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https://github.com/status-im/nim-raft.git
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127 lines
4.9 KiB
Nim
127 lines
4.9 KiB
Nim
# nim-raft
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# Copyright (c) 2023 Status Research & Development GmbH
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# Licensed under either of
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# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
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# * MIT license ([LICENSE-MIT](LICENSE-MIT))
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# at your option.
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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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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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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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# Define callback to use with Terminals. Node states are updated/read in-place in the node object
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ConsensusFsmTransActionType*[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, RaftMessageBase] =
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proc(n: NodeTytpe, msg: Option[RaftMessageBase]): LogicalConditionValueType
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LogicalConditionsLut*[RaftNodeState, EventType, NodeType, RaftMessageBase] =
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Table[(RaftNodeState, EventType), seq[LogicalCondition[NodeType, Option[RaftMessageBase]]]]
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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 RaftMessageBase
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# (kind of Truth Table)
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TerminalSymbol*[EventType, NodeType, RaftMessageBase] =
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(EventType, seq[LogicalConditionValueType])
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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, RaftMessageBase] = Table[
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(RaftNodeState, TerminalSymbol[NodeType, EventType, Option[RaftMessageBase]]),
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(RaftNodeState, Option[ConsensusFsmTransActionType])
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]
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# FSM type definition
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ConsensusFsm*[RaftNodeState, EventType, NodeType, RaftMessageBase] = ref object
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mtx: RLock
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state: RaftNodeState
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logicalFunctionsLut: LogicalConditionsLut[RaftNodeState, EventType, NodeType, RaftMessageBase]
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stateTransitionsLut: StateTransitionsRulesLut[RaftNodeState, EventType, NodeType, RaftMessageBase]
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# FSM type constructor
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proc new*[RaftNodeState, EventType, NodeType, RaftNodeStates](
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T: type ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageBase], startSymbol: RaftNodeState): T =
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result = new(ConsensusFsm[NodeType, EventType, RaftNodeStates])
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initRLock(result.mtx)
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result.state = startSymbol
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debug "new: ", fsm=repr(result)
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proc addFsmTransition*[RaftNodeState, EventType, NodeType, RaftMessageBase](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageBase],
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fromState: RaftNodeState,
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termSymb: TerminalSymbol[EventType, NodeType, RaftMessageBase],
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toState: RaftNodeState,
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action: Option[ConsensusFsmTransActionType]) =
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fsm.stateTransitionsLut[(fromState.state, termSymb)] = (toState, action)
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proc addFsmTransitionLogicalConditions*[RaftNodeState, EventType, NodeType, RaftMessageBase](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageBase],
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state: RaftNodeState,
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event: EventType,
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logicalConditions: seq[LogicalCondition[NodeType, Option[RaftMessageBase]]]) =
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fsm.logicalFunctionsLut[(state, event)] = logicalConditions
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proc computeFsmLogicFunctionsPermutationValuе*[RaftNodeState, NodeType, EventType, RaftMessageBase](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageBase],
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node: NodeType,
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termSymb: TerminalSymbol,
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msg: Option[RaftMessageBase]): TerminalSymbol =
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let
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e = termSymb[0]
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debug "computeFSMLogicFunctionsPermutationValue: ", eventType=e, " ", nonTermSymb=nts, " ", msg=msg
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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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debug "computeFSMLogicFunctionsPermutationValue: ", logicFunctionsConds=logicFunctionsConds
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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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termSymb[1] = logicFunctionsConds
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result = termSymb
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proc fsmAdvance*[RaftNodeState, EventType, NodeType, RaftMessageBase](
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fsm: ConsensusFsm[RaftNodeState, EventType, NodeType, RaftMessageBase],
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node: NodeType,
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termSymb: TerminalSymbol[EventType, NodeType, RaftMessageBase],
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msg: Option[RaftMessageBase]): RaftNodeState =
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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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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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