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e = termSymb[0]
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RaftStateMachineConfig* = object
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debug "computeFSMLogicFunctionsPermutationValue: ", eventType=e, " ", nonTermSymb=nts, " ", msg=msg
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func append(rf: var RaftLog, entry: LogEntry) =
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rf.logEntries.add(entry)
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var
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logicFunctionsConds = fsm.logicalFunctionsLut[(e, NodeType)]
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logicFunctionsCondsValues = seq[LogicalConditionValueType]
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func debug*(sm: var RaftStateMachine, log: string) =
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sm.output.debugLogs.add(log)
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debug "computeFSMLogicFunctionsPermutationValue: ", logicFunctionsConds=logicFunctionsConds
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func initRaftStateMachine*(config: RaftStateMachineConfig): RaftStateMachine =
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var st = RaftStateMachine()
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st.term = 0
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st.commitIndex = 0
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st.state = RaftNodeState.rnsFollower
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return st
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for f in logicFunctionsConds:
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logicFunctionsCondsValues.add f(node, msg)
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debug "computeFSMLogicFunctionsPermutationValue: ", logicFunctionsCondsValues=logicFunctionsCondsValues
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func createVoteRequest*(sm: var RaftStateMachine): RaftRpcMessage =
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return RaftRpcMessage(currentTerm: sm.term, sender: sm.myId, kind: Vote, voteRequest: RaftRpcVoteRequest())
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termSymb[1] = logicFunctionsConds
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result = termSymb
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func advance*(sm: var RaftStateMachine, msg: RaftRpcMessage,currentTime: Time) =
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if sm.term > msg.currentTerm:
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sm.debug "Current node is behind"
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elif sm.term < msg.currentTerm:
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sm.debug "The leader is behind"
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else:
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case sm.state:
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of rnsCandidate:
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sm.state = rnsFollower
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sm.follower.leader = msg.sender
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of rnsFollower:
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sm.follower.leader = msg.sender
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of rnsLeader:
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sm.debug "For now it should be impossible to have msg from a non leader to a leader"
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proc fsmAdvance*[RaftNodeState, EventType, NodeType, RaftMessageType](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageType],
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node: NodeType,
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termSymb: TerminalSymbol[EventType, NodeType, RaftMessageType],
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msg: Option[RaftMessageType]): RaftNodeState =
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case msg.kind:
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of RaftRpcMessageType.Vote:
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sm.debug "Handle vote request"
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else:
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sm.debug "Unhandle msg type"
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withRLock():
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var
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input = computeFsmLogicFunctionsPermutationValue(fsm, node, termSymb, msg)
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let trans = fsm.stateTransitionsLut[(fsm.state, input)]
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let action = trans[1]
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func addEntry*(sm: var RaftStateMachine, entry: LogEntry) =
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if sm.state != RaftNodeState.rnsLeader:
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sm.debug "Error: only the leader can handle new entries"
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sm.log.append(entry)
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fsm.state = trans[0]
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debug "ConsensusFsmAdvance", fsmState=fsm.state, " ", input=input, " ", action=repr(action)
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if action.isSome:
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action(node)
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result = fsm.state
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func poll*(sm: var RaftStateMachine): RaftStateMachineOutput =
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# Should initiate replication if we have new entries
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let output = sm.output
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sm.output = RaftStateMachineOutput()
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return output
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@ -27,10 +27,9 @@ const
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type
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RaftNodeState* = enum
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rnsError = 0, # Error state
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rnsFollower = 1, # Follower state
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rnsCandidate = 2 # Candidate state
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rnsLeader = 3 # Leader state
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rnsFollower = 0, # Follower state
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rnsCandidate = 1 # Candidate state
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rnsLeader = 2 # Leader state
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RaftNodeId* = UUID # uuid4 uniquely identifying every Raft Node
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RaftNodeTerm* = int # Raft Node Term Type
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@ -14,4 +14,5 @@ import ../misc/test_macro
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cliBuilder:
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import ./test_basic_timers,
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./test_basic_state_machine,
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./test_basic_cluster_election
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#./test_basic_cluster_election,
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./test_consensus_state_machine
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@ -9,16 +9,34 @@
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import unittest2
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import ../raft/types
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import basic_state_machine
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import ../raft/consensus_state_machine
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import std/[times]
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var
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csm: ConsensusFsm[RaftNodeState, EventType, RaftNode[SmCommand, SmState], RaftMessageBase[SmCommand, SmState]]
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proc consensusstatemachineMain*() =
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suite "Create and test Consensus State Machine":
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test "Create Consensus State Machine":
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csm = ConsensusFsm[RaftNodeState, EventType, RaftNode[SmCommand, SmState], RaftMessageBase[SmCommand, SmState]].new
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check csm != nil
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suite "Basic state machine tests":
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test "create state machine":
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let config = RaftStateMachineConfig()
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let sm = initRaftStateMachine(config)
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echo sm
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# test "Add state transitions / logic conditions":
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test "advance empty state machine":
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var sm = RaftStateMachine()
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var msg = sm.createVoteRequest()
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sm.advance(msg ,getTime())
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echo sm.poll()
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echo sm.poll()
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echo getTime()
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test "two machines":
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var sm = RaftStateMachine()
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var sm2 = RaftStateMachine(myId: genUUID())
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var msg = sm2.createVoteRequest()
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sm.advance(msg ,getTime())
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echo sm2
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echo getTime()
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if isMainModule:
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consensusstatemachineMain()
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